文章基本信息

标题：The metal-ion-dependent adhesion site in the Von Willebrand factor-A domain of α2δ subunits is key to trafficking voltage-gated Ca2+ channels
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作者：C. Cantí ; M. Nieto-Rostro ; I. Foucault 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：2005
卷号：102
期号：32
页码：11230-11235
DOI：10.1073/pnas.0504183102
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：All auxiliary {alpha}2{delta} subunits of voltage-gated Ca2+ (CaV) channels contain an extracellular Von Willebrand factor-A (VWA) domain that, in {alpha}2{delta}-1 and -2, has a perfect metal-ion-dependent adhesion site (MIDAS). Modeling of the {alpha}2{delta}-2 VWA domain shows it to be highly likely to bind a divalent cation. Mutating the three key MIDAS residues responsible for divalent cation binding resulted in a MIDAS mutant {alpha}2{delta}-2 subunit that was still processed and trafficked normally when it was expressed alone. However, unlike WT {alpha}2{delta}-2, the MIDAS mutant {alpha}2{delta}-2 subunit did not enhance and, in some cases, further diminished CaV1.2, -2.1, and -2.2 currents coexpressed with {beta}1b by using either Ba2+ or Na+ as a permeant ion. Furthermore, expression of the MIDAS mutant {alpha}2{delta}-2 reduced surface expression and strongly increased the perinuclear retention of CaV{alpha}1 subunits at the earliest time at which expression was observed in both Cos-7 and NG108-15 cells. Despite the presence of endogenous {alpha}2{delta} subunits, heterologous expression of {alpha}2{delta}-2 in differentiated NG108-15 cells further enhanced the endogenous high-threshold Ca2+ currents, whereas this enhancement was prevented by the MIDAS mutations. Our results indicate that {alpha}2{delta} subunits normally interact with the CaV{alpha}1 subunit early in their maturation, before the appearance of functional plasma membrane channels, and an intact MIDAS motif in the {alpha}2{delta} subunit is required to promote trafficking of the {alpha}1 subunit to the plasma membrane by an integrin-like switch. This finding provides evidence for a primary role of a VWA domain in intracellular trafficking of a multimeric complex, in contrast to the more usual roles in binding extracellular ligands in other exofacial VWA domains.
关键词：integrin ; neuron ; motif ; expression