基本情報

所属

• 医学研究院　病理系部門　微生物学免疫学分野

職名

• 助教

学位

• 博士（理学）（2017年03月 首都大学東京）

J-Global ID

• 202001016704534507

研究キーワード

• 細胞生物学   ウイルス学   

研究分野

• ライフサイエンス / ウイルス学
• ライフサイエンス / 機能生物化学

担当教育組織

•  学士課程　医学部（医学科）
•  修士課程　医学院
•  博士課程　医学院

研究活動情報

論文

• Akaluc bioluminescence offers superior sensitivity to trackin vivodynamics of SARS-CoV-2 infection

  Tomokazu Tamura, Hayato Ito, Shiho Torii, Lei Wang, Rigel Suzuki, Shuhei Tusjino, Akifumi Kamiyama, Yoshitaka Oda, Yuhei Morioka, Saori Suzuki, Kotaro Shirakawa, Kei Sato, Kumiko Yoshimatsu, Yoshiharu Matsuura, Satoshi Iwano, Shinya Tanaka, Takasuke Fukuhara

  2023年10月13日 

  Summary Monitoringin vivoviral dynamics can improve our understanding of pathogenicity and tissue tropism. For positive-sense, single-stranded RNA viruses, several studies have attempted to monitor viral kineticsin vivousing reporter genomes. The application of such recombinant viruses can be limited by challenges in accommodating bioluminescent reporter genes in the viral genome. Conventional luminescence also exhibits relatively low tissue permeability and thus less sensitivity for visualizationin vivo. Here we show that unlike NanoLuc bioluminescence, the improved method, termed AkaBLI, allows visualization of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in Syrian hamsters. By successfully incorporating a codon-optimized Akaluc luciferase gene into the SARS-CoV-2 genome, we visualizedin vivoinfection, including the tissue-specific differences associated with particular variants. Additionally, we could evaluate the efficacy of neutralizing antibodies and mRNA vaccination by monitoring changes in Akaluc signals. Overall, AkaBLI is an effective technology for monitoring viral dynamics in live animals.
• Multiple mutations of SARS-CoV-2 Omicron BA.2 variant orchestrate its virological characteristics.

  Izumi Kimura, Daichi Yamasoba, Hesham Nasser, Hayato Ito, Jiri Zahradnik, Jiaqi Wu, Shigeru Fujita, Keiya Uriu, Jiei Sasaki, Tomokazu Tamura, Rigel Suzuki, Sayaka Deguchi, Arnon Plianchaisuk, Kumiko Yoshimatsu, Yasuhiro Kazuma, Shuya Mitoma, Gideon Schreiber, Hiroyuki Asakura, Mami Nagashima, Kenji Sadamasu, Kazuhisa Yoshimura, Akifumi Takaori-Kondo, Jumpei Ito, Kotaro Shirakawa, Kazuo Takayama, Takashi Irie, Takao Hashiguchi, So Nakagawa, Takasuke Fukuhara, Akatsuki Saito, Terumasa Ikeda, Kei Sato

  Journal of virology e0101123  2023年10月05日 

  Previous studies on the Omicron BA.2 variant suggested that the virological characteristics of BA.2 are determined by the mutations in at least two different regions of the viral genome: in the BA.2 spike gene (enhancing viral fusogenicity and intrinsic pathogenicity) and the non-spike region of the BA.2 genome (leading to intrinsic pathogenicity attenuation). However, the mutations modulating the BA.2 virological properties remain elusive. In this study, we demonstrated that the L371F substitution in the BA.2 spike protein confers greater fusogenicity and intrinsic pathogenicity. Furthermore, we revealed that multiple mutations downstream of the spike gene in the BA.2 genome are responsible for attenuating intrinsic viral pathogenicity and replication capacity. As mutations in the SARS-CoV-2 variant spike proteins could modulate certain virological properties, such as immune evasion and infectivity, most studies have previously focused on spike protein mutations. Our results underpin the importance of non-spike protein-related mutations in SARS-CoV-2 variants. IMPORTANCE Most studies investigating the characteristics of emerging SARS-CoV-2 variants have been focusing on mutations in the spike proteins that affect viral infectivity, fusogenicity, and pathogenicity. However, few studies have addressed how naturally occurring mutations in the non-spike regions of the SARS-CoV-2 genome impact virological properties. In this study, we proved that multiple SARS-CoV-2 Omicron BA.2 mutations, one in the spike protein and another downstream of the spike gene, orchestrally characterize this variant, shedding light on the importance of Omicron BA.2 mutations out of the spike protein.
• Comparative pathogenicity of SARS-CoV-2 Omicron subvariants including BA.1, BA.2, and BA.5.

  Tomokazu Tamura, Daichi Yamasoba, Yoshitaka Oda, Jumpei Ito, Tomoko Kamasaki, Naganori Nao, Rina Hashimoto, Yoichiro Fujioka, Rigel Suzuki, Lei Wang, Hayato Ito, Yukie Kashima, Izumi Kimura, Mai Kishimoto, Masumi Tsuda, Hirofumi Sawa, Kumiko Yoshimatsu, Yuki Yamamoto, Tetsuharu Nagamoto, Jun Kanamune, Yutaka Suzuki, Yusuke Ohba, Isao Yokota, Keita Matsuno, Kazuo Takayama, Shinya Tanaka, Kei Sato, Takasuke Fukuhara

  Communications biology 6 1 772 - 772 2023年07月24日 

  The unremitting emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants necessitates ongoing control measures. Given its rapid spread, the new Omicron subvariant BA.5 requires urgent characterization. Here, we comprehensively analyzed BA.5 with the other Omicron variants BA.1, BA.2, and ancestral B.1.1. Although in vitro growth kinetics of BA.5 was comparable among the Omicron subvariants, BA.5 was much more fusogenic than BA.1 and BA.2. Airway-on-a-chip analysis showed that, among Omicron subvariants, BA.5 had enhanced ability to disrupt the respiratory epithelial and endothelial barriers. Furthermore, in our hamster model, in vivo pathogenicity of BA.5 was slightly higher than that of the other Omicron variants and less than that of ancestral B.1.1. Notably, BA.5 gains efficient virus spread compared with BA.1 and BA.2, leading to prompt immune responses. Our findings suggest that BA.5 has low pathogenicity compared with the ancestral strain but enhanced virus spread /inflammation compared with earlier Omicron subvariants.
• saRNA vaccine expressing membrane-anchored RBD elicits broad and durable immunity against SARS-CoV-2 variants of concern.

  Mai Komori, Takuto Nogimori, Amber L Morey, Takashi Sekida, Keiko Ishimoto, Matthew R Hassett, Yuji Masuta, Hirotaka Ode, Tomokazu Tamura, Rigel Suzuki, Jeff Alexander, Yasutoshi Kido, Kenta Matsuda, Takasuke Fukuhara, Yasumasa Iwatani, Takuya Yamamoto, Jonathan F Smith, Wataru Akahata

  Nature communications 14 1 2810 - 2810 2023年05月19日 

  Several vaccines have been widely used to counteract the global pandemic caused by SARS-CoV-2. However, due to the rapid emergence of SARS-CoV-2 variants of concern (VOCs), further development of vaccines that confer broad and longer-lasting protection against emerging VOCs are needed. Here, we report the immunological characteristics of a self-amplifying RNA (saRNA) vaccine expressing the SARS-CoV-2 Spike (S) receptor binding domain (RBD), which is membrane-anchored by fusing with an N-terminal signal sequence and a C-terminal transmembrane domain (RBD-TM). Immunization with saRNA RBD-TM delivered in lipid nanoparticles (LNP) efficiently induces T-cell and B-cell responses in non-human primates (NHPs). In addition, immunized hamsters and NHPs are protected against SARS-CoV-2 challenge. Importantly, RBD-specific antibodies against VOCs are maintained for at least 12 months in NHPs. These findings suggest that this saRNA platform expressing RBD-TM will be a useful vaccine candidate inducing durable immunity against emerging SARS-CoV-2 strains.
• Virological characteristics of the SARS-CoV-2 XBB variant derived from recombination of two Omicron subvariants.

  Tomokazu Tamura, Jumpei Ito, Keiya Uriu, Jiri Zahradnik, Izumi Kida, Yuki Anraku, Hesham Nasser, Maya Shofa, Yoshitaka Oda, Spyros Lytras, Naganori Nao, Yukari Itakura, Sayaka Deguchi, Rigel Suzuki, Lei Wang, Mst Monira Begum, Shunsuke Kita, Hisano Yajima, Jiei Sasaki, Kaori Sasaki-Tabata, Ryo Shimizu, Masumi Tsuda, Yusuke Kosugi, Shigeru Fujita, Lin Pan, Daniel Sauter, Kumiko Yoshimatsu, Saori Suzuki, Hiroyuki Asakura, Mami Nagashima, Kenji Sadamasu, Kazuhisa Yoshimura, Yuki Yamamoto, Tetsuharu Nagamoto, Gideon Schreiber, Katsumi Maenaka, Takao Hashiguchi, Terumasa Ikeda, Takasuke Fukuhara, Akatsuki Saito, Shinya Tanaka, Keita Matsuno, Kazuo Takayama, Kei Sato

  Nature communications 14 1 2800 - 2800 2023年05月16日 

  In late 2022, SARS-CoV-2 Omicron subvariants have become highly diversified, and XBB is spreading rapidly around the world. Our phylogenetic analyses suggested that XBB emerged through the recombination of two cocirculating BA.2 lineages, BJ.1 and BM.1.1.1 (a progeny of BA.2.75), during the summer of 2022. XBB.1 is the variant most profoundly resistant to BA.2/5 breakthrough infection sera to date and is more fusogenic than BA.2.75. The recombination breakpoint is located in the receptor-binding domain of spike, and each region of the recombinant spike confers immune evasion and increases fusogenicity. We further provide the structural basis for the interaction between XBB.1 spike and human ACE2. Finally, the intrinsic pathogenicity of XBB.1 in male hamsters is comparable to or even lower than that of BA.2.75. Our multiscale investigation provides evidence suggesting that XBB is the first observed SARS-CoV-2 variant to increase its fitness through recombination rather than substitutions.
• Convergent evolution of SARS-CoV-2 Omicron subvariants leading to the emergence of BQ.1.1 variant.

  Jumpei Ito, Rigel Suzuki, Keiya Uriu, Yukari Itakura, Jiri Zahradnik, Kanako Terakado Kimura, Sayaka Deguchi, Lei Wang, Spyros Lytras, Tomokazu Tamura, Izumi Kida, Hesham Nasser, Maya Shofa, Mst Monira Begum, Masumi Tsuda, Yoshitaka Oda, Tateki Suzuki, Jiei Sasaki, Kaori Sasaki-Tabata, Shigeru Fujita, Kumiko Yoshimatsu, Hayato Ito, Naganori Nao, Hiroyuki Asakura, Mami Nagashima, Kenji Sadamasu, Kazuhisa Yoshimura, Yuki Yamamoto, Tetsuharu Nagamoto, Jin Kuramochi, Gideon Schreiber, Akatsuki Saito, Keita Matsuno, Kazuo Takayama, Takao Hashiguchi, Shinya Tanaka, Takasuke Fukuhara, Terumasa Ikeda, Kei Sato

  Nature communications 14 1 2671 - 2671 2023年05月11日 

  In late 2022, various Omicron subvariants emerged and cocirculated worldwide. These variants convergently acquired amino acid substitutions at critical residues in the spike protein, including residues R346, K444, L452, N460, and F486. Here, we characterize the convergent evolution of Omicron subvariants and the properties of one recent lineage of concern, BQ.1.1. Our phylogenetic analysis suggests that these five substitutions are recurrently acquired, particularly in younger Omicron lineages. Epidemic dynamics modelling suggests that the five substitutions increase viral fitness, and a large proportion of the fitness variation within Omicron lineages can be explained by these substitutions. Compared to BA.5, BQ.1.1 evades breakthrough BA.2 and BA.5 infection sera more efficiently, as demonstrated by neutralization assays. The pathogenicity of BQ.1.1 in hamsters is lower than that of BA.5. Our multiscale investigations illuminate the evolutionary rules governing the convergent evolution for known Omicron lineages as of 2022.
• Protein quality control machinery supports primary ciliogenesis by eliminating GDP-bound Rab8-family GTPases.

  Takahashi, T, Shirai, J, Matsuda, M, Nakanaga, S, Matsushita, S, Wakita, K, Hayashishita, M, Suzuki, R, Noguchi, A, Yokota, N, Kawahara, H

  iScience 2023年04月 [査読有り]
  
• Increased flexibility of the SARS-CoV-2 RNA-binding site causes resistance to remdesivir

  Shiho Torii, Kwang Su Kim, Jun Koseki, Rigel Suzuki, Shoya Iwanami, Yasuhisa Fujita, Yong Dam Jeong, Jumpei Ito, Hiroyuki Asakura, Mami Nagashima, Kenji Sadamasu, Kazuhisa Yoshimura, Kei Sato, Yoshiharu Matsuura, Teppei Shimamura, Shingo Iwami, Takasuke Fukuhara

  PLOS Pathogens 19 3 e1011231 - e1011231 2023年03月27日 

  Mutations continue to accumulate within the SARS-CoV-2 genome, and the ongoing epidemic has shown no signs of ending. It is critical to predict problematic mutations that may arise in clinical environments and assess their properties in advance to quickly implement countermeasures against future variant infections. In this study, we identified mutations resistant to remdesivir, which is widely administered to SARS-CoV-2-infected patients, and discuss the cause of resistance. First, we simultaneously constructed eight recombinant viruses carrying the mutations detected in in vitro serial passages of SARS-CoV-2 in the presence of remdesivir. We confirmed that all the mutant viruses didn’t gain the virus production efficiency without remdesivir treatment. Time course analyses of cellular virus infections showed significantly higher infectious titers and infection rates in mutant viruses than wild type virus under treatment with remdesivir. Next, we developed a mathematical model in consideration of the changing dynamic of cells infected with mutant viruses with distinct propagation properties and defined that mutations detected in in vitro passages canceled the antiviral activities of remdesivir without raising virus production capacity. Finally, molecular dynamics simulations of the NSP12 protein of SARS-CoV-2 revealed that the molecular vibration around the RNA-binding site was increased by the introduction of mutations on NSP12. Taken together, we identified multiple mutations that affected the flexibility of the RNA binding site and decreased the antiviral activity of remdesivir. Our new insights will contribute to developing further antiviral measures against SARS-CoV-2 infection.
• Antiviral Activity of Micafungin and Its Derivatives against SARS-CoV-2 RNA Replication.

  Shogo Nakajima, Hirofumi Ohashi, Daisuke Akazawa, Shiho Torii, Rigel Suzuki, Takasuke Fukuhara, Koichi Watashi

  Viruses 15 2 2023年02月06日 

  Echinocandin antifungal drugs, including micafungin, anidulafungin, and caspofungin, have been recently reported to exhibit antiviral effects against various viruses such as flavivirus, alphavirus, and coronavirus. In this study, we focused on micafungin and its derivatives and analyzed their antiviral activities against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The micafungin derivatives Mi-2 and Mi-5 showed higher antiviral activity than micafungin, with 50% maximal inhibitory concentration (IC50) of 5.25 and 6.51 µM, respectively (3.8 to 4.7-fold stronger than micafungin) and 50% cytotoxic concentration (CC50) of >64 µM in VeroE6/TMPRSS2 cells. This high anti-SARS-CoV-2 activity was also conserved in human lung epithelial cell-derived Calu-3 cells. Micafungin, Mi-2, and Mi-5 were suggested to inhibit the intracellular virus replication process; additionally, these compounds were active against SARS-CoV-2 variants, including Delta (AY.122, hCoV-19/Japan/TY11-927/2021), Omicron (BA.1.18, hCoV-19/Japan/TY38-873/2021), a variant resistant to remdesivir (R10/E796G C799F), and a variant resistant to casirivimab/imdevimab antibody cocktail (E406W); thus, our results provide basic evidence for the potential use of micafungin derivatives for developing antiviral agents.
• A third dose of the BNT162b2 mRNA vaccine sufficiently improves the neutralizing activity against SARS-CoV-2 variants in liver transplant recipients.

  Takahiro Tomiyama, Rigel Suzuki, Noboru Harada, Tomokazu Tamura, Katsuya Toshida, Yukiko- Kosai-Fujimoto, Takahiro Tomino, Shohei Yoshiya, Yoshihiro Nagao, Kazuki Takeishi, Shinji Itoh, Nobuhiro Kobayashi, Hayato Ito, Sachiyo Yoshio, Tatsuya Kanto, Tomoharu Yoshizumi, Takasuke Fukuhara

  Frontiers in cellular and infection microbiology 13 1197349 - 1197349 2023年 

  INTRODUCTION: We examined the neutralizing antibody production efficiency of the second and third severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine doses (2nd- and 3rd-dose) and neutralizing activity on mutant strains, including, the Ancestral, Beta and Omicron strains using green fluorescent protein-carrying recombinant SARS-CoV-2, in living-donor liver transplantation (LDLT) recipients. METHODS: The patients who were administered vaccines other than Pfizer- BioNTechBNT162b2 and who had coronavirus disease 2019 in this study period were excluded. We enrolled 154 LDLT recipients and 50 healthy controls. RESULT: The median time were 21 days (between 1st and 2nd vaccination) and 244 days (between 2nd and 3rd vaccination). The median neutralizing antibody titer after 2nd-dose was lower in LDLT recipients than in controls (0.46 vs 1.00, P<0.0001). All controls had SARS-CoV-2 neutralizing antibodies, whereas 39 LDLT recipients (25.3%) had no neutralizing antibodies after 2nd-dose; age at vaccination, presence of ascites, multiple immunosuppressive treatments, and mycophenolate mofetil treatment were significant risk factors for nonresponder. The neutralizing activities of recipient sera were approximately 3-fold and 5-fold lower than those of control sera against the Ancestral and Beta strains, respectively. The median antibody titer after 3rd-dose was not significantly different between recipients and controls (1.02 vs 1.22, p=0.0758); only 5% recipients was non-responder. The neutralizing activity after third dose to Omicron strains were enhanced and had no significant difference between two groups. CONCLUSION: Only the 2nd-dose was not sufficiently effective in recipients; however, 3rd-dose had sufficient neutralizing activity against the mutant strain and was as effective as that in healthy controls.
• Monitoring fusion kinetics of viral and target cell membranes in living cells using a SARS-CoV-2 spike-protein-mediated membrane fusion assay

  Hesham Nasser, Ryo Shimizu, Jumpei Ito, Akatsuki Saito, Kei Sato, Terumasa Ikeda, Keita Matsuno, Naganori Nao, Hirofumi Sawa, Mai Kishimoto, Shinya Tanaka, Masumi Tsuda, Lei Wang, Yoshikata Oda, Marie Kato, Zannatul Ferdous, Hiromi Mouri, Kenji Shishido, Takasuke Fukuhara, Tomokazu Tamura, Rigel Suzuki, Hayato Ito, Daichi Yamasoba, Izumi Kimura, Naoko Misawa, Keiya Uriu, Yusuke Kosugi, Shigeru Fujita, Mai Suganami, Mika Chiba, Ryo Yoshimura, So Nakagawa, Jiaqi Wu, Akifumi Takaori-Kondo, Kotaro Shirakawa, Kayoko Nagata, Yasuhiro Kazuma, Ryosuke Nomura, Yoshihito Horisawa, Yusuke Tashiro, Yugo Kawai, Takashi Irie, Ryoko Kawabata, MST Monira Begum, Otowa Takahashi, Kimiko Ichihara, Takamasa Ueno, Chihiro Motozono, Mako Toyoda, Yuri L. Tanaka, Erika P. Butlertanaka, Maya Shofa, Kazuo Takayama, Rina Hashimoto, Sayaka Deguchi, Takao Hashiguchi, Tateki Suzuki, Kanako Kimura, Jiei Sasaki, Yukari Nakajima, Kaori Tabata

  STAR Protocols 3 4 101773 - 101773 2022年12月
• Safety and immunogenicity of SARS-CoV-2 self-amplifying RNA vaccine expressing anchored RBD: a randomised, observer-blind, phase 1 study

  Wataru Akahata, Takashi Sekida, Takuto Nogimori, Hirotaka Ode, Tomokazu Tamura, Kaoru Kono, Yoko Kazami, Ayaka Washizaki, Yuji Masuta, Rigel Suzuki, Kenta Matsuda, Mai Komori, Amber Morey, Keiko Ishimoto, Misako Nakata, Tomoko Hasunuma, Takasuke Fukuhara, Yasumasa Iwatani, Takuya Yamamoto, Jonathan F Smith, Nobuaki Sato

  2022年11月22日 

  Summary BACKGROUND VLPCOV-01 is a lipid nanoparticle-encapsulated self-amplifying RNA (saRNA) vaccine that expresses a membrane-anchored receptor-binding domain (RBD) derived from the SARS-CoV-2 spike protein. METHODS A phase 1 study of VLPCOV-01 was conducted at Medical Corporation Heishinkai OPHAC Hospital, Japan. Participants aged 18 to 55 or ≥65 years who had completed two doses of the BNT162b2 mRNA vaccine 6 to 12 months previously were randomised to receive one intramuscular vaccination of 0·3, 1·0, or 3·0 μg VLPCOV-01, 30 μg BNT162b2, or placebo between February 16, 2022, and March 17, 2022. Solicited adverse events were collected up to 6 days post-administration. Interim immunogenicity analyses included SARS-CoV-2 IgG and neutralising antibody titres. Follow-up for safety and immunogenicity evaluation is ongoing. (The trial is registered: jRCT2051210164). FINDINGS 92 healthy adults were enrolled, with 60 participants receiving VLPCOV-01. No serious adverse events were reported up to 26 weeks, and no prespecified trial-halting events were met. VLPCOV-01 induced robust IgG titres against SARS-CoV-2 RBD protein that were maintained up to 26 weeks in non-elderly participants, with geometric means ranging from 5037 (95% CI 1272–19,940) at 0·3 μg to 12,873 (95% CI 937–17,686) at 3 μg, in comparison to 3166 (95% CI 1619–6191) with 30 μg BNT162b2. Among elderly participants, IgG titres at 26 weeks post-vaccination with 3 μg VLPCOV-01 were 9865 (95% CI 4396–22138) compared to 4183 (95% CI 1436–12180) following vaccination with 30 μg BNT162b2. Pseudovirus neutralising antibody responses were observed against multiple SARS-CoV-2 variants and strongly correlated with anti-SARS-CoV-2 IgG (r=0·950, p<0·001). INTERPRETATION VLPCOV-01 is immunogenic following low dose administration, with anti-SARS-CoV-2 immune responses comparable to BNT162b2. These findings support further development of VLPCOV-01 as a COVID-19 booster vaccine and the potential for saRNA vectors as a vaccine platform. FUNDING Supported by AMED, Grant No. JP21nf0101627.
• Virological characteristics of the SARS-CoV-2 Omicron BA.2.75 variant.

  Akatsuki Saito, Tomokazu Tamura, Jiri Zahradnik, Sayaka Deguchi, Koshiro Tabata, Yuki Anraku, Izumi Kimura, Jumpei Ito, Daichi Yamasoba, Hesham Nasser, Mako Toyoda, Kayoko Nagata, Keiya Uriu, Yusuke Kosugi, Shigeru Fujita, Maya Shofa, Mst Monira Begum, Ryo Shimizu, Yoshitaka Oda, Rigel Suzuki, Hayato Ito, Naganori Nao, Lei Wang, Masumi Tsuda, Kumiko Yoshimatsu, Jin Kuramochi, Shunsuke Kita, Kaori Sasaki-Tabata, Hideo Fukuhara, Katsumi Maenaka, Yuki Yamamoto, Tetsuharu Nagamoto, Hiroyuki Asakura, Mami Nagashima, Kenji Sadamasu, Kazuhisa Yoshimura, Takamasa Ueno, Gideon Schreiber, Akifumi Takaori-Kondo, Kotaro Shirakawa, Hirofumi Sawa, Takashi Irie, Takao Hashiguchi, Kazuo Takayama, Keita Matsuno, Shinya Tanaka, Terumasa Ikeda, Takasuke Fukuhara, Kei Sato

  Cell host & microbe 30 11 1540 - 1555 2022年11月09日 

  The SARS-CoV-2 Omicron BA.2.75 variant emerged in May 2022. BA.2.75 is a BA.2 descendant but is phylogenetically distinct from BA.5, the currently predominant BA.2 descendant. Here, we show that BA.2.75 has a greater effective reproduction number and different immunogenicity profile than BA.5. We determined the sensitivity of BA.2.75 to vaccinee and convalescent sera as well as a panel of clinically available antiviral drugs and antibodies. Antiviral drugs largely retained potency, but antibody sensitivity varied depending on several key BA.2.75-specific substitutions. The BA.2.75 spike exhibited a profoundly higher affinity for its human receptor, ACE2. Additionally, the fusogenicity, growth efficiency in human alveolar epithelial cells, and intrinsic pathogenicity in hamsters of BA.2.75 were greater than those of BA.2. Our multilevel investigations suggest that BA.2.75 acquired virological properties independent of BA.5, and the potential risk of BA.2.75 to global health is greater than that of BA.5.
• SARS-CoV-2 Omicron detection by antigen tests using saliva.

  Kaoru Murakami, Sumio Iwasaki, Satoshi Oguri, Kumiko Tanaka, Rigel Suzuki, Kasumi Hayasaka, Shinichi Fujisawa, Chiaki Watanabe, Satoshi Konno, Isao Yokota, Takasuke Fukuhara, Masaaki Murakami, Takanori Teshima

  Journal of clinical virology plus 2 4 100109 - 100109 2022年11月 

  The Omicron emerged in November 2021 and became the predominant SARS-CoV-2 variant globally. It spreads more rapidly than ancestral lineages and its rapid detection is critical for the prevention of disease outbreaks. Antigen tests such as immunochromatographic assay (ICA) and chemiluminescent enzyme immunoassay (CLEIA) yield results more quickly than standard polymerase chain reaction (PCR). However, their utility for the detection of the Omicron variant remains unclear. We herein evaluated the performance of ICA and CLEIA in saliva from 51 patients with Omicron and 60 PCR negative individuals. The sensitivity and specificity of CLEIA were 98.0% (95%CI: 89.6-100.0%) and 100.0% (95%CI: 94.0-100.0%), respectively, with fine correlation with cycle threshold (Ct) values. The sensitivity and specificity of ICA were 58.8% (95%CI: 44.2-72.4%) and 100.0% (95%CI: 94.0-100.0%), respectively. The sensitivity of ICA was 100.0% (95%CI: 80.5-100.0%) when PCR Ct was less than 25. The Omicron can be efficiently detected in saliva by CLEIA. ICA also detects high viral load Omicron using saliva.
• Smoking Enhances the Expression of Angiotensin-Converting Enzyme 2 Involved in the Efficiency of Severe Acute Respiratory Syndrome Coronavirus 2 Infection.

  Rigel Suzuki, Yuki Ono, Koji Noshita, Kwang Su Kim, Hayato Ito, Yuhei Morioka, Tomokazu Tamura, Daisuke Okuzaki, Tetsuzo Tagawa, Tomoyoshi Takenaka, Tomoharu Yoshizumi, Teppei Shimamura, Shingo Iwami, Takasuke Fukuhara

  Microbiology and immunology 67 1 22 - 31 2022年10月18日 

  Smoking is one of the risk factors most closely related to the severity of COVID-19. However, the relationship between smoking history and SARS-CoV-2 infectivity is unknown. In this study, we evaluated the ACE2 expression level in the lungs of current smokers, ex-smokers, and non-smokers. The ACE2 expression level of ex-smokers who smoked cigarettes until recently (cessation period shorter than 6 months) was higher than that of non-smokers and ex-smokers with a long history of non-smoking (cessation period longer than 6 months). We also showed that the efficiency of SARS-CoV-2 infection was enhanced in a manner dependent on the ACE2 expression level. Using RNA-seq analysis on the lungs of smokers, we identified that the expression of inflammatory signaling genes was correlated with ACE2 expression. Notably, with increasing duration of smoking cessation among ex-smokers, not only ACE2 expression level but also the expression levels of inflammatory signaling genes decreased. These results indicated that smoking enhances the expression levels of ACE2 and inflammatory signaling genes. Our data suggest that the efficiency of SARS-CoV-2 infection is enhanced by smoking-mediated upregulation of ACE2 expression level. This article is protected by copyright. All rights reserved.
• Virological characteristics of the SARS-CoV-2 Omicron BA.2 subvariants, including BA.4 and BA.5.

  Izumi Kimura, Daichi Yamasoba, Tomokazu Tamura, Naganori Nao, Tateki Suzuki, Yoshitaka Oda, Shuya Mitoma, Jumpei Ito, Hesham Nasser, Jiri Zahradnik, Keiya Uriu, Shigeru Fujita, Yusuke Kosugi, Lei Wang, Masumi Tsuda, Mai Kishimoto, Hayato Ito, Rigel Suzuki, Ryo Shimizu, Mst Monira Begum, Kumiko Yoshimatsu, Kanako Terakado Kimura, Jiei Sasaki, Kaori Sasaki-Tabata, Yuki Yamamoto, Tetsuharu Nagamoto, Jun Kanamune, Kouji Kobiyama, Hiroyuki Asakura, Mami Nagashima, Kenji Sadamasu, Kazuhisa Yoshimura, Kotaro Shirakawa, Akifumi Takaori-Kondo, Jin Kuramochi, Gideon Schreiber, Ken J Ishii, Takao Hashiguchi, Terumasa Ikeda, Akatsuki Saito, Takasuke Fukuhara, Shinya Tanaka, Keita Matsuno, Kei Sato

  Cell 185 21 3992 - 4007 2022年10月13日 

  After the global spread of the SARS-CoV-2 Omicron BA.2, some BA.2 subvariants, including BA.2.9.1, BA.2.11, BA.2.12.1, BA.4, and BA.5, emerged in multiple countries. Our statistical analysis showed that the effective reproduction numbers of these BA.2 subvariants are greater than that of the original BA.2. Neutralization experiments revealed that the immunity induced by BA.1/2 infections is less effective against BA.4/5. Cell culture experiments showed that BA.2.12.1 and BA.4/5 replicate more efficiently in human alveolar epithelial cells than BA.2, and particularly, BA.4/5 is more fusogenic than BA.2. We further provided the structure of the BA.4/5 spike receptor-binding domain that binds to human ACE2 and considered how the substitutions in the BA.4/5 spike play roles in ACE2 binding and immune evasion. Moreover, experiments using hamsters suggested that BA.4/5 is more pathogenic than BA.2. Our multiscale investigations suggest that the risk of BA.2 subvariants, particularly BA.4/5, to global health is greater than that of original BA.2.
• Antiviral activity of ciclesonide acetal derivatives blocking SARS-CoV-2 RNA replication

  Genichiro Tsuji, Shogo Nakajima, Koichi Watashi, Shiho Torii, Rigel Suzuki, Takasuke Fukuhara, Nobumichi Ohoka, Takao Inoue, Yosuke Demizu

  Journal of Pharmacological Sciences 149 3 81 - 84 2022年07月 

  Ciclesonide (Cic) is approved as an inhalant for asthma and was clinically tested as a candidate therapy for coronavirus disease 2019 (COVID-19). Its active metabolite Cic2 was recently reported to suppress genomic RNA replication of severe acute respiratory syndrome coronavirus 2. In this study, we designed and synthesized a set of ciclesonide-acetal (Cic-acetal) derivatives. Among designated compounds, some Cic-acetal derivatives with a linear alkyl chain exhibited strong viral copy-number reduction activities compared with Cic2. These compounds might serve as lead compounds for developing novel anti-COVID-19 agents.
• Secretory glycoprotein NS1 plays a crucial role in the particle formation of flaviviruses.

  Tomokazu Tamura, Shiho Torii, Kentaro Kajiwara, Itsuki Anzai, Yoichiro Fujioka, Kisho Noda, Shuhei Taguwa, Yuhei Morioka, Rigel Suzuki, Yuzy Fauzyah, Chikako Ono, Yusuke Ohba, Masato Okada, Takasuke Fukuhara, Yoshiharu Matsuura

  PLoS pathogens 18 6 e1010593  2022年06月03日 

  Flaviviruses, which are globally distributed and cause a spectrum of potentially severe illnesses, pose a major threat to public health. Although Flaviviridae viruses, including flaviviruses, possess similar genome structures, only the flaviviruses encode the non-structural protein NS1, which resides in the endoplasmic reticulum (ER) and is secreted from cells after oligomerization. The ER-resident NS1 is known to be involved in viral genome replication, but the essential roles of secretory NS1 in the virus life cycle are not fully understood. Here we characterized the roles of secretory NS1 in the particle formation of flaviviruses. We first identified an amino acid residue essential for the NS1 secretion but not for viral genome replication by using protein-protein interaction network analyses and mutagenesis scanning. By using the recombinant flaviviruses carrying the identified NS1 mutation, we clarified that the mutant flaviviruses employed viral genome replication. We then constructed a recombinant NS1 with the identified mutation and demonstrated by physicochemical assays that the mutant NS1 was unable to form a proper oligomer or associate with liposomes. Finally, we showed that the functions of NS1 that were lost by the identified mutation could be compensated for by the in trans-expression of Erns of pestiviruses and host exchangeable apolipoproteins, which participate in the infectious particle formation of pestiviruses and hepaciviruses in the family Flaviviridae, respectively. Collectively, our study suggests that secretory NS1 plays a role in the particle formation of flaviviruses through its interaction with the lipid membrane.
• Virological characteristics of the SARS-CoV-2 Omicron BA.2 spike.

  Daichi Yamasoba, Izumi Kimura, Hesham Nasser, Yuhei Morioka, Naganori Nao, Jumpei Ito, Keiya Uriu, Masumi Tsuda, Jiri Zahradnik, Kotaro Shirakawa, Rigel Suzuki, Mai Kishimoto, Yusuke Kosugi, Kouji Kobiyama, Teppei Hara, Mako Toyoda, Yuri L Tanaka, Erika P Butlertanaka, Ryo Shimizu, Hayato Ito, Lei Wang, Yoshitaka Oda, Yasuko Orba, Michihito Sasaki, Kayoko Nagata, Kumiko Yoshimatsu, Hiroyuki Asakura, Mami Nagashima, Kenji Sadamasu, Kazuhisa Yoshimura, Jin Kuramochi, Motoaki Seki, Ryoji Fujiki, Atsushi Kaneda, Tadanaga Shimada, Taka-Aki Nakada, Seiichiro Sakao, Takuji Suzuki, Takamasa Ueno, Akifumi Takaori-Kondo, Ken J Ishii, Gideon Schreiber, Hirofumi Sawa, Akatsuki Saito, Takashi Irie, Shinya Tanaka, Keita Matsuno, Takasuke Fukuhara, Terumasa Ikeda, Kei Sato

  Cell 185 12 2103 - 2115 2022年05月02日 [査読有り][通常論文]
   

  Soon after the emergence and global spread of the SARS-CoV-2 Omicron lineage BA.1, another Omicron lineage, BA.2, began outcompeting BA.1. The results of statistical analysis showed that the effective reproduction number of BA.2 is 1.4-fold higher than that of BA.1. Neutralization experiments revealed that immunity induced by COVID vaccines widely administered to human populations is not effective against BA.2, similar to BA.1, and that the antigenicity of BA.2 is notably different from that of BA.1. Cell culture experiments showed that the BA.2 spike confers higher replication efficacy in human nasal epithelial cells and is more efficient in mediating syncytia formation than the BA.1 spike. Furthermore, infection experiments using hamsters indicated that the BA.2 spike-bearing virus is more pathogenic than the BA.1 spike-bearing virus. Altogether, the results of our multiscale investigations suggest that the risk of BA.2 to global health is potentially higher than that of BA.1.
• Characterization of various remdesivir-resistant mutations of SARS-CoV-2 by mathematical modeling and molecular dynamics simulation

  Shiho Torii, Kwang Su Kim, Jun Koseki, Rigel Suzuki, Shoya Iwanami, Yasuhisa Fujita, Yong Dam Jeong, Yoshiharu Matsuura, Teppei Shimamura, Shingo Iwami, Takasuke Fukuhara

  2022年02月24日
• Attenuated fusogenicity and pathogenicity of SARS-CoV-2 Omicron variant.

  Rigel Suzuki, Daichi Yamasoba, Izumi Kimura, Lei Wang, Mai Kishimoto, Jumpei Ito, Yuhei Morioka, Naganori Nao, Hesham Nasser, Keiya Uriu, Yusuke Kosugi, Masumi Tsuda, Yasuko Orba, Michihito Sasaki, Ryo Shimizu, Ryoko Kawabata, Kumiko Yoshimatsu, Hiroyuki Asakura, Mami Nagashima, Kenji Sadamasu, Kazuhisa Yoshimura, Hirofumi Sawa, Terumasa Ikeda, Takashi Irie, Keita Matsuno, Shinya Tanaka, Takasuke Fukuhara, Kei Sato

  Nature 603 7902 700 - 705 2022年02月01日 

  The emergence of a new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant, Omicron, is an urgent global health concern (ref.1). Our statistical modelling suggests that Omicron has spread more rapidly than the Delta variant in several countries including South Africa. Cell culture experiments show that Omicron is less fusogenic than Delta and an ancestral SARS-CoV-2 strain. Although the spike (S) protein of Delta is efficiently cleaved into two subunits, which facilitates cell-cell fusion2,3, Omicron S is less efficiently cleaved compared to Delta S and ancestral SARS-CoV-2 S. Furthermore, in a hamster model, Omicron shows decreased lung infectivity and is less pathogenic compared to Delta and ancestral SARS-CoV-2.
• Enhanced fusogenicity and pathogenicity of SARS-CoV-2 Delta P681R mutation.

  Akatsuki Saito, Takashi Irie, Rigel Suzuki, Tadashi Maemura, Hesham Nasser, Keiya Uriu, Yusuke Kosugi, Kotaro Shirakawa, Kenji Sadamasu, Izumi Kimura, Jumpei Ito, Jiaqi Wu, Kiyoko Iwatsuki-Horimoto, Mutsumi Ito, Seiya Yamayoshi, Samantha Loeber, Masumi Tsuda, Lei Wang, Seiya Ozono, Erika P Butlertanaka, Yuri L Tanaka, Ryo Shimizu, Kenta Shimizu, Kumiko Yoshimatsu, Ryoko Kawabata, Takemasa Sakaguchi, Kenzo Tokunaga, Isao Yoshida, Hiroyuki Asakura, Mami Nagashima, Yasuhiro Kazuma, Ryosuke Nomura, Yoshihito Horisawa, Kazuhisa Yoshimura, Akifumi Takaori-Kondo, Masaki Imai, Shinya Tanaka, So Nakagawa, Terumasa Ikeda, Takasuke Fukuhara, Yoshihiro Kawaoka, Kei Sato

  Nature 602 7896 300 - 306 2021年11月25日 

  During the current coronavirus disease 2019 (COVID-19) pandemic, a variety of mutations have accumulated in the viral genome of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and, at the time of writing, four variants of concern are considered to be potentially hazardous to human society1. The recently emerged B.1.617.2/Delta variant of concern is closely associated with the COVID-19 surge that occurred in India in the spring of 2021 (ref. 2). However, the virological properties of B.1.617.2/Delta remain unclear. Here we show that the B.1.617.2/Delta variant is highly fusogenic and notably more pathogenic than prototypic SARS-CoV-2 in infected hamsters. The P681R mutation in the spike protein, which is highly conserved in this lineage, facilitates cleavage of the spike protein and enhances viral fusogenicity. Moreover, we demonstrate that the P681R-bearing virus exhibits higher pathogenicity compared with its parental virus. Our data suggest that the P681R mutation is a hallmark of the virological phenotype of the B.1.617.2/Delta variant and is associated with enhanced pathogenicity.
• Establishment of a reverse genetics system for SARS-CoV-2 using circular polymerase extension reaction.

  Shiho Torii, Chikako Ono, Rigel Suzuki, Yuhei Morioka, Itsuki Anzai, Yuzy Fauzyah, Yusuke Maeda, Wataru Kamitani, Takasuke Fukuhara, Yoshiharu Matsuura

  Cell reports 35 3 109014 - 109014 2021年04月01日 

  Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been identified as the causative agent of coronavirus disease 2019 (COVID-19). Although multiple mutations have been observed in SARS-CoV-2, functional analysis of each mutation of SARS-CoV-2 has been limited by the lack of convenient mutagenesis methods. In this study, we establish a PCR-based, bacterium-free method to generate SARS-CoV-2 infectious clones. Recombinant SARS-CoV-2 could be rescued at high titer with high accuracy after assembling 10 SARS-CoV-2 cDNA fragments by circular polymerase extension reaction (CPER) and transfection of the resulting circular genome into susceptible cells. The construction of infectious clones for reporter viruses and mutant viruses could be completed in two simple steps: introduction of reporter genes or mutations into the desirable DNA fragments (∼5,000 base pairs) by PCR and assembly of the DNA fragments by CPER. This reverse genetics system may potentially advance further understanding of SARS-CoV-2.
• Ponesimod suppresses hepatitis B virus infection by inhibiting endosome maturation.

  Yuzy Fauzyah, Chikako Ono, Shiho Torii, Itsuki Anzai, Rigel Suzuki, Takuma Izumi, Yuhei Morioka, Yusuke Maeda, Toru Okamoto, Takasuke Fukuhara, Yoshiharu Matsuura

  Antiviral research 186 104999 - 104999 2020年12月18日 

  The discovery of novel antivirals to treat hepatitis B virus (HBV) infection is urgently needed, as the currently available drugs mainly target viral proteins at replication step, whereas host factors also play significant roles in HBV infection. Although numerous studies have reported candidate drugs for HBV treatment, there remains a need to find a new drug that may target other steps of the HBV life cycle. In this study, by drug screening of a 533 G-protein-coupled receptors (GPCRs)-associated compound library, we identified ponesimod, a selective agonist of sphingosine-1-phosphate receptor 1 (S1P1), as a drug candidate for the suppression of HBV infection. However, the anti-HBV effect of ponesimod is independent of S1P1 and other sphingosine-1-phosphate receptors (S1PRs). Treatment with ponesimod at an early step of infection but not at a post-entry step significantly reduced the HBV relaxed circular DNA (rcDNA) level in a dose-dependent manner. Ponesimod treatment did not inhibit attachment, binding, or internalization of HBV particles via endocytosis through an interaction with sodium taurocholate cotransporting polypeptide (NTCP) or epidermal growth factor receptor (EGFR). Importantly, during the transportation of HBV particles to the nucleus, co-localization of HBV with early endosomes but not with late endosomes and lysosomes was induced by the treatment with ponesimod, suggesting that ponesimod interferes with the conversion of early endosomes to late endosomes without significant damage to cellular growth. Conclusion: Ponesimod is a promising anti-HBV drug targeting the endosome maturation of HBV. This finding can be applied to the development of novel antivirals that target the trafficking pathway of HBV particles.
• UBQLN4 recognizes mislocalized transmembrane domain proteins and targets these to proteasomal degradation.

  Rigel Suzuki, Hiroyuki Kawahara

  EMBO reports 17 6 842 - 57 2016年06月 [査読有り][通常論文]
   

  The majority of transmembrane proteins are integrated into the endoplasmic reticulum (ER) by virtue of a signal sequence-mediated co-translational process. However, a substantial portion of transmembrane proteins fails to reach the ER, leading to mislocalized cytosolic polypeptides. Their appropriate recognition and removal are of the utmost importance to avoid proteotoxic stress. Here, we identified UBQLN4 as a BAG6-binding factor that eliminates newly synthesized defective polypeptides. Using a truncated transmembrane domain protein whose degradation occurs during a pre-ER incorporation process as a model, we show that UBQLN4 recognizes misassembled proteins in the cytoplasm and targets these to the proteasome. We suggest that the exposed transmembrane segment of the defective polypeptides is essential for the UBQLN4-mediated substrate discrimination. Importantly, UBQLN4 recognizes not only the defective model substrate but also a pool of endogenous defective proteins that were induced by the depletion of the SRP54 subunit of the signal recognition particle. This study identifies a novel quality control mechanism for newly synthesized and defective transmembrane domain polypeptides that fail to reach their correct destination at the ER membrane.
• A conserved island of BAG6/Scythe is related to ubiquitin domains and participates in short hydrophobicity recognition.

  Hirofumi Tanaka, Toshiki Takahashi, Yiming Xie, Ryosuke Minami, Yuko Yanagi, Mizuki Hayashishita, Rigel Suzuki, Naoto Yokota, Masumi Shimada, Tsunehiro Mizushima, Naoyuki Kuwabara, Ryuichi Kato, Hiroyuki Kawahara

  The FEBS journal 283 4 662 - 77 2016年02月 [査読有り][通常論文]
   

  BAG6 (also called Scythe) interacts with the exposed hydrophobic regions of newly synthesized proteins and escorts them to the degradation machinery through mechanisms that remain to be elucidated. In this study, we provide evidence that BAG6 physically interacts with the model defective protein substrate CL1 in a manner that depends directly on its short hydrophobicity. We found that the N terminus of BAG6 contains an evolutionarily conserved island tentatively designated the BAG6 ubiquitin-linked domain. Partial deletion of this domain in the BAG6 N-terminal fragment abolished in cell recognition of polyubiquitinated polypeptides as well as the hydrophobicity-mediated recognition of the CL1 degron in cell and in vitro. These observations suggest a mechanism whereby the BAG6 ubiquitin-linked domain provides a platform for discriminating substrates with shorter hydrophobicity stretches as a signal for defective proteins.

その他活動・業績

• 高速リーバースジェネティクスのキャップ非依存性+ssRNAウイルスへの応用

  山本紘嵩, 田村友和, 伊藤駿, 鈴木理滋, 福原崇介 日本ウイルス学会学術集会プログラム・予稿集(Web) 69th 2022年
• HBV感染に関与するRNA結合タンパク質の同定とその機能解析

  小林展大, 小林展大, 齋藤智哉, 齋藤智哉, 鈴木理滋, 田村友和, 武冨紹信, 福原崇介 日本ウイルス学会学術集会プログラム・予稿集(Web) 69th 2022年
• 数理モデルと分子動力学シミュレーションを用いたレムデシビル耐性SARS-CoV-2変異株の解析

  鈴木理滋, 鳥居志保, 鳥居志保, キム クァンス, 小関準, 岩波翔也, 藤田泰久, チョン ヨンダム, 田村友和, 松浦善治, 島村徹平, 岩見真吾, 岩見真吾, 岩見真吾, 岩見真吾, 岩見真吾, 岩見真吾, 福原崇介 日本ウイルス学会学術集会プログラム・予稿集(Web) 69th 2022年
• フラビウイルスの粒子産生における分泌型NS1タンパク質の役割

  田村友和, 田村友和, 鳥居志保, 鳥居志保, 梶原健太郎, 安齋樹, 藤岡容一朗, 野田暉翔, 田鍬修平, 森岡佑平, 森岡佑平, 鈴木理滋, YUZY Fauzyah, 小野慎子, 小野慎子, 大場雄介, 岡田雅人, 福原崇介, 福原崇介, 松浦善治, 松浦善治 日本ウイルス学会学術集会プログラム・予稿集(Web) 69th 2022年
• 肝疾患患者の変異株に対するワクチン効果の評価系の確立と免疫抑制の影響

  伊藤駿, 冨山貴央, 鈴木理滋, 田村友和, 吉住朋晴, 福原崇介 日本ウイルス学会学術集会プログラム・予稿集(Web) 69th 2022年
• SARS-CoV-2の新規リバースジェネティクス法の確立

  鳥居志保, 小野慎子, 鈴木理滋, 森岡佑平, 安齋樹, FAUZYAH Yuzy, 前田裕輔, 神谷亘, 福原崇介, 福原崇介, 松浦善治 日本分子生物学会年会プログラム・要旨集(Web) 43rd 2020年

共同研究・競争的資金等の研究課題

• オートファジーを介した新型コロナウイルスの新しい病原性機構の解明

  日本学術振興会：科学研究費助成事業 若手研究

  研究期間 : 2021年04月 -2023年03月 

  代表者 : 鈴木 理滋
• HBc抗体陽性非ウイルス性肝癌のHBVゲノム挿入部位の同定及び発癌機構の解明

  日本学術振興会：科学研究費助成事業 研究活動スタート支援

  研究期間 : 2020年09月 -2022年03月 

  代表者 : 鈴木 理滋
• ＵＢＱＬＮ４複合体が司る膜タンパク質の新しい品質管理機構

  日本学術振興会：科学研究費助成事業 特別研究員奨励費

  研究期間 : 2014年04月 -2017年03月 

  代表者 : 鈴木 理滋

   

  本研究の目的は、埋め込みに失敗した不良膜タンパク質の代謝メカニズムの解明である。この目的を達成するため、本研究者はこれまで不良膜タンパク質モデルをデザインし、このモデル基質の認識・分解に関わる因子としてUBALN4を同定した。しかしながら、UBQLN4が不良膜タンパク質モデルだけでなく、細胞内に生じうる内在性不良膜タンパク質の分解に関与するかは謎に満ちていた。そこで本研究者は内在性不良膜タンパク質を誘導するため、トランスロコン特異的阻害剤を用いて検証した。UBQLN4 KD条件下かつトランスロコン阻害剤を用いると、コントロールKD条件下に比べ、細胞内に蓄積するユビキチン化タンパク質量が増加した。また、免疫染色法を行った結果、ユビキチン陽性凝集体が観察された。この結果はUBQLN4が細胞内に生じる内在性不良膜タンパク質の分解に関わることを示唆している。次に本研究者は蓄積したユビキチン化タンパク質の中に膜タンパク質が含まれていることを検証するため、一回膜貫通型タンパク質VCAM1の挙動を調査した。VCAM1はトランスロコン阻害剤存在下で不良膜タンパク質として速やかに分解されるタンパク質である。UBQLN4 KD条件下かつトランスロコン阻害剤存在下で、不良VCAM1が安定化すること、また可溶性・不溶性分画を行った結果、不溶性画分に不良VCAM1が多く存在することを見出した。これらの結果から、UBQLN4は内在性不良膜タンパク質の分解に関与することを初めて明らかにした。

教育活動情報

主要な担当授業