文章基本信息

标题：Direct inhibition of P/Q-type voltage-gated Ca2+ channels by Gem does not require a direct Gem/Cavβ interaction
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作者：Mingming Fan ; Zafir Buraei ; Huai-Rong Luo 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2010
卷号：107
期号：33
页码：14887-14892
DOI：10.1073/pnas.1007543107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The Rem, Rem2, Rad, and Gem/Kir (RGK) family of small GTP-binding proteins potently inhibits high voltage-activated (HVA) Ca2+ channels, providing a powerful means of modulating neural, endocrine, and muscle functions. The molecular mechanisms of this inhibition are controversial and remain largely unclear. RGK proteins associate directly with Ca2+ channel {beta} subunits (Cav{beta}), and this interaction is widely thought to be essential for their inhibitory action. In this study, we investigate the molecular underpinnings of Gem inhibition of P/Q-type Ca2+ channels. We find that a purified Gem protein markedly and acutely suppresses P/Q channel activity in inside-out membrane patches, that this action requires Cav{beta} but not the Gem/Cav{beta} interaction, and that Gem coimmunoprecipitates with the P/Q channel {alpha}1 subunit (Cav{alpha}1) in a Cav{beta}-independent manner. By constructing chimeras between P/Q channels and Gem-insensitive low voltage-activated T-type channels, we identify a region encompassing transmembrane segments S1, S2, and S3 in the second homologous repeat of Cav{alpha}1 critical for Gem inhibition. Exchanging this region between P/Q and T channel Cav{alpha}1 abolishes Gem inhibition of P/Q channels and confers Cav{beta}-dependent Gem inhibition to a chimeric T channel that also carries the P/Q I-II loop (a cytoplasmic region of Cav{alpha}1 that binds Cav{beta}). Our results challenge the prevailing view regarding the role of Cav{beta} in RGK inhibition of high voltage-activated Ca2+ channels and prompt a paradigm in which Gem directly binds and inhibits Cav{beta}-primed Cav{alpha}1 on the plasma membrane.
关键词：β subunit ; electrophysiology ; modulation ; Rem, Rem2, Rad, and Gem/Kir proteins ; T-type Ca²⁺ channels