研究者データベース

山口 聡一郎(ヤマグチ ソウイチロウ)
獣医学研究院 獣医学部門 基礎獣医科学分野
准教授

基本情報

所属

  • 獣医学研究院 獣医学部門 基礎獣医科学分野

職名

  • 准教授

学位

  • 博士(獣医学)(2009年03月 北海道大学)

科研費研究者番号

  • 50596864

J-Global ID

研究キーワード

  • イオンチャネル   トランスポーター   

研究分野

  • ライフサイエンス / 生理学 / イオンチャネル
  • ライフサイエンス / 獣医学

職歴

  • 2018年08月 - 現在 北海道大学 大学院獣医学研究院 基礎獣医科学部門 生理学教室 准教授
  • 2013年11月 - 2018年08月 北海道大学大学院獣医学研究科 比較形態機能学講座薬理学教室 助教
  • 2012年10月 - 2013年10月 北海道大学大学院獣医学研究科比較形態機能学講座薬理学教室 特任助教
  • 2010年09月 - 2012年10月 新潟大学医歯学総合研究科器官生理学分野 助教
  • 2009年04月 - 2010年08月 テキサス大学サウスウェスタンメディカルセンター (米国) 博士研究員

学歴

  • 2005年04月 - 2009年03月   北海道大学   大学院獣医学研究科
  • 1999年04月 - 2005年03月   北海道大学   獣医学部

所属学協会

  • 日本生理学会   日本獣医学会   日本薬理学会   

研究活動情報

論文

  • Taisuke Kitano, Ryota Eguchi, Yuko Okamatsu-Ogura, Soichiro Yamaguchi, Ken-Ichi Otsuguro
    Journal of pharmacological sciences 145 3 228 - 240 2021年03月 [査読有り]
     
    Astrocytes are glial cells with numerous fine processes which are important for the functions of the central nervous system. The activation of β-adrenoceptors induces process formation of astrocytes via cyclic AMP (cAMP) signaling. However, the role of α-adrenoceptors in the astrocyte morphology has not been elucidated. Here, we examined it by using cultured astrocytes from neonatal rat spinal cords and cortices. Exposure of these cells to noradrenaline and the β-adrenoceptor agonist isoproterenol increased intracellular cAMP levels and induced the formation of processes. Noradrenaline-induced process formation was enhanced with the α1-adrenoceptor antagonist prazosin and α2-adrenoceptor antagonist atipamezole. Atipamezole also enhanced noradrenaline-induced cAMP elevation. Isoproterenol-induced process formation was not inhibited by the α1-adrenoceptor agonist phenylephrine but was inhibited by the α2-adrenoceptor agonist dexmedetomidine. Dexmedetomidine also inhibited process formation induced by the adenylate cyclase activator forskolin and the membrane-permeable cAMP analog dibutyryl-cAMP. Moreover, dexmedetomidine inhibited cAMP-independent process formation induced by adenosine or the Rho-associated kinase inhibitor Y27632. In the presence of propranolol, noradrenaline inhibited Y27632-induced process formation, which was abolished by prazosin or atipamezole. These results demonstrate that α-adrenoceptors inhibit both cAMP-dependent and -independent astrocytic process formation.
  • Takeshi Nii, Ryota Eguchi, Soichiro Yamaguchi, Ken-Ichi Otsuguro
    European journal of pharmacology 891 173684 - 173684 2021年01月15日 [査読有り]
     
    Hydrogen sulfide (H2S) has a variety of physiological functions. H2S reportedly increases intracellular Ca2+ concentration ([Ca2+]i) in astrocytes. However, the precise mechanism and functional role of this increase are not known. Here, we examined the effects of H2S on [Ca2+]i in astrocytes from the rat spinal cord and whether H2S affects ATP-induced Ca2+ signaling, which is known to be involved in synaptic function. Na2S (150 μM), an H2S donor, produced a nontoxic increase in [Ca2+]i. The [Ca2+]i increase by Na2S was inhibited by Ca2+ depletion in the endoplasmic reticulum (ER) but not by removal of extracellular Ca2+, indicating that H2S releases Ca2+ from the ER. On the other hand, Na2S inhibited ATP-induced [Ca2+]i increase when Na2S clearly increased [Ca2+]i in the astrocytes, which was not suppressed by a reducing agent. In addition, Na2S had no effect on intracellular cyclic AMP (cAMP) level. These results indicate that oxidative post-translational modification of proteins and cAMP are not involved in the inhibitory effect of H2S on ATP-induced Ca2+ signaling. We conclude that H2S indirectly inhibits ATP-induced Ca2+ signaling by decreasing Ca2+ content in the ER in astrocytes. In this way, H2S may influence intercellular communication between astrocytes and neurons, thereby contributing to neuronal signaling in the nervous system.
  • Soichiro Yamaguchi, Maho Hamamura, Ken-Ichi Otsuguro
    International journal of molecular sciences 21 18 2020年09月04日 [査読有り][通常論文]
     
    Mechanical stimuli caused by sound waves are detected by hair cells in the cochlea through the opening of mechanoelectrical transduction (MET) channels. Transmembrane channel-like protein 1 (TMC1) has been revealed to be the pore-forming component of the MET channel. The two splice variants for mouse Tmc1 (mTmc1ex1 and mTmc1ex2) were reported to be expressed in the cochlea of infant mice, though only the sequence of mTmc1ex2 had been deposited in GenBank. However, due to the presence of an upstream open reading frame (uORF) and the absence of a typical Kozak sequence in mTmc1ex2, we questioned whether mTMC1 was translated from mTmc1ex2. Therefore, in this study, we evaluated which splice variant was protein-coding mRNA. Firstly, the results of RT-PCR and cDNA cloning of mTmc1 using mRNA isolated from the cochlea of five-week-old mice suggested that more Tmc1ex1 were expressed than mTmc1ex2. Secondly, mTMC1 was translated from mTmc1ex1 but not from mTmc1ex2 in a heterologous expression system. Finally, analyses using site-directed mutagenesis revealed that the uORF and the weak Kozak sequence in mTmc1ex2 prevented the translation of mTMC1 from mTmc1ex2. These results suggest that mTmc1ex1 plays a main role in the expression of mTMC1 in the mouse cochlea, and therefore, mTmc1ex1 should be the mRNA for mTMC1 hereafter.
  • Soichiro Yamaguchi, Akira Tanimoto, Shinsuke Iwasa, Ken-Ichi Otsuguro
    International journal of molecular sciences 20 8 2019年04月24日 [査読有り][通常論文]
     
    Transient receptor potential melastatin member 4 (TRPM4) and 5 (TRPM5) channels are Ca2+-activated nonselective cation channels. Intracellular Ca2+ is the most important regulator for them to open, though PI(4,5)P2, a membrane phosphoinositide, has been reported to regulate their Ca2+-sensitivities. We previously reported that negatively-charged amino acid residues near and in the TRP domain are necessary for the normal Ca2+ sensitivity of TRPM4. More recently, a cryo-electron microscopy structure of Ca2+-bound (but closed) TRPM4 was reported, proposing a Ca2+-binding site within an intracellular cavity formed by S2 and S3. Here, we examined the functional effects of mutations of the amino acid residues related to the proposed Ca2+-binding site on TRPM4 and also TRPM5 using mutagenesis and patch clamp techniques. The mutations of the amino acid residues of TRPM4 and TRPM5 reduced their Ca2+-sensitivities in a similar way. On the other hand, intracellular applications of PI(4,5)P2 recovered Ca2+-sensitivity of desensitized TRPM4, but its effect on TRPM5 was negligible. From these results, the Ca2+-binding sites of TRPM4 and TRPM5 were shown to be formed by the same amino acid residues by functional analyses, but the impact of PI(4,5)P2 on the regulation of TRPM5 seemed to be smaller than that on the regulation of TRPM4.
  • Kitano T, Kobayashi T, Yamaguchi S, Otsuguro KI
    Journal of veterinary pharmacology and therapeutics 42 2 243 - 247 2019年03月 [査読有り][通常論文]
  • Eguchi R, Yamaguchi S, Otsuguro KI
    Journal of pharmacological sciences 139 2 98 - 104 2019年02月 [査読有り][通常論文]
  • Ujike A, Kuraishi T, Yamaguchi S, Eguchi R, Kitano T, Kamise J, Ito S, Otsuguro KI
    European journal of pharmacology 821 88 - 96 2018年02月15日 [査読有り][通常論文]
     
    H2S has excitatory and inhibitory effects on Ca2+ signals via transient receptor potential ankyrin 1 (TRPA1) and ATP-sensitive K+ channels, respectively. H2S converts intracellularly to polysulfides, which are more potent agonists for TRPA1 than H2S. Under inflammatory conditions, changes in the expression and activity of these H2S target channels and/or the conversion of H2S to polysulfides may modulate H2S effects. Effects of proinflammatory cytokines on H2S-induced Ca2+ signals and polysulfide production in RIN14B cells were examined using fluorescence imaging with fura-2 and SSP4, respectively. Na2S, a H2S donor, induced 1) the inhibition of spontaneous Ca2+ signals, 2) inhibition followed by [Ca2+]i increase, and 3) rapid [Ca2+]i increase without inhibition in 50% (23/46), 22% (10/46), and 17% (8/46) of cells tested, respectively. IL-1β augmented H2S-induced [Ca2+]i increases, which were inhibited by TRPA1 and voltage-dependent L-type Ca2+ channel blockers. However, IL-1β treatment did not affect [Ca2+]i increases evoked by a TRPA1 agonist or high concentration of KCl. Na2S increased intracellular polysulfide levels, which were enhanced by IL-1β treatment. A NOS inhibitor suppressed the increased polysulfide production and [Ca2+]i increase in IL-1β-treated cells. These results suggest that IL-1β augments H2S-induced [Ca2+]i increases via the conversion of H2S to polysulfides through NO synthesis, but not via changes in the activity and expression of target channels. Polysulfides may play an important role in the effects of H2S during inflammation.
  • Soichiro Yamaguchi, Ken-ichi Otsuguro
    NEUROSCIENCE LETTERS 653 139 - 145 2017年07月 [査読有り][通常論文]
     
    Mas-related G-protein coupled receptor B4 (MrgprB4) has been reported to be expressed in the dorsal root ganglion (DRG) neurons which detect stroking of hairy skin of mice. However, the mechanisms by which the MrgprB4 positive (+) neurons respond to adequate stimulus remain unsolved as it was also reported that electrophysiological analysis of cultured MrgprB4+ neurons did not reveal responses to mechanical stimuli. Contrary to the observation, however, in this study we show that the MrgprB4+ neurons functionally express a mechanically activated channel using DRG neurons dissociated from genetically-modified mice whose MrgprB4+ neurons express a red fluorescent protein. Hypotonicity-induced cell swelling increased intracellular Ca2+ concentrations ([Ca2+](i)) of MrgprB4+ neurons. The [Ca2+](i) increases were prevented by extracellular Ca2+ removal and by applications of nonselective Piezo channel blockers. Patch clamp analysis revealed that the MrgprB4+ neurons exhibited rapidly-adapting mechanically-activated currents. The MrgprB4+ neurons were stained with anti-Piezo2 antibody. These results raise the possibility that the MrgprB4+ neurons directly detect the stroking-like stimuli of hairy skin. (C) 2017 Elsevier B.V. All rights reserved.
  • Dugar Delgermurun, Soichiro Yamaguchi, Osamu Ichii, Yasuhiro Kon, Shigeo Ito, Ken-ichi Otsuguro
    COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY C-TOXICOLOGY & PHARMACOLOGY 187 43 - 49 2016年09月 [査読有り][通常論文]
     
    Epithelioid cells in the chicken thoracic aorta are chemoreceptor cells that release 5-HT in response to hypoxia. It is likely that these cells play a role in chemoreception similar to that of glomus cells in the carotid bodies of mammals. Recently, H2S was reported to be a key mediator of carotid glomus cell responses to hypoxia. The aim of the present study was to reveal the mechanism of action of H2S on 5-HT outflow from chemoreceptor cells in the chicken thoracic aorta. The 5-HT outflow induced by NaHS, an H2S donor, and Na2S3, a polysulfide, was measured by using a HPLC equipped with an electrochemical detector. NaHS (0.3-3 mM) caused a concentration-dependent increase in 5-HT outflow, which was significantly inhibited by the removal of extracellular Ca2+. outflow induced by NaHS (0.3 mM) was also significantly inhibited by voltage-dependent L- and N-type Ca2+ channel blockers and a selective TRPA1 channel blocker. Cinnamaldehyde, a TRPA1 agonist, mimicked the secretory response to H2S. 5-HT outflow induced by Na2S3 (10 M) was also inhibited by the TRPA1 channel blocker. Furthermore, the expression of TRPA1 was localized to 5-HT-containing chemoreceptor cells in the aortic wall. These findings suggest that the activation of TRPA1 and voltage-dependent Ca2+ channels is involved in H2S-evoked 5-HT release from chemoreceptor cells in the chicken aorta. (C) 2016 Elsevier Inc. All rights reserved.
  • Dugar Delgermurun, Shigeo Ito, Toshio Ohta, Soichiro Yamaguchi, Ken-ichi Otsuguro
    JOURNAL OF VETERINARY MEDICAL SCIENCE 78 1 71 - 76 2016年01月 [査読有り][通常論文]
     
    Chemoreceptor cells aggregating in clusters in the chicken thoracic aorta contain 5-hydroxytryptamine (5-HT) and have voltage dependent ion channels and nicotinic acetylcholine receptors, which are characteristics typically associated with neurons. The aim of the present study was to investigate the effects of 5-HT uptake inhibitors, fluvoxamine, fluoxetine and clomipramine (CLM), and amphetamine derivatives, p-chloroamphetamine (PCA) and methamphetamine (MET), on endogenous 5-HT outflow from the isolated chick thoracic aorta in vitro. 5-HT was measured by using a HPLC system with electrochemical detection. The amphetamine derivatives and 5-HT uptake inhibitors caused concentration-dependent increases in endogenous 5-HT outflow. PCA was about ten times more effective in eliciting 5-HT outflow than MET. The 5-HT uptake inhibitors examined had similar potency for 5-HT outflow. PCA and CLM increased 5-HT outflow in a temperature-dependent manner. The outflow of 5-HT induced by PCA or 5-HT uptake inhibitors was independent of extracellular Ca2+ concentration. The 5-HT outflow induced by CLM, but not that by PCA, was dependent on the extracellular NaCl concentration. These results suggest that the 5-HT uptake system of 5-HT-containing chemoreceptor cells in the chicken thoracic aorta has characteristics similar to those of 5-HT-containing neurons in the mammalian central nervous system (CNS).
  • Ken-ichi Otsuguro, Yuki Tomonari, Saori Otsuka, Soichiro Yamaguchi, Yasuhiro Kon, Shigeo Ito
    NEUROPHARMACOLOGY 97 160 - 170 2015年10月 [査読有り][通常論文]
     
    Adenosine kinase (AK) inhibitor is a potential candidate for controlling pain, but some AK inhibitors have problems of adverse effects such as motor impairment. ABT-702, a non-nucleoside AK inhibitor, shows analgesic effect in animal models of pain. Here, we investigated the effects of ABT-702 on synaptic transmission via nociceptive and motor reflex pathways in the isolated spinal cord of neonatal rats. The release of adenosine from the spinal cord was measured by HPLC. ABT-702 inhibited slow ventral root potentials (sVRPs) in the nociceptive pathway more potently than monosynaptic reflex potentials (MSRs) in the motor reflex pathway. The inhibitory effects of ABT-702 were mimicked by exogenously applied adenosine, blocked by 8CPT (8-cyclopentyl-1,3-dipropylxanthine), an adenosine A(1) receptor antagonist, and augmented by EHNA (erythro-9-(2-hydroxy-3-nonyl) adenine), an adenosine deaminase (ADA) inhibitor. Equilibrative nucleoside transporter (ENT) inhibitors reversed the effects of ABT-702, but not those of adenosine. ABT-702 released adenosine from the spinal cord, an effect that was also reversed by ENT inhibitors. The ABT-702-facilitated release of adenosine by way of ENTs inhibits nociceptive pathways more potently than motor reflex pathways in the spinal cord via activation of A1 receptors. This feature is expected to lead to good analgesic effects, but, caution may be required for the use of AK inhibitors in the case of ADA dysfunction or a combination with ENT inhibitors. (C) 2015 Elsevier Ltd. All rights reserved.
  • Ayako Ujike, Ken-ichi Otsuguro, Ryo Miyamoto, Soichiro Yamaguchi, Shigeo Ito
    EUROPEAN JOURNAL OF PHARMACOLOGY 764 463 - 470 2015年10月 [査読有り][通常論文]
     
    Hydrogen sulfide (H2S) reportedly acts as a gasotransmitter because it mediates various cellular responses through several ion channels including ATP-sensitive K+ (K-ATP) channels and transient receptor potential (TRP) A1 channels. H2S can activate both K-ATP, and TRPA1 channels at a similar concentration range. In a single cell expressing both channels, however, it remains unknown what happens when both channels are simultaneously activated by H2S. In this study, we examined the effects of H2S on RIN14B cells that express both K-ATP and TRPA1 channels. RIN14B cells showed several intracellular Ca2+ concentration ([Ca2+](i)) responses to NaHS (300 mu M), an H2S donor, i.e., inhibition of spontaneous Ca2+ oscillations (37%), inhibition followed by [Ca2+](i) increase (24%), and a rapid increase in [Ca2+](i) (25%). K-ATP channel blockers, glibenclamide or tolbutamide, abolished any inhibitory effects of NaHS and enhanced NaHS-mediated [Ca2+](i) increases, which were inhibited by extracellular Ca2+ removal, HC030031 (a TRPA1 antagonist), and disulfide bond-reducing agents. NaHS induced 5-hydroxytryptamine (5-HT) release from RIN14B cells, which was also inhibited by TRPA1 antagonists. These results indicate that H2S has both inhibitory and excitatory effects by opening K-ATP and TRPA1 channels, respectively, in RIN14B cells, suggesting potential bidirectional modulation of secretory functions. (C) 2015 Elsevier B.V. All rights reserved.
  • Kobayashi T, Otsuguro K, Yamaguchi S, Ito S
    European journal of pharmacology 761 321 - 329 2015年08月 [査読有り][通常論文]
     
    Alpha-2A adrenergic receptor (AR) subtype plays an important role in the analgesic effect of alpha(2)-AR agonists. Here, we examined the effects of alpha(2)-AR agonists, dexmedetomidine and xylazine, on spinal synaptic transmission in newborn C57BL/6J and alpha(2A)-AR mutant mice. Spinal reflex potentials, the monosynaptic reflex potential (MSR) and the slow ventral root potential (sVRP), were measured in isolated spinal cords. The compound action potential was measured in isolated lumbar nerve. Dexmedetomidine and xylazine suppressed both the MSR and sVRP in a concentration-dependent manner. In alpha(2A)-AR mutant mice, sVRP suppression by dexmedetomidine was greatly weakened, while that by xylazine (30-100 mu M) showed only slight attenuation. A high concentration (300 mu M) of xylazine completely suppressed the sVRP, even in alpha(2A)-AR mutant mice spinal cords, and also suppressed the compound action potential. MSR suppression by these alpha(2)-AR agonists had no difference between wild-type and alpha(2A)-AR mutant mice. These results suggest that sVRP suppression by dexmerletomidine and xylazine is mainly mediated by alpha(2A)-AR. In addition, a high concentration of xylazine inhibits conduction of the action potential, which is not mediated by alpha(2A)-AR. alpha(2)-AR is not responsible for the dexmedetomidineand xylazine-mediated inhibition of the MSR. (C) 2015 Elsevier B.V. All rights reserved.
  • Miyamoto R, Otsuguro KI, Yamaguchi S, Ito S
    Neuroscience research 97 52 - 59 2015年08月 [査読有り][通常論文]
     
    Cystathionine beta-synthase (CBS), expressed in astrocytes, generates a gaseous neuromodulator, hydrogen sulfide (H2S) in the central nervous system (CNS). However, little is known about the regulatory mechanisms of astrocytic CBS expression and activity. This study evaluated the influence of neurons on astrocytic CBS expression by employing multiple culture systems. Substantial CBS expression was observed in the intact neonatal rat spinal cord, while CBS content was markedly reduced in an astrocyte-enriched culture prepared from the neonatal spinal cord. Immunofluorescence analysis confirmed the localization of spinal cord CBS in astrocytes, but not in neurons. Although CBS expression was weak in the embryonic rat spinal cord, enzyme levels were time-dependently increased in a neuron/astrocyte mixed culture originating from embryonic spinal cord. The reduced CBS expression in isolated neonatal astrocytes was restored by co-culture with embryonic neurons. Together with the observed CBS expression levels, H2S production was relatively low in astrocytes cultured alone, but was considerably higher in astrocytes cultured with neurons. These results indicate that neurons are essential for maintaining the expression and H2S-producing activity of astrocytic CBS in the rat spinal cord. (C) 2015 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.
  • Ryota Eguchi, Sanae Akao, Ken-ichi Otsuguro, Soichiro Yamaguchi, Shigeo Ito
    JOURNAL OF PHARMACOLOGICAL SCIENCES 128 1 47 - 53 2015年05月 [査読有り][通常論文]
     
    Extracellular adenosine is a neuromodulator in the central nervous system. Astrocytes mainly participate in adenosine production, and extracellular adenosine accumulates under physiological and pathophysiological conditions. Inhibition of intracellular adenosine metabolism and reduction of the external Ca2+ concentration ([Ca2+](e)) participate in adenosine accumulation, but the precise mechanisms remain unclear. This study investigated the mechanisms underlying extracellular adenosine accumulation in cultured rat spinal astrocytes. The combination of adenosine kinase and deaminase (ADK/ADA) inhibition and a reduced [Ca2+](e) increased the extracellular adenosine level. ADK/ADA inhibitors increased the level of extracellular adenosine but not of adenine nucleotides, which was suppressed by inhibition of equilibrative nucleoside transporter (ENT) 2. Unlike ADK/ADA inhibition, a reduced [Ca2+](e) increased the extracellular level not only of adenosine but also of ATP. This adenosine increase was enhanced by ENT2 inhibition, and suppressed by sodium polyoxotungstate (ecto-nucleoside triphosphate diphosphohydrolase inhibitor). Gap junction inhibitors suppressed the increases in adenosine and adenine nucleotide levels by reduction of [Ca2+](e). These results indicate that extracellular adenosine accumulation by ADK/ADA inhibition is due to the adenosine release via ENT2, while that by reduction of [Ca2+] e is due to breakdown of ATP released via gap junction hemichannels, after which ENT2 incorporates adenosine into the cells. (C) 2015 The Authors. Production and hosting by Elsevier B.V. on behalf of Japanese Pharmacological Society.
  • Soichiro Yamaguchi, Akira Tanimoto, Ken-ichi Otsuguro, Hiroshi Hibino, Shigeo Ito
    JOURNAL OF BIOLOGICAL CHEMISTRY 289 51 35265 - 35282 2014年12月 [査読有り][通常論文]
     
    Transient receptor potential (TRP) channel melastatin subfamily member 4 (TRPM4) is a broadly expressed nonselective monovalent cation channel. TRPM4 is activated by membrane depolarization and intracellular Ca2+, which is essential for the activation. The Ca2+ sensitivity is known to be regulated by calmodulin and membrane phosphoinositides, such as phosphatidylinositol 4,5-bisphosphate (PI(4,5)P-2). Although these regulators must play important roles in controlling TRPM4 activity, mutation analyses of the calmodulin-binding sites have suggested that Ca2+ binds to TRPM4 directly. However, the intrinsic binding sites in TRPM4 remain to be elucidated. Here, by using patch clamp and molecular biological techniques, we show that there are at least two functionally different divalent cation-binding sites, and the negatively charged amino acids near and in the TRP domain in the C-terminal tail of TRPM4 (Asp-1049 and Glu-1062 of rat TRPM4) are required for maintaining the normal Ca2+ sensitivity of one of the binding sites. Applications of Co2+, Mn2+, or Ni2+ to the cytosolic side potentiated TRPM4 currents, increased the Ca2+ sensitivity, but were unable to evoke TRPM4 currents without Ca2+. Mutations of the acidic amino acids near and in the TRP domain, which are conserved in TRPM2, TRPM5, and TRPM8, deteriorated the Ca2+ sensitivity in the presence of Co2+ or PI(4,5)P-2 but hardly affected the sensitivity to Co2+ and PI(4,5)P-2. These results suggest a novel role of the TRP domain in TRPM4 as a site responsible for maintaining the normal Ca2+ sensitivity. These findings provide more insights into the molecular mechanisms of the regulation of TRPM4 by Ca2+.
  • Ryo Miyamoto, Ken-ichi Otsuguro, Soichiro Yamaguchi, Shigeo Ito
    JOURNAL OF NEUROCHEMISTRY 130 1 29 - 40 2014年07月 [査読有り][通常論文]
     
    Hydrogen sulfide (H2S) is a gaseous neuromodulator produced from L-cysteine. H2S is generated by three distinct enzymatic pathways mediated by cystathionine -lyase (CSE), cystathionine -synthase (CBS), and mercaptopyruvate sulfurtransferase (MPST) coupled with cysteine aminotransferase (CAT). This study investigated the relative contributions of these three pathways to H2S production in PC12 cells (rat pheochromocytoma-derived cells) and the rat dorsal root ganglion. CBS, CAT, and MPST, but not CSE, were expressed in the cells and tissues, and appreciable amounts of H2S were produced from L-cysteine in the presence of -ketoglutarate, together with dithiothreitol. The production of H2S was inhibited by a CAT inhibitor (aminooxyacetic acid), competitive CAT substrates (L-aspartate and oxaloacetate), and RNA interference (RNAi) against MPST. Immunocytochemistry revealed a mitochondrial localization of MPST in PC12 cells and dorsal root ganglion neurons, and the amount of H2S produced by CAT/MPST at pH 8.0, a physiological mitochondrial matrix pH, was comparable to that produced by CSE and CBS in the liver and the brain, respectively. Furthermore, H2S production was markedly increased by alkalization. These results indicate that CAT and MPST are primarily responsible for H2S production in peripheral neurons, and that the regulation of mitochondrial metabolism may influence neuronal H2S generation. In the peripheral nervous system, hydrogen sulfide (H2S) has been implicated in neurogenic pain or hyperalgesia. This study provides evidence that H2S is synthesized in peripheral neurons through two mitochondrial enzymes, cysteine aminotransferase (CAT) and mercaptopyruvate sulfurtransferase (MPST). We propose that mitochondrial metabolism plays key roles in the physiology and pathophysiology of the peripheral nervous system via regulation of neuronal H2S production.
  • Soichiro Yamaguchi, Toru Ishikawa
    FEBS LETTERS 588 5 672 - 677 2014年03月 [査読有り][通常論文]
     
    Although AHCYL2 (long-IRBIT) is highly homologous to IRBIT, which regulates ion-transporting proteins including the electrogenic Na+-HCO(3)(-)cotransporter NBCe1-B, its functions are poorly understood. Here, we found that AHCYL2 interacts with NBCe1-B in bovine parotid acinar cells using yeast two-hybrid, immunofluorescence confocal microscopy and co-immunoprecipitation analyses. Whole-cell patch-clamp experiments revealed that co-expression of AHCYL2 reduces the apparent affinity for intracellular Mg2+ in inhibition of NBCe1-B currents specifically in a HCO3- -deficient cellular condition. Our data unveil AHCYL2 as a potential regulator of NBCe1-B in mammalian cells. We propose that cytosolic ionic condition appropriate for AHCYL2 to function might be different from IRBIT. (C) 2014 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
  • Naoko Adachi, Takamasa Yoshida, Fumiaki Nin, Genki Ogata, Soichiro Yamaguchi, Toshihiro Suzuki, Sizuo Komune, Yasuo Hisa, Hiroshi Hibino, Yoshihisa Kurachi
    JOURNAL OF PHYSIOLOGY-LONDON 591 18 4459 - 4472 2013年09月 [査読有り][通常論文]
     
    The endocochlear potential (EP) of +80 mV in the scala media, which is indispensable for audition, is controlled by K+ transport across the lateral cochlear wall. This wall includes two epithelial barriers, the syncytium and the marginal cells. The former contains multiple cell types, such as fibrocytes, which are exposed to perilymph on their basolateral surfaces. The apical surfaces of the marginal cells face endolymph. Between the two barriers lies the intrastrial space (IS), an extracellular space with a low K+ concentration ([K+]) and a potential similar to the EP. This intrastrial potential (ISP) dominates the EP and represents the sum of the diffusion potential elicited by a large K+ gradient across the apical surface of the syncytium and the syncytium's potential, which is slightly positive relative to perilymph. Although a K+ transport system in fibrocytes seems to contribute to the EP, the mechanism remains uncertain. We examined the electrochemical properties of the lateral wall of guinea pigs with electrodes sensitive to potential and K+ while perfusing into the perilymph of the scala tympani blockers of Na+,K+-ATPase, the K+ pump thought to be essential to the system. Inhibiting Na+,K+-ATPase barely affected [K+] in the IS but greatly decreased [K+] within the syncytium, reducing the K+ gradient across its apical surface. The treatment hyperpolarized the syncytium only moderately. Consequently, both the ISP and the EP declined. Fibrocytes evidently use the Na+,K+-ATPase to achieve local K+ transport, maintaining the syncytium's high [K+] that is crucial for the K+ diffusion underlying the positive ISP.
  • Yamaguchi S, Ishikawa T
    Biochemical and biophysical research communications 424 3 433 - 438 3 2012年08月 [査読有り][通常論文]
     
    The electrogenic Na+-HCO3- cotransporter NBCe1-B can be regulated by intracellular Mg2+ (Mg-i(2+)). We previously reported that under whole-cell voltage-clamp conditions, bovine NBCe1-B (bNBCe1-B) currents heterologously expressed in mammalian cells are strongly inhibited by Mg-i(2+), and the inhibition is likely mediated by electrostatic interaction and relieved by truncation of the cytosolic NBCe1-B specific N-terminal region. Intriguingly, NBCe1-B-like currents natively expressed in bovine parotid acinar (BPA) cells are much less sensitive to Mg-i(2+) inhibition than bNBCe1-B currents. Here, we hypothesized that this apparent discrepancy may involve IRBIT, a previously identified NBCe1-B-interacting protein. RT-PCR, Western blot and immunofluorescence confocal microscopy revealed that IRBIT was not only expressed in the cytosol, but also colocalized with NBCe1-B in the region of plasma membranes of BPA cells. IRBIT was coimmunoprecipitated with NBCe1-B by an anti-NBCe1 antibody in bovine parotid cell lysate. Whole-cell patch-clamp experiments showed that coexpression of IRBIT lowered the Mg-i(2+) sensitivity of bNBCe1-B currents stably expressed in HEK293 cells. Collectively, these results suggest that IRBIT may reduce the apparent affinity for Mg-i(2+) in inhibition of NBCe1-B activity in mammalian cells. (C) 2012 Elsevier Inc. All rights reserved.
  • Soichiro Yamaguchi, Archana Jha, Qin Li, Abigail A. Soyombo, George D. Dickinson, Dev Churamani, Eugen Brailoiu, Sandip Patel, Shmuel Muallem
    JOURNAL OF BIOLOGICAL CHEMISTRY 286 26 22934 - 22942 2011年07月 [査読有り][通常論文]
     
    NAADP is a potent second messenger that mobilizes Ca(2+) from acidic organelles such as endosomes and lysosomes. The molecular basis for Ca(2+) release by NAADP, however, is uncertain. TRP mucolipins (TRPMLs) and two-pore channels (TPCs) are Ca(2+)-permeable ion channels present within the endolysosomal system. Both have been proposed as targets for NAADP. In the present study, we probed possible physical and functional association of these ion channels. Exogenously expressed TRPML1 showed near complete colocalization with TPC2 and partial colocalization with TPC1. TRPML3 overlap with TPC2 was more modest. TRPML1 and to some extent TRPML3 co-immuno-precipitated with TPC2 but less so with TPC1. Current recording, however, showed that TPC1 and TPC2 did not affect the activity of wild-type TRPML1 or constitutively active TRPML1(V432P). N-terminally truncated TPC2 (TPC2delN), which is targeted to the plasma membrane, also failed to affect TRPML1 and TRPML1(V432P) channel function or TRPML1(V432P)-mediated Ca(2+) influx. Whereas overexpression of TPCs enhanced NAADP-mediated Ca(2+) signals, overexpression of TRPML1 did not, and the dominant negative TRPML1(D471K) was without affect on endogenous NAADP-mediated Ca(2+) signals. Furthermore, the single channel properties of NAADP-activated TPC2delN were not affected by TRPML1. Finally, NAADP-evoked Ca(2+) oscillations in pancreatic acinar cells were identical in wild-type and TRPML1(-/-) cells. We conclude that although TRPML1 and TPCs are present in the same complex, they function as two independent organellar ion channels and that TPCs, not TRPMLs, are the targets for NAADP.
  • Hyun Jin Kim, Soichiro Yamaguchi, Qin Li, Insuk So, Shmuel Muallem
    JOURNAL OF BIOLOGICAL CHEMISTRY 285 22 16513 - 16520 2010年05月 [査読有り][通常論文]
     
    TRPML3 is a H(+)-regulated Ca(2+) channel that shuttles between intracellular compartments and the plasma membrane. The A419P mutation causes the varitint-waddler phenotype as a result of gain-of-function (GOF). The mechanism by which A419P leads to GOF is not known. Here, we show that the TRPML3 pore is dynamic when conducting Ca(2+) to change its conductance and permeability, which appears to be mediated by trapping Ca(2+) within the pore. The pore properties can be restored by strong depolarization or by conducting Na(+) through the pore. The A419P mutation results in expanded channel pore with altered permeability that limits modulation of the pore by Ca(2+). This effect is specific for the A419P mutation and is not reproduced by other GOF mutations, including A419G, H283A, and proline mutations in the fifth transmembrane domain. These findings describe a novel mode of a transient receptor potential channel behavior and suggest that pore expansion by the A419P mutation may contribute to the varitint-waddler phenotype.
  • Akihiro Inagaki, Soichiro Yamaguchi, Hiromi Takahashi-Iwanaga, Toshihiko Iwanaga, Toru Ishikawa
    JOURNAL OF MEMBRANE BIOLOGY 235 1 27 - 41 2010年05月 [査読有り][通常論文]
     
    ClC-2, a member of the voltage-gated Cl- channel family, is expressed in the distal colonic surface epithelial cells of various species, but its functional significance remains unclear. Here, by means of electrophysiological and molecular biological techniques, we have identified and characterized a ClC-2-like conductance naturally expressed by surface epithelial cells acutely dissociated from rectal colon of rats fed a standard diet. Whole-cell patch-clamp experiments showed that the surface cells, whether an amiloride-sensitive Na+ conductance was present or not, displayed a strong hyperpolarization-activated, inwardly rectifying Cl- current. Analysis both by in situ hybridization and immunohistochemistry confirmed the expression of ClC-2 in the rectal surface epithelium. The native Cl- current shared common electrophysiological properties including voltage-dependent activation, anion selectivity sequence, and Zn2+ sensitivity with that recorded from HEK293 cells transfected with ClC-2 cloned from rat rectal colon (rClC-2). Cell-attached patch recordings on the surface cells revealed that native ClC-2-like currents activated only at potentials at least 40 mV more negative than resting membrane potentials. In Ussing chamber experiments with rat rectal mucosa, either basolateral or apical application of Zn2+ (0.1 mM), which inhibited both native ClC-2-like currents and recombinant rClC-2 currents, had little, if any, effects on basal amiloride-sensitive short-circuit current. Collectively, these results not only demonstrate that a functional ClC-2-type Cl- channel is expressed in rat rectal surface epithelium, but also suggest that the channel activity may be negligible and thus nonessential for controlling electrogenic Na+ transport in this surface epithelium under basal physiological conditions.
  • Soichiro Yamaguchi, Shmuel Muallem
    CHEMISTRY & BIOLOGY 17 3 209 - 210 2010年03月 [査読有り][通常論文]
     
    The intracellular TRPML channels have multiple biological roles, but the physiological stimuli that open them remained unknown. In a previous issue of Chemistry & Biology, Grimm et al. report a high-throughput chemical screen that identified a plethora of selective activators of TRPML3 that should open the way to fully characterize these channels and their physiological roles.
  • Kirill Kiselyov, Soichiro Yamaguchi, Christopher W. Lyons, Shmuel Muallem
    CELL CALCIUM 47 2 103 - 111 2010年02月 [査読有り][通常論文]
     
    Lysosomal storage diseases (LSDs) are caused by inability of cells to process the material captured during endocytosis. While they are essentially diseases of cellular "indigestion", LSDs affect large number of cellular activities and, as such, they teach us about the integrative function of the cell, as well as about the gaps ill our knowledge of the endocytic pathway and membrane transport. The present review summarizes recent findings on Ca2+ handling in LSDs and attempts to identify the key questions on alterations in Ca2+ signaling and membrane transport in this group of diseases, answers to which may lie in delineating the cellular pathogeneses of LSDs. (C) 2009 Elsevier Ltd. All rights reserved.
  • Soichiro Yamaguchi, Toru Ishikawa
    BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS 376 1 100 - 104 2008年11月 [査読有り][通常論文]
     
    NBCe1-B, a major splice variant of the electrogenic Na+-HCO3- cotransporter (NBCe1) fulfills basic cellular functions including regulation of intracellular pH and epithelial HCO3- secretion. However, its cellular regulatory mechanism still remains elusive. Here, we provide evidence for the first time that NBCe1-B activity can be controlled by intracellular Mg2+ (Mg-i(2+)), the physiologically most abundant intracellular divalent cation. Using the whole-cell patch-clamp technique, we found that recombinant NBCe1-B currents expressed in HEK293 and NIH3T3 cells were inhibited voltage-independently by Mg-i(2+) in a concentration-dependent manner (K-i approximate to 0.01 mM). The Mg-i(2+) inhibition was partially relieved by truncation of the NBCe1-B specific N-terminal region (K-i approximate to 0.3 mM), and was also observed for native electrogenic Na+-HCO3- cotransporter current in bovine parotid acinar cells that endogenously express NBCe1-B (K-i approximate to 1 mM). These results suggest that Mg2+ may be a cytosolic factor that limits intrinsic cotransport activity of NBCe1-B in mammalian cells. (C) 2008 Elsevier Inc. All Fights reserved.
  • S Yamaguchi, T Ishikawa
    JOURNAL OF PHYSIOLOGY-LONDON 568 1 181 - 197 2005年10月 [査読有り][通常論文]
     
    Using patch-clamp and molecular biological techniques, we identified and characterized membrane currents most likely generated by an electrogenic Na+-HCO3- cotransporter (NBCe) in acutely dissociated bovine parotid acinar (BPA) cells. When BPA cells were dialysed with a N-methyl-D-glucamine (NMDG)-glutamate-rich pipette solution, switching a Na-glutamate-rich, nominally HCO3- -free bath solution to the one containing 25 mM HCO3-, but not Cl-, elicited a whole-cell current with a linear current-voltage relation. The HCO3- evoked current was abolished by total replacement of extracellular Na+ (Na-0(+)) with NMDG or by 0.5 mM 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS), and was only partially supported by Li-0(+), but not by K-0(+), Cs-0(+), and cholinle(0). The reversal potential shift of DIDS (0.5 mm)-sensitive current induced by a change of [Na+](0) corresponded to an apparent coupling ratio of HCO3- to Na+ of 2. RT-PCR analysis showed the presence of transcripts of NBCel-B, but not NBCel-A in BPA cells. Electrophysiological and pharmacological properties of whole-cell currents recorded from HEK293 cells transfected with the NBCel-B, which was cloned from BPA cells resembled those of the native currents. Non-invasive measurements of membrane potential changes in the cell-attached patch configuration indicated that an NBCe activity is present in intact unstimulated BPA cells bathed in a 25 mM HCO3--containing solution. Collectively, these results not only suggest that an NBCe is present, functional and may be mediated, at least in part, by NBCel-B in BPA cells, but also provide the first electrophysiological characterization of transport properties of NBCe expressed in native exocrine glands.
  • A Inagaki, S Yamaguchi, T Ishikawa
    AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY 286 2 C380 - C390 2004年02月 [査読有り][通常論文]
     
    Surface cells of the mammalian distal colon are shown to molecularly express the amiloride-sensitive epithelial Na+ channel composed of three homologous subunits (alpha-, beta-, and gamma-ENaC). However, because basic electrophysiological properties of amiloride-sensitive Na+ channels expressed in these cells are largely unknown at the cellular level, functional evidence for the involvement of the subunits in the native channels is incomplete. Using electrophysiological techniques, we have now characterized functional properties of native ENaC in surface cells of rectal colon ( RC) of rats fed a normal Na+ diet. Ussing chamber experiments showed that apical amiloride inhibited a basal short-circuit current in mucosal preparation of RC with an apparent half-inhibition constant (K-i) value of 0.20 muM. RT-PCR analysis confirmed the presence of transcripts of alpha-, beta-, and gamma-rENaC in rectal mucosa. Whole cell patch-clamp experiments in surface cells of intact crypts acutely isolated from rectal mucosa identified an inward cationic current, which was inhibited by amiloride with a K-i value of 0.12 muM at a membrane potential of -64 mV, the inhibition being weakly voltage dependent. Conductance ratios of the currents were Li+ (1.8)>Na+ (1)much greater thanK(+) (approximate to0), respectively. Amiloride-sensitive current amplitude was almost the same at 15 or 150 mM extracellular Na+, suggesting a high Na+ affinity for current activation. These results are consistent with the hypothesis that a heterooligomer composed of alpha-, beta-, and gamma-ENaC may be the molecular basis of the native channels, which are responsible for amiloride-sensitive electrogenic Na+ absorption in rat rectal colon.

その他活動・業績

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    Yamaguchi Soichiro, Kamino Maho, Hamamura Maho, Otsuguro Ken-ichi The Journal of Physiological Sciences 70 (Suppl.1) S107 -S107 2020年03月
  • TMC1の細胞内N端領域における核移行機序および切断部位の同定
    神野 真帆, 濱村 眞帆, 山口 聡一郎, 乙黒 兼一 日本獣医学会学術集会講演要旨集 162回 497 -497 2019年08月
  • アストロサイトの突起形成におけるα2アドレナリン受容体の役割
    北野 泰佑, 江口 遼太, 山口 聡一郎, 乙黒 兼一 日本獣医学会学術集会講演要旨集 162回 499 -499 2019年08月
  • ラット脊髄アストロサイトにおけるH2S誘発性Ca2+上昇機構
    新居 剛, 江口 遼太, 山口 聡一郎, 乙黒 兼一 日本獣医学会学術集会講演要旨集 162回 499 -499 2019年08月
  • TRPM4およびTRPM5チャネルのCa2+結合部位に関する機能分析(Functional analyses for a Ca2+ binding site of TRPM4 and TRPM5 channels)
    Yamaguchi Soichiro, Tanimoto Akira, Iwasa Shinsuke, Otsuguro Ken-ichi The Journal of Physiological Sciences 69 (Suppl.1) S166 -S166 2019年06月
  • FGF2によるアストロサイトの細胞外アデノシンデアミナーゼ発現および活性の増強作用
    江口 遼太, 山口 聡一郎, 乙黒 兼一 日本獣医学会学術集会講演要旨集 161回 465 -465 2018年08月
  • 低Ca2+によるアストロサイトの細胞外アデノシン蓄積に対するFGF2の影響
    江口 遼太, 山口 聡一郎, 乙黒 兼一 日本獣医学会学術集会講演要旨集 160回 503 -503 2017年08月
  • キシラジンによるブタα2Aアドレナリン受容体活性化作用
    北野 泰佑, 小林 武志, 山口 聡一郎, 乙黒 兼一 日本獣医学会学術集会講演要旨集 160回 503 -503 2017年08月
  • 鶏胸大動脈におけるグロムス細胞からの5-HT放出に対するH2Sの作用(Effect of H2S on 5-HT release from glomus cells in the chicken thoracic aorta)
    Delgermurun Dugar, 山口 聡一郎, 市居 修, 昆 泰寛, 伊藤 茂男, 乙黒 兼一 日本獣医学会学術集会講演要旨集 159回 495 -495 2016年08月 [査読無し][通常論文]
  • 5-HT取り込み阻害剤とamphetamine誘導体がトリ大動脈体の5-HT流出に与える影響(Effects of 5-HT uptake inhibitors and amphetamine derivatives on 5-HT outflow from chicken aortic body)
    Dugar Delgermurun, Ito Shigeo, Yamaguchi Soichiro, Ohta Toshio, Otsuguro Ken-ichi Journal of Pharmacological Sciences 130 (3Suppl.) S190 -S190 2016年03月
  • ラット脊髄アストロサイトでの虚血刺激によるadenosineの細胞外蓄積(Extracellular accumulation of adenosine by ischemic stimulations in rat spinal astrocytes)
    Eguchi Ryota, Yamaguchi Soichiro, Otsuguro Ken-ichi Journal of Pharmacological Sciences 130 (3Suppl.) S227 -S227 2016年03月
  • 炎症性サイトカインがRIN14B細胞におけるH2S誘発性のCa2+反応に及ぼす影響(Effect of pro-inflammatory cytokine on H2S-induced Ca2+ responses in RIN14B cells)
    Ujike Ayako, Yamaguchi Soichiro, Ito Shigeo, Otsuguro Ken-ichi Journal of Pharmacological Sciences 130 (3Suppl.) S251 -S251 2016年03月
  • MrgprB4陽性後根神経節神経における細胞膨張によるCa2+流入経路(A swelling-induced Ca2+ entry pathway in MrgprB4+ dorsal root ganglion neurons)
    Yamaguchi Soichiro, Otsuguro Ken-ichi The Journal of Physiological Sciences 66 (Suppl.1) S159 -S159 2016年03月
  • ラット脊髄における硫化水素産生酵素CBSの発現はニューロンにより維持される
    宮本 亮, 乙黒 兼一, 山口 聡一郎, 伊藤 茂男 日本生化学会大会・日本分子生物学会年会合同大会講演要旨集 88回・38回 [1P0515] -[1P0515] 2015年12月
  • ニューロンによるラット脊髄アストロサイトの硫化水素産生酵素の発現調節
    宮本 亮, 乙黒 兼一, 山口 聡一郎, 伊藤 茂男 日本獣医学会学術集会講演要旨集 158回 436 -436 2015年08月
  • 5-HT取り込み阻害剤とアンフェタミン誘導体による鶏大動脈からの5-HT流出(5-HT outflow from chicken aorta by 5-HT uptake inhibitors and amphetamine derivatives)
    Dugar Delgermurun, 山口 聡一郎, 太田 利男, 乙黒 兼一, 伊藤 茂男 日本獣医学会学術集会講演要旨集 158回 436 -436 2015年08月
  • ラット脊髄アストロサイトにおける細胞外Ca2+低下によるアデノシンの細胞外蓄積に対するギャップ結合ヘミチャネルの関与(Gap junction hemichannels contribute to extracellular accumulation of adenosine by external Ca2+ reduction in rat spinal astrocytes)
    Eguchi Ryota, Akao Sanae, Otsuguro Ken-ichi, Yamaguchi Soichiro, Ito Shigeo Journal of Pharmacological Sciences 128 (3Suppl.) S157 -S157 2015年07月
  • ラット脊髄アストロサイトにおける硫化水素産生は神経シグナルにより制御される(Hydrogen sulfide production is controled by neuronal signals in rat spinal cord astrrocytes)
    Miyamoto Ryo, Otsuguro Ken-ichi, Yamaguchi Soichiro, Ito Shigeo Journal of Pharmacological Sciences 128 (3Suppl.) S158 -S158 2015年07月
  • TRPM4チャネルの一過性受容器電位(TRP)ドメイン内及び近辺の酸性アミノ酸はその正常なCa2+感受性の維持に必要である(Acidic amino acids near and in Transient Receptor Potential (TRP) domain of TRPM4 channel are required for maintaining its normal Ca2+ sensitivity)
    Yamaguchi Soichiro, Tanimoto Akira, Otsuguro Ken-ichi, Hibino Hiroshi, Ito Shigeo The Journal of Physiological Sciences 65 (Suppl.1) S113 -S113 2015年03月
  • 脊髄アストロサイトのCa2+除去下で見られる細胞外アデノシン増加におけるギャップジャンクションヘミチャネルの関与
    江口 遼太, 増本 早苗, 乙黒 兼一, 山口 聡一郎, 伊藤 茂男 日本獣医学会学術集会講演要旨集 157回 521 -521 2014年08月
  • 細胞内Ca2+によって活性化されるTRPM4チャネルの二価陽イオン結合部位の解析
    山口 聡一郎, 谷本 章, 乙黒 兼一, 伊藤 茂男 日本獣医学会学術集会講演要旨集 157回 521 -521 2014年08月
  • A. Ujike, K. Otsuguro, R. Miyamoto, S. Yamaguchi, S. Ito BASIC & CLINICAL PHARMACOLOGY & TOXICOLOGY 115 264 -264 2014年07月 [査読無し][通常論文]
  • Ryo Miyamoto, Ken-ichi Otsuguro, Soichiro Yamaguchi, Shigeo Ito NITRIC OXIDE-BIOLOGY AND CHEMISTRY 39 S34 -S34 2014年05月 [査読無し][通常論文]
  • Ayako Ujike, Ken-ichi Otsuguro, Ryo Miyamoto, Soichiro Yamaguchi, Shigeo Ito NITRIC OXIDE-BIOLOGY AND CHEMISTRY 39 S37 -S38 2014年05月 [査読無し][通常論文]
  • Ayako Ujike, Ken-ichi Otsuguro, Ryo Miyamoto, Soichiro Yamaguchi, Shigeo Ito JOURNAL OF PHARMACOLOGICAL SCIENCES 124 (Suppl.1) 165P -165P 2014年 [査読無し][通常論文]
  • Ryo Miyamoto, Ken-ichi Otsuguro, Soichiro Yamaguchi, Shigeo Ito JOURNAL OF PHARMACOLOGICAL SCIENCES 124 191P -191P 2014年 [査読無し][通常論文]
  • デクスメデトミジンとキシラジンの脊髄シナプス伝達抑制作用におけるα2A-アドレナリン受容体の関与の違い
    小林 武志, 乙黒 兼一, 山口 聡一郎, 伊藤 茂男 日本獣医学会学術集会講演要旨集 156回 378 -378 2013年08月
  • ウシ耳下腺腺房細胞を用いた起電性Na+-HCO3-共輸送体の細胞内Mg2+感受性を調節する相互作用タンパク質の探索
    山口 聡一郎, 石川 透 日本獣医学会学術集会講演要旨集 156回 379 -379 2013年08月
  • 内耳機能に重要な蝸牛外側壁の電気化学的特性(Electrochemical property of the cochlear lateral wall crucial for inner ear function)
    Yoshida Takamasa, Nin Fumiaki, Adachi Naoko, Yamaguchi Soichiro, Kurachi Yoshihisa, Hibino Hiroshi Journal of Pharmacological Sciences 121 (Suppl.1) 172P -172P 2013年03月
  • アデノシン代謝阻害薬と細胞外Ca2+除去によるラット脊髄アストロサイトでの細胞外アデノシン蓄積について
    増本 早苗, 乙黒 兼一, 山口 聡一郎, 伊藤 茂男 日本獣医学会学術集会講演要旨集 155回 263 -263 2013年03月
  • Sanae Masumoto, Ken-ichi Otsuguro, Soichiro Yamaguchi, Shigeo Ito JOURNAL OF PHARMACOLOGICAL SCIENCES 121 (Suppl.1) 215P -215P 2013年 [査読無し][通常論文]
  • Takamasa Yoshida, Fumiaki Nin, Naoko Adachi, Soichiro Yamaguchi, Yoshihisa Kurachi, Hiroshi Hibino JOURNAL OF PHYSIOLOGICAL SCIENCES 63 S142 -S142 2013年 [査読無し][通常論文]
  • Soichiro Yamaguchi, Toru Ishikawa JOURNAL OF PHYSIOLOGICAL SCIENCES 63 S136 -S136 2013年 [査読無し][通常論文]
  • Takeshi Kobayashi, Ken-ichi Otsuguro, Soichiro Yamaguchi, Shigeo Ito JOURNAL OF PHARMACOLOGICAL SCIENCES 121 (Suppl.1) 213P -213P 2013年 [査読無し][通常論文]
  • 【聴覚-分子機構から先端治療まで】内耳の神経科学 内リンパ液の電位・イオン環境と聴覚
    日比野 浩, 任 書晃, 山口 聡一郎, 倉智 嘉久 Clinical Neuroscience 29 (12) 1344 -1347 2011年12月
  • 酸性細胞内小器官におけるNAADP受容体Ca2+チャネルの二つの候補(TRPML1とTPCチャネル)からの分子基盤の決着
    山口 聡一郎, Jha Archana, Li Qin, Soyombo Abigail, Dickinson George, Churamani Dev, Brailoiu Eugen, Patel Sandip, Muallem Shumel 日本獣医学会学術集会講演要旨集 152回 314 -314 2011年08月
  • 細胞内Mg2+は起電性Na+-HCO3-共輸送体活性を制御する(Intraceilular Mg2+ can regulate the electrogenic Na+-HCO3- cotransporter activity)
    Yamaguchi Soichiro, Ishikawa Toru The Journal of Physiological Sciences 58 (Suppl.) S210 -S210 2008年04月
  • 山口 聡一郎, 石川 透 日本生理学会大会発表要旨集 2008 210 -210 2008年 
    The electrogenic Na+-HCO3 cotransporter (NBCe) plays a critical role in secretion and absorption of HCO3 and regulation of intracellular pH in various tissues, and thus its activity is necessary to be regulated tightly. Despite intensive studies, the regulatory mechanisms of NBCe activity have not been fully understood. It has been shown that intracellular Mg2+ (Mg2+i) regulates various ion channels and transporters in several ways. In this presentation, we show using the standard whole-cell patch clamp technique that Mg2+i can control natively and heterologously expressed NBCe currents. Mg2+i concentration was varied by pipette solutions having different calculated free Mg2+. Native NBCe currents recorded from freshly dissociated bovine parotid acinar cells were inhibited by increasing Mg2+i in a dose-dependent manner (Ki =–1 mM). The native currents were also inhibited by intracellular polyvalent cationic compounds such as neomycin and spermine. Mg2+i and neomycin inhibited heterologous NBCe currents in mammalian cultured cells transiently transfected with the cloned bovine parotid NBCe1-B. These results suggest that Mg2+i might regulate the NBCe1-B activity under physiological conditions, and the underlying mechanism will be discussed. [J Physiol Sci. 2008;58 Suppl:S210]
  • 山口 聡一郎 日本生理学雜誌 = JOURNAL OF THE PHYSIOLOGICAL SOCIETY OF JAPAN 68 (6) 197 -197 2006年06月01日
  • 山口 聡一郎, 石川 透 日本生理学会大会発表要旨集 2006 112 -112 2006年 
    Electrogenic Na+-HCO3 cotransporter (NBCe) plays an important role in mediating HCO3 efflux and influx across the basolateral membrane in various HCO3-transporting epithelia, including kidney proximal tubules and pancreatic ducts. Its activity has been generally assessed by monitoring intracellular pH, Na+ concentration, or membrane potential, but electrophysiological properties of the cotransporter at the native state still remain largely unknown. Using the whole-cell patch clamp technique, we have recently, for the first time, identified and characterized membrane currents attributable to the activity of a NBCe expressed in acutely dissociated acinar cells (BPA cells) from bovine parotid that secretes large volumes of a HCO3-rich fluid. Under voltage-clamp conditions, the currents were dependent upon extracellular Na+ and HCO3 and DIDS-sensitive. Further analysis of the currents indicated that the stoichiometry of the native cotransporter is most likely to be 2 HCO3 : 1 Na+. We could also demonstrate that BPA cells express transcripts of NBCe1-B (bNBCe1-B) and that recombinant bNBCe1-B currents in HEK293 cells shares common electrophysiological and pharmacological properties with those of the native currents. This study represents an initial attempt to provide electrophysiological characterization of a NBCe expressed in a native HCO3-secreting exocrine gland. [J Physiol Sci. 2006;56 Suppl:S112]
  • 稲垣 明浩, 山口 聡一郎, 石川 透 日本生理学会大会発表要旨集 2004 S58 -S58 2004年 
    The epithelial Na+ channel (ENaC), composed of three homologous subunits (α, β, and γ), is shown to be molecularly expressed in the apical membrane of surface cells of the distal colon. We have recently demonstrated that electrophysiological properties of an amiloride-sensitive macroscopic Na+ current in surface cells, which are freshly isolated from rectal colon of rats fed a normal Na+ diet resemble those reported for heterologously expressed αβγ-ENaC and that the currents are most likely responsible for electrogenic Na+ transport in rat rectum (Inagaki et al., Am.J.Physiol. Cell Physiol. 286 (2): C380-C390, 2004). Using the standard whole-cell patch-clamp technique, we have found that the surface cells also exhibit an inwardly rectifying anion current, which is activated by membrane hyperpolarization, has an anion selectivity sequence of Cl > I, and is blocked by external Zn2+. RT-PCR analysis showed the presence of transcripts of rClC-2 in rat rectal mucosa. Electrophysiological properties of the native currents were similar to those of whole-cell currents recorded from HEK-293 cells heterologously expressing rClC-2 cloned from rat rectal mucosa. We also demonstrated that both ENaC and ClC-2-like currents were recorded in the same surface cells. Collectively, these results provide the electrophysiological evidence for functional coexpression of ENaC and ClC-2-like channel in rat rectal surface cells. Possible role of ClC-2-like channel in electrogenic Na+ transport in the distal colon is also discussed. [Jpn J Physiol 54 Suppl:S58 (2004)]

受賞

  • 2011年09月 日本獣医学会 生理学・生化学分科会 生理学・生化学分科会奨励賞
     
    受賞者: 山口 聡一郎

共同研究・競争的資金等の研究課題

  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2016年04月 -2020年03月 
    代表者 : 山口 聡一郎
     
    本研究はTMC1の細胞内N端領域の機能解明を目的とする。本年度は、western blot法による、切断部位についての解析が進んだ。昨年度までにN端側から二か所の切断部位を示唆する断片が二つ確認できていた。ここで、N端側から順に断片1、2、あるいは切断部位1、2とする。切断部位1の領域のアミノ酸を欠損させたTMC1では、新たに、さらにC端側の切断部位3と切断部位4の存在を示唆する断片が増加し、よりはっきりと検出された。切断部位4の場所を、推定されるアミノ酸を含む断片を作製し、電気泳動上の位置を比較する、あるいは周囲のアミノ酸を欠損させた変異体により解析したところ、第一膜貫通領域内で切断されている可能性が浮上した。これは、膜関連タンパク分解という機構が働き、第一膜貫通領域が切断されることによって、遊離した細胞内断片が、さらに切断されてN端の断片が作成されている可能性を示唆する。次年度は、膜関連タンパク分解の機構の関与も調べていく。 また、転写調節への影響を調べるため、断片1あるいは断片2を安定的に発現するHEK293細胞の作成を試みたところ、断片2を少ないながら発現する細胞クローンを作成することができた。この細胞からmRNAを抽出し、次世代シーケンサーにかけるためのcDNAライブラリーの作成も行った。シーケンスおよび解析を次年度行う。 一方で、TMC1を発現する蝸牛や精巣の抽出物からTMC1タンパク質のwestern blotによる解析を試みたが、切断されていない全長のタンパク質も検出できなかった。これは発現する有毛細胞が蝸牛内では数が少ないことと、精巣では発現量が全体として低いことに起因すると思われる。内因性細胞での切断現象の有無を検討するため、マウス有毛細胞を分離して、免疫染色によりTMC1を検出することを考慮している。
  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2014年04月 -2017年03月 
    代表者 : 乙黒 兼一, 山口 聡一郎
     
    神経保護作用を示すことが知られているアデノシンや硫化水素のアストロサイトにおける産生・放出機構と作用を培養脊髄アストロサイトを用いて検討した。低Ca2+刺激ではアストロサイトからATPが放出され、これが細胞外で代謝されることでアデノシン濃度が増加することが示された。また硫化水素産生酵素CBSのアストロサイトでの発現は、ニューロンによって調節・維持されていることが示唆される。アデノシンや硫化水素は受容体やイオンチャネルを介して細胞機能に影響を与えることが示された。虚血病態で起こる低Ca2+やニューロン死によるアデノシンや硫化水素の動態変化が、病態の形成・進展に関わっている可能性が示唆される。
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2014年 -2015年 
    代表者 : 山口 聡一郎
     
    本研究は、マウスにおいて心地よい触覚を感知する知覚神経であると報告されているMrgprB4陽性後根神経節神経がどのように触覚を感知しているのかを明らかにすることを目的としている。低張圧の細胞外液を適用し、細胞を膨化させる方法で機械刺激を行った時の細胞内カルシウム濃度変化を測定した。すると、低張圧の細胞外液の適用により、細胞内カルシウム濃度の上昇が確認された。この反応はPiezoチャネルの阻害薬で阻害された。免疫染色によってもMrgprB4陽性神経においてPiezo2チャネルの発現が示された。よって、分離MrgprB4陽性神経においてPiezo2チャネルが機能的に働く可能性が示唆された。
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2011年 -2011年 
    代表者 : 山口 聡一郎
     
    内耳血管条におけるpH調整機構の一端を明らかにするために以下の実験を行った。RT-PCR法により、起電性ナトリウム・重炭酸イオン共輸送体の一つであるNBCe1-Bが血管条に発現することが示された。組織学的実験により、血管条の基底細胞と思われる細胞にNBCe1-Bが発現することが示唆された。麻酔下のモルモットを用いた内リンパ電位測定の実験において、外リンパ液へのNBCe1-B阻害薬であるDIDSの適用により、内リンパ電位が低下したことから、NBCe1-Bが内耳血管条におけるpH環境を正常に保つことに関与している可能性が示唆された。
  • ウシ耳下腺でのナトリウム重炭酸イオン共輸送体の分子基盤の解明:複合体形成の可能性
    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 : 2006年 -2008年 
    代表者 : 山口 聡一郎
     
    Yeast two-hybrid法を用いたウシ耳下腺cDNAライブラリーの探索によりNBCe1-BのN端領域との結合タンパク質候補として浮上した2種類のタンパク質(以下、タンパク質Aとタンパク質B)について、以下の実験を行った。共焦点顕微鏡を用いたimmunocytochemistryの実験により、分離したウシ耳下腺腺房細胞において、NBCe1-B、タンパク質A、およびタンパク質Bが発現し、形質膜上にそれらが集積し共局在している傾向が見られた。導管細胞と思われる細胞からはいずれのシグナルも検出されなかった。また、タンパク質AあるいはBをNBCe1-Bと共発現させたHEK293細胞を用いた実験でも、タンパク質AあるいはBとNBCe1-Bの共局在を示唆する結果が得られた。さらに、関連する実験テーマとしてNBCe1-Bの輸送活性が細胞内Mg^<2+>によって抑制され、その抑制作用にNBCe1-Bの特異的N端領域が関与することを明らかにしたことから、N端領域に結合するタンパク質AあるいはBの共発現によるNBCe1-Bに対する細胞内Mg^<2+>の抑制作用への影響を調べた。HEK293細胞にタンパク質AあるいはBとNBCe1-Bを共発現させ、パッチクランプ法によりNBCe1-B電流を測定したところ、条件によっては共発現により細胞内Mg^<2+>による抑制作用が減弱することが明らかとなった。これはタンパク質AあるいはBの結合によるNBCe1-Bの活性化のメカニズムに細胞内Mg^<2+>による抑制作用が関与する可能性を示唆する結果である。以上、本研究によりNBCe1-Bに対する新たな相互作用タンパク質が明らかとなり、それらによる機能的修飾のメカニズムの一つの可能性を提唱することができた。現在、これらの成果を論文としてまとめているところである。

教育活動情報

主要な担当授業

  • 獣医科学特別研究
    開講年度 : 2020年
    課程区分 : 博士後期課程
    開講学部 : 獣医学研究科
  • ケミカルハザード対策専門特論
    開講年度 : 2020年
    課程区分 : 博士後期課程
    開講学部 : 獣医学院
    キーワード : chemical hazard, food safety, toxicology, environmental pollution, LC/MS/MS, GC/MS, GC/ECD, ICP/MS
  • ケミカルハザード対策専門特論
    開講年度 : 2020年
    課程区分 : 博士後期課程
    開講学部 : 獣医学研究科
  • 生命科学特論
    開講年度 : 2020年
    課程区分 : 博士後期課程
    開講学部 : 獣医学院
  • 獣医科学特論演習
    開講年度 : 2020年
    課程区分 : 博士後期課程
    開講学部 : 獣医学研究科
  • 先端生命科学特論Ⅱ:細胞生理学
    開講年度 : 2020年
    課程区分 : 博士後期課程
    開講学部 : 獣医学院
  • 先端獣医科学特論B 生命科学特論Ⅱ:生物現象のイメージング:不可視から可視へ
    開講年度 : 2020年
    課程区分 : 博士後期課程
    開講学部 : 獣医学研究科
  • 札幌基礎獣医学演習・獣医学概論
    開講年度 : 2020年
    課程区分 : 学士課程
    開講学部 : 獣医学部
    キーワード : 獣医学、獣医師、伴侶動物、産業動物、野生動物、公衆衛生、動物実験
  • 先端獣医科学特論B 生命科学特論Ⅲ:細胞膜の興奮性
    開講年度 : 2020年
    課程区分 : 博士後期課程
    開講学部 : 獣医学研究科
  • 草地飼料学
    開講年度 : 2020年
    課程区分 : 学士課程
    開講学部 : 獣医学部
    キーワード : 飼料資源 試料評価 飼料調製 放牧 草地からの家畜生産
  • 獣医科学特別研究
    開講年度 : 2020年
    課程区分 : 博士後期課程
    開講学部 : 獣医学院
  • 生理学Ⅱ
    開講年度 : 2020年
    課程区分 : 学士課程
    開講学部 : 獣医学部
    キーワード : 神経生理学、環境生理学、内分泌生理学、消化生理学
  • 獣医科学特論演習
    開講年度 : 2020年
    課程区分 : 博士後期課程
    開講学部 : 獣医学院
  • 生理学実習
    開講年度 : 2020年
    課程区分 : 学士課程
    開講学部 : 獣医学部
    キーワード : 血液、循環系、神経機能、筋収縮、消化と吸収、外分泌、内分泌、恒常性維持機構
  • 神経生理学・環境生理学
    開講年度 : 2020年
    課程区分 : 学士課程
    開講学部 : 獣医学部
  • 循環生理学・呼吸生理学・消化生理学・内分泌生理学
    開講年度 : 2020年
    課程区分 : 学士課程
    開講学部 : 獣医学部
  • 生理学実習
    開講年度 : 2020年
    課程区分 : 学士課程
    開講学部 : 獣医学部
  • 草地飼料学
    開講年度 : 2020年
    課程区分 : 学士課程
    開講学部 : 獣医学部
  • アドバンスト演習
    開講年度 : 2020年
    課程区分 : 学士課程
    開講学部 : 獣医学部


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