Membrane-Proximal Tryptophans of Synaptobrevin II Stabilize Priming of Secretory Vesicles
Membrane-Proximal Tryptophans of Synaptobrevin II Stabilize Priming of Secretory Vesicles
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DOI：
10.1523/jneurosci.6282-11.2012
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发表时间：
2012-11-07
影响因子：
5.3
通讯作者：
Bruns, Dieter
中科院分区：
文献类型：
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作者：
Borisovska, Maria;Schwarz, Yvonne N.;Bruns, Dieter
跨溶性N-乙基马来酰亚胺敏感因子附着蛋白（SNAP）受体（SNARE）复合物之间形成的SNARE基序的小突触蛋白II，SNAP-25，和syntaxin在Ca 2+调节的胞吐中发挥重要作用。除了已被充分研究过的SNARE结构域之间的相互作用外，对SNARE蛋白中其他进化上保守的结构的功能相关性知之甚少。在这里，我们表明，两个高度保守的色氨酸残基内的囊泡陷阱Synaptobrevin II（Syb II）的囊泡膜结构域（JMD）的取代深刻损害启动的颗粒在小鼠嗜铬细胞中不改变从单个囊泡释放的儿茶酚胺。使用分子动力学模拟的膜嵌入SybII，我们表明，色氨酸残基的JMD的影响静电表面电位通过控制相邻的赖氨酸和精氨酸残基在膜-水界面的位置。我们的观察表明，SybII的色氨酸部分在保持囊泡在释放准备状态的决定性作用，并支持一个模型，其中色氨酸介导的蛋白质-脂质相互作用有助于桥接融合前的并列膜。
Trans-soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP) receptor (SNARE) complexes formed between the SNARE motifs of synaptobrevin II, SNAP-25, and syntaxin play an essential role in Ca2+-regulated exocytosis. Apart from the well studied interactions of the SNARE domains, little is known about the functional relevance of other evolutionarily conserved structures in the SNARE proteins. Here, we show that substitution of two highly conserved tryptophan residues within the juxtamembrane domain (JMD) of the vesicular SNARE Synaptobrevin II (SybII) profoundly impairs priming of granules in mouse chromaffin cells without altering catecholamine release from single vesicles. Using molecular dynamic simulations of membrane-embedded SybII, we show that Trp residues of the JMD influence the electrostatic surface potential by controlling the position of neighboring lysine and arginine residues at the membrane-water interface. Our observations indicate a decisive role of the tryptophan moiety of SybII in keeping the vesicles in the release-ready state and support a model wherein tryptophan-mediated protein-lipid interactions assist in bridging the apposing membranes before fusion.