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大矢 進オオヤ ススム

所属部署医学研究科薬理学分野
職名教授
メールアドレス
ホームページURLhttp://www.nagoya-cu.ac.jp/med/labo/pharma/index.html
生年月日
Last Updated :2020/06/03

研究者基本情報

基本情報

    ORCID ID:0000-0002-5765-0667

学歴

  • 1992年04月 - 1994年03月, 名古屋市立大学, 大学院薬学研究科
  •  - 1993年, 名古屋市立大学
  • 1988年04月 - 1992年03月, 名古屋市立大学, 薬学部
  •  - 1991年, 名古屋市立大学

学位

  • 博士(薬学), 名古屋市立大学

所属学協会

  • 日本免疫学会
  • 日本癌学会
  • 米国生理学会
  • 北米生物物理学会
  • 日本平滑筋学会
  • 日本薬学会
  • 日本薬理学会
  • Physiological Society
  • Biophysical Society

委員歴

  •   2018年 - 現在, 日本薬理学会, 企画教育委員
  •   2001年 - 現在, 日本薬理学会, 学術評議員
  •   2014年04月 - 2017年03月, 日本薬学会, 学術誌編集委員

経歴

  •   2017年09月 - 現在, 名古屋市立大学, 大学院医学研究科, 教授
  •   2012年04月 - 2017年08月, 京都薬科大学, 薬学部, 教授
  •   2005年04月 - 2012年03月, 名古屋市立大学, 大学院薬学研究科, 准教授
  •   1995年04月 - 2005年03月, 名古屋市立大学, 大学院薬学研究科, 助手

研究活動情報

研究分野

  • ライフサイエンス, 薬理学
  • ライフサイエンス, 薬理学

研究キーワード

    薬理学, Physiology

論文

  • Castration Induces Down-Regulation of A-Type K+ Channel in Rat Vas Deferens Smooth Muscle., Ohya S, Ito K, Hatano N, Ohno A, Muraki K, Imaizumi Y, International journal of molecular sciences, 20, (17) ,   2019年08月, 査読有り
  • Inhibition of Interleukin 10 Transcription through the SMAD2/3 Signaling Pathway by Ca2+-Activated K+ Channel KCa3.1 Activation in Human T-Cell Lymphoma HuT-78 Cells., Matsui M, Kajikuri J, Kito H, Endo K, Hasegawa Y, Murate S, Ohya S, Molecular pharmacology, 95, (3) 294 - 302,   2019年03月, 査読有り
  • Conversion of Ca2+ oscillation into propagative electrical signals by Ca2+-activated ion channels and connexin as a reconstituted Ca2+ clock model for the pacemaker activity., Saeki T, Kimura T, Hashidume K, Murayama T, Yamamura H, Ohya S, Suzuki Y, Nakayama S, Imaizumi Y, Biochemical and biophysical research communications, 510, (2) 242 - 247,   2019年03月, 査読有り
  • Brain allopregnanolone induces marked scratching behaviour in diet-induced atopic dermatitis mouse model., Fujii M, Ohgami S, Asano E, Nakayama T, Toda T, Nabe T, Ohya S, Scientific reports, 9, (1) ,   2019年02月, 査読有り
  • [Ca2+-activated K+ channels as cancer therapeutic targets]., Ohya S, Kito H, Kajikuri J, Nihon yakurigaku zasshi. Folia pharmacologica Japonica, 154, (3) 108 - 113,   2019年, 査読有り
  • Histone Deacetylases Enhance Ca2+-Activated K⁺ Channel KCa3.1 Expression in Murine Inflammatory CD4⁺ T Cells., Matsui M, Terasawa K, Kajikuri J, Kito H, Endo K, Jaikhan P, Suzuki T, Ohya S, International journal of molecular sciences, 19, (10) ,   2018年09月, 査読有り
  • Transcriptional repression of human epidermal growth factor receptor 2 by ClC-3 Cl- /H+ transporter inhibition in human breast cancer cells., Fujimoto M, Kito H, Kajikuri J, Ohya S, Cancer science, 109, (9) 2781 - 2791,   2018年09月, 査読有り
  • Eicosapentaenoic acid ethyl ester ameliorates atopic dermatitis-like symptoms in special diet-fed hairless mice, partly by restoring covalently bound ceramides in the stratum corneum., Fujii M, Ohyanagi C, Kawaguchi N, Matsuda H, Miyamoto Y, Ohya S, Nabe T, Experimental dermatology, 27, (8) 837 - 840,   2018年08月, 査読有り
  • Negative regulation of cellular Ca2+ mobilization by ryanodine receptor type 3 in mouse mesenteric artery smooth muscle., Matsuki K, Kato D, Takemoto M, Suzuki Y, Yamamura H, Ohya S, Takeshima H, Imaizumi Y, American journal of physiology. Cell physiology, 315, (1) C1 - C9,   2018年07月, 査読有り
  • ATP increases [Ca2+ ]i and activates a Ca2+ -dependent Cl- current in rat ventricular fibroblasts., Hatano N, Ohya S, Imaizumi Y, Clark RB, Belke D, Giles WR, Experimental physiology, 103, (5) 666 - 682,   2018年05月, 査読有り
  • Transcriptional Repression and Protein Degradation of the Ca2+-Activated K+ Channel KCa1.1 by Androgen Receptor Inhibition in Human Breast Cancer Cells., Khatun A, Shimozawa M, Kito H, Kawaguchi M, Fujimoto M, Ri M, Kajikuri J, Niwa S, Fujii M, Ohya S, Frontiers in physiology, 9,   2018年, 査読有り
  • Ca2+-Activated K+ Channel KCa3.1 as a Therapeutic Target for Immune Disorders., Ohya S, Kito H, Biological & pharmaceutical bulletin, 41, (8) 1158 - 1163,   2018年, 査読有り
  • Up-Regulation of the Voltage-Gated K(v)2.1 K+ Channel in the Renal Arterial Myocytes of Dahl Salt-Sensitive Hypertensive Rats, Kazunobu Ogiwara, Susumu Ohya, Yoshiaki Suzuki, Hisao Yamamura, Yuji Imaizumi, BIOLOGICAL & PHARMACEUTICAL BULLETIN, 40, (9) 1468 - 1474,   2017年09月, 査読有り, Salt-sensitive hypertension induces renal injury via decreased blood flow in the renal artery (RA), and ion channel dysfunction in RA myocytes (RAMs) may be involved in the higher renal vascular resistance. We examined the effects of several voltage-gated K+ (K-v) channel blockers on the resting tension in endothelium-denuded RA strips and delayed-rectifier K+ currents in RAMs of Dahl salt-sensitive hypertensive rats (Dahl-S) fed with low- (Dahl-LS) and high-salt diets (Dahl-HS). The tetraethylammonium (TEA)-induced contraction in RA strips were significantly larger in Dahl-HS than Dahl-LS. Correspondingly, TEA-sensitive K-v currents were significantly larger in the RAMs of Dahl-HS than Dahl-LS. Among the TEA-sensitive Kv channel subtypes, the expression levels of K(v)2.1 transcript and protein were significantly higher in the RA of Dahl-HS than Dahl-LS, while those of K(v)1.5, K(v)7.1, and K(v)7.4 transcripts was comparable in two groups. K(v)2.1 currents detected as the guangxitoxin-1E-sensitive component were larger in the RAMs of Dahl-HS than Dahl-LS. These suggest that the up-regulation of the K(v)2.1 channel in RAMs may be involved in the compensatory mechanisms against decreased renal blood flow in salt-sensitive hypertension.
  • Proliferative Role of Kv11 Channels in Murine Arteries, Vincenzo Barrese, Pilar Cidad, Shuk Y. Yeung, Jose R. Lopez-Lopez, Alister J. McNeish, Susumu Ohya, Maria T. Perez-Garcia, Iain A. Greenwood, FRONTIERS IN PHYSIOLOGY, 8,   2017年07月, 査読有り
  • Molecular mechanisms underlying pimaric acid-induced modulation of voltage-gated K+ channels, Kazuho Sakamoto, Yoshiaki Suzuki, Hisao Yamamura, Susumu Ohya, Katsuhiko Muraki, Yuji Imaizumi, JOURNAL OF PHARMACOLOGICAL SCIENCES, 133, (4) 223 - 231,   2017年04月, 査読有り, Voltage-gated K+ (K-V) channels, which control firing and shape of action potentials in excitable cells, are supposed to be potential therapeutic targets in many types of diseases. Pimaric acid (PiMA) is a unique opener of large conductance Ca2+-activated K+ channel. Here, we report that PiMA modulates recombinant rodent K-V channel activity. The enhancement was significant at low potentials (<0 mV) but not at more positive potentials. Application of PiMA significantly shifted the voltage-activation relationships (V-1/2) of rodent K(V)1.1, 1.2, 1.3, 1.4, 1.6 and 2.1 channels (K(V)1.1-K(V)2.1) but K(V)4.3 to lower potentials and prolonged their half-decay times of the deactivation (T-1/2D). The amino acid sequence which is responsible for the difference in response to PiMA was examined between K(V)1.1-K(V)2.1 and K(V)4.3 by site-directed mutagenesis of residues in S5 and S6 segments of Kv1.1. The point mutation of Phe(332) into Tyr mimics the effects of PiMA on V-1/2 and T-1/2D and also abolished the further change by addition of PiMA. The results indicate that PiMA enhances voltage sensitivity of K(V)1.1-K(V)2.1 channels and suggest that the lipophilic residues including Phe(332) in S5 of K(V)1.1-K(V)2.1 channels may be critical for the effects of PiMA, providing beneficial information for drug development of K-V channel openers. (C) 2017 The Authors. Production and hosting by Elsevier B.V. on behalf of Japanese Pharmacological Society.
  • Ryanodine receptor type 3 does not contribute to contractions in the mouse myometrium regardless of pregnancy, Katsuhito Matsuki, Masashi Takemoto, Yoshiaki Suzuki, Hisao Yamamura, Susumu Ohya, Hiroshi Takeshima, Yuji Imaizumi, PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY, 469, (2) 313 - 326,   2017年02月, 査読有り, Ryanodine receptor type 3 (RyR3) is expressed in myometrial smooth muscle cells(MSMCs). The short isoform of RyR3 is a dominant negative varian (DN-RyR3) and negatively regulates the functions of RyR2 and full-length (FL)RyR3. DN-RyR3 has been suggested to function as a major RyR3 isoform in non-pregnant (NP) mouse MSMCs, and FLRyR3 may also be upregulated during pregnancy(P). This increase in the FL-RyR3/DN-RyR3 ratio may contribute to the strong contractions by MSMCs for parturition. In the present study, spontaneous contractions by the myometrium in NP and P mice were highly susceptible to nifedipine but were not affected by ryanodine. Ca2+ image analyses under a voltage clamp revealed that the influx of Ca2+ through voltagedependent Ca2+ channels did not cause the release of Ca2+ from the sarcoplasmic reticulum (SR). Cytosolic Ca2+ concentrations ([Ca2+](cyt)) in MSMCs were not affected by caffeine. Despite the abundant expression of large conductance Ca(2+)activated K+ channels in MSMCs, spontaneous transient outward currents were not observed in the resting state because of the substantive lack of Ca2+ sparks. Quantitative PCR and Western blot analyses indicated that DN-RyR3 was strongly expressed in the NP myometrium, while the expression of FLRyR3 and DN-RyR3 was markedly reduced in the P myometrium. The messenger RNA(mRNA) expression of RyR2 and RyR1 was negligible in the NP and P myometria. Moreover, RyR3 knockout mice may become pregnant and deliver normally. Thus, we concluded that none of the RyR subtypes, including RyR3, play a significant role in the regulation of [Ca2+](cyt) in or contractions by mouse MSMCs regardless of pregnancy.
  • Transcriptional repression of HER2 by ANO1 Cl- channel inhibition in human breast cancer cells with resistance to trastuzumab, Mayu Fujimoto, Takahiro Inoue, Hiroaki Kito, Satomi Niwa, Takayoshi Suzuki, Katsuhiko Muraki, Susumu Ohya, BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS, 482, (1) 188 - 194,   2017年01月, 査読有り, The Ca2+-activated channel ANO1 contributes to tumorigenesis and metastasis in several carcinomas including breast cancer (BCA). Cl- channels have recently been attracting attention as 'transcriptional modulators'. Human epidermal growth factor receptor 2 (HER2) is overexpressed in approximately 30% of patients with BCA, and anti-HER2 monoclonal antibodies such as trastuzumab have emerged as a treatment for metastatic BCA. Among the seven human BCA cell lines examined in the present study, MDA-MB-453 and YMB-1 cells were HER2-positive; however, YMB-1 cell viability showed resistance to trastuzumab. Whole-cell patch-clamp configurations indicated that ANO1 was the main conductance in YMB-1 cells, and the pharmacological and siRNA-mediated inhibition of ANO1 significantly prevented HER2 transcription in YMB-1 cells. The expression levels of insulin-like growth factor-binding protein 5 (IGFBP5), which is a risk factor for BCA recurrence and metastasis, was not affected by the inhibition of ANO1 in YMB-1 cells. These results suggest that ANO1 Cl- channels may function as a transcriptional regulator of HER2, and ANO1 inhibitors have potential in the treatment of BCA patients with resistance to HER2-targeted therapy. (C) 2016 Elsevier Inc. All rights reserved.
  • Down-Regulation of Ca2+-Activated K⁺ Channel KCa1.1 in Human Breast Cancer MDA-MB-453 Cells Treated with Vitamin D Receptor Agonists., Khatun A, Fujimoto M, Kito H, Niwa S, Suzuki T, Ohya S, International journal of molecular sciences, 17, (12) ,   2016年12月, 査読有り
  • A New Splice Variant of Large Conductance Ca2+-activated K+ (BK) Channel α Subunit Alters Human Chondrocyte Function., Suzuki Y, Ohya S, Yamamura H, Giles WR, Imaizumi Y, The Journal of biological chemistry, 291, (46) 24247 - 24260,   2016年11月, 査読有り
  • Defective splicing of the background K+ channel K(2P)5.1 by the pre-mRNA splicing inhibitor, pladienolide B in lectin-activated mouse splenic CD4(+) T cells, Kazutaka Tagishi, Ayaka Shimizu, Kyoko Endo, Hiroaki Kito, Satomi Niwa, Masanori Fujii, Susumu Ohya, JOURNAL OF PHARMACOLOGICAL SCIENCES, 132, (3) 205 - 209,   2016年11月, 査読有り, The two-pore domain K+ channel K(2P)5.1 has been implicated in the pathogenesis of autoimmune diseases. We investigated the changes in K(2P)5.1 activity caused by a defect in normal pre-mRNA splicing in concanavalin A-activated mouse splenic CD4(+) T cells. The pre-mRNA splicing inhibitor, pladienolide B (1 mu M) markedly decreased full-length K(2P)5.1 transcription in activated CD4(+) T cells, resulting in the disappearance of K(2P)5.1 activity and an imbalance in Th17 and T-reg cytokines. These results suggest that the defect in K(2P)5.1 splicing by the pre-mRNA splicing inhibitor regulates pro- and/or anti-inflammatory cytokine production in K(2P)5.1-associated autoimmune diseases. (C) 2016 The Authors. Production and hosting by Elsevier B.V. on behalf of Japanese Pharmacological Society. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
  • Hypomorphic mutation in the hairless gene accelerates pruritic atopic skin caused by feeding a special diet to mice, Masanori Fujii, Fumiko Endo-Okuno, Asuka Iwai, Keisuke Doi, Junko Tomozawa, Shigekatsu Kohno, Naoki Inagaki, Takeshi Nabe, Susumu Ohya, EXPERIMENTAL DERMATOLOGY, 25, (7) 565 - 567,   2016年07月, 査読有り
  • Physiological Role of K+ Channels in the Regulation of T Cell Function, Susumu Ohya, YAKUGAKU ZASSHI-JOURNAL OF THE PHARMACEUTICAL SOCIETY OF JAPAN, 136, (3) 479 - 483,   2016年03月, 査読有り, Potassium ion (K+) channels play an important role in the modulation of calcium ion (Ca2+) signaling via control of the membrane potential. In T-lymphocytes, the voltage-gated K+ channel, K(v)1.3, and the intermediate-conductance Ca2+-activated K+ channel, K(Ca)3.1, predominantly contribute to K+ conductance, and are responsible for cell proliferation, differentiation, apoptosis and infiltration. Inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease, afflicts more than 0.1% of the population worldwide. In the chemically-induced IBD model mouse, an increase in K(Ca)3.1 activity was observed in mesenteric lymph node CD4(+) T-lymphocytes, concomitant with an upregulation of K(Ca)3.1 and a positive K(Ca)3.1 regulator, NDPK-B. Pharmacological blockade of the K(Ca)3.1 K+ channel by TRAM-34 and/or ICA17043 elicited 1) a significant decrease in IBD severity, as assessed by diarrhea, visible fecal blood, inflammation and crypt damage of the colon; and 2) restoration of the expression levels of K(Ca)3.1 and Th1 cytokines in CD4(+) T-lymphocytes in the IBD model. Recent studies have indicated the impact of K(2P)5.1 upregulation in T lymphocytes on the pathogenesis of autoimmune diseases such as rheumatoid arthritis and multiple sclerosis. The K(2P)5.1 K+ channel is therefore highlighted as a potent therapeutic target in managing the pathogenesis of autoimmune diseases. Alternatively, pre-mRNA splicing of ion channels is associated with the development and progression of various diseases, including autoimmune diseases. Therefore, mRNA-splicing mechanisms underlying the transcriptional regulation of K(2P)5.1 K+ channels may be a new strategic therapeutic target for autoimmune and inflammatory diseases.
  • Production of interleukin (IL)-33 in the lungs during multiple antigen challenge-induced airway inflammation in mice, and its modulation by a glucocorticoid., Nabe T, Wakamori H, Yano C, Nishiguchi A, Yuasa R, Kido H, Tomiyama Y, Tomoda A, Kida H, Takiguchi A, Matsuda M, Ishihara K, Akiba S, Ohya S, Fukui H, Mizutani N, Yoshino S, European journal of pharmacology, 757, 34 - 41,   2015年06月, 査読有り
  • Orail-Orai2 complex is involved in store-operated calcium entry in chondrocyte cell lines, Munenori Inayama, Yoshiaki Suzuki, Satoshi Yamada, Takashi Kurita, Hisao Yamamura, Susumu Ohya, Wayne R. Giles, Yuji Imaizumi, CELL CALCIUM, 57, (5-6) 337 - 347,   2015年05月, 査読有り, Ca2+ influx via store-operated Ca2+ entry (SOCE) plays critical roles in many essential cellular functions. The Ca2+ release-activated Ca2+ (CRAC) channel complex, consisting of Oral and STIM, is one of the major components of store-operated Ca2+ (SOC) channels. Our previous study demonstrated that histamine can cause sustained Ca2+ entry through SOC channels in OUMS-27 cells derived from human chondrosarcoma. This SOCE was increased by low- and decreased by high-concentrations of 2-aminoethoxydiphenyl borate. Quantitative reverse transcription PCR and Western blot analyses revealed abundant expressions of Orai1 Orai2 and STIM1. Introduction of dominant negative mutant of Orai1, or siOrai1 knockdown significantly attenuated SOCE. Following histamine application, single molecule imaging using total internal reflection fluorescence (TIRF) microscopy demonstrated punctate Orai1-STIM1 complex formation in plasma membrane. In contrast, knockdown or over-expression of Orai2 resulted in an increase or a decrease in SOCE, respectively. Finally, TIRF imaging revealed direct coupling between Orai1 and Orai2, and suggested that Orai2 reduces Orai1 function by formation of a hetero-tetramer. These results provide substantial evidence that Orai1, Orai2 and STIM1 form functional CRAC channels in OUMS-27 cells and that these complexes are responsible for sustained Ca2+ entry in response to agonist stimulation. (C) 2015 Elsevier Ltd. All rights reserved.
  • Regulation of store-operated Ca2+ entry activity by cell cycle dependent up-regulation of Orai2 in brain capillary endothelial cells., Kito H, Yamamura H, Suzuki Y, Yamamura H, Ohya S, Asai K, Imaizumi Y, Biochemical and biophysical research communications, 459, (3) 457 - 462,   2015年04月, 査読有り
  • Dietary deficiencies of unsaturated fatty acids and starch cause atopic dermatitis-like pruritus in hairless mice., Fujii M, Shimazaki Y, Muto Y, Kohno S, Ohya S, Nabe T, Experimental dermatology, 24, (2) 108 - 113,   2015年02月, 査読有り
  • Spontaneous and nicotine-induced Ca2+ oscillations mediated by Ca2+ influx in rat pinealocytes, Hiroya Mizutani, Hisao Yamamura, Makoto Muramatsu, Keiko Kiyota, Kaori Nishimura, Yoshiaki Suzuki, Susumu Ohya, Yuji Imaizumi, AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY, 306, (11) C1008 - C1016,   2014年06月, 査読有り, The pineal gland regulates circadian rhythm through the synthesis and secretion of melatonin. The rise of intracellular Ca2+ concentration ([Ca2+](i)) following nicotinic acetylcholine receptor (nAChR) stimulation due to parasympathetic nerve activity downregulates melatonin production. Important characteristics and roles of Ca2+ mobilization due to nAChR stimulation remain to be clarified. We report here that spontaneous Ca2+ oscillations can be observed in similar to 15% of the pinealocytes in slice preparations from rat pineal glands when this dissociation procedure is done within 6 h from a dark-to-light change. The frequency and half-life of [Ca2+](i) rise were 0.86 min(-1) and 19 s, respectively. Similar spontaneous Ca2+ oscillations were recorded in 17% of rat pinealocytes that were primary cultured for several days. Simultaneous measurement of [Ca2+] i and membrane potential revealed that spontaneous Ca2+ oscillations were triggered by periodic membrane depolarizations. Spontaneous Ca2+ oscillations in cultured pinealocytes were abolished by extracellular Ca2+ removal or application of nifedipine, a blocker of voltage-dependent Ca2+ channel (VDCC). In contrast, blockers of intracellular Ca2+-release channels, 2-aminoethoxydiphenylborate and ryanodine, have no effect. Our results also reveal that, in 23% quiescent pinealocytes, Ca2+ oscillations were observed following the withdrawal of nicotine. Norepinephrine-induced melatonin secretion from whole pineal glands was significantly decreased by the coapplication of acetylcholine (ACh). This inhibitory effect of ACh was attenuated by nifedipine. In conclusion, both spontaneous and evoked Ca2+ oscillations are due to membrane depolarization following activation of VDCCs. This consists of VDCC alpha 1F subunit, and the associated Ca2+ influx can strongly regulate melatonin secretion in pineal glands.
  • Membrane Hyperpolarization Induced by Endoplasmic Reticulum Stress Facilitates Ca2+ Influx to Regulate Cell Cycle Progression in Brain Capillary Endothelial Cells, Hiroaki Kito, Hisao Yamamura, Yoshiaki Suzuki, Susumu Ohya, Kiyofumi Asai, Yuji Imaizumi, JOURNAL OF PHARMACOLOGICAL SCIENCES, 125, (2) 227 - 232,   2014年06月, 査読有り, Upregulation of the Kir2.1 channel during endoplasmic reticulum (ER) stress in t-BBEC117, an immortalized bovine brain endothelial cell line, caused a sustained increase in intracellular Ca2+ concentration ([Ca2+]i) and a facilitation of cell death. Expressions of Ca2+ influx channels (TRPC, Orail, STIM1) were unchanged by ER stress. The ER stress-induced [Ca2+]i increase was mainly attributed to the deeper resting membrane potential due to Kir2.1 upregulation. ER stress arrested at the G2/M phase and it was attenuated by an inhibitor of Kir2.1. These results indicate that Kir2.1 upregulation by ER stress facilitates cell death via regulation of cell cycle progression in t-BBEC117.
  • Caveolin-1 Facilitates the Direct Coupling between Large Conductance Ca2+-activated K+ (BKCa) and Cav1.2 Ca2+ Channels and Their Clustering to Regulate Membrane Excitability in Vascular Myocytes, Yoshiaki Suzuki, Hisao Yamamura, Susumu Ohya, Yuji Imaizumi, JOURNAL OF BIOLOGICAL CHEMISTRY, 288, (51) 36750 - 36761,   2013年12月, 査読有り, Background: The contribution of caveolae to physiological interaction between two major ion channels, large conductance Ca2+-activated K+ (BKCa) and Ca2+ (Cav1.2) channels, is unknown in vascular myocytes. Results: The loss of caveola by caveolin-1 deficiency reduced BKCa-Cav1.2 coupling, Cav1.2 clustering, and membrane excitability regulation. Conclusion: Caveolin-1 provides platform for BKCa-Cav1.2 molecular complex. Significance: Caveolin-1-BKCa-Cav1.2 in caveola forms a novel Ca2+ signal domain for arterial tonus regulation. L-type voltage-dependent Ca2+ channels (LVDCC) and large conductance Ca2+-activated K+ channels (BKCa) are the major factors defining membrane excitability in vascular smooth muscle cells (VSMCs). The Ca2+ release from sarcoplasmic reticulum through ryanodine receptor significantly contributes to BKCa activation in VSMCs. In this study direct coupling between LVDCC (Cav1.2) and BKCa and the role of caveoline-1 on their interaction in mouse mesenteric artery SMCs were examined. The direct activation of BKCa by Ca2+ influx through coupling LVDCC was demonstrated by patch clamp recordings in freshly isolated VSMCs. Using total internal reflection fluorescence microscopy, it was found that a large part of yellow fluorescent protein-tagged BKCa co-localized with the cyan fluorescent protein-tagged Cav1.2 expressed in the plasma membrane of primary cultured mouse VSMCs and that the two molecules often exhibited FRET. It is notable that each BK subunit of a tetramer in BKCa can directly interact with Cav1.2 and promotes Cav1.2 cluster in the molecular complex. Furthermore, caveolin-1 deficiency in knock-out (KO) mice significantly reduced not only the direct coupling between BKCa and Cav1.2 but also the functional coupling between BKCa and ryanodine receptor in VSMCs. The measurement of single cell shortening by 40 mm K+ revealed enhanced contractility in VSMCs from KO mice than wild type. Taken together, caveolin-1 facilitates the accumulation/clustering of BKCa-LVDCC complex in caveolae, which effectively regulates spatiotemporal Ca2+ dynamics including the negative feedback, to control the arterial excitability and contractility.
  • Enhancement of Ca2+ Influx and Ciliary Beating by Membrane Hyperpolarization due to ATP-Sensitive K+ Channel Opening in Mouse Airway Epithelial Cells, Teruya Ohba, Eiji Sawada, Yoshiaki Suzuki, Hisao Yamamura, Susumu Ohya, Hiroyuki Tsuda, Yuji Imaizumi, JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS, 347, (1) 145 - 153,   2013年10月, 査読有り, Among the several types of cells composing the airway epithelium, the ciliary cells are responsible for one of the most important defense mechanisms of the airway epithelium: the transport of inhaled particles back up into the throat by coordinated ciliary movement. Changes in the cytoplasmic Ca2+ concentration ([Ca2+](i)) are the main driving force controlling the ciliary activity. In mouse ciliary cells, membrane hyperpolarization from -20 to -60 mV under whole-cell voltage-clamp induced a slow but significant [Ca2+](i) rise in a reversible manner. This rise was completely inhibited by the removal of Ca2+ from the extracellular solution. Application of diazoxide, an ATP-dependent K+ channel opener, dose-dependently induced a membrane hyperpolarization (EC50 = 2.3 mu M), which was prevented by the addition of 5 mu M glibenclamide. An inwardly rectifying current was elicited by the application of 10 mu M diazoxide and suppressed by subsequent addition of 5 mu M glibenclamide. Moreover, the application of 10 mu M diazoxide induced a significant [Ca2+](i) rise and facilitated ciliary movement. Multi-cell reverse-transcription polymerase chain reaction analyses and immunocytochemical staining suggested that the subunit combination of Kir6.2/SUR2B and possibly also Kir6.1/SUR2B is expressed in ciliary cells. The confocal Ca2+ imaging analyses suggested that the [Ca2+](i) rise induced by diazoxide occurred preferentially in the apical submembrane region. In conclusion, the application of a K-ATP channel opener to airway ciliary cells induces membrane hyperpolarization and thereby induces a [Ca2+](i) rise via the facilitation of Ca2+ influx through the non-voltage-dependent Ca2+ permeable channels. Therefore, a K-ATP opener may be beneficial in facilitating ciliary movement.
  • Overactive bladder mediated by accelerated Ca2+ influx mode of Na+/Ca2+ exchanger in smooth muscle, Hisao Yamamura, William C. Cole, Satomi Kita, Shingo Hotta, Hidemichi Murata, Yoshiaki Suzuki, Susumu Ohya, Takahiro Iwamoto, Yuji Imaizumi, AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY, 305, (3) C299 - C308,   2013年08月, 査読有り, The Na+/Ca2+ exchanger (NCX) is thought to be a key molecule in the regulation of cytosolic Ca2+ dynamics. The relative importance of the two Ca2+ transport modes of NCX activity leading to Ca2+ efflux (forward) and influx (reverse) in smooth muscle, however, remains unclear. Unexpectedly, spontaneous contractions of urinary bladder smooth muscle (UBSM) were enhanced in transgenic mice overexpressing NCX1.3 (NCX1.3(tg/tg)). The enhanced activity was attenuated by KB-R7943 or SN-6. Whole cell outward NCX current sensitive to KB-R7943 or Ni2+ was readily detected in UBSM cells from NCX1.3(tg/tg) but not wild-type mice. Spontaneous Ca2+ transients in myocytes of NCX1.3(tg/tg) were larger and frequently resulted in propagating events and global elevations in cytosolic Ca2+ concentration. Significantly, NCX1.3(tg/tg) mice exhibited a pattern of more frequent urination of smaller volumes and this phenotype was reversed by oral administration of KB-R7943. On the other hand, KB-R7943 did not improve it in KB-R7943-insensitive (G833C-) NCX1.3(tg/tg) mice. We conclude that NCX1.3 overexpression is associated with abnormal urination owing to enhanced Ca2+ influx via reverse mode NCX leading to prolonged, propagating spontaneous Ca2+ release events and a potentiation of spontaneous UBSM contraction. These findings suggest the possibility that NCX is a candidate molecular target for overactive bladder therapy.
  • Role of the KCa3.1 K+ channel in auricular lymph node CD4+ T-lymphocyte function of the delayed-type hypersensitivity model, Susumu Ohya, Erina Nakamura, Sayuri Horiba, Hiroaki Kito, Miki Matsui, Hisao Yamamura, Yuji Imaizumi, BRITISH JOURNAL OF PHARMACOLOGY, 169, (5) 1011 - 1023,   2013年07月, 査読有り, Background and Purpose The intermediate-conductance Ca2+-activated K+ channel (KCa3.1) modulates the Ca2+ response through the control of the membrane potential in the immune system. We investigated the role of KCa3.1 on the pathogenesis of delayed-type hypersensitivity (DTH) in auricular lymph node (ALN) CD4+ T-lymphocytes of oxazolone (Ox)-induced DTH model mice. Experimental Approach The expression patterns of KCa3.1 and its possible transcriptional regulators were compared among ALN T-lymphocytes of three groups [non-sensitized (Ox-/-), Ox-sensitized, but non-challenged (Ox+/-) and Ox-sensitized and -challenged (Ox+/+)] using real-time polymerase chain reaction, Western blotting and flow cytometry. KCa3.1 activity was measured by whole-cell patch clamp and the voltage-sensitive dye imaging. The effects of KCa3.1 blockade were examined by the administration of selective KCa3.1 blockers. Key Results Significant up-regulation of KCa3.1a was observed in CD4+ T-lymphocytes of Ox+/- and Ox+/+, without any evident changes in the expression of the dominant-negative form, KCa3.1b. Negatively correlated with this, the repressor element-1 silencing transcription factor (REST) was significantly down-regulated. Pharmacological blockade of KCa3.1 resulted in an accumulation of the CD4+ T-lymphocytes of Ox+/+ at the G0/G1 phase of the cell cycle, and also significantly recovered not only the pathogenesis of DTH, but also the changes in the KCa3.1 expression and activity in the CD4+ T-lymphocytes of Ox+/- and Ox+/+. Conclusions and Implications The up-regulation of KCa3.1a in conjunction with the down-regulation of REST may be involved in CD4+ T-lymphocyte proliferation in the ALNs of DTH model mice; and KCa3.1 may be an important target for therapeutic intervention in allergy diseases such as DTH.
  • Deficiency of n-6 polyunsaturated fatty acids is mainly responsible for atopic dermatitis-like pruritic skin inflammation in special diet-fed hairless mice, Masanori Fujii, Hiroyuki Nakashima, Junko Tomozawa, Yuki Shimazaki, Chie Ohyanagi, Naomi Kawaguchi, Susumu Ohya, Shigekatsu Kohno, Takeshi Nabe, EXPERIMENTAL DERMATOLOGY, 22, (4) 272 - 277,   2013年04月, 査読有り, Hairless mice fed a special diet, HR-AD, develop atopic dermatitis (AD)-like skin inflammation with skin barrier defects and itch-related scratching; however, the ingredient(s) causing the dermatitis remains unclear. In this study, we examined whether deficiency of certain polyunsaturated fatty acids (PUFAs) is involved in HR-AD-induced AD. High-purity PUFAs were given to HR-AD-fed mice by dietary supplementation or gavage. Fatty acid levels in the serum and skin were determined by using gas chromatography-mass spectrometry. In serum from HR-AD-fed mice, linoleic acid (LA, 18:2n-6) and a-linolenic acid (ALA, 18:3n-3), as well as their metabolites, were markedly decreased. When mice were fed HR-AD supplemented with LA or ALA in an amount equal to that contained in a normal diet, the development of AD-like symptoms was completely prevented by supplementation with LA but not with ALA. Relatively high dose of ALA slightly alleviated skin barrier defects, but did neither itch-related scratching nor skin inflammation. On the other hand, gavage administration of LA metabolites, such as gamma-linolenic acid and arachidonic acid (AA), significantly ameliorated established dermatitis without increasing LA in the serum and skin. Moreover, AA-induced amelioration of dermatitis was not affected by pharmacological blockade of 5-lipoxygenase (5-LOX) and cyclooxygenase (COX), suggesting no involvement of 5-LOX-or COX-mediated AA metabolites in the amelioration. In conclusion, our results indicate that deficiency of n-6 PUFAs is mainly responsible for AD-like symptoms by HR-AD feeding. Thus, this model could be useful for studying the pathomechanisms associated with deficiency of n-6 PUFAs in AD.
  • Direct molecular interaction of caveolin-3 with KCa1.1 channel in living HEK293 cell expression system, Yoshiaki Suzuki, Hisao Yamamura, Susumu Ohya, Yuji Imaizumi, BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS, 430, (3) 1169 - 1174,   2013年01月, 査読有り, Caveolin family is supposed to be essential molecules for the formation of not only caveola structure on cell membrane but also functional molecular complexes in them with direct and/or indirect interaction with other membrane and/or submembrane associated proteins. The direct coupling of caveolin-1 (cav1) with large conductance Ca2+-activated K+ channel, KCa1.1 has been established in several types of cells and in expression system as well. The possible interaction of caveolin-3 (cav3), which shows expression in some differential tissues from cav1, with KCa1.1 remains to be determined. In the present study, the density of KCa1.1 current expressed in HEK293 cells was significantly reduced by the co-expression of cav3, as well as cav1. The co-localization and direct interaction of GFP- or CFP-labeled cav3 (GFP/CFP-cav3) with YFP- or mCherry-labeled KCa1.1 (KCa1.1-YFP/mCherry) were clearly demonstrated by single molecular image analyses using total internal reflection fluorescence (TIRF) microscopy and fluorescence resonance energy transfer (FRET) analyses with acceptor photobleaching method. The deletion of suggested cav1-binding motif in C terminus region of KCa1.1 (KCa1.1 Delta CB-YFP) resulted in the marked decrease in cell surface expression, co-localization and FRET efficiency with CFP-cav3 and CFP-cav1. The FLAG-KCa1.1 co-immunoprecipitation with GFP-cav3 or GFP-cav1 also supported their direct molecular interaction. These results strongly suggest that cav3 possesses direct interaction with KCa1.1, presumably at the same domain for cavl binding. This interaction regulates KCa1.1 expression to cell surface and the formation of functional molecular complex in caveolae in living cells. (C) 2012 Elsevier Inc. All rights reserved.
  • New screening system for selective blockers of voltage-gated K(+) channels using recombinant cell lines dying upon single action potential., Fujii M, Hayashi K, Ohya S, Yamamura H, Imaizumi Y, Journal of pharmacological sciences, 123, (2) 147 - 158,   2013年, 査読有り
  • Involvement of Inositol 1,4,5-Trisphosphate Formation in the Voltage-Dependent Regulation of the Ca2+ Concentration in Porcine Coronary Arterial Smooth Muscle Cells, Hisao Yamamura, Susumu Ohya, Katsuhiko Muraki, Yuji Imaizumi, JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS, 342, (2) 486 - 496,   2012年08月, 査読有り, The involvement of inositol 1,4,5-trisphosphate (IP3) formation in the voltage-dependent regulation of intracellular Ca2+ concentration ([Ca2+](i)) was examined in smooth muscle cells of the porcine coronary artery. Slow ramp depolarization from -90 to 0 mV induced progressive [Ca2+](i) increase. The slope was reduced or increased in the presence of Cd2+ or (+/-)-1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-[trifluoromethyl]-phenyl)pyridine-3-carboxlic acid methyl ester (Bay K 8644), respectively. The decrease in [Ca2+](i) via the membrane hyperpolarization induced by K+ channel openers (levcromakalim and Evans blue) under current clamp was identical to that under voltage clamp. The step hyperpolarization from -40 to -80 mV reduced [Ca2+](i) uniformly over the whole-cell area with a time constant of similar to 10 s. The [Ca2+](i) at either potential was unaffected by heparin, an inhibitor of IP3 receptors. Alternatively, [Ca2+](i) rapidly increased in the peripheral regions by depolarization from -80 to 0 mV and stayed at that level (similar to 400 nM) during a 60-s pulse. When the pipette solution contained IP3 pathway blockers [heparin, 2-aminoethoxydiphenylborate, xestospongin C, or 1-[6-[((17 beta)-3-methoxyestra-1,3,5[10]-trien-17-yl)amino]hexyl]-1H-pyrrole-2,5-dione (U73122)], the peak [Ca2+](i) was unchanged, but the sustained [Ca2+](i) was gradually reduced by similar to 250 nM within 30 s. In the presence of Cd2+, a long depolarization period slightly increased the [Ca2+](i), which was lower than that in the presence of heparin alone. In coronary arterial myocytes, the sustained increase in the [Ca2+](i) during depolarization was partly caused by the Ca2+ release mediated by the enhanced formation of IP3. The initial [Ca2+](i) elevation triggered by the Ca2+ influx though voltage-dependent Ca2+ channels may be predominantly responsible for the activation of phospholipase C for IP3 formation.
  • Development of Recombinant Cell Line Co-expressing Mutated Nav1.5, Kir2.1, and hERG for the Safety Assay of Drug Candidates, Masato Fujii, Susumu Ohya, Hisao Yamamura, Yuji Imaizumi, JOURNAL OF BIOMOLECULAR SCREENING, 17, (6) 773 - 784,   2012年07月, 査読有り, To provide a high-throughput screening method for human ether-a-go-go-gene-related gene (hERG) K+ channel inhibition, a new recombinant cell line, in which single action potential (AP)-induced cell death was produced by gene transfection. Mutated human cardiac Na+ channel Nav1.5 (IFM/Q3), which shows extremely slow inactivation, and wild-type inward rectifier K+ channel, Kir2.1, were stably co-expressed in HEK293 cells (IFM/Q3+Kir2.1). In IFM/Q3+Kir2.1, application of single electrical stimulation (ES) elicited a long AP lasting more than 30 s and led cells to die by more than 70%, whereas HEK293 co-transfected with wild-type Nav1.5 and Kir2.1 fully survived. The additional expression of hERG K+ channels in IFM/Q3+Kir2.1 shortened the duration of evoked AP and thereby markedly reduced the cell death. The treatment of the cells with hERG channel inhibitors such as nifekalant, E-4031, cisapride, terfenadine, and verapamil, recovered the prolonged AP and dose-dependently facilitated cell death upon ES. The EC50 values to induce the cell death were 3 mu M, 19 nM, 17 nM, 74 nM, and 3 mu M, respectively, whereas 10 mu M nifedipine did not induce cell death. Results indicate the high utility of this cell system for hERG K+ channel safety assay.
  • Down-Regulation of the Large-Conductance Ca2+-Activated K+ Channel, K(Ca)1.1 in the Prostatic Stromal Cells of Benign Prostate Hyperplasia, Satomi Niwa, Susumu Ohya, Yoshiyuki Kojima, Shoichi Sasaki, Hisao Yamamura, Motomu Sakuragi, Kenjiro Kohri, Yuji Imaizumi, BIOLOGICAL & PHARMACEUTICAL BULLETIN, 35, (5) 737 - 744,   2012年05月, 査読有り, Large-conductance Ca2+-activated K+ (BKCa) channel encoded by K(Ca)1.1 plays an important role in the control of smooth muscle tone by modulating membrane potential and intracellular Ca2+ mobilization. BKCa channel is functionally expressed in prostatic smooth muscle cells, and is activated by alpha(1)-adrenoceptor agonists. The main objective of this study was to elucidate the pathophysiological significance of changes in prostatic K(Ca)1.1 expressions in benign prostatic hyperplasia (BPH). Our previous study has shown that K(Ca)3.1 encoding intermediate-conductance K-Ca (IKCa) channel is up-regulated in stromal cells of implanted urogenital sinuses (UGSs) of stromal hyperplasia BPH model rats and in those of prostatic tissues from BPH patients. In the present study, the results from real-time polymerase chain reaction (PCR), Western blot, and immunohistochemical analyses showed significant down-regulation of K(Ca)1.1 transcripts and proteins and negative correlation between K(Ca)1.1 and K(Ca)3.1 transcript expressions in prostatic stromal cells of both BPH model rats and BPH patients. Corresponding to down-regulation of K(Ca)1.1 expression in stromal cells of implanted UGSs, membrane depolarization by application of the BKCa channel blocker was disappeared. Down-regulation of K(Ca)1.1 may be involved in the phenotype switch from contractile profile to proliferative one in prostatic stromal cells of BPH patients.
  • Molecular assembly and dynamics of fluorescent protein-tagged single K(Ca)1.1 channel in expression system and vascular smooth muscle cells, Hisao Yamamura, Chikako Ikeda, Yoshiaki Suzuki, Susumu Ohya, Yuji Imaizumi, AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY, 302, (8) C1257 - C1268,   2012年04月, 査読有り, Yamamura H, Ikeda C, Suzuki Y, Ohya S, Imaizumi Y. Molecular assembly and dynamics of fluorescent protein-tagged single K(Ca)1.1 channel in expression system and vascular smooth muscle cells. Am J Physiol Cell Physiol 302: C1257-C1268, 2012. First published February 1, 2012; doi:10.1152/ajpcell.00191.2011.-The large-conductance Ca2+-activated K+ (K(Ca)1.1, BK) channel has pivotal roles in the regulation of vascular tone. To clarify the molecular dynamics of BK channels and their functionally coupled protein on the membrane surface, we examined single-molecule imaging of fluorescent-labeled BK subunits in the plasma membrane using total internal reflection fluorescence (TIRF) microscopy. The dynamic mobility of yellow fluorescent protein (YFP)-tagged BK alpha subunit (BK alpha-YFP) expressed in human embryo kidney 293 (HEK) cells was detected in TIRF regions at the level of individual channels and their clusters on the plasma membrane with a diffusion coefficient of 6.7 x 10(3) nm(2)/s. When BK alpha-YFP was coexpressed with cyan fluorescent protein (CFP)-tagged BK beta 1 subunit (BK beta 1-CFP) in HEK cells, the mobility was reduced by similar to 50%. Fluorescent image analyses suggest that green fluorescent protein (GFP)-tagged BK alpha subunit (BK alpha-GFP) expressed in vascular smooth muscle cells (VSMCs), at low density, preferentially formed a heterotetrameric molecular assembly with native BK alpha subunits, rather than homotetrameric BK alpha-GFP. Movement of BK alpha-YFP in VSMCs (0.29 x 10(3) nm(2)/s) was far more restricted than BK alpha-YFP/BK beta 1-CFP in HEK cells (2.5 x 10(3) nm(2)/s). Actin disruption by pretreatment with cytochalasin D in VSMCs appeared to increase the mobile behavior of BK alpha-YFP, which was then significantly reduced by addition of jasplakinolide. Most BK alpha-YFP colocalized with caveolin 1 (Cav1)-CFP in VSMCs, but unexpectedly not frequently in HEK cells. Fluorescence resonance energy transfer analyses showed the direct interaction between BK alpha-YFP and Cav1-CFP, particularly in VSMCs. These results, obtained by single molecule imaging in living cells, indicate that the dynamics of BK alpha molecules on the membrane surface are strongly restricted or regulated by its auxiliary beta-subunit, cytoskeleton, and direct interaction with Cav1 in VSMCs.
  • [Screening methods for ion-channels drug discovery and new ideas]., Fujii M, Ohya S, Yamamura H, Imaizumi Y, Nihon yakurigaku zasshi. Folia pharmacologica Japonica, 138, (6) 229 - 233,   2011年12月, 査読有り
  • Serotonin Augments Gut Pacemaker Activity via 5-HT3 Receptors, Hong-Nian Liu, Susumu Ohya, Yuji Nishizawa, Kenta Sawamura, Satoshi Iino, Mohsin Md Syed, Kazunori Goto, Yuji Imaizumi, Shinsuke Nakayama, PLOS ONE, 6, (9) ,   2011年09月, 査読有り, Serotonin (5-hydroxytryptamine: 5-HT) affects numerous functions in the gut, such as secretion, muscle contraction, and enteric nervous activity, and therefore to clarify details of 5-HT's actions leads to good therapeutic strategies for gut functional disorders. The role of interstitial cells of Cajal (ICC), as pacemaker cells, has been recognised relatively recently. We thus investigated 5-HT actions on ICC pacemaker activity. Muscle preparations with myenteric plexus were isolated from the murine ileum. Spatio-temporal measurements of intracellular Ca2+ and electric activities in ICC were performed by employing fluorescent Ca2+ imaging and microelectrode array (MEA) systems, respectively. Dihydropyridine (DHP) Ca2+ antagonists and tetrodotoxin (TTX) were applied to suppress smooth muscle and nerve activities, respectively. 5-HT significantly enhanced spontaneous Ca2+ oscillations that are considered to underlie electric pacemaker activity in ICC. LY-278584, a 5-HT3 receptor antagonist suppressed spontaneous Ca2+ activity in ICC, while 2-methylserotonin (2-Me-5-HT), a 5-HT3 receptor agonist, restored it. GR113808, a selective antagonist for 5-HT4, and O-methyl-5-HT (O-Me-5-HT), a non-selective 5-HT receptor agonist lacking affinity for 5-HT3 receptors, had little effect on ICC Ca2+ activity. In MEA measurements of ICC electric activity, 5-HT and 2-Me-5-HT caused excitatory effects. RT-PCR and immunostaining confirmed expression of 5-HT3 receptors in ICC. The results indicate that 5-HT augments ICC pacemaker activity via 5-HT3 receptors. ICC appear to be a promising target for treatment of functional motility disorders of the gut, for example, irritable bowel syndrome.
  • Intermediate-Conductance Ca2+-Activated K+ Channel, K(Ca)3.1, as a Novel Therapeutic Target for Benign Prostatic Hyperplasia, Susumu Ohya, Satomi Niwa, Yoshiyuki Kojima, Shoichi Sasaki, Motomu Sakuragi, Kenjiro Kohri, Yuji Imaizumi, JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS, 338, (2) 528 - 536,   2011年08月, 査読有り, Recently, a new experimental stromal hyperplasia animal model corresponding to clinical benign prostatic hyperplasia (BPH) was established. The main objective of this study was to elucidate the roles of the intermediate-conductance Ca2+-activated K+ channel (K(Ca)3.1) in the implanted urogenital sinus (UGS) of stromal hyperplasia BPH model rats. Using DNA microarray, real-time polymerase chain reaction, Western blot, and/or immunohistochemical analyses, we identified the expression of K(Ca)3.1 and its transcriptional regulators in implanted UGS of BPH model rats and prostate needle-biopsy samples and surgical prostate specimens of BPH patients. We also examined the in vivo effects of a K(Ca)3.1 blocker, 1-[(2-chlorophenyl) diphenylmethyl]-1H-pyrazole (TRAM-34), on the proliferation index of implanted UGS by measurement of UGS weights and proliferating cell nuclear antigen immunostaining. K(Ca)3.1 genes and proteins were highly expressed in implanted UGS rather than in the normal host prostate. In the implanted UGS, the gene expressions of two transcriptional regulators of K(Ca)3.1, repressor element 1-silencing transcription factor and c-Jun, were significantly down-and up-regulated, and the regulations were correlated negatively or positively with K(Ca)3.1 expression, respectively. Positive signals of K(Ca)3.1 proteins were detected exclusively in stromal cells, whereas they were scarcely immunolocalized to basal cells of the epithelium in implanted UGS. In vivo treatment with TRAM-34 significantly suppressed the increase in implanted UGS weights compared with the decrease in stromal cell components. Moreover, significant levels of K(Ca)3.1 expression were observed in human BPH samples. K(Ca)3.1 blockers may be a novel treatment option for patients suffering from BPH.
  • Up-regulation of K(ir)2.1 by ER stress facilitates cell death of brain capillary endothelial cells, Hiroaki Kito, Daiju Yamazaki, Susumu Ohya, Hisao Yamamura, Kiyofumi Asai, Yuji Imaizumi, BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS, 411, (2) 293 - 298,   2011年07月, 査読有り, Brain capillary endothelial cells (BCECs) form blood brain barrier (BBB) to maintain brain homeostasis. Cell turnover of BCECs by the balance of cell proliferation and cell death is critical for maintaining the integrity of BBB. Here we found that stimuli with tunicamycin, endoplasmic reticulum (ER) stress inducer, up-regulated inward rectifier K+ channel (K(ir)2.1) and facilitated cell death in t-BBEC117, a cell line derived from bovine BCECs. The activation of K-ir channels contributed to the establishment of deeply negative resting membrane potential in t-BBEC117. The deep resting membrane potential increased the resting intracellular Ca2+ concentration due to Ca2+ influx through non-selective cation channels and thereby partly but significantly regulated cell death in t-BBEC117. The present results suggest that the up-regulation of K(ir)2.1 is, at least in part, responsible for cell death/cell turnover of BCECs induced by a variety of cellular stresses, particularly ER stress, under pathological conditions. (C) 2011 Elsevier Inc. All rights reserved.
  • Involvement of Dominant-negative Spliced Variants of the Intermediate Conductance Ca2+-activated K+ Channel, K(Ca)3.1, in Immune Function of Lymphoid Cells, Susumu Ohya, Satomi Niwa, Ayano Yanagi, Yuka Fukuyo, Hisao Yamamura, Yuji Imaizumi, JOURNAL OF BIOLOGICAL CHEMISTRY, 286, (19) 16940 - 16952,   2011年05月, 査読有り, The intermediate conductance Ca2+-activated K+ channel (IKCa channel) encoded by K(Ca)3.1 is responsible for the control of proliferation and differentiation in various types of cells. We identified novel spliced variants of K(Ca)3.1 (human (h) K(Ca)3.1b) from the human thymus, which were lacking the N-terminal domains of the original hK(Ca)3.1a as a result of alternative splicing events. hK(Ca)3.1b was significantly expressed in human lymphoid tissues. Western blot analysis showed that hK(Ca)3.1a proteins were mainly expressed in the plasma membrane fraction, whereas hK(Ca)3.1b was in the cytoplasmic fraction. We also identified a similar N terminus lacking K(Ca)3.1 variants from mice and rat lymphoid tissues (mK(Ca)3.1b and rK(Ca)3.1b). In the HEK293 heterologous expression system, the cellular distribution of cyan fluorescent protein-tagged hK(Ca)3.1a and/or YFP-tagged hK(Ca)3.1b isoforms showed that hK(Ca)3.1b suppressed the localization of hK(Ca)3.1a to the plasma membrane. In the Xenopus oocyte translation system, co-expression of hK(Ca)3.1b with hK(Ca)3.1a suppressed IKCa channel activity of hK(Ca)3.1a in a dominant-negative manner. In addition, this study indicated that up-regulation of mK(Ca)3.1b in mouse thymocytes differentiated CD4(+) CD8(+) phenotype thymocytes into CD4(-) CD8(-) ones and suppressed concanavalin-A-stimulated thymocyte growth by down-regulation of mIL-2 transcripts. Anti-proliferative effects and down-regulation of mIL-2 transcripts were also observed in mK(Ca)3.1b-overexpressing mouse thymocytes. These suggest that the N-terminal domain of K(Ca)3.1 is critical for channel trafficking to the plasma membrane and that the fine-tuning of IKCa channel activity modulated through alternative splicing events may be related to the control in physiological and pathophysiological conditions in T-lymphocytes.
  • Contribution of K(ir)2 potassium channels to ATP-induced cell death in brain capillary endothelial cells and reconstructed HEK293 cell model, Daiju Yamazaki, Hiroaki Kito, Seiji Yamamoto, Susumu Ohya, Hisao Yamamura, Kiyofumi Asai, Yuji Imaizumi, AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY, 300, (1) C75 - C86,   2011年01月, 査読有り, Yamazaki D, Kito H, Yamamoto S, Ohya S, Yamamura H, Asai K, Imaizumi Y. Contribution of K(ir)2 potassium channels to ATP-induced cell death in brain capillary endothelial cells and reconstructed HEK293 cell model. Am J Physiol Cell Physiol 300: C75-C86, 2011. First published October 27, 2010; doi: 10.1152/ajpcell.00135.2010.-Cellular turnover of brain capillary endothelial cells (BCECs) by the balance of cell proliferation and death is essential for maintaining the homeostasis of the blood-brain barrier. Stimulation of metabotropic ATP receptors (P2Y) transiently increased intracellular Ca2+ concentration ([Ca2+](i)) in t-BBEC 117, a cell line derived from bovine BCECs. The [Ca2+](i) rise induced membrane hyperpolarization via the activation of apamin-sensitive small-conductance Ca2+-activated K+ channels (SK2) and enhanced cell proliferation in t-BBEC 117. Here, we found anomalous membrane hyperpolarization lasting for over 10 min in response to ATP in similar to 15% of t-BBEC 117, in which inward rectifier K+ channel (K(ir)2.1) was extensively expressed. Once anomalous hyperpolarization was triggered by ATP, it was removed by Ba2+ but not by apamin. Prolonged exposure to ATP gamma S increased the relative population of t-BBEC 117, in which the expression of K(ir)2.1 mRNAs was significantly higher and Ba2+ -sensitive anomalous hyperpolarization was observed. The cultivation of t-BBEC 117 in serum-free medium also increased this population and reduced the cell number. The reduction of cell number was enhanced by the addition of ATP+ S and the enhancement was antagonized by Ba2+. In the human embryonic kidney 293 cell model, where SK2 and K(ir)2.1 were heterologously coexpressed, [Ca2+] i rise by P2Y stimulation triggered anomalous hyperpolarization and cell death. In conclusion, P2Y stimulation in BCECs enhances cell proliferation by SK2 activation in the majority of cells but also triggers cell death in a certain population showing a substantial expression of K(ir)2.1. This dual action of P2Y stimulation may effectively facilitate BCEC turnover.
  • Novel spliced variants of large-conductance Ca(2+)-activated K(+)-channel β2-subunit in human and rodent pancreas., Ohya S, Fujimori T, Kimura T, Yamamura H, Imaizumi Y, Journal of pharmacological sciences, 114, (2) 198 - 205,   2010年10月, 査読有り
  • Participation of KCNQ (Kv7) potassium channels in myogenic control of cerebral arterial diameter, Xi Zoe Zhong, Maksym I. Harhun, Soren P. Olesen, Susumu Ohya, James D. Moffatt, William C. Cole, Iain A. Greenwood, JOURNAL OF PHYSIOLOGY-LONDON, 588, (17) 3277 - 3293,   2010年09月, 査読有り, KCNQ gene expression was previously shown in various rodent blood vessels, where the products of KCNQ4 and KCNQ5, Kv7.4 and Kv7.5 potassium channel subunits, respectively, have an influence on vascular reactivity. The aim of this study was to determine if small cerebral resistance arteries of the rat express KCNQ genes and whether Kv7 channels participate in the regulation of myogenic control of diameter. Quantitative reverse transcription polymerase chain reaction (QPCR) was undertaken using RNA isolated from rat middle cerebral arteries (RMCAs) and immunocytochemistry was performed using Kv7 subunit-specific antibodies and freshly isolated RMCA myocytes. KCNQ4 message was more abundant than KCNQ5 = KCNQ1, but KCNQ2 and KCNQ3 message levels were negligible. Kv7.1, Kv7.4 and Kv7.5 immunoreactivity was present at the sarcolemma of freshly isolated RMCA myocytes. Linopirdine (1 mu m) partially depressed, whereas the Kv7 activator S-1 (3 and/or 20 mu m) enhanced whole-cell Kv7.4 (in HEK 293 cells), as well as native RMCA myocyte Kv current amplitude. The effects of S-1 were voltage-dependent, with progressive loss of stimulation at potentials of >-15 mV. At the concentrations employed linopirdine and S-1 did not alter currents due to recombinant Kv1.2/Kv1.5 or Kv2.1/Kv9.3 channels (in HEK 293 cells) that are also expressed by RMCA myocytes. In contrast, another widely used Kv7 blocker, XE991 (10 mu m), significantly attenuated native Kv current and also reduced Kv1.2/Kv1.5 and Kv2.1/Kv9.3 currents. Pressurized arterial myography was performed using RMCAs exposed to intravascular pressures of 10-100 mmHg. Linopirdine (1 mu m) enhanced the myogenic response at >= 20 mmHg, whereas the activation of Kv7 channels with S-1 (20 mu m) inhibited myogenic constriction at > 20 mmHg and reversed the increased myogenic response produced by suppression of Kv2-containing channels with 30 nm stromatoxin (ScTx1). These data reveal a novel contribution of KCNQ gene products to the regulation of myogenic control of cerebral arterial diameter and suggest that Kv7 channel activating drugs may be appropriate candidates for the development of an effective therapy to ameliorate cerebral vasospasm.
  • Contribution of Chloride Channel Conductance to the Regulation of Resting Membrane Potential in Chondrocytes, Kenji Funabashi, Masato Fujii, Hisao Yamamura, Susumu Ohya, Yuji Imaizumi, JOURNAL OF PHARMACOLOGICAL SCIENCES, 113, (1) 94 - 99,   2010年05月, 査読有り, The contribution of Cl(-) conductance relative to that of K(+) in the regulation of membrane potential was examined using OUMS-27 cells, a model cell-line of human chondrocytes. Application of 100 mu M niflumic acid (NFA) and other anion-channel blockers induced significant membrane hyperpolarization. The NFA-sensitive membrane current under voltage-clamp was predominantly Cl(-) current. Application of NFA induced small but significant increase in intracellular Ca(2+) concentration ([Ca(2+)]i) and markedly enhanced the late component of [Ca(2+)]i rise induced by 1 mu M histamine. In conclusion, Cl(-) conductance substantially contributes to the regulation of resting membrane potential and [Ca(2+)]i in OUMS-27 cells.
  • TRPV4-like non-selective cation currents in cultured aortic myocytes., Tanaka R, Muraki K, Ohya S, Yamamura H, Hatano N, Itoh Y, Imaizumi Y, Journal of pharmacological sciences, 108, (2) 179 - 189,   2008年10月, 査読有り
  • A novel opener of large-conductance Ca2+ -activated K+ (BK) channel reduces ischemic injury in rat cardiac myocytes by activating mitochondrial K(Ca) channel., Sakamoto K, Ohya S, Muraki K, Imaizumi Y, Journal of pharmacological sciences, 108, (1) 135 - 139,   2008年09月, 査読有り
  • Cell-cycle-dependent regulation of Ca2+-activated K+ channel in Jurkat T-lymphocyte, Takashi Morimoto, Susumu Ohya, Hidetoshi Hayashi, Kikuo Onozaki, Yuji Imaizumi, JOURNAL OF PHARMACOLOGICAL SCIENCES, 104, (1) 94 - 98,   2007年05月, 査読有り, Small-conductance Ca2+-activated K+ (SK2) channel plays an important role in the activation of Jurkat T-lymphocytes by maintaining electrical gradients for the sustained Ca2+ influx. Apamin-sensitive K+ current was significantly decreased with cell-cycle progression from G(0)/G(1) into G(2)/M phases, and protein expression of SK2 channels showed parallel down-regulation, with its highest expression at early G(0)/G(1) phase. In the G(0)/G(1) phase, the apamin-sensitive component of thapsigargin-induced Ca2+ influx was significantly larger than that in the G(2)/M phase. These observations suggest that SK2-channel activation may largely contribute to the sustained Ca2+ influx in the G(0)/G(1) phase in comparison of that in the G(2)/M phase in Jurkat T-lymphocytes.
  • Characteristics of the ATP-induced Ca2+-entry pathway in the t-BBEC 117 cell line derived from bovine brain endothelial cells, Daiju Yamazaki, Susumu Ohya, Kiyofumi Asai, Yuji Imaizumi, JOURNAL OF PHARMACOLOGICAL SCIENCES, 104, (1) 103 - 107,   2007年05月, 査読有り, ATP-receptor (P2Y) stimulation induced sustained Ca2+-entry, which was essential for the enhanced cell-proliferation in t-BBEC 117, an immortalized cell-line derived from bovine brain endothelial cells. Application of Ca2+ following store-depletion with thapsigargin in Ca2+-free solution induced Ca2+-entry through store-operated channels (SOCs). Ca2+-entry induced by ATP or 1-oleoyl-2-acetyl-sn-glycerol (OAG) together with Ca2+ was significantly larger than that by Ca2+ alone, suggesting the involvement of receptor-operated channels (ROCs) in the Ca2+-entry. Results obtained using pharmacological tools suggest that the contribution of Ca2+ sources to ATP-induced [Ca2+](i) rise in t-BBEC117 is estimated as approximately 2:1:2 for Ca2+-release and Ca2+-entry though SOCs and ROCs, respectively.
  • Methyl-beta-cyclodextrin prevents Ca2+-induced Ca2+ release in smooth muscle cells of mouse urinary bladder, Shingo Hotta, Hisao Yamamura, Susumu Ohya, Yuji Imaizumi, JOURNAL OF PHARMACOLOGICAL SCIENCES, 103, (1) 121 - 126,   2007年01月, 査読有り, We examined the effects of methyl-,8-cyclodextrin (MPCD) on Ca2+-induced Ca2+ release (CICR) in smooth muscle cells (SMCs) of mouse urinary bladder (UB). Short depolarization of UBSMCs under voltage-clamp elicited several local Ca2+ transients (Ca2+ hot spots) via CICR within 20 ms in discrete sub-sarcolemmal areas. Then, the Ca2+ wave spread to whole areas. The pretreatment with 10 mM M beta CD significantly attenuated Ca2+ hot spots in UBSMCs and reduced contraction by single direct electrical pulse stimulation in UBSM strips. M beta CD may prevent CICR by attenuating the coupling between voltage-dependent Ca2+ channels and ryanodine receptors in Ca2+ hot spot areas.
  • Molecular and electrophysiological characteristics of K+ conductance sensitive to acidic pH in aortic smooth muscle cells of WKY and SHR, Hidekazu Kiyoshi, Daiju Yamazaki, Susumu Ohya, Mika Kitsukawa, Katsuhiko Muraki, Shin-ya Saito, Yasushi Ohizumi, Yuji Imaizumi, AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 291, (6) H2723 - H2734,   2006年12月, 査読有り, Changes in K+ conductances and their contribution to membrane depolarization in the setting of an acidic pH environment have been studied in myocytes from aortic smooth muscle cells of spontaneously hypertensive rats (SHR) compared with those from Wistar-Kyoto (WKY) rats. The resting membrane potential (RMP) of aortic smooth muscle at extracellular pH (pHo) of 7.4 was significantly more depolarized in SHR than in WKY rats. Acidification to pHo 6.5 made this difference in RMP between SHR and WKY rats more significant by further depolarizing the SHR myocytes. Large-conductance Ca2+-activated K+ (BK) currents, which were markedly suppressed by acidification, were larger in aortic myocytes of SHR than in those of WKY rats. In contrast, acid-sensitive, non-BK currents were smaller in SHR. Western blot analyses showed that expression of BK-alpha- and -beta(1) subunits in SHR aortas was upregulated and comparable with those in WKY rats, respectively. Additional electrophysiological and molecular studies showed that pH- and halothanesensitive two-pore domain weakly inward rectifying K+ channel (TWIK)-like acid-sensitive K+ (TASK) channel subtypes were functionally expressed in aortas, and TASK1 expression was significantly higher in WKY than in SHR. Although the background current through TASK channels at normal pHo ( 7.4) was small and may not contribute significantly to the regulation of RMP, TASK channel activation by halothane or alkalization (pH(o) 8.0) induced significant hyperpolarization in WKY but not in SHR. In conclusion, the larger depolarization and subsequent abnormal contractions after acidification in aortic myocytes in the setting of SHR hypertension are mainly attributable to the larger contribution of BK current to the total membrane conductance than in WKY aortas.
  • Novel functions of small conductance Ca2+-activated K+ channel in enhanced cell proliferation by ATP in brain endothelial cells, Daiju Yamazaki, Mineyoshi Aoyama, Susumu Ohya, Katsuhiko Muraki, Kiyofumi Asai, Yuji Imaizumi, JOURNAL OF BIOLOGICAL CHEMISTRY, 281, (50) 38430 - 38439,   2006年12月, 査読有り, Brain capillary endothelial cells (BCECs) form the blood-brain barrier (BBB), which is essential for maintaining homeostasis of the brain. Net cellular turnover, which results from the balance between cell death and proliferation, is important in maintaining BBB homeostasis. Here we report a novel mechanism that underlies ATP-induced cell proliferation in t-BBEC 117, a cell line derived from bovine brain endothelial cells. Application of 0.1-30 mu M ATP to t-BBEC 117 concentration-dependently increased intracellular Ca2+ concentration ([Ca2+](i)) in two phases: an initial transient phase and a later and smaller sustained one. These two phases of [Ca2+](i) rise were mainly due to Ca2+ release and sustained Ca2+ influx, respectively. The pretreatment with apamin, a selective blocker of small conductance Ca2+-activated K+ channels (SK), significantly reduced both the [Ca2+](i) increase and K+ current induced by ATP. Transcripts corresponding to P2Yx, SK2, and transient receptor potential channels were detected in t-BBEC 117. Knock down of SK2 protein, which was the predominant Ca2+-activated K+ channel expressed in t-BBEC 117, by siRNA significantly reduced both the sustained phase of the [Ca2+](i) rise and the K+ current induced by ATP. Cell proliferation was increased significantly by the presence of the stable ATP analogue ATP gamma S. This effect was blunted by UCL1684, a synthesized SK blocker. In conclusion, in brain endothelial cells ATP-induced [Ca2+](i) rise activates SK2 current, and the subsequent membrane hyperpolarization enhances Ca2+ entry presumably through transient receptor potential channels. This positive feedback mechanism can account for the augmented cell proliferation by ATP.
  • Voltage-dependent Ca2+-channel block by openers of intermediate and small conductance Ca2+-activated K+ channels in urinary bladder smooth muscle cells, K Morimura, H Yamamura, S Ohya, Y Imaizumi, JOURNAL OF PHARMACOLOGICAL SCIENCES, 100, (3) 237 - 241,   2006年03月, 査読有り, We examined effects of small and intermediate conductance Ca2+-activated K+ (SK and IK) channel openers, DCEBIO (5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one) and NS309 (3-oxime-6,7-dichloro-1H-indole-2,3-dione), on L-type Ca2+ channel current (I-Ca) that was measured in smooth muscle cells isolated from mouse urinary bladder under whole cell voltage-clamp. The I-Ca was concentration-dependently inhibited by DCEBIO and NS309; half inhibition was obtained at 71.6 and 10.61 mu M, respectively. The specificity of NS309 to the IK channel over the Ca2+ channel appears to be high and higher than that of DCEBIO. DCEBIO and even NS309 may, however, substantially block Ca2+ channels when used as SK channel openers.
  • Two-step Ca2+ intracellular release underlies excitation-contraction coupling in mouse urinary bladder myocytes., Morimura K, Ohi Y, Yamamura H, Ohya S, Muraki K, Imaizumi Y, American journal of physiology. Cell physiology, 290, (2) C388 - 403,   2006年02月, 査読有り
  • Activation of large-conductance, Ca2+-activated K+ channels by cannabinoids, H Sade, K Muraki, S Ohya, N Hatano, Y Imaizumi, AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY, 290, (1) C77 - C86,   2006年01月, 査読有り, We have examined the effects of the cannabinoid anandamide (AEA) and its stable analog, methanandamide (methAEA), on large-conductance, Ca2+-activated K+ (BK) channels using human embryonic kidney (HEK)-293 cells, in which the alpha-subunit of the BK channel (BK-alpha), both alpha- and beta(1)-subunits (BK-alpha beta(1)), or both alpha- and beta(4)- subunits (BK-alpha beta 4) were heterologously expressed. In a whole cell voltage-clamp configuration, each cannabinoid activated BK-alpha beta 1 within a similar concentration range. Because methAEA could potentiate BK-alpha, BK-alpha beta 1, and BK-alpha beta 4 with similar efficacy, the beta-subunits may not be involved at the site of action for cannabinoids. Under cell-attached patch-clamp conditions, application of methAEA to the bathing solution increased BK channel activity; however, methAEA did not alter channel activity in the excised inside-out patch mode even when ATP was present on the cytoplasmic side of the membrane. Application of methAEA to HEK-BK-alpha and HEK-BK-alpha beta 1 did not change intracellular Ca2+ concentration. Moreover, methAEA-induced potentiation of BK channel currents was not affected by pretreatment with a CB1 antagonist (AM251), modulators of G proteins (cholera and pertussis toxins) or by application of a selective CB2 agonist (JWH133). Inhibitors of CaM, PKG, and MAPKs (W7, KT5823, and PD-98059) did not affect the potentiation. Application of methAEA to mouse aortic myocytes significantly increased BK channel currents. This study provides the first direct evidence that unknown factors in the cytoplasm mediate the ability of endogenous cannabinoids to activate BK channel currents. Cannabinoids may be hyperpolarizing factors in cells, such as arterial myocytes, in which BK channels are highly expressed.
  • Inherent pacemaker function of duodenal GIST, S Furuzono, S Ohya, S Inoue, A Nakao, Y Imaizumi, S Nakayama, EUROPEAN JOURNAL OF CANCER, 42, (2) 243 - 248,   2006年01月, 査読有り, Gastrointestinal stromal tumours (GIST) are thought to derive from interstitial cells of Cajal (ICCs), which are putative pacemaker cells for gut motility. Isolated cells were obtained by enzymatic treatment of human duodenum GIST tissue having a frequent gain- of-function gene mutation. After cell culturing, c-Kit immunoreactivity was preserved and the cells developed long processes. Whole cell patch clamp recordings revealed voltage-dependent outward currents, without transient inward currents. Intracellular Ca" measurements showed oscillation-like spontaneous activity in some GIST cells. RT-PCR revealed expression of ion channels (Kv1.1, Kv1.6 and KCNH2; IP3R1, and IP3R2; TRPC1, 3, 6 and 7; Cx43) which have been suggested to play important roles in pacemaker activity. However, SCN5A, a TTX-resistant Na+ channel known to be expressed in human ICCs, was below detectable levels. These data suggest that GIST cells appear to preserve some, but not all ionic mechanisms underlying pacemaker activity in ICC. (c) 2005 Elsevier Ltd. All rights reserved.
  • Molecular pharmacological studies on potassium channels and their regulatory molecules, Susumu Ohya, YAKUGAKU ZASSHI-JOURNAL OF THE PHARMACEUTICAL SOCIETY OF JAPAN, 126, (10) 945 - 953,   2006年, 査読有り, K+ channels play important roles in the control of a large variety of physiological functions such as muscle contraction, neurotransmitter release, hormone secretion, and cell proliferation. Over 100 cloned K+ channel pore-forming a and accessory beta subunits have been identified so far. Here, we introduce a series of molecular pharmacological and physiological studies on some types of voltage-dependent K+ channels and Ca2+-activated K+ channels. We examined molecular cloning and functional characterization of novel, fast-inactivating, A-type K+ channel alpha (Kv4.3L) and beta (KChIP2S) subunits predominantly expressed in mammalian heart and found the sites in Kv4 channels for 1) the regulation of voltage dependency and 2) the CaMKII phosphorylation in the C-terminal cytoplasmic domain. Moreover, we found that delayed rectifier-type K+ channels (ERG1 and KCNQ) contribute to the resting membrane conductance in vascular and gastrointestinal smooth muscles. The large-conductance Ca2+-activated K+ (BK) channel is ubiquitously expressed and contributes to diverse physiological processes. Recent reports have shown that a BK-like channel (mitoK(Ca)) is expressed in cardiac mitochondria, suggesting that BK channel openers protect mammalian hearts against ischentic injury. Our studies revealed that BK beta 1 interacts with cytochrorne c oxidase I (Ccol) in cardiac mitochondria, and that the activation of BK channels by 17 beta-estradiol results in a significant increase in the survival rate of ventricular myocytes. These findings suggest that BK beta 1 may play an important role in the regulation of cell respiration in cardiac myocytes and be a target for the modulation by female gonadal hormones.
  • Sulphonylurea receptors differently modulate ICC pacemaker Ca2+ activity and smooth muscle contractility, S Nakayama, S Ohya, HN Liu, T Watanabe, S Furuzono, J Wang, Y Nishizawa, M Aoyama, N Murase, T Matsubara, M Ito, Y Imaizumi, S Kajioka, JOURNAL OF CELL SCIENCE, 118, (18) 4163 - 4173,   2005年09月, 査読有り, Appropriate gastrointestinal motility is essential to properly control the body energy level. Intracellular Ca2+ ([Ca2+](i)) oscillations in interstitial cells of Cajal (ICCs; identified with c-Kit immunoreactivity) are considered to be the primary mechanism for the pacemaker activity in gastrointestinal motility. In the present study, RT-PCR examinations revealed predominant expression of the type 1 isoform of sulphonylurea receptors (SUR1) in ICCs of the mouse ileum, but expression of SUR2 was predominant in smooth muscle. In cell clusters prepared from the same tissue, smooth muscle contractility and pacemaker [Ca2+](i) activity in ICCs were found to be differentially modulated by K-ATP channel openers and sulphonylurea compounds, in accordance with the expression of SUR isoforms. 1 mu M cromakalim nearly fully suppressed the mechanical activity in smooth muscle, whereas ICC pacemaker [Ca2+](i) oscillations persisted. Greater concentrations (similar to 10 mu M) of cromakalim attenuated pacemaker [Ca2+](i) oscillations. This effect was not reversed by changing the reversal potential of K+, but was prevented by glibenclamide. Diazoxide at 30 mu M terminated ICC pacemaker [Ca2+](i) oscillations, but again treatment with high extracellular K+ did not restore them. These results suggest that SUR can modulate pacemaker [Ca2+](i) oscillations via voltage-independent mechanism(s), and also that intestinal pacemaking and glucose control are closely associated with SUR.
  • [Investigation into gastrointestinal pacemaker mechanism using cultured cell cluster preparation]., Nakayama S, Ohya S, Imaizumi Y, Nihon yakurigaku zasshi. Folia pharmacologica Japonica, 123, (3) 149 - 154,   2004年03月, 査読有り
  • Dihydropyridine Ca2+ channel antagonists and agonists block Kv4.2, Kv4.3 and Kv1.4 K+ channels expressed in HEK293 cells, N Hatano, S Ohya, K Muraki, W Giles, Y Imaizumi, BRITISH JOURNAL OF PHARMACOLOGY, 139, (3) 533 - 544,   2003年06月, 査読有り, 1 We have determined the molecular basis of nicardipine-induced block of cardiac transient outward K+ currents (I-to). Inhibition of I-to was studied using cloned voltage-dependent K+ channels (Kv) channels, rat Kv4.3L, Kv4.2, and Kv1.4, expressed in human embryonic kindey cell line 293 (HEK293) cells. 2 Application of the dihydropyridine Ca2+ channel antagonist, nicardipine, accelerated the inactivation rate and reduced the peak amplitude of Kv4.3L currents in a concentration-dependent manner (IC50: 0.42 muM). The dihydropyridine (DHP) Ca2+ channel agonist, Bay K 8644, also blocked this K+ current (IC50: 1.74 muM). 3 Nicardipine (1 muM) slightly, but significantly, shifted the voltage dependence of activation and steady-state inactivation to more negative potentials, and also slowed markedly the recovery from inactivation of Kv4.3L currents. 4 Coexpression of K+ channel-interacting protein 2 (KChIP2) significantly slowed the inactivation of Kv4.3L currents as expected. However, the features of DHP-induced block of K+ current were not substantially altered. 5 Nicardipine exhibited similar block of Kv1.4 and Kv4.2 channels stably expressed in HEK293 cells; IC50' s were 0.80 and 0.62 muM, respectively. 6 Thus, at submicromolar concentrations, DHP Ca2+ antagonist and agonist inhibit Kv4.3L and have similar inhibiting effects on other components of cardiac I-to, Kv4.2 and Kv1.4.
  • Molecular basis of pimarane compounds as novel activators of large-conductance Ca2+-activated K+ channel alpha-subunit, Y Imaizumi, K Sakamoto, A Yamada, A Hotta, S Ohya, K Muraki, M Uchiyama, T Ohwada, MOLECULAR PHARMACOLOGY, 62, (4) 836 - 846,   2002年10月, 査読有り, Effects of pimaric acid (PiMA) and eight closely related compounds on large-conductance K+ (BK) channels were examined using human embryonic kidney (HEK) 293 cells, in which either the alpha subunit of BK channel (HEKBKalpha) or both alpha and beta1 (HEKBKalphabeta1) subunits were heterologously expressed. Effects of these compounds (10 muM) on the membrane potential of HEKBKalphabeta1 were monitored by use of DiBAC(4) (3), a voltage-sensitive dye. PiMA, isopimaric acid, sandaracoisopimaric acid, dihydropimaric acid, dihydroisopimaric acid, hyperpolarization. The direct measurement of BKalphabeta1 opening under whole-cell voltage clamp showed that these six compounds activated BKalphabeta1 in a very similar concentration range (1-10 muM); in contrast, abietic acid, sclareol, and methyl pimarate had no effect. PiMA did not affect the charybdotoxin-induced block of macroscopic BKalphabeta1 current. Single channel recordings of BKalphabeta1 in inside-out patches showed that 10 muM PiMA did not change channel conductance significantly increased its open probability as a result of increase in sensitivity to Ca2+ and voltage. Because coexpression of the beta1 subunit did not affect PiMA-induced potentiation, the site of action for PiMA is suggested to be BKalpha subunit. PiMA was selective to BK over cloned small and intermediate Ca2+ activated K+ channels. In conclusion, PiMA (>1 muM) increases Ca2+ and voltage-sensitivity of BKalpha when applied from either side of the cell membrane. The marked difference in potency as BK channel openers between PiMA and abietic acid, despite only very small differences in their chemical structures, may provide insight into the fundamental structure-activity relationship governing BKalpha activation.
  • Functional and molecular identification of ERG channels in murine portal vein myocytes, S Ohya, B Horowitz, IA Greenwood, AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY, 283, (3) C866 - C877,   2002年09月, 査読有り, Ion channels encoded by ether-a`-go-go-related genes (ERG) have been implicated in repolarization of the cardiac action potential and also as components of the resting membrane conductance in various cells. The aim of the present study was to determine whether ERG channels were expressed in smooth muscle cells isolated from portal vein. RT-PCR demonstrated the expression of murine ERG (mERG), and real-time quantitative PCR showed that the mERG1b isoform predominated over the mERG1a, mERG2, and mERG3 in portal vein. Single myocytes from portal vein displayed membrane staining with an ERG1-specific antibody. Whole cell voltage-clamp experiments were performed to determine whether portal vein myocytes expressed functional ERG channels. Large inward currents with distinctive kinetics were elicited that were inhibited rapidly by E-4031 (mean amplitude of the E-4031-sensitive current at -120 mV was -205 +/- 24 pA; n = 14). Deactivation of the E-4031-sensitive current was voltage dependent (mean time constants at -80 and -120 mV were 103 +/- 9 and 33 +/- 2 ms, respectively; n = 13). Because of the rapid kinetics of mERG currents at more negative potentials, there was a substantial noninactivating "window" current that reached a maximum of -6 +/- 10 pA at -70 mV. Complete portal veins exhibited spontaneous contractile activity in isometric tension experiments, and this activity was modified significantly by E-4031. These data show that ERG channels are expressed in murine portal vein myocytes that may contribute to the resting membrane conductance.
  • Molecular and functional characterization of ERG, KCNQ, and KCNE subtypes in rat stomach smooth muscle., Ohya S, Asakura K, Muraki K, Watanabe M, Imaizumi Y, American journal of physiology. Gastrointestinal and liver physiology, 282, (2) G277 - 87,   2002年02月, 査読有り

書籍等出版物

  • 医療薬学III, 大矢 進, 分担執筆, 感覚器・皮膚の疾患に用いられる代表的な薬物の基本構造と薬効(薬理・薬物動態), 東京化学同人,   2017年04月
  • 詳解 薬理学, 大矢 進, 分担執筆, 自律神経系に作用する薬物, 廣川書店,   2015年08月

受賞

  •   2006年, 日本薬学会奨励賞(平成18年度)
  •   2006年, The PSJ Award for Young Scientists
  •   2005年, 最優秀ポスター発表賞(US-Jpan Conference on Drug Development & Rational Drug Design)

競争的資金

  • 炎症慢性化によるイオンチャネル発現・活性変動の機序解明とその創薬への応用, 文部科学省, 基盤研究(C),   2016年04月 - 2019年03月
  • カリウムチャネル阻害による抗炎症性サイトカインIL-10産生増大機構の解明, ソルト・サイエンス研究財団, 平成29年度助成,   2017年04月 - 2018年03月
  • Tリンパ球におけるtwo-pore型K+チャネルK2P5.1の生理的役割とその新規阻害機構の解明, ソルト・サイエンス研究財団, 平成27年度助成,   2015年04月 - 2016年03月
  • 免疫疾患、癌治療標的分子としての酸感受性カリウムチャネルの制御機構解明, 文部科学省, 基盤研究(C),   2013年04月 - 2016年03月
  • 新規カルシウム活性化カリウムチャネル機能不全体の発現調節と関連疾患での役割, 文部科学省, 科学研究費補助金「基盤研究C」,   2013年04月 - 2016年03月
  • カリウムチャネル新規阻害機構の解明, 上原記念生命科学財団, 平成24年度研究推進特別奨励金,   2014年04月 - 2015年03月
  • ストレス応答性調節におけるリンパ球Ca2+活性化K+チャネルKCa3.1の役割, 薬理研究会, 平成24年度研究助成,   2012年04月 - 2013年03月
  • 免疫シナプスにおけるTwo-pore domain K+チャネル輸送機構の解明, 持田記念医学薬学振興財団, 第30回(平成24年度)研究助成金,   2012年04月 - 2013年03月
  • カルシウム活性化カリウムチャネルの新規発現調節機構とその創薬への応用, 武田科学研究振興財団, 2011年度 薬学系研究奨励継続助成,   2011年04月 - 2013年03月
  • 炎症性疾患におけるTリンパ球カリウムチャネル活性・発現調節, 鈴木謙三記念医科学応用研究財団, 平成23年度調査研究助成金,   2011年04月 - 2012年03月
  • カルシウム活性化カリウムチャネルの新規発現調節機構とその創薬への応用, 武田科学研究振興財団, 2009年度 薬学系研究奨励助成,   2009年04月 - 2011年03月
  • イオンチャネル病
  • 新規カルシウム活性化カリウムチャネル機能不全体の発現調節と疾患での役割
  • Molecular Pharmacology of ion channels

教育活動情報

担当経験のある科目

  • 薬品作用学, 名古屋市立大学薬学部
  • 薬理学, 京都薬科大学
  • 薬理学, 名古屋市立大学医学部


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