Researcher Database

Koichi S Kobayashi
Faculty of Medicine Pathological Science Department of Microbiology and Immunology

Researcher Profile and Settings


  • Faculty of Medicine Pathological Science Department of Microbiology and Immunology

Job Title

  • Professor

J-Global ID

Research Activities

Published Papers

  • Vijayan S, Sidiq T, Yousuf S, van den Elsen PJ, Kobayashi KS
    Immunogenetics 71 (3) 273 - 282 0093-7711 2019/03 [Refereed][Not invited]
  • The IL-33-PIN1-IRAK-M axis is critical for type 2 immunity in IL-33-induced allergic airway inflammation.
    Nechama M, Kwon J, Wei S, Kyi AT, Welner RS, Ben-Dov IZ, Arredouani MS, Asara JM, Chen CH, Tsai CY, Nelson KF, Kobayashi KS, Israel E, Zhou XZ, Nicholson LK, Lu KP
    Nat Commun. 23;9(1):1603. 2018/04 [Refereed][Not invited]
  • Judith Agudo, Eun Sook Park, Samuel A. Rose, Eziwoma Alibo, Robert Sweeney, Maxime Dhainaut, Koichi S. Kobayashi, Ravi Sachidanandam, Alessia Baccarini, Miriam Merad, Brian D. Brown
    Immunity 48 (2) 271 - 285.e5 1097-4180 2018/02/20 [Refereed][Not invited]
    Stem cells are critical for the maintenance of many tissues, but whether their integrity is maintained in the face of immunity is unclear. Here we found that cycling epithelial stem cells, including Lgr5+ intestinal stem cells, as well as ovary and mammary stem cells, were eliminated by activated T cells, but quiescent stem cells in the hair follicle and muscle were resistant to T cell killing. Immune evasion was an intrinsic property of the quiescent stem cells resulting from systemic downregulation of the antigen presentation machinery, including MHC class I and TAP proteins, and is mediated by the transactivator NLRC5. This process was reversed upon stem cell entry into the cell cycle. These studies identify a link between stem cell quiescence, antigen presentation, and immune evasion. As cancer-initiating cells can derive from stem cells, these findings may help explain how the earliest cancer cells evade immune surveillance. Agudo et al. find that cycling tissue stem cells are subject to immune clearance, but quiescent stem cells downregulate the antigen presentation machinery and evade immune surveillance.
  • Bist P, Cheong WS, Ng A, Dikshit N, Kim BH, Pulloor NK, Khameneh HJ, Hedl M, Shenoy AR, Balamuralidhar V, Malik NBA, Hong M, Neutzner A, Chin KC, Kobayashi KS, Bertoletti A, Mortellaro A, Abraham C, MacMicking JD, Xavier RJ, Sukumaran B
    Nature communications 8 16141  2017/08 [Refereed][Not invited]
  • Pradeep Bist, Wan Shoo Cheong, Aylwin Ng, Neha Dikshit, Bae-Hoon Kim, Niyas Kudukkil Pulloor, Hanif Javanmard Khameneh, Matija Hedl, Avinash R. Shenoy, Vanniarajan Balamuralidhar, Najib Bin Abdul Malik, Michelle Hong, Albert Neutzner, Keh-Chuang Chin, Koichi S. Kobayashi, Antonio Bertoletti, Alessandra Mortellaro, Clara Abraham, John D. MacMicking, Ramnik J. Xavier, Bindu Sukumaran
    NATURE COMMUNICATIONS 8 15865  2041-1723 2017/06 [Refereed][Not invited]
    Optimal regulation of the innate immune receptor nucleotide-binding oligomerization domain-containing protein 2 (NOD2) is essential for controlling bacterial infections and inflammatory disorders. Chronic NOD2 stimulation induces non-responsiveness to restimulation, termed NOD2-induced tolerance. Although the levels of the NOD2 adaptor, RIP2, are reported to regulate both acute and chronic NOD2 signalling, how RIP2 levels are modulated is unclear. Here we show that ZNRF4 induces K48-linked ubiquitination of RIP2 and promotes RIP2 degradation. A fraction of RIP2 localizes to the endoplasmic reticulum (ER), where it interacts with ZNRF4 under either 55 unstimulated and muramyl dipeptide-stimulated conditions. Znrf4 knockdown monocytes have sustained nuclear factor kappalight- chain-enhancer of activated B cells (NF-kappa B) activation, and Znrf4 knockdown mice have reduced NOD2-induced tolerance and more effective control of Listeria monocytogenes infection. Our results thus demonstrate E3-ubiquitin ligase ZNRF4-mediated RIP2 degradation as a negative regulatory mechanism of NOD2-induced NF-kappa B, cytokine and anti-bacterial responses in vitro and in vivo, and identify a ZNRF4-RIP2 axis of fine-tuning NOD2 signalling to promote protective host immunity.
  • Aseem Pandey, Sheng Li Ding, Qing-Ming Qin, Rahul Gupta, Gabriel Gomez, Furong Lin, Xuehuan Feng, Luciana Fachini da Costa, Sankar P. Chaki, Madhu Katepalli, Elizabeth D. Case, Erin J. van Schaik, Tabasum Sidiq, Omar Khalaf, Angela Arenas, Koichi S. Kobayashi, James E. Samuel, Gonzalo M. Rivera, Robert C. Alaniz, Sing-Hoi Sze, Xiaoning Qian, William J. Brown, Allison Rice-Ficht, William K. Russell, Thomas A. Ficht, Paul de Figueiredo
    CELL HOST & MICROBE 21 (5) 637 - + 1931-3128 2017/05 [Refereed][Not invited]
    Cryptococcus neoformans (Cn) is a deadly fungal pathogen whose intracellular lifestyle is important for virulence. Host mechanisms controlling fungal phagocytosis and replication remain obscure. Here, we perform a global phosphoproteomic analysis of the host response to Cryptococcus infection. Our analysis reveals numerous and diverse host proteins that are differentially phosphorylated following fungal ingestion by macrophages, thereby indicating global reprogramming of host kinase signaling. Notably, phagocytosis of the pathogen activates the host autophagy initiation complex (AIC) and the upstream regulatory components LKB1 and AMPK alpha, which regulate autophagy induction through their kinase activities. Deletion of Prkaa1, the gene encoding AMPK alpha 1, in monocytes results in resistance to fungal colonization of mice. Finally, the recruitment of AIC components to nascent Cryptococcus-containing vacuoles (CnCVs) regulates the intracellular trafficking and replication of the pathogen. These findings demonstrate that host AIC regulatory networks confer susceptibility to infection and establish a proteomic resource for elucidating host mechanisms that regulate fungal intracellular parasitism.
  • Sayuri Yoshihama, Saptha Vijayan, Tabasum Sidiq, Koichi S. Kobayashi
    Trends in Cancer 3 (1) 28 - 38 2405-8033 2017/01/01 [Refereed][Not invited]
    Cancer cells need to escape immune surveillance for successful tumor growth. Loss of MHC class I has been described as a major immune evasion strategy in many cancers. MHC class I transactivator (CITA), NLRC5 [nucleotide-binding domain and leucine-rich repeats containing (NLR) family, caspase activation and recruitment domain (CARD) domain containing 5], is a key transcription coactivator of MHC class I genes. Recent genetic studies have revealed that NLRC5 is a major target for cancer immune evasion mechanisms. The reduced expression or activity of NLRC5 caused by promoter methylation, copy number loss, or somatic mutations is associated with defective MHC class I expression, impaired cytotoxic T cell activation, and poor patient prognosis. Here, we review the role of NLRC5 in cancer immune evasion and the future prospects for cancer research.
  • Tabasum Sidiq, Sayuri Yoshihama, Isaac Downs, Koichi S. Kobayashi
    FRONTIERS IN IMMUNOLOGY 7 367  1664-3224 2016/09 [Refereed][Not invited]
    The human intestinal tract harbors large bacterial community consisting of commensal, symbiotic, and pathogenic strains, which are constantly interacting with the intestinal immune system. This interaction elicits a non-pathological basal level of immune responses and contributes to shaping both the intestinal immune system and bacterial community. Recent studies on human microbiota are revealing the critical role of intestinal bacterial community in the pathogenesis of both systemic and intestinal diseases, including Crohn's disease (CD). NOD2 plays a key role in the regulation of microbiota in the small intestine. NOD2 is highly expressed in ileal Paneth cells that provide critical mechanism for the regulation of ileal microbiota through the secretion of anti-bacterial compounds. Genome mapping of CD patients revealed that loss of function mutations in NOD2 are associated with ileal CD. Genome-wide association studies further demonstrated that NOD2 is one of the most critical genetic factor linked to ileal CD. The bacterial community in the ileum is indeed dysregulated in Nod2-deficient mice. Nod2-deficient ileal epithelia exhibit impaired ability of killing bacteria. Thus, altered interactions between ileal microbiota and mucosal immunity through NOD2 mutations play significant roles in the disease susceptibility and pathogenesis in CD patients, thereby depicting NOD2 as a critical regulator of ileal microbiota and CD.
  • Isaac Downs, Saptha Vijayan, Tabasum Sidiq, Koichi S. Kobayashi
    BIOFACTORS 42 (4) 349 - 357 0951-6433 2016/07 [Refereed][Not invited]
    Major histocompatibility complex (MHC) class I and class II molecules play essential roles in the development and activation of the human adaptive immune system. An NLR protein, CIITA (MHC class II transactivator) has been recognized as a master regulator of MHC class II gene expression, albeit knowledge about the regulatory mechanism of MHC class I gene expression had been limited. Recently identified MHC class I transactivator (CITA), or NLRC5, also belongs to the NLR protein family and constitutes a critical regulator for the transcriptional activation of MHC class I genes. In addition to MHC class I genes, CITA/NLRC5 induces the expression of (2)-microglobulin, TAP1 and LMP2, essential components of the MHC class I antigen presentation pathway. Therefore, CITA/NLRC5 and CIITA are transcriptional regulators that orchestrate the concerted expression of critical components in the MHC class I and class II pathways, respectively. (c) 2016 BioFactors, 42(4):349-357, 2016
  • Sayuri Yoshihama, Jason Roszik, Isaac Downs, Torsten B. Meissner, Saptha Vijayan, Bjoern Chapuy, Tabasum Sidiq, Margaret A. Shipp, Gregory A. Lizee, Koichi S. Kobayashi
    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 113 (21) 5999 - 6004 0027-8424 2016/05 [Refereed][Not invited]
    Cancer cells develop under immune surveillance, thus necessitating immune escape for successful growth. Loss of MHC class I expression provides a key immune evasion strategy in many cancers, although the molecular mechanisms remain elusive. MHC class I transactivator (CITA), known as "NLRC5" [NOD-like receptor (NLR) family, caspase recruitment (CARD) domain containing 5], has recently been identified as a critical transcriptional coactivator of MHC class I gene expression. Here we show that the MHC class I transactivation pathway mediated by CITA/NLRC5 constitutes a target for cancer immune evasion. In all the 21 tumor types we examined, NLRC5 expression was highly correlated with the expression of MHC class I, with cytotoxic T-cell markers, and with genes in the MHC class I antigen-presentation pathway, including LMP2/LMP7, TAP1, and beta 2-microglobulin. Epigenetic and genetic alterations in cancers, including promoter methylation, copy number loss, and somatic mutations, were most prevalent in NLRC5 among all MHC class I-related genes and were associated with the impaired expression of components of the MHC class I pathway. Strikingly, NLRC5 expression was significantly associated with the activation of CD8(+) cytotoxic T cells and patient survival in multiple cancer types. Thus, NLRC5 constitutes a novel prognostic biomarker and potential therapeutic target of cancers.
  • Michael P. Burrows, Pavel Volchkov, Koichi S. Kobayashi, Alexander V. Chervonsky
    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 112 (32) 9973 - 9977 0027-8424 2015/08 [Refereed][Not invited]
    Deletion of the innate immune adaptor myeloid differentiation primary response gene 88 (MyD88) in the nonobese diabetic (NOD) mouse model of type 1 diabetes (T1D) results in microbiota-dependent protection from the disease: MyD88-negative mice in germfree (GF), but not in specific pathogen-free conditions develop the disease. These results could be explained by expansion of particular protective bacteria ("specific lineage hypothesis") or by dominance of negative (tolerizing) signaling over proinflammatory signaling ("balanced signal hypothesis") in mutant mice. Here we found that colonization of GF mice with a variety of intestinal bacteria was capable of reducing T1D in MyD88-negative (but not wild-type NOD mice), favoring the balanced signal hypothesis. However, the receptors and signaling pathways involved in prevention or facilitation of the disease remained unknown. The protective signals triggered by the microbiota were revealed by testing NOD mice lacking MyD88 in combination with knockouts of several critical components of innate immune sensing for development of T1D. Only MyD88-and TIR-domain containing adapter inducing IFN beta (TRIF) double deficient NOD mice developed the disease. Thus, TRIF signaling (likely downstream of Toll-like receptor 4, TLR4) serves as one of the microbiota-induced tolerizing pathways. At the same time another TLR (TLR2) provided prodiabetic signaling by controlling the microbiota, as reduction in T1D incidence caused by TLR2 deletion was reversed in GF TLR2-negative mice. Our results support the balanced signal hypothesis, in which microbes provide signals that both promote and inhibit autoimmunity by signaling through different receptors, including receptors of the TLR family.
  • Masanori Miyata, Ji-Yun Lee, Seiko Susuki-Miyata, Wenzhuo Y. Wang, Haidong Xu, Hirofumi Kai, Koichi S. Kobayashi, Richard A. Flavell, Jian-Dong Li
    NATURE COMMUNICATIONS 6 6062  2041-1723 2015/01 [Refereed][Not invited]
    Glucocorticoids are among the most commonly used anti-inflammatory agents. Despite the enormous efforts in elucidating the glucocorticoid-mediated anti-inflammatory actions, how glucocorticoids tightly control overactive inflammatory response is not fully understood. Here we show that glucocorticoids suppress bacteria-induced inflammation by enhancing IRAK-M, a central negative regulator of Toll-like receptor signalling. The ability of glucocorticoids to suppress pulmonary inflammation induced by non-typeable Haemophilus influenzae is significantly attenuated in IRAK-M-deficient mice. Glucocorticoids improve the survival rate after a lethal non-typeable Haemophilus influenzae infection in wild-type mice, but not in IRAK-M-deficient mice. Moreover, we show that glucocorticoids and non-typeable Haemophilus influenzae synergistically upregulate IRAK-M expression via mutually and synergistically enhancing p65 and glucocorticoid receptor binding to the IRAK-M promoter. Together, our studies unveil a mechanism by which glucocorticoids tightly control the inflammatory response and host defense via the induction of IRAK-M and may lead to further development of anti-inflammatory therapeutic strategies.
  • Maciej Lech, Regina Groebmayr, Mi Ryu, Georg Lorenz, Ingo Hartter, Shrikant R. Mulay, Heni Eka Susanti, Koichi S. Kobayashi, Richard A. Flavell, Hans-Joachim Anders
    JOURNAL OF THE AMERICAN SOCIETY OF NEPHROLOGY 25 (2) 292 - 304 1046-6673 2014/02 [Refereed][Not invited]
    The mechanisms that determine full recovery versus subsequent progressive CKD after AKI are largely unknown. Because macrophages regulate inflammation as well as epithelial recovery, we investigated whether macrophage activation influences AKI outcomes. IL-1 receptor-associated kinase-M (IRAK-M) is a macrophage-specific inhibitor of Toll-like receptor (TLR) and IL-1 receptor signaling that prevents polarization toward a proinflammatory phenotype. In postischemic kidneys of wild-type mice, IRAK-M expression increased for 3 weeks after AKI and declined thereafter. However, genetic depletion of IRAK-M did not affect immunopathology and renal dysfunction during early postischemic AKI. Regarding long-term outcomes, wild-type kidneys regenerated completely within 5 weeks after AKI. In contrast, IRAK-M-/- kidneys progressively lost up to two-thirds of their original mass due to tubule loss, leaving atubular glomeruli and interstitial scarring. Moreover, M1 macrophages accumulated in the renal interstitial compartment, coincident with increased expression of proinflammatory cytokines and chemokines. Injection of bacterial CpG DNA induced the same effects in wild-type mice, and TNF-alpha blockade with etanercept partially prevented renal atrophy in IRAK-M-/- mice. These results suggest that IRAK-M induction during the healing phase of AKI supports the resolution of M1 macrophage- and TNF-alpha-dependent renal inflammation, allowing structural regeneration and functional recovery of the injured kidney. Conversely, IRAK-M loss-of-function mutations or transient exposure to bacterial DNA may drive persistent inflammatory mononuclear phagocyte infiltrates, which impair kidney regeneration and promote CKD. Overall, these results support a novel role for IRAK-M in the regulation of wound healing and tissue regeneration.
  • Jessica Shiu, Steven J. Czinn, Koichi S. Kobayashi, Yezhou Sun, Thomas G. Blanchard
    PLOS ONE 8 (6) e66914  1932-6203 2013/06 [Refereed][Not invited]
    Helicobacter pylori (H. pylori) infects the gastric mucosa and persists for the life of the host. Bacterial persistence may be due to the induction of regulatory T cells (T-regs) which may have protective effects against other diseases such as asthma. It has been shown that H. pylori modulates the T cell response through dendritic cell reprogramming but the molecular pathways involved are relatively unknown. The goal of this study was to identify critical elements of dendritic cell (DC) activation and evaluate potential influence on immune activation. Microarray analysis was used to demonstrate limited gene expression changes in H. pylori stimulated bone marrow derived DCs (BMDCs) compared to the BMDCs stimulated with E. coli. IRAK-M, a negative regulator of TLR signaling, was upregulated and we selectedit for investigation of its role in modulating the DC and T cell responses. IRAK-M-/- and wild type BMDC were compared for their response to H. pylori. Cells lacking IRAK-M produced significantly greater amounts of proinflammatory MIP-2 and reduced amounts of immunomodulatory IL-10 than wild type BMDC. IRAK-M-/- cells also demonstrated increased MHC II expression upon activation. However, IRAK-M-/- BMDCs were comparable to wild type BMDCs in inducing T-helper 17 (T(H)17) and T-reg responses as demonstrated in vitro using BMDC CD4+ T cells co-culture assays, and in vivo though the adoptive transfer of CD4(+) FoxP3-GFP T cells into H. pylori infected IRAK-M-/- mice. These results suggest that H. pylori infection leads to the upregulation of anti-inflammatory molecules like IRAK-M and that IRAK-M has a direct impact on innate functions in DCs such as cytokine and costimulation molecule upregulation but may not affect T cell skewing.
  • Klara Klimesova, Miloslav Kverka, Zuzana Zakostelska, Tomas Hudcovic, Tomas Hrncir, Renata Stepankova, Pavel Rossmann, Jakub Ridl, Martin Kostovcik, Jakub Mrazek, Jan Kopecny, Koichi S. Kobayashi, Helena Tlaskalova-Hogenova
    INFLAMMATORY BOWEL DISEASES 19 (6) 1266 - 1277 1078-0998 2013/05 [Refereed][Not invited]
    Background:Microbial sensing by Toll-like receptors (TLR) and its negative regulation have an important role in the pathogenesis of inflammation-related cancer. In this study, we investigated the role of negative regulation of Toll-like receptors signaling and gut microbiota in the development of colitis-associated cancer in mouse model.Methods:Colitis-associated cancer was induced by azoxymethane and dextran sodium sulfate in wild-type and in interleukin-1 receptor-associated kinase M (IRAK-M)-deficient mice with or without antibiotic (ATB) treatment. Local cytokine production was analyzed by multiplex cytokine assay or enzyme-linked immunosorbent assay, and regulatory T cells were analyzed by flow cytometry. Changes in microbiota composition during tumorigenesis were analyzed by pyrosequencing, and -glucuronidase activity was measured in intestinal content by fluorescence assay.Results:ATB treatment of wild-type mice reduced the incidence and severity of tumors. Compared with nontreated mice, ATB-treated mice had significantly lower numbers of regulatory T cells in colon, altered gut microbiota composition, and decreased -glucuronidase activity. However, the -glucuronidase activity was not as low as in germ-free mice. IRAK-M-deficient mice not only developed invasive tumors, but ATB-induced decrease in -glucuronidase activity did not rescue them from severe carcinogenesis phenotype. Furthermore, IRAK-M-deficient mice had significantly increased levels of proinflammatory cytokines in the tumor tissue.Conclusions:We conclude that gut microbiota promotes tumorigenesis by increasing the exposure of gut epithelium to carcinogens and that IRAK-M-negative regulation is essential for colon cancer resistance even in conditions of altered microbiota. Therefore, gut microbiota and its metabolic activity could be potential targets for colitis-associated cancer therapy.
  • Amlan Biswas, Koichi S. Kobayashi
    INTERNATIONAL IMMUNOLOGY 25 (4) 207 - 214 0953-8178 2013/04 [Refereed][Not invited]
    Regulation of intestinal microbiota by NLR proteins.The human intestine harbors a diverse microbial community consisting of a large number of bacteria and other micro-organisms that have co-evolved with the host intestinal immune system. During this process, microbiota and the host immune system shape one another by various mechanisms to achieve a successful symbiotic relationship. An increasing amount of evidence suggests that dysbiosisuthe breakdown of such harmonized colonizationumay result in infectious and inflammatory disorders, and recent advances in our studies indicate that receptors such as Toll-like receptors and NLR (nucleotide-binding oligomerization domain-like receptor; or nucleotide-binding domain- and leucine-rich repeat-containing receptor) proteins that detect micro-organisms and their products play a critical role in maintaining intestinal homeostasis. In this review, we summarize the role of NLR proteins in the regulation of intestinal microbiota. NLR proteins belong to a diverse family of cytoplasmic microbial sensors, mutations of which are involved in various disorders, including inflammatory bowel diseases. Understanding of the different roles of NLR family proteins in the intestine is, therefore, an important step towards the development of therapeutics against digestive diseases.
  • Koichi S. Kobayashi, Peter J. van den Elsen
    NATURE REVIEWS IMMUNOLOGY 12 (12) 813 - 820 1474-1733 2012/12 [Refereed][Not invited]
    The expression of MHC class I molecules is crucial for the initiation and regulation of adaptive immune responses against pathogens. NOD-, LRR- and CARD-containing 5 (NLRC5) was recently identified as a specific transactivator of MHC class I genes (CITA). NLRC5 and the master regulator for MHC class II genes, class II transactivator (CIITA), interact with similar MHC promoter-bound factors. Here, we provide a broad overview of the molecular mechanisms behind MHC class I transcription and the role of the class I transactivator NLRC5 in MHC class I-dependent immune responses.
  • Bindu Sukumaran, Yasunori Ogura, Joao H. F. Pedra, Koichi S. Kobayashi, Richard A. Flavell, Erol Fikrig
    FEMS IMMUNOLOGY AND MEDICAL MICROBIOLOGY 66 (2) 211 - 219 0928-8244 2012/11 [Refereed][Not invited]
    The Gram-negative obligate intracellular bacterium Anaplasma phagocytophilum is the causative agent of human granulocytic anaplasmosis (HGA), an emerging tick-borne infectious disease occurring worldwide. HGA is generally self-limiting; however, the underlying mechanisms, particularly the innate immune pathways that mediate the immune clearance of A. phagocytophilum, are less understood. We herein report an unexpected role for Receptor interacting protein-2 (Rip2), the adaptor protein for the Nod-like receptors (NLRs), Nod1/Nod2, in the host immune response against A. phagocytophilum infection. Although A. phagocytophilum genome is reported to lack the genes encoding the known ligands of Nod1 and Nod2, its infection upregulated the transcription of Rip2 in human primary neutrophils. Our results revealed that Rip2-deficient mice had significantly higher bacterial load than wild-type controls throughout the infection period. In addition, the Rip2-deficient mice took strikingly longer duration to clear A. phagocytophilum infection. Detailed analysis identified that interferon gamma (IFN?) and interleukin (IL)-18 but not IL-12, macrophage inflammatory protein-2, and KC response were diminished in A. phagocytophilum-challenged Rip2-deficient mice. Together, these results revealed that Rip2 plays important roles in the immune control of A. phagocytophilum and may contribute to our understanding of the host response to Rickettsiales.
  • Kyoung-Hee Lee, Amlan Biswas, Yuen-Joyce Liu, Koichi S. Kobayashi
    JOURNAL OF BIOLOGICAL CHEMISTRY 287 (47) 39800 - 39811 0021-9258 2012/11 [Refereed][Not invited]
    The innate immune system serves as the first line of defense by detecting microbes and initiating inflammatory responses. Although both Toll-like receptor (TLR) and nucleotide binding domain and leucine-rich repeat (NLR) proteins are important for this process, their excessive activation is hazardous to hosts; thus, tight regulation is required. Endotoxin tolerance is refractory to repeated lipopolysaccharide (LPS) stimulation and serves as a host defense mechanism against septic shock caused by an excessive TLR4 response during Gram-negative bacterial infection. Gram-positive bacteria as well as their cell wall components also induce shock. However, the mechanism underlying tolerance is not understood. Here, we show that activation of Nod2 by its ligand, muramyl dipeptide (MDP) in the bacterial cell wall, induces rapid degradation of Nod2, which confers MDP tolerance in vitro and in vivo. Nod2 is constitutively associated with a chaperone protein, Hsp90, which is required for Nod2 stability and protects Nod2 from degradation. Upon MDP stimulation, Hsp90 rapidly dissociates from Nod2, which subsequently undergoes ubiquitination and proteasomal degradation. The SOCS-3 protein induced by Nod2 activation further facilitates this degradation process. Therefore, Nod2 protein stability is a key factor in determining responsiveness to MDP stimulation. This indicates that TLRs and NLRs induce a tolerant state through distinct molecular mechanisms that protect the host from septic shock.
  • Amlan Biswas, Torsten B. Meissner, Taro Kawai, Koichi S. Kobayashi
    JOURNAL OF IMMUNOLOGY 189 (2) 516 - 520 0022-1767 2012/07 [Refereed][Not invited]
    MHC class I and class II are crucial for the adaptive immune system. Although regulation of MHC class II expression by CIITA has long been recognized, the mechanism of MHC class I transactivation has been largely unknown until the recent discovery of NLRC5/class I transactivator. In this study, we show using Nlrc5-deficient mice that NLRC5 is required for both constitutive and inducible MHC class I expression. Loss of Nlrc5 resulted in severe reduction in the expression of MHC class I and related genes such as beta(2)-microglobulin, Tap1, or Lmp2, but did not affect MHC class II levels. IFN-gamma stimulation could not overcome the impaired MHC class I expression in Nlrc5-deficient cells. Upon infection with Listeria monocyogenes, Nlrc5-deficient mice displayed impaired CD8(+) T cell activation, accompanied with increased bacterial loads. These findings illustrate critical roles of NLRC5/class I transactivator in MHC class I gene regulation and host defense by CD8(+) T cell responses. The Journal of Immunology, 2012, 189: 516-520.
  • Jacobien J. Hoogerwerf, Gerritje J. W. van der Windt, Dana C. Blok, Arie J. Hoogendijk, Alex F. de Vos, Cornelis van 't Veer, Sandrine Florquin, Koichi S. Kobayashi, Richard A. Flavell, Tom van der Poll
    MOLECULAR MEDICINE 18 (7) 1067 - 1075 1076-1551 2012/07 [Refereed][Not invited]
    Pneumonia is a common cause of morbidity and mortality and the most frequent source of sepsis. Bacteria that try to invade normally sterile body sites are recognized by innate immune cells through pattern recognition receptors, among which toll-like receptors (TLRs) feature prominently. Interleukin-1 receptor (IL-1R)-associated kinase (IRAK)-M is a proximal inhibitor of TLR signaling expressed by epithelial cells and macrophages in the lung. To determine the role of IRAK-M in host defense against bacterial pneumonia, IRAK-M-deficient (IRAK-M-/-) and normal wild-type (WT) mice were infected intranasally with Klebsiella pneumoniae. IRAK-M mRNA was upregulated in lungs of WT mice with Klebsiella pneumonia, and the absence of IRAK-M resulted in a strongly improved host defense as reflected by reduced bacterial growth in the lungs, diminished dissemination to distant body sites, less peripheral tissue injury and better survival rates. Although IRAK-M-/- alveolar macrophages displayed enhanced responsiveness toward intact K. pneumoniae and Klebsiella lipopolysaccharide (LPS) in vitro, IRAK-M-/- mice did not show increased cytokine or chemokine levels in their lungs after infection in vivo. The extent of lung inflammation was increased in IRAK-M-/- mice shortly after K. pneumoniae infection, as determined by semiquantitative scoring of specific components of the inflammatory response in lung tissue slides. These data indicate that IRAK-M impairs host defense during pneumonia caused by a common gram-negative respiratory pathogen. Online address: doi: 10.2119/molmed.2011.00450
  • Torsten B. Meissner, Amy Li, Koichi S. Kobayashi
    MICROBES AND INFECTION 14 (6) 477 - 484 1286-4579 2012/06 [Refereed][Not invited]
    Major histocompatibility complex (MHC) class I and class II are crucial for the function of the human adaptive immune system. An NLR protein, CIITA (MHC class II transactivator), is a master regulator of MHC class 11 gene expression as well as of some of the genes involved in MHC class II antigen presentation. It has recently been discovered that another member of the NI:.,R protein family, NLRC5, transcriptionally activates MHC class I genes, and thus acts as "CITA" (MHC class I transactivator), a counterpart to CIITA. In addition to MHC class I genes, NLRC5 can induce the expression of beta 2M, TAP1 and LMP2, essential components of MHC class I antigen presentation. These findings indicate that NLRC5 and CIITA are transcriptional regulators that orchestrate the concerted expression of critical components in the MHC class I and MHC class 11 pathways, respectively. (C) 2011 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.
  • Gerritje J. W. van der Windt, Dana C. Blok, Jacobien J. Hoogerwerf, Adriana J. J. Lammers, Alex F. de Vos, Cornelis van't Veer, Sandrine Florquin, Koichi S. Kobayashi, Richard A. Flavell, Tom van der Poll
    JOURNAL OF INFECTIOUS DISEASES 205 (12) 1849 - 1857 0022-1899 2012/06 [Refereed][Not invited]
    Background. Streptococcus pneumoniae is the most common causative organism in community-acquired pneumonia. Pneumococci that try to invade the lower airways are recognized by innate immune cells through pattern recognition receptors, including Toll-like receptors 2, 4, and 9. Interleukin 1 (IL-1) receptor-associated kinase (IRAK)-M is a proximal inhibitor of Toll-like receptor signaling. Methods. To determine the role of IRAK-M in host defense during pneumococcal pneumonia, IRAK-M-deficient and wild-type mice were intranasally infected with S. pneumoniae. Results. IRAK-M-deficient mice demonstrated a reduced lethality after infection with S. pneumoniae via the airways. Whereas bacterial burdens were similar in IRAK-M-deficient and wild-type mice early (3 hours) after infection, from 24 hours onward the number of pneumococci recovered from lungs and distant body sites were 10-100-fold lower in the former mouse strain. The diminished bacterial growth and dissemination in IRAK-M-deficient mice were preceded by an increased early influx of neutrophils into lung tissue and elevated pulmonary levels of IL-1 beta and CXCL1. IRAK-M deficiency did not influence bacterial growth after intravenous administration of S. pneumoniae. Conclusions. These data suggest that IRAK-M impairs host defense during pneumococcal pneumonia at the primary site of infection at least in part by inhibiting the early immune response.
  • Jung-Eun Koo, Hye-Jin Hong, Andrea Dearth, Koichi S. Kobayashi, Young-Sang Koh
    PLOS ONE 7 (6) e39042  1932-6203 2012/06 [Refereed][Not invited]
    Orientia tsutsugamushi, a causative agent of scrub typhus, is an obligate intracellular bacterium, which escapes from the endo/phagosome and replicates in the host cytoplasm. O. tsutsugamushi infection induces production of pro-inflammatory mediators including interleukin-1 beta (IL-1 beta), which is secreted mainly from macrophages upon cytosolic stimuli by activating cysteine protease caspase-1 within a complex called the inflammasome, and is a key player in initiating and maintaining the inflammatory response. However, the mechanism for IL-1 beta maturation upon O. tsutsugamushi infection has not been identified. In this study, we show that IL-1 receptor signaling is required for efficient host protection from O. tsutsugamushi infection. Live Orientia, but not heat-or UV-inactivated Orientia, activates the inflammasome through active bacterial uptake and endo/phagosomal maturation. Furthermore, Orientia-stimulated secretion of IL-1 beta and activation of caspase-1 are ASC- and caspase-1- dependent since IL-1 beta production was impaired in Asc- and caspase-1-deficient macrophages but not in Nlrp3-, Nlrc4- and Aim2-deficient macrophages. Therefore, live O. tsutsugamushi triggers ASC inflammasome activation leading to IL-1 beta production, which is a critical innate immune response for effective host defense.
  • Torsten B. Meissner, Yuen-Joyce Liu, Kyoung-Hee Lee, Amy Li, Amlan Biswas, Marja C. J. A. van Eggermond, Peter J. van den Elsen, Koichi S. Kobayashi
    JOURNAL OF IMMUNOLOGY 188 (10) 4951 - 4958 0022-1767 2012/05 [Refereed][Not invited]
    Tight regulation of MHC class I gene expression is critical for CD8 T cell activation and host adaptive-immune responses. The promoters of MHC class I genes contain a well-conserved core module, the W/S-X-Y motif, which assembles a nucleoprotein complex termed MHC enhanceosome. A member of the nucleotide-binding domain, leucine-rich repeat (NLR) protein family, NLRC5, is a newly identified transcriptional regulator of MHC class I genes. NLRC5 associates with and transactivates the proximal promoters of MHC class I genes, although the molecular mechanism of transactivation has not been understood. In this article, we show that NLRC5-mediated MHC class I gene induction requires the W/S and X1, X2 cis-regulatory elements. The transcription factors RFX5, RFXAP, and RFXANK/B, which compose the RFX protein complex and associate with the X1 box, cooperate with NLRC5 for MHC class I expression. Coimmunoprecipitation experiments revealed that NLRC5 specifically interacts with the RFX subunit RFXANK/B via its ankyrin repeats. In addition, we show that NLRC5 can cooperate with ATF1 and the transcriptional coactivators CBP/p300 and general control nonderepressible 5, which display histone acetyltransferase activity. Taken together, our data suggest that NLRC5 participates in an MHC class I-specific enhanceosome, which assembles on the conserved W/S-X-Y core module of the MHC class I proximal promoters, including the RFX factor components and CREB/ATF1 family transcription factors, to promote MHC class I gene expression. The Journal of Immunology, 2012,188: 4951-4958.
  • Yun Zhao, Carmen Alonso, Isabel Ballester, Joo Hye Song, Sun Young Chang, Bayasi Guleng, Seiji Arihiro, Peter J. Murray, Ramnik Xavier, Koichi S. Kobayashi, Hans-Christian Reinecker
    INFLAMMATORY BOWEL DISEASES 18 (4) 603 - 612 1078-0998 2012/04 [Refereed][Not invited]
    Background: Genetic variants of nucleotide-binding oligomerization domain 2 (NOD2) lead to aberrant microbial recognition and can cause chronic inflammatory diseases in patients with Crohn's disease (CD). Methods: We utilized gene-specific siRNA mediated knockdown and expression of guanine nucleotide exchange factor H1 (GEF-H1) in wildtype, Rip2-, and Nod2-deficient macrophages, HCT-116 and HEK 293 cells to determine the role of GEF-H1 in NOD2 and Rip2-mediated NF kappa B- dependent induction of proinflammatory cytokine expression. Confocal microscopy was used to determine subcellular distribution of GEFH1, Rip2, and NOD2. Results: We identified GEF-H1 as an unexpected component of innate immune regulation during microbial pattern recognition by NOD2. Surprisingly, GEF-H1-mediated the activation of Rip2 during signaling by NOD2, but not in the presence of the 3020insC variant of NOD2 associated with CD. GEF-H1 functioned downstream of NOD2 as part of Rip2-containing signaling complexes and was responsible for phosphorylation of Rip2 by Src tyrosine kinase. Rip2 variants lacking the tyrosine target of GEF-H1-mediated phosphorylation were unable to mediate NF-kappa B activation in Rip2-deficient macrophages and failed to transduce NOD2 signaling. GEF-H1 is required downstream of NOD2 as part of Rip2-containing signaling complexes for the activation of innate immune responses. Conclusions: GEF-H1 connects tyrosine kinase function to NOD-like receptor signaling and is fundamental to the regulation of microbial recognition by ubiquitous innate immune mechanisms mediated by Rip2 kinase.
  • Torsten B. Meissner, Amy Li, Yuen-Joyce Liu, Etienne Gagnon, Koichi S. Kobayashi
    BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS 418 (4) 786 - 791 0006-291X 2012/02 [Refereed][Not invited]
    Major histocompatibility complex (MHC) class I and class II are crucial for the function of the human adaptive immune system. A member of the NLR (nucleotide-binding domain, leucine-rich repeat) protein family, NLRC5, has recently been identified as a transcriptional regulator of MHC class land related genes. While a 'master regulator' of MHC class II genes, CIITA, has long been known, NLRC5 specifically associates with and transactivates the proximal promoters of MHC class I genes. In this study, we analyzed the molecular requirements of NLRC5 nuclear import and transactivation activity. We show that NLRC5-mediated MHC class I gene induction requires an intact nuclear localization signal and nuclear distribution of NLRC5. In addition, we find that the nucleotide-binding domain (NBD) of NLRC5 is critical not only for nuclear translocation but also for the transactivation of MHC class I genes. Changing the cellular localization of NLRC5 is likely to immediately impact MHC class I expression as well as MHC class I-mediated antigen presentation. NLRC5 may thus provide a promising target for the modulation of MHC class I antigen presentation, especially in the setting of transplant medicine. (C) 2012 Elsevier Inc. All rights reserved.
  • Amlan Biswas, Tanja Petnicki-Ocwieja, Koichi S. Kobayashi
    JOURNAL OF MOLECULAR MEDICINE-JMM 90 (1) 15 - 24 0946-2716 2012/01 [Refereed][Not invited]
    The human intestine harbors a large number of bacteria that are constantly interacting with the intestinal immune system, eliciting non-pathological basal level immune responses. Increasing evidence points to dysbiosis of microbiota in the intestine as an underlying factor in inflammatory bowel disease susceptibility. Loss-of-function mutations in NOD2 are among the stronger genetic factors linked to ileal Crohn's disease. Indeed, Nod2 is a key regulator of microbiota in the intestine, as microflora in the terminal ileum is dysregulated in Nod2-deficient mice. Nod2 is highly expressed in Paneth cells, which are responsible for the regulation of ileal microflora by antimicrobial compounds, and Nod2-deficient ileal intestinal epithelia are unable to kill bacteria efficiently. It is therefore likely that NOD2 mutations in Crohn's disease may increase disease susceptibility by altering interactions between ileal microbiota and mucosal immunity.
  • Delhase M, Kim SY, Lee H, Naiki-Ito A, Chen Y, Ahn ER, Murata K, Kim SJ, Lautsch N, Kobayashi KS, Shirai T, Karin M, Nakanishi M
    Proceedings of the National Academy of Sciences of the United States of America 109 (4) E177 - 86 0027-8424 2012/01 [Refereed][Not invited]
  • Kobayashi KS
    Journal of immunodeficiency & disorders 1 (1) 2012 [Refereed][Not invited]
  • Maciej Lech, Claudia Kantner, Onkar P. Kulkarni, Mi Ryu, Ekaterina Vlasova, Juergen Heesemann, David Anz, Stefan Endres, Koichi S. Kobayashi, Richard A. Flavell, Javier Martin, Hans-Joachim Anders
    ANNALS OF THE RHEUMATIC DISEASES 70 (12) 2207 - 2217 0003-4967 2011/12 [Refereed][Not invited]
    Objectives Interleukin-1 receptor-associated kinase (IRAK)-M suppresses Toll-like receptor (TLR)-mediated activation of innate immunity during infection. A similar role was hypothesised for IRAK-M in autoimmunity. Methods Irak-m-deficient mice were crossed with autoimmune C57BL/6-lpr/lpr mice and detailed phenotype analysis was performed. Results Irak-m deficiency converted the mild autoimmune phenotype of C57BL/6-lpr/lpr mice into a massive lymphoproliferative syndrome with lethal autoimmune lung disease and lupus nephritis. Irak-m deficiency induced a number of interferon-related genes, cytokines and plasma cell survival factors in spleen cells of these mice. Irak-m-deficient C57BL/6-lpr/lpr mice showed expansion of autoreactive T cells, dysfunctional regulatory T cells and plasma cells which was associated with increased lupus autoantibody production. TLR7 antagonism almost completely abrogated this phenotype consistent with IRAK-M-mediated suppression of TLR7 signalling in vitro. Conclusions These data identify a previously unknown function of IRAK-M-namely, suppression of TLR7-mediated autoimmunity-and mutant IRAK-M as a previously unknown genetic risk for murine SLE.
  • Braulia C. Caetano, Amlan Biswas, Djalma S. Lima-Junior, Luciana Benevides, Tiago W. P. Mineo, Catarina V. Horta, Kyoung-Hee Lee, Joao S. Silva, Ricardo T. Gazzinelli, Dario S. Zamboni, Koichi S. Kobayashi
    EUROPEAN JOURNAL OF IMMUNOLOGY 41 (12) 3627 - 3631 0014-2980 2011/12 [Refereed][Not invited]
    Nod2 belongs to the nucleotide-binding domain leucine-rich repeat family of proteins and senses bacterial cell wall components to initiate innate immune responses against various pathogens. Recently, it has been reported that T-cell-intrinsic expression of Nod2 promotes host defense against Toxoplasma gondii infection by inducing type 1 immunity. Here, we present results that demonstrate that Nod2 does not play a role in the defense against T. gondii infection. Nod2-deficient mice were fully capable of inducing Th1 immune responses and did not show enhanced susceptibility to infection. Upon TCR stimulation in vitro, Nod2-deficient CD4(+) T cells showed normal activation, IL-2 production, proliferation, and Th1/2 differentiation. Nod2 mRNA and protein were expressed in CD4(+) T and CD8(+) T cells at substantial levels. Therefore, Nod2, although expressed in CD4(+) T cells, does not have an intrinsic function in T-cell activation and differentiation.
  • Theivanthiran Balamayooran, Sanjay Batra, Gayathriy Balamayooran, Shanshan Cai, Koichi S. Kobayashi, Richard A. Flavell, Samithamby Jeyaseelan
    INFECTION AND IMMUNITY 79 (11) 4588 - 4599 0019-9567 2011/11 [Refereed][Not invited]
    Recognition of microbial patterns by host receptors is the first step in a multistep sequence leading to neutrophil-dependent host resistance. Although the role of membrane-bound sensors in bacterial recognition has been examined in detail, the importance of cytosolic sensors in the lungs is largely unexplored. In this context, there is a major lack of understanding related to the downstream signaling mediators, such as cells and/or molecules, during acute extracellular Gram-negative bacterial pneumonia. In order to determine the role of NOD-like receptors (NLRs), we used an experimental Escherichia coli infection model using mice deficient in the gene coding for the NLR adaptor, receptor-interacting protein 2 (RIP2). RIP2(-/-) mice with E. coli infection displayed higher bacterial burden and reduced neutrophil recruitment and tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), macrophage inflammatory protein 2 (MIP-2), and CXCL5/LIX expression, along with attenuated histopathological changes in the lungs. Decreased IL-17A levels were observed, along with lower numbers of IL-17A-producing T cells, in RIP2(-/-) mice after infection. RIP2(-/-) mice also show reduced IL-6 and IL-23 levels in the lungs, along with decreased activation of STAT3 after infection. Furthermore, activation of NF-kappa B and mitogen-activated protein kinases (MAPKs) and expression of intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) in the lungs of infected RIP2(-/-) mice were attenuated following infection. Although neutrophil mobilization to the blood was impaired in RIP2(-/-) mice following infection, the expression of CD62P, CD11a/18, CD11b, and CXCR2 on blood and lung neutrophils was not altered between infected wild-type (WT) and RIP2(-/-) mice. Thus, RIP2 contributes to neutrophil-dependent host defense against an extracellular Gram-negative pathogen via (i) IL-17A regulation and (ii) neutrophil mobilization to the blood.
  • Ogawa C, Liu YJ, Kobayashi KS
    Current bioactive compounds 7 (3) 180 - 197 1573-4072 2011/09 [Refereed][Not invited]
  • Kyoung-Hee Lee, Yuen-Joyce Liu, Amlan Biswas, Chikako Ogawa, Koichi S. Kobayashi
    JOURNAL OF BIOLOGICAL CHEMISTRY 286 (7) 5727 - 5735 0021-9258 2011/02 [Refereed][Not invited]
    Toll-like receptors (TLRs) and nucleotide-binding domain, leucine-rich repeat (NLR) proteins are two major forms of innate immune receptors that trigger inflammatory responses by various biological mechanisms such as cytokine production, recruitment of inflammatory cells, or activation of adaptive immunity. Although the innate immune system is designed to fight against infectious pathogens, excessive activation of TLR or NLR signaling pathways may lead to unwarranted inflammation with hazardous outcomes, including septic shock or inflammatory diseases. As part of the search for effective therapeutics to regulate these responses, here we show that a novel aminosaccharide compound, named DFK1012, inhibits immune responses caused by TLR and NLR activation. Treatment with DFK1012, but not its derivatives DFK845 or DFK846, strongly inhibited pro-inflammatory cytokine production upon stimulation via either TLR or NLR proteins in macrophages. Importantly, we have not observed cytotoxicity in any range of its working concentration. Treatment with DFK1012 did not interfere with TLR- or NLR-induced activation of p38 and JNK, phosphorylation/degradation of I kappa B, and subsequent nuclear translocation of NF-kappa B subunit p65, suggesting that the inhibitory activity of DFK1012 is not due to the suppression of downstream signaling. Indeed, DFK1012 did not impair transcription of pro-inflammatory cytokine genes but rather promoted post-translational degradation of pro-inflammatory cytokines. Therefore, DFK1012 is a novel anti-inflammatory compound that drives proteolysis of proinflammatory cytokines induced by TLR and NLR stimulation. DFK1012 may represent a novel class of potential therapeutic agents aimed at the treatment of inflammatory disorders.
  • Tanja Petnicki-Ocwieja, Alicia S. DeFrancesco, Erin Chung, Courtney T. Darcy, Roderick T. Bronson, Koichi S. Kobayashi, Linden T. Hu
    PLOS ONE 6 (2) e17414  1932-6203 2011/02 [Refereed][Not invited]
    The internalization of Borrelia burgdorferi, the causative agent of Lyme disease, by phagocytes is essential for an effective activation of the immune response to this pathogen. The intracellular, cytosolic receptor Nod2 has been shown to play varying roles in either enhancing or attenuating inflammation in response to different infectious agents. We examined the role of Nod2 in responses to B. burgdorferi. In vitro stimulation of Nod2 deficient bone marrow derived macrophages (BMDM) resulted in decreased induction of multiple cytokines, interferons and interferon regulated genes compared with wild-type cells. However, B. burgdorferi infection of Nod2 deficient mice resulted in increased rather than decreased arthritis and carditis compared to control mice. We explored multiple potential mechanisms for the paradoxical response in in vivo versus in vitro systems and found that prolonged stimulation with a Nod2 ligand, muramyl dipeptide (MDP), resulted in tolerance to stimulation by B. burgdorferi. This tolerance was lost with stimulation of Nod2 deficient cells that cannot respond to MDP. Cytokine patterns in the tolerance model closely paralleled cytokine profiles in infected Nod2 deficient mice. We propose a model where Nod2 has an enhancing role in activating inflammation in early infection, but moderates inflammation after prolonged exposure to the organism through induction of tolerance.
  • Amlan Biswas, Jeanette Wilmanski, Huamei Forsman, Tomas Hrncir, Liming Hao, Helena Tlaskalova-Hogenova, Koichi S. Kobayashi
    EUROPEAN JOURNAL OF IMMUNOLOGY 41 (1) 182 - 194 0014-2980 2011/01 [Refereed][Not invited]
    A healthy intestinal tract is characterized by controlled homeostasis due to the balanced interaction between commensal bacteria and the host mucosal immune system. Human and animal model studies have supported the hypothesis that breakdown of this homeostasis may underlie the pathogenesis of inflammatory bowel diseases. However, it is not well understood how intestinal microflora stimulate the intestinal mucosal immune system and how such activation is regulated. Using a spontaneous, commensal bacteria-dependent colitis model in IL-10-deficient mice, we investigated the role of TLR and their negative regulation in intestinal homeostasis. In addition to IL-10(-/-)MyD88(-/-) mice, IL-10(-/-)TLR4(-/-) mice exhibited reduced colitis compared to IL-10(-/-) mice, indicating that TLR4 signaling plays an important role in inducing colitis. Interestingly, the expression of IRAK-M, a negative regulator of TLR signaling, is dependent on intestinal commensal flora, as IRAK-M expression was reduced in mice re-derived into a germ-free environment, and introduction of commensal bacteria into germ-free mice induced IRAK-M expression. IL-10(-/-)IRAK-M(-/-) mice exhibited exacerbated colitis with increased inflammatory cytokine gene expression. Therefore, this study indicates that intestinal microflora stimulate the colitogenic immune system through TLR and negative regulation of TLR signaling is essential in maintaining intestinal homeostasis.
  • Mariana S. Frutuoso, Juliana I. Hori, Marcelo S. F. Pereira, Djalma S. L. Junior, Fabiane Sonego, Koichi S. Kobayashi, Richard A. Flavell, Fernando Q. Cunha, Dario S. Zamboni
    MICROBES AND INFECTION 12 (11) 819 - 827 1286-4579 2010/10 [Refereed][Not invited]
    The intracellular bacterium Legionella pneumophila induces a severe form of pneumonia called Legionnaires diseases, which is characterized by a strong neutrophil (NE) infiltrate to the lungs of infected individuals. Although the participation of pattern recognition receptors, such as Toll-like receptors, was recently demonstrated, there is no information on the role of nod-like receptors (NLRs) for bacterial recognition in vivo and for NE recruitment to the lungs. Here, we employed a murine model of Legionnaires disease to evaluate host and bacterial factors involved in NE recruitment to the mice lungs. We found that L. pneumophila type four secretion system, known as Dot/Icm, was required for NE recruitment as dot/icm mutants fail to trigger NE recruitment in a process independent of bacterial multiplication. By using mice deficient for Nod1, Nod2, and Rip2, we found that these receptors accounted for NE recruitment to the lungs of infected mice. In addition, Rip2-dependent responses were important for cytokine production and bacterial clearance. Collectively, these studies show that Nod1, Nod2, and Rip2 account for generation of innate immune responses in vivo, which are important for NE recruitment and bacterial clearance in a murine model of Legionnaires diseases. (C) 2010 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.
  • Martin Berglund, Silvia Melgar, Koichi S. Kobayashi, Richard A. Flavell, Elisabeth Hultgren Hornquist, Olof H. Hultgren
    INFLAMMATORY BOWEL DISEASES 16 (10) 1778 - 1786 1078-0998 2010/10 [Refereed][Not invited]
    Background: Ulcerative colitis is associated with increased colon permeability resulting in bacterial translocation into the lamina propria. We investigate the importance of the Toll-like receptor (TLR) regulating protein IL-1 receptor-associated kinase M (IRAK-M) using the erosive dextran sulfate sodium (DSS)-induced model of colitis. Methods: IRAK-M-competent and -incompetent mice were treated with 3% DSS for 5 days followed by 2 days of regular drinking water. Clinical signs of disease were followed for 7 days. At day 7 the mice were sacrificed and plasma and tissue were collected for histopathological examination and analyses of the production of cytokines and chemokines as well as expression of T-cell transcription factors. Results: At day 7 IRAK-M-deficient mice display a reduced total body weight (77.1 +/- 2.1 versus 88.5 +/- 2.0, *P=0.002) and an increased macroscopical (2.7 +/- 0.2 versus 1.6 +/- 0.1, *P 0.002) and histopathological (6.0 +/- 0 versus 3.3 +/- 60.5, *P < 0.001) colon score compared to wildtype mice. Furthermore, IRAK-M-deficient mice have increased colon mRNA expression of proinflammatory cytokines and increased tumor necrosis factor concentrations (41.1 +/- 13.5 versus 12.8 +/- 2.0 pg/mL, *P = 0.010) in plasma. Conclusions: This is the first report examining the role of IRAK-M in colitis. We find that IRAK-M is of critical importance in downregulating induction and progression of DSS colitis, and thereby suggesting that IRAK-M might be a target for future interventional therapies. (Inflamm Bowel Dis 2010; 16: 1778-1786)
  • Torsten B. Meissner, Amy Li, Amlan Biswas, Kyoung-Hee Lee, Yuen-Joyce Liu, Erkan Bayir, Dimitrios Iliopoulos, Peter J. van den Elsen, Koichi S. Kobayashi
    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 107 (31) 13794 - 13799 0027-8424 2010/08 [Refereed][Not invited]
    MHC class I plays a critical role in the immune defense against viruses and tumors by presenting antigens to CD8 T cells. An NLR protein, class II transactivator (CIITA), is a key regulator of MHC class II gene expression that associates and cooperates with transcription factors in the MHC class II promoter. Although CIITA also transactivates MHC class I gene promoters, loss of CIITA in humans and mice results in the severe reduction of only MHC class II expression, suggesting that additional mechanisms regulate the expression of MHC class I. Here, we identify another member of the NLR protein family, NLRC5, as a transcriptional regulator of MHC class I genes. Similar to CIITA, NLRC5 is an IFN-gamma-inducible nuclear protein, and the expression of NLRC5 resulted in enhanced MHC class I expression in lymphoid as well as epithelial cell lines. Using chromatin immunoprecipitation and reporter gene assays, we show that NLRC5 associates with and activates the promoters of MHC class I genes. Furthermore, we show that the IFN-gamma-induced up-regulation of MHC class I requires NLRC5, because knockdown of NLRC5 specifically impaired the expression of MHC class I. In addition to MHC class I genes, NLRC5 also induced the expression of beta 2-microglobulin, transporter associated with antigen processing, and large multifunctional protease, which are essential for MHC class I antigen presentation. Our results suggest that NLRC5 is a transcriptional regulator, orchestrating the concerted expression of critical components in the MHC class I pathway.
  • Amlan Biswas, Yuen-Joyce Liu, Liming Hao, Atsushi Mizoguchi, Nita H. Salzman, Charles L. Bevins, Koichi S. Kobayashi
    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 107 (33) 14739 - 14744 0027-8424 2010/08 [Refereed][Not invited]
    Mutations in the NOD2 gene are strong genetic risk factors for ileal Crohn's disease. However, the mechanism by which these mutations predispose to intestinal inflammation remains a subject of controversy. We report that Nod2-deficient mice inoculated with Helicobacter hepaticus, an opportunistic pathogenic bacterium, developed granulomatous inflammation of the ileum, characterized by an increased expression of Th1-related genes and inflammatory cytokines. The Peyer's patches and mesenteric lymph nodes were markedly enlarged with expansion of IFN-gamma-producing CD4 and CD8 T cells. Rip2-deficient mice exhibited a similar phenotype, suggesting that Nod2 function likely depends on the Rip2 kinase in this model. Transferring wild-type bone marrow cells into irradiated Nod2-deficient mice did not rescue the phenotype. However, restoring crypt antimicrobial function of Nod2-deficient mice by transgenic expression of alpha-defensin in Paneth cells rescued the Th1 inflammatory phenotype. Therefore, through the regulation of intestinal microbes, Nod2 function in nonhematopoietic cells of the small intestinal crypts is critical for protecting mice from a Th1-driven granulomatous inflammation in the ileum. The model may provide insight into Nod2 function relevant to inflammation of ileal Crohn's disease.
  • Young-Sang Koh, Jung-Eun Koo, Amlan Biswas, Koichi S. Kobayashi
    PLOS ONE 5 (7) e11758  1932-6203 2010/07 [Refereed][Not invited]
    The ehrlichiae are small Gram-negative obligate intracellular bacteria in the family Anaplasmataceae. Ehrlichial infection in an accidental host may result in fatal diseases such as human monocytotropic ehrlichiosis, an emerging, tick-borne disease. Although the role of adaptive immune responses in the protection against ehrlichiosis has been well studied, the mechanism by which the innate immune system is activated is not fully understood. Using Ehrlichia muris as a model organism, we show here that MyD88-dependent signaling pathways play a pivotal role in the host defense against ehrlichial infection. Upon E. muris infection, MyD88-deficient mice had significantly impaired clearance of E. muris, as well as decreased inflammation, characterized by reduced splenomegaly and recruitment of macrophages and neutrophils. Furthermore, MyD88-deficient mice produced markedly lower levels of IL-12, which correlated well with an impaired Th1 immune response. In vitro, dendritic cells, but not macrophages, efficiently produced IL-12 upon E. muris infection through a MyD88-dependent mechanism. Therefore, MyD88-dependent signaling is required for controlling ehrlichial infection by playing an essential role in the immediate activation of the innate immune system and inflammatory cytokine production, as well as in the activation of the adaptive immune system at a later stage by providing for optimal Th1 immune responses.
  • Kristina A. Archer, Florence Ader, Koichi S. Kobayashi, Richard A. Flavell, Craig R. Roy
    INFECTION AND IMMUNITY 78 (6) 2477 - 2487 0019-9567 2010/06 [Refereed][Not invited]
    Multiple pattern recognition systems have been shown to initiate innate immune responses to microbial pathogens. The degree to which these detection systems cooperate with each other to provide host protection is unknown. Here, we investigated the importance of several immune surveillance pathways in protecting mice against lethal infection by the intracellular pathogen Legionella pneumophila, the causative agent of a severe pneumonia called Legionnaires' disease. Rip2 and Naip5/NLRC4 signaling was found to contribute to the innate immune response generated against L. pneumophila in the lung. Elimination of Rip2 or Naip5/NLRC4 signaling in MyD88-deficient mice resulted in increased replication and dissemination of L. pneumophila and higher rates of mortality. Irradiated wild-type mice receiving bone marrow cells from pattern recognition receptor-deficient mice displayed L. pneumophila infection phenotypes similar to those of donor mice. Rip2 and Naip5/NLRC4 signaling provided additive effects in protecting MyD88-deficient mice from lethal infection by L. pneumophila, with the contribution of Naip5/NLRC4 being slightly greater than that of Rip2. Thus, activation of the Rip2, MyD88, and Naip5/NLRC4 signaling pathways triggers a coordinated and synergistic response that protects the host against lethal infection by L. pneumophila. These data provide new insight into how different pattern recognition systems interact functionally to generate innate immune responses that protect the host from lethal infection by activating cellular pathways that restrict intracellular replication of L. pneumophila and by recruiting to the site of infection additional phagocytes that eliminate extracellular bacteria.
  • Guillaume M. Charriere, W. K. Eddie Ip, Stephanie Dejardin, Laurent Boyer, Anna Sokolovska, Michael P. Cappillino, Bobby J. Cherayil, Daniel K. Podolsky, Koichi S. Kobayashi, Neal Silverman, Adam Lacy-Hulbert, Lynda M. Stuart
    JOURNAL OF BIOLOGICAL CHEMISTRY 285 (26) 20147 - 20154 0021-9258 2010/06 [Refereed][Not invited]
    NOD2 (nucleotide-binding oligomerization domain containing 2) is an important cytosolic pattern recognition receptor that activates NF-kappa B and other immune effector pathways such as autophagy and antigen presentation. Despite its intracellular localization, NOD2 participates in sensing of extracellular microbes such as Staphylococcus aureus. NOD2 ligands similar to the minimal synthetic ligand muramyl dipeptide (MDP) are generated by internalization and processing of bacteria in hydrolytic phagolysosomes. However, how these derived ligands exit this organelle and access the cytosol to activate NOD2 is poorly understood. Here, we address how phagosome-derived NOD2 ligands access the cytosol in human phagocytes. Drawing on data from Drosophila phagosomes, we identify an evolutionarily conserved role of SLC15A transporters, Drosophila Yin and PEPT2, as MDP transporters in fly and human phagocytes, respectively. We show that PEPT2 is highly expressed by human myeloid cells. Ectopic expression of both Yin and PEPT2 increases the sensitivity of NOD2-dependent NF-kappa B activation. Additionally, we show that PEPT2 associates with phagosome membranes. Together, these data identify Drosophila Yin and PEPT2 as evolutionarily conserved phagosome-associated transporters that are likely to be of particular importance in delivery of bacteria-derived ligands generated in phagosomes to cytosolic sensors recruited to the vicinity of these organelles.
  • Leah L. N. Hubbard, Megan N. Ballinger, Peedikayil E. Thomas, Carol A. Wilke, Theodore J. Standiford, Koichi S. Kobayashi, Richard A. Flavell, Bethany B. Moore
    JOURNAL OF IMMUNOLOGY 184 (11) 6299 - 6308 0022-1767 2010/06 [Refereed][Not invited]
    Following immune reconstitution, hematopoietic stem cell transplant patients often display reduced immune function and are especially susceptible to lung infections. In a mouse model of syngeneic bone marrow transplantation (BMT), we previously reported that PGE(2) is overproduced in lungs of BMT mice, significantly impairing host defense against Pseudomonas aeruginosa. This impairment in host defense post-BMT is also marked by diminished alveolar macrophage (AM) phagocytosis, bacterial killing, and production of TNF-alpha and cysteinyl leukotrienes. However, a mechanism by which overproduction of PGE(2) suppresses pulmonary host defense post-BMT is unknown. As IL-1R-associated kinase (IRAK)-M is a known inhibitor of MyD88-dependent IL-1R/TLR signaling and macrophage function, we sought to determine whether IRAK-M is involved in PGE(2)-induced immunosuppression post-BMT. We found that IRAK-M expression is elevated 3.5-fold in BMT AMs relative to control AMs, and this is related to AM overproduction of PGE(2). Furthermore, genetic ablation of IRAK-M in the bone marrow of BMT mice restores host defense against P. aeruginosa. Despite AM overproduction of PGE(2) and elevated E prostanoid 2 receptor expression, AM phagocytosis, killing, and production of cysteinyl leukotrienes and TNF-alpha are restored in the absence of IRAK-M post-BMT. Also, treatment with PGE(2) does not inhibit AM phagocytosis in the absence of IRAK-M. These data suggest that the absence of IRAK-M in the hematopoietic compartment post-BMT enhances pulmonary host defense and mitigates AM sensitivity to the inhibitory effects of PGE(2). Therefore, strategies to limit IRAK-M elevation post-BMT may be efficacious in reducing patient susceptibility to infection. The Journal of Immunology, 2010, 184: 6299-6308.
  • Grace K. Silva, Fredy R. S. Gutierrez, Paulo M. M. Guedes, Catarina V. Horta, Larissa D. Cunha, Tiago W. P. Mineo, Juliana Santiago-Silva, Koichi S. Kobayashi, Richard A. Flavell, Joao S. Silva, Dario S. Zamboni
    JOURNAL OF IMMUNOLOGY 184 (3) 1148 - 1152 0022-1767 2010/02 [Refereed][Not invited]
    An effective innate immune recognition of the intracellular protozoan parasite Trypanosoma cruzi is critical for host resistance against Chagas disease, a severe and chronic illness that affects millions of people in Latin America. In this study, we evaluated the participation of nucleotide-binding oligomerization domain (Nod)like receptor proteins in host response to T cruzi infection and found that Nod1-dependent, but not Nod2-dependent, responses are required for host resistance against infection. Bone marrow-derived macrophages from Nod1(-/-) mice showed an impaired induction of NF-kappa B-dependent products in response to infection and failed to restrict T cruzi infection in presence of IFN-gamma. Despite normal cytokine production in the sera, Nod1(-/-) mice were highly susceptible to T cruzi infection, in a similar manner to MyD88(-/-) and NO synthase 2(-/-) mice. These studies indicate that Nod1-dependent responses account for host resistance against T cruzi infection by mechanisms independent of cytokine production. The Journal of Immunology, 2010, 184: 1148-1152.
  • Tanja Petnicki-Ocwieja, Tomas Hrncir, Yuen-Joyce Liu, Amlan Biswas, Tomas Hudcovic, Helena Tlaskalova-Hogenova, Koichi S. Kobayashi
    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 106 (37) 15813 - 15818 0027-8424 2009/09 [Refereed][Not invited]
    Mutations in the Nod2 gene are among the strongest genetic risk factors in the pathogenesis of ileal Crohn's disease, but the exact contributions of Nod2 to intestinal mucosal homeostasis are not understood. Here we show that Nod2 plays an essential role in controlling commensal bacterial flora in the intestine. Analysis of intestinal bacteria from the terminal ilea of Nod2-deficient mice showed that they harbor an increased load of commensal resident bacteria. Furthermore, Nod2-deficient mice had a diminished ability to prevent intestinal colonization of pathogenic bacteria. In vitro, intestinal crypts isolated from terminal ilea of Nod2-deficient mice were unable to kill bacteria effectively, suggesting an important role of Nod2 signaling in crypt function. Interestingly, the expression of Nod2 is dependent on the presence of commensal bacteria, because mice re-derived into germ-free conditions expressed significantly less Nod2 in their terminal ilea, and complementation of commensal bacteria into germ-free mice induced Nod2 expression. Therefore, Nod2 and intestinal commensal bacterial flora maintain a balance by regulating each other through a feedback mechanism. Dysfunction of Nod2 results in a break-down of this homeostasis.
  • Pierre Sicard, Sebastien Jacquet, Koichi S. Kobayashi, Richard A. Flavell, Michael S. Marber
    CARDIOVASCULAR RESEARCH 83 (2) 277 - 284 0008-6363 2009/07 [Refereed][Not invited]
    Despite their ability to cause septic shock and myocardial dysfunction, components of Gram-negative bacterial cell walls, like lipopolysaccharide, have been shown in numerous studies to induce myocardial protection during ischaemia-reperfusion injury. Muramyl dipeptide (MDP) is another such component recognized by an intracellular receptor, nucleotide-binding oligomerization domain 2. Receptor activation leads to intracellular signals through receptor interacting protein-2 (RIP2) and tumour growth factor-beta-activated kinase-1 (TAK1). However, little is known about the RIP2/TAK1 pathway in the heart. The aim of this study was to determine whether the RIP2/TAK1 pathway has a cardioprotective role in a mouse model of myocardial infarction. We isolated and subjected wild-type (WT) and RIP2(-/-) mouse hearts to 30 min of global ischaemia and 120 min of reperfusion with or without perfusion of MDP (10 mu g/mL) before or after the ischaemic period and determined the infarct size. We examined activation of the TAK1/nuclear factor kappa B (NF kappa B) signalling pathway. The effect of TAK1 inhibition on MDP-induced cardioprotection was also evaluated. Exposure to MDP during reperfusion significantly reduced infarct size in WT hearts (from 51.7 +/- 5.6% in control to 38.1 +/- 6.7%, P < 0.05), but not in RIP2(-/-) hearts or in WT hearts with coincident pharmacological inhibition of TAK1. MDP treatment significantly increased the levels of p-TAK1 and p-JNK (Jun N-terminal kinase) and led to NF kappa B activation via phosphorylation and degradation of IkappaB in the WT, but not in the RIP2(-/-), myocardium. These results indicate that MDP at reperfusion induced cardioprotection through an RIP2/TAK1-dependent mechanism.
  • Didi Matza, Abdallah Badou, Mithilesh K. Jha, Tim Willinger, Andrey Antov, Shomyseh Sanjabi, Koichi S. Kobayashi, Vincent T. Marchesi, Richard A. Flavell
    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 106 (24) 9785 - 9790 0027-8424 2009/06 [Refereed][Not invited]
    Cytolytic CD8(+) T cells (CTLs) kill virally infected cells, tumor cells, or other potentially autoreactive T cells in a calcium-dependent manner. To date, the molecular mechanism that leads to calcium intake during CTL differentiation and function has remained unresolved. We demonstrate that desmoyokin (AHNAK1) is expressed in mature CTLs, but not in naive CD8(+) T cells, and is critical for calcium entry required for their proper function during immune response. We show that mature AHNAK1-deficient CTLs exhibit reduced Ca(v)1.1 alpha 1 subunit expression (also referred to as L-type calcium channels or alpha 1S pore-forming subunits), which recently were suggested to play a role in calcium entry into CD4(+) T cells. AHNAK1-deficient CTLs show marked reduction in granzyme-B production, cytolytic activity, and IFN-gamma secretion after T cell receptor stimulation. Our results demonstrate an AHNAK1-dependent mechanism controlling calcium entry during CTL effector function.
  • NOD2-deficient mice have impaired resistance to Mycobacterium tuberculosis infection through defective innate and adaptive immunity.
    Divangahi M, Mostowy S, Coulombe F, Kozak R, Guillot L, Veyrier F, Kobayashi KS, Flavell RA, Gros P, Behr MA
    Journal of immunology (Baltimore, Md. : 1950) 181 (10) 7157 - 7165 0022-1767 2008/11 [Refereed][Not invited]
  • Sunny Shin, Christopher L. Case, Kristina A. Archer, Catarina V. Nogueira, Koichi S. Kobayashi, Richard A. Flavell, Craig R. Roy, Dario S. Zamboni
    PLOS PATHOGENS 4 (11) e1000220  1553-7366 2008/11 [Refereed][Not invited]
    The immune system must discriminate between pathogenic and nonpathogenic microbes in order to initiate an appropriate response. Toll-like receptors (TLRs) detect microbial components common to both pathogenic and nonpathogenic bacteria, whereas Nod-like receptors (NLRs) sense microbial components introduced into the host cytosol by the specialized secretion systems or pore-forming toxins of bacterial pathogens. The host signaling pathways that respond to bacterial secretion systems remain poorly understood. Infection with the pathogen Legionella pneumophila, which utilizes a type IV secretion system (T4SS), induced an increased proinflammatory cytokine response compared to avirulent bacteria in which the T4SS was inactivated. This enhanced response involved NF-kappa B activation by TLR signaling as well as Nod1 and Nod2 detection of type IV secretion. Furthermore, a TLR- and RIP2-independent pathway leading to p38 and SAPK/JNK MAPK activation was found to play an equally important role in the host response to virulent L. pneumophila. Activation of this MAPK pathway was T4SS-dependent and coordinated with TLR signaling to mount a robust proinflammatory cytokine response to virulent L. pneumophila. These findings define a previously uncharacterized host response to bacterial type IV secretion that activates MAPK signaling and demonstrate that coincident detection of multiple bacterial components enables immune discrimination between virulent and avirulent bacteria.
  • Sebastien Jacquet, Yasuhiro Nishino, Sarawut Kumphune, Pierre Sicard, James E. Clark, Koichi S. Kobayashi, Richard A. Flavell, Jan Eickhoff, Matt Cotten, Michael S. Marber
    JOURNAL OF BIOLOGICAL CHEMISTRY 283 (18) 11964 - 11971 0021-9258 2008/05 [Refereed][Not invited]
    The activation of p38 MAPK by dual phosphorylation aggravates myocardial ischemic injury and depresses cardiac contractile function. SB203580, an ATP-competitive inhibitor of p38 MAPK and other kinases, prevents this dual phosphorylation during ischemia. Studies in non-cardiac tissue have shown receptor-interacting protein 2 (RIP2) lies upstream of p38 MAPK, is SB203580-sensitive and ischemia-responsive, and aggravates ischemic injury. We therefore examined the RIP2-p38 MAPK signaling axis in the heart. Adenovirus-driven expression of wild-type RIP2 in adult rat ventricular myocytes caused robust, SB203580-sensitive dual phosphorylation of p38 MAPK associated with activation of p38 MAPK kinases MKK3, MKK4, and MKK6. The effect of SB203580 was recapitulated by unrelated inhibitors of RIP2 or the downstream MAPK kinase kinase, TAK1. However, overexpression of wild-type, kinase-dead, caspase recruitment domain-deleted, or kinase-dead and caspase recruitment domain-deleted forms of RIP2 had no effect on the activating dual phosphorylation of p38 MAPK during simulated ischemia. Similarly, p38 MAPK activation and myocardial infarction size in response to true ischemia did not differ between hearts from wild-type and RIP2 null mice. However, both p38 MAPK activation and the contractile depression caused by the endotoxin component muramyl dipeptide were attenuated by SB203580 and in RIP2 null hearts. Although RIP2 can cause myocardial p38 MAPK dual phosphorylation in the heart under some circumstances, it is not responsible for the SB203580-sensitive pattern of activation during ischemia.
  • Jeanette M. Wilmanski, Tanja Petnicki-Ocwieja, Koichi S. Kobayashi
    JOURNAL OF LEUKOCYTE BIOLOGY 83 (1) 13 - 30 0741-5400 2008/01 [Refereed][Not invited]
    The innate immune system is the first line of defense against microorganisms and is conserved in plants and animals. The nucleotide-binding domain, leucine rich containing (NLR) protein family is a recent addition to the members of innate immunity effector molecules. These proteins are characterized by a central oligomerization domain, termed nucleotide-binding domain (NBD) and a protein interaction domain, leucine-rich repeats (LRRs) at the C terminus. It has been shown that NLR proteins are localized to the cytoplasm and recognize microbial products. To date, it is known that Nod1 and Nod2 detect bacterial cell wall components, whereas Ipaf and Naip detect bacterial flagellin, and NACHT/LRR/Pyrin 1 has been shown to detect anthrax lethal toxin. NLR proteins comprise a diverse protein family ( over 20 in humans), indicating that NLRs have evolved to acquire specificity to various pathogenic microorganisms, thereby controlling host-pathogen interactions. Activation of NLR proteins results in inflammatory responses mediated by NF-kappa B, MAPK, or Caspase-1 activation, accompanied by subsequent secretion of proinflammatory cytokines. Mutations in several members of the NLR protein family have been linked to inflammatory diseases, suggesting these molecules play important roles in maintaining host-pathogen interactions and inflammatory responses. Therefore, understanding NLR signaling is important for the therapeutic intervention of various infectious and inflammatory diseases.
  • Didi Matza, Abdallah Badou, Koichi S. Kobayashi, Karen Goldsmith-Pestana, Yutaka Masuda, Akihiko Komuro, Diane McMahon-Pratt, Vincent T. Marchesi, Richard A. Flavell
    IMMUNITY 28 (1) 64 - 74 1074-7613 2008/01 [Refereed][Not invited]
    Engagement of the T cell antigen receptor (TCR) during antigen presentation initiates a coordinated action of a large number of signaling proteins and ion channels. AHNAK1 is a scaffold protein, highly expressed by CD4(+) T cells, and is a critical component for calcium signaling. We showed that AHNAK1-deficient mice were highly susceptible to Leishmania major infection. AHNAK1-deficient CD4(+) T cells responded poorly to TCR stimulation in vitro with low proliferation and low Interleukin-2 production. Furthermore, AHNAK1 deficiency resulted in a reduced calcium influx upon TCR crosslinking and subsequent poor activation of the transcription factor NFAT. AHNAK1 was required for plasma membrane expression of L-type calcium channels alpha 1S (Ca(v)1.1), probably through its interaction with the beta regulatory subunit. Thus, AHNAK1 plays an essential role in T cell Ca2+ signaling through Ca(v)1 channels, triggered via TCR activation; therefore, AHNAK1 is a potential target for therapeutic intervention.
  • Qilin Pan, John Mathison, Colleen Fearns, Vladimir V. Kravchenko, Jean Da Silva Correia, Hal M. Hoffman, Koichi S. Kobayashi, John Bertin, Ethan P. Grant, Anthony J. Coyle, Fayyaz S. Sutterwala, Yasunori Ogura, Richard A. Flavell, Richard J. Ulevitch
    JOURNAL OF LEUKOCYTE BIOLOGY 82 (1) 177 - 183 0741-5400 2007/07 [Refereed][Not invited]
    Nucleotide-binding oligomerization domain (Nod)2 is a sensor of muramyl dipeptides (AIDP) derived from bacterial peptidoglycan. Nod2 also plays a role in some autoinflammatory diseases. Cold-induced autoinflammatory syndrome I (CIAS1)/NACHT domain, leucine-rich repeat, and pyrin domain-containing protein 3 (NALP3) has been suggested to be sufficient for MDP-dependent release of mature IL-1 beta, but the role of Nod2 in this process is unclear. Using mice bearing selective gene deletions, we provide in vitro and in vivo data showing that AIDP-induced IL-1 beta release requires Nod2 and CIASI/NALP3 as well as receptor-interacting protein-2 (Rip2), apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (ASC), and caspase-1. In contrast, AIDP-dependent IL-6 production only requires Nod2 and Rip2. Together, our data provide a new understanding of this important pathway of IL-I beta production and allow for further studies of the role of these proteins within the broader context of inflammatory disease.
  • ML Shinohara, LR Lu, J Bu, MBF Werneck, KS Kobayashi, LH Glimcher, H Cantor
    NATURE IMMUNOLOGY 7 (5) 498 - 506 1529-2908 2006/05 [Refereed][Not invited]
    The observation that the T-bet transcription factor allows tissue-specific upregulation of intracellular osteopontin (Opn-i) in plasmacytoid dendritic cells (pDCs) suggests that Opn might contribute to the expression of interferon-alpha (IFN-alpha) in those cells. Here we show that Opn deficiency substantially reduced Toll-like receptor 9 (TLR9)-dependent IFN-alpha responses but spared expression of transcription factor NF-kappa B-dependent proinflammatory cytokines. Shortly after TLR9 engagement, colocalization of Opn-i and the adaptor molecule MyD88 was associated with induction of transcription factor IRF7-dependent IFN-alpha gene expression, whereas deficient expression of Opn-i was associated with defective nuclear translocation of IRF7 in pDCs. The importance of the Opn-IFN-alpha pathway was emphasized by its essential involvement in cross-presentation in vitro and in anti herpes simplex virus 1 IFN-alpha response in vivo. The finding that Opn-i selectively coupled TLR9 signaling to expression of IFN-alpha but not to that of other proinflammatory cytokines provides new molecular insight into the biology of pDCs.
  • DS Zamboni, KS Kobayashi, T Kohlsdorf, Y Ogura, EM Long, RE Vance, K Kuida, S Mariathasan, VM Dixit, RA Flavell, WF Dietrich, CR Roy
    NATURE IMMUNOLOGY 7 (3) 318 - 325 1529-2908 2006/03 [Refereed][Not invited]
    Baculovirus inhibitor of apoptosis repeat-containing 1 (Birc1) proteins have homology to several germline-encoded receptors of the innate immune system. However, their function in immune surveillance is not clear. Here we describe a Birc1e-dependent signaling pathway that restricted replication of the intracellular pathogen Legionella pneumophila in mouse macrophages. Translocation of bacterial products into host-cell cytosol was essential for Birc1e-mediated control of bacterial replication. Caspase-1 was required for Birc1e-dependent antibacterial responses ex vivo in macrophages and in a mouse model of Legionnaires' disease. The interleukin 1 beta converting enzyme-protease-activating factor was necessary for L. pneumophila growth restriction, but interleukin 1 beta was not required. These results establish Birc1e as a nucleotide-binding oligomerization-leucine-rich repeat protein involved in the detection and control of intracellular L. pneumophila.
  • HM Li, E Cuartas, WG Cui, YW Choi, TD Crawford, HZ Ke, KS Kobayashi, RA Flavell, A Vignery
    JOURNAL OF EXPERIMENTAL MEDICINE 201 (7) 1169 - 1177 0022-1007 2005/04 [Refereed][Not invited]
    Osteoporosis is a serious problem worldwide; it is characterized by bone fractures in response to relatively mild trauma. Osteoclasts originate from the fusion of macrophages and they play a central role in bone development and remodeling via the resorption of bone. Therefore, osteoclasts are important mediators of bone loss that leads, for example, to osteoporosis. Interleukin (IL)-1 receptor (IL-1R)-associated kinase M (IRAK-M) is only expressed in cells of the myeloid lineage and it inhibits signaling downstream of IL-1R and Toll-like receptors (TLRs). However, it lacks a functional catalytic site and, thus, cannot function as a kinase. IRAK-M associates with, and prevents the dissociation of, IRAK-IRAK-4-TNF receptor-associated factor 6 from the TLR signaling complex, with resultant disruption of downstream signaling. Thus, IRAK-M acts as a dominant negative IRAK. We show here that mice that lack IRAK-M develop severe osteoporosis, which is associated with the accelerated differentiation of osteoclasts, an increase in the half-life of osteoclasts, and their activation. Ligation of IL-1R or TLRs results in hyperactivation of NF-kappa B and mitogen-activated protein kinase signaling pathways, which are essential for osteoclast differentiation. Thus, IRAK-M is a key regulator of the bone loss that is due to osteoclastic resorption of bone.
  • KS Kobayashi, M Chamaillard, Y Ogura, O Henegariu, N Inohara, G Nunez, RA Flavell
    SCIENCE 307 (5710) 731 - 734 0036-8075 2005/02 [Refereed][Not invited]
    The gene encoding the Nod2 protein is frequently mutated in Crohn's disease (CD) patients, although the physiological function of Nod2 in the intestine remains elusive. Here we show that protective immunity mediated by Nod2 recognition of bacterial muramyl dipeptide is abolished in Nod2-deficient mice. These animals are susceptible to bacterial infection via the oral route but not through intravenous or peritoneal delivery. Nod2 is required for the expression of a subgroup of intestinal anti-microbial peptides, known as cryptdins. The Nod2 protein is thus a critical regulator of bacterial immunity within the intestine, providing a possible mechanism for Nod2 mutations in CD.
  • KS Kobayashi, RA Flavell
    JOURNAL OF LEUKOCYTE BIOLOGY 75 (3) 428 - 433 0741-5400 2004/03 [Refereed][Not invited]
    The innate immune system is evolutionarily conserved among all multicellular organisms and is the first line of defense against microorganisms. It enables the host not only to combat pathogenic organisms but also to cohabit with nonpathogenic microorganisms by balancing the host-microorganism interaction. The innate immune response is activated rapidly (within hours) compared with adaptive immunity. Activation of the innate immune system allows the activation of the adaptive immune response by production of proinflammatory cytokines and by providing stimulatory signals via major histocompatibility complex molecules and costimulatory molecules such as CD40, CD80, or CD86; together, these lead to the full activation of both immune systems to fight against pathogenic microorganisms. Activation of the innate immune system, however, can be a double-edged sword for the host. Proinflammatory cytokines mediate a positive feedback loop on the innate immune system, and overproduction of cytokines, if unchecked, is hazardous to the host and may cause severe outcomes such as hyperthermia, organ failure, and even death in extreme cases. Moreover, if the overproduction of proinflammatory cytokines persists, it may cause chronic inflammatory diseases. During evolution, the innate immune system has acquired complicated regulatory systems to control itself so that this "sword" will not kill the host. Various mechanisms including inhibition of Toll-like receptor signaling by interleukin-1 receptor-associated kinase-M have evolved for this purpose and are important not only to fight against pathogenic microorganisms efficiently but also are critical for the peaceful coexistence with commensal bacterial flora.
  • S Chakrabarti, KS Kobayashi, RA Flavell, CB Marks, K Miyake, DR Liston, KT Fowler, FS Gorelick, NW Andrews
    JOURNAL OF CELL BIOLOGY 162 (4) 543 - 549 0021-9525 2003/08 [Refereed][Not invited]
    Members of the synaptotagmin family have been proposed to function as Ca2+ sensors in membrane fusion. Syt VII is a ubiquitously expressed synaptotagmin previously implicated in plasma membrane repair and Trypanosoma cruzi invasion, events which are mediated by the Ca2+-regulated exocytosis of lysosomes. Here, we show that embryonic fibroblasts from Syt VII-deficient mice are less susceptible to trypanosome invasion, and defective in lysosomal exocytosis and resealing after wounding. Examination of mutant mouse tissues revealed extensive fibrosis in the skin and skeletal muscle. inflammatory myopathy, with muscle fiber invasion by leukocytes and endomysial collagen deposition, was associated with elevated creatine kinase release and progressive muscle weakness. Interestingly, similar to what is observed in human polymyositis/dermatomyositis, the mice developed a strong antinuclear antibody response, characteristic of autoimmune disorders. Thus, defective plasma membrane repair in tissues under mechanical stress may favor the development of inflammatory autoimmune disease.
  • KS Kobayashi, EE Eynon, RA Flavell
    NATURE IMMUNOLOGY 4 (7) 652 - 654 1529-2908 2003/07 [Refereed][Not invited]
    A family of intracellular molecules called NODs has been proposed to sense bacteria within the cell. New data now show that NOD1 senses a distinct bacterial component and may thus be important in responding to bacteria with this molecular signature.

Awards & Honors

  • 2006/10 Cancer Research Institute Investigator Award
    受賞者: Koichi S Kobayashi
  • 2004/07 Arthritis National Research Foundation Fellow
    受賞者: Koichi S Kobayashi
  • 1999/06 Cancer Research Institute Postdoctoral Fellowship
    受賞者: Koichi S Kobayashi
  • 1998/03 The Naito Foundation The Naito Foundation Scholarship
    受賞者: Koichi S Kobayashi

Educational Activities

Teaching Experience

  • 研究発表技法Ⅰ
    開講年度 : 2018
    課程区分 : 博士後期課程
    開講学部 : 医学研究科
  • Basic Principles of Medicine
    開講年度 : 2018
    課程区分 : 修士課程
    開講学部 : 医学院
    キーワード : 免疫学、自然免疫、獲得免疫、炎症、感染免疫、がん免疫
  • 研究発表技法Ⅱ
    開講年度 : 2018
    課程区分 : 博士後期課程
    開講学部 : 医学研究科
  • Principles of Medicine
    開講年度 : 2018
    課程区分 : 博士後期課程
    開講学部 : 医学院
    キーワード : 免疫学、自然免疫、獲得免疫、炎症、感染免疫、がん免疫
  • 基盤医学研究Ⅱ
    開講年度 : 2018
    課程区分 : 博士後期課程
    開講学部 : 医学研究科
  • Microbiology-Immunology Laboratory
    開講年度 : 2018
    課程区分 : 学士課程
    開講学部 : 医学部
    キーワード : 細菌、ウイルス、無菌操作、グラム染色、抗酸菌染色、培養、細胞培養、定量、抗生物質、CPE、PCR、ELISA、IFA、蛍光抗体法、抗体、ブロッティング、炎症性サイトカイン、フローサイトメトリー、リンパ球、マクロファージ
  • 基盤医学研究Ⅰ
    開講年度 : 2018
    課程区分 : 博士後期課程
    開講学部 : 医学研究科
  • 医学総論
    開講年度 : 2018
    課程区分 : 博士後期課程
    開講学部 : 医学研究科
  • 研究発表技法Ⅰ
    開講年度 : 2018
    課程区分 : 博士後期課程
    開講学部 : 医学院
  • 研究発表技法Ⅱ
    開講年度 : 2018
    課程区分 : 博士後期課程
    開講学部 : 医学院
  • 免疫学
    開講年度 : 2018
    課程区分 : 学士課程
    開講学部 : 医学部

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