title: TRPC1 associates with BK(Ca) channel to form a signal complex in vascular smooth muscle cells.
abstract: TRPC1 (transient receptor potential canonical 1) is a Ca(2+)-permeable cation channel involved in diverse physiological function. TRPC1 may associate with other proteins to form a signaling complex, which is crucial for channel function. In the present study, we investigated the interaction between TRPC1 and large conductance Ca(2+)-sensitive K(+) channel (BK(Ca)). With the use of potentiometric fluorescence dye DiBAC(4)(3), we found that store-operated Ca(2+) influx resulted in membrane hyperpolarization of vascular smooth muscle cells (VSMCs). The hyperpolarization was inhibited by an anti-TRPC1 blocking antibody T1E3 and 2 BK(Ca) channel blockers, charybdotoxin and iberiotoxin. These data were confirmed by sharp microelectrode measurement of membrane potential in VSMCs of intact arteries. Furthermore, T1E3 treatment markedly enhanced the membrane depolarization and contraction of VSMCs in response to several contractile agonists including phenylephrine, endothelin-1, and U-46619. In coimmunoprecipitation experiments, an antibody against BK(Ca) alpha-subunit [BK(Ca)(alpha)] could pull down TRPC1, and moreover an anti-TRPC1 antibody could reciprocally pull down BK(Ca)(alpha). Double-labeling immunocytochemistry showed that TRPC1 and BK(Ca) were colocalized in the same subcellular regions, mainly on the plasma membrane, in VSMCs. These data suggest that, TRPC1 physically associates with BK(Ca) in VSMCs and that Ca(2+) influx through TRPC1 activates BK(Ca) to induce membrane hyperpolarization. The hyperpolarizing effect of TRPC1-BK(Ca) coupling could serve to reduce agonist-induced membrane depolarization, thereby preventing excessive contraction of VSMCs to contractile agonists.
authors.affiliation: Institute of Vascular Medicine, Li Ka Shing Institute of Health Sciences, and Department of Physiology, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Hiu-Yee
authors.initials: HY
authors.lastname: Kwan
authors.forename: Bing
authors.initials: B
authors.lastname: Shen
authors.forename: Xin
authors.initials: X
authors.lastname: Ma
authors.forename: Yuk-Chi
authors.initials: YC
authors.lastname: Kwok
authors.forename: Yu
authors.initials: Y
authors.lastname: Huang
authors.forename: Yu-Bun
authors.initials: YB
authors.lastname: Man
authors.forename: Shan
authors.initials: S
authors.lastname: Yu
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: Yao
mesh_terms: D000818:Animals; D001463:Barbiturates; D020013:Calcium Signaling; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005456:Fluorescent Dyes; D006801:Humans; D007150:Immunohistochemistry; D007555:Isoxazoles; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials; D008839:Microelectrodes; D018613:Microscopy, Confocal; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014661:Vasoconstriction; D014662:Vasoconstrictor Agents / Q000494:pharmacology
chemical_list: D001463:Barbiturates; D005456:Fluorescent Dyes; D007555:Isoxazoles; C494841:KCNMA1 protein, human; C494842:Kcnma1 protein, rat; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D050052:TRPC Cation Channels; D014662:Vasoconstrictor Agents; C096351:transient receptor potential cation channel, subfamily C, member 1; C052795:bis(1,3-dibutylbarbiturate)trimethine oxonol