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CaV2.1(P/Q 通道)与突触蛋白的相互作用对于去极化引发的释放是必不可少的。

CaV2.1 (P/Q channel) interaction with synaptic proteins is essential for depolarization-evoked release.

机构信息

Department of Biological Chemistry, The Silverman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel.

出版信息

Channels (Austin). 2010 Jul-Aug;4(4):266-77. doi: 10.4161/chan.4.4.12130. Epub 2010 Jul 18.

Abstract

It is well-established that syntaxin 1A (Sx1A), SNAP-25 and synaptotagmin (Syt1) either alone or in combination, modify the kinetic properties of voltage-gated Ca(2+) channels (VGCCs). The interaction interface resides mainly at the cytosolic II-III domain of the alpha1 subunit of the channels, while Sx1A interacts with the channel also via two highly conserved cysteine residues at the transmembrane domain. In the present study, we characterized Ca(2+)-independent coupling of the human neuronal P/Q-type calcium channel (Ca(V)2.1) with Sx1A, SNAP-25, Syt1 and synaptobrevin (VAMP) in BAPTA-injected Xenopus oocytes. The co-expression of Ca(V)2.1 with Sx1A, SNAP-25 and Syt1, produced a multiprotein complex with distinctive kinetic properties analogous to the excitosome complexes generated by Ca(V)1.2, Ca(V)2.2 and Ca(V)2.3. The distinct kinetic properties of Ca(V)2.1 acquired by close association with Syt1 and t-SNAREs, suggests that the vesicle is tethered to the neuronal channel and to the exocytotic machinery independently of intracellular Ca(2+). To explore the relevance of these interactions to secretion we exploited a BotC1-and a BotA-sensitive secretion system developed for Xenopus oocytes not buffered by BAPTA, in which depolarization-evoked secretion is monitored by a change in membrane capacitance. The reconstituted release mediated by Ca(V)2.1 is consistent with the model in which the VGCC plays a signaling role in triggering release, acting from within the exocytotic complex. The relevance of these results to secretion posits the role of possible rearrangements within the excitosome subsequent to Ca(2+) entry, setting the stage for the fusion of channel-tethered-vesicles upon the arrival of an action potential.

摘要

已证实,突触结合蛋白 1A(Sx1A)、突触融合蛋白 25(SNAP-25)和突触结合蛋白 1(Syt1)无论是单独存在还是组合存在,都可以改变电压门控钙通道(VGCCs)的动力学特性。相互作用界面主要位于通道的α1 亚基胞质 II-III 结构域,而 Sx1A 还通过通道跨膜结构域中的两个高度保守的半胱氨酸残基与通道相互作用。在本研究中,我们在 BAPTA 注射的非洲爪蟾卵母细胞中,对人神经元 P/Q 型钙通道(Ca(V)2.1)与 Sx1A、SNAP-25、Syt1 和突触融合蛋白(VAMP)之间的 Ca(2+)-非依赖性偶联进行了表征。Ca(V)2.1 与 Sx1A、SNAP-25 和 Syt1 的共表达产生了一个具有独特动力学特性的多蛋白复合物,类似于由 Ca(V)1.2、Ca(V)2.2 和 Ca(V)2.3 产生的 exocitosome 复合物。通过与 Syt1 和 t-SNAREs 的紧密关联获得的 Ca(V)2.1 的独特动力学特性表明,囊泡独立于细胞内 Ca(2+)被拴在神经元通道和胞吐机制上。为了探索这些相互作用与分泌的相关性,我们利用了为非洲爪蟾卵母细胞开发的、不受 BAPTA 缓冲的 BotC1 和 BotA 敏感的分泌系统,其中通过膜电容的变化来监测去极化诱导的分泌。由 Ca(V)2.1 介导的重建释放与该模型一致,即 VGCC 在触发释放中发挥信号作用,作用于胞吐复合物内。这些结果与分泌的相关性提出了在 Ca(2+)进入后 exocitosome 内可能发生的重排的作用,为动作电位到达时通道拴系囊泡的融合奠定了基础。

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