title: Orai1 forms a signal complex with SK3 channel in gallbladder smooth muscle.
abstract: Orai1 is one of the key components of store-operated Ca(2+) entry (SOCE) involved in diverse physiological functions. Orai1 may associate with other proteins to form a signaling complex. In the present study, we investigated the interaction between Orai1 and small conductance Ca(2+)-activated potassium channel 3 (SK3). With the use of RNA interference technique, we found that the SOCE and its associated membrane hyperpolarization were reduced while Orai1 was knocked down by a specific Orai1 siRNA in guinea pig gallbladder smooth muscle. However, with the use of isometric tension measurements, our results revealed that agonist-induced muscle contractility was significantly enhanced after Orai1 protein was knocked down or the tissue was treated by SK3 inhibitor apamin, but not affected by larger conductance Ca(2+)-activated potassium channel inhibitor iberiotoxin or intermediate conductance Ca(2+)-activated potassium channel inhibitor TRAM-34. In addition, in the presence of apamin, Orai1 siRNA had no additional effect on agonist-induced contraction. In coimmunoprecipitation experiment, SK3 and Orai1 pulled down each other. These data suggest that, Orai1 physically associated with SK3 to form a signaling complex in gallbladder smooth muscle. Ca(2+) entry via Orai1 activates SK3, resulting in membrane hyperpolarization in gallbladder smooth muscle. This hyperpolarizing effect of Orai1-SK3 coupling could serve to prevent excessive contraction of gallbladder smooth muscle in response to contractile agonists.
authors.affiliation: Department of Physiology, School of Basic Medicine, Anhui Medical University, Hefei, Anhui, 230032, China; Department of Gastrointestinal Surgery, The First Affiliated Hospital of Anhui Medical University, Hefei, 230022, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Song
authors.affiliation: Department of Surgery, Anhui Provincial Corps Hospital of Chinese People's Armed Police Force, Heifei, Anhui, 230041, China.
authors.forename: Xing-Guo
authors.initials: XG
authors.lastname: Zhong
authors.affiliation: Department of Gastroenterology and Hepatology, The Fourth Affiliated Hospital of Anhui Medical University, Hefei, Anhui, 230032, China.
authors.forename: Xian-Ming
authors.initials: XM
authors.lastname: Xia
authors.affiliation: Department of Sports and Health, Guangzhou Sport University, Guangzhou, 510500, China.
authors.forename: Jun-Hao
authors.initials: JH
authors.lastname: Huang
authors.affiliation: Department of Physiology, School of Basic Medicine, Anhui Medical University, Hefei, Anhui, 230032, China.
authors.forename: Yi-Fei
authors.initials: YF
authors.lastname: Fan
authors.affiliation: Department of Physiology, School of Basic Medicine, Anhui Medical University, Hefei, Anhui, 230032, China.
authors.forename: Ren-Xiang
authors.initials: RX
authors.lastname: Yuan
authors.affiliation: Department of Physiology, School of Basic Medicine, Anhui Medical University, Hefei, Anhui, 230032, China.
authors.forename: Nai-Rui
authors.initials: NR
authors.lastname: Xue
authors.affiliation: Department of Physiology, School of Basic Medicine, Anhui Medical University, Hefei, Anhui, 230032, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Du
authors.affiliation: Department of Gastrointestinal Surgery, The First Affiliated Hospital of Anhui Medical University, Hefei, 230022, China.
authors.forename: Wen-Xiu
authors.initials: WX
authors.lastname: Han
authors.affiliation: Department of Gastrointestinal Surgery, The First Affiliated Hospital of Anhui Medical University, Hefei, 230022, China; Department of Gastroenterology and Hepatology, The Fourth Affiliated Hospital of Anhui Medical University, Hefei, Anhui, 230032, China. Electronic address: 297866606@qq.com.
authors.forename: A-Man
authors.initials: AM
authors.lastname: Xu
authors.affiliation: Department of Physiology, School of Basic Medicine, Anhui Medical University, Hefei, Anhui, 230032, China. Electronic address: shenbing@ahmu.edu.cn.
authors.forename: Bing
authors.initials: B
authors.lastname: Shen
mesh_terms: D000818:Animals; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020013:Calcium Signaling; D005704:Gallbladder / Q000187:drug effects / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D034622:RNA Interference; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D046912:Multiprotein Complexes; D051640:Small-Conductance Calcium-Activated Potassium Channels
keywords: Gallbladder smooth muscle; Hyperpolarization; Orai1; Small conductance Ca(2+)-activated potassium channel; Store-operated Ca(2+) entry