A Structural Role for the Synaptobrevin 2 Transmembrane Domain in Dense-Core Vesicle Fusion Pores
A Structural Role for the Synaptobrevin 2 Transmembrane Domain in Dense-Core Vesicle Fusion Pores
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DOI：
10.1523/jneurosci.3983-14.2015
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发表时间：
2015-04-08
影响因子：
5.3
通讯作者：
Jackson, Meyer B.
中科院分区：
文献类型：
--
作者：
Chang, Che-Wei;Hui, Enfu;Jackson, Meyer B.
Ca 2+触发的神经递质和激素的释放依赖于可溶性N-乙基马来酰亚胺敏感因子附着蛋白受体（SNARE）来驱动囊泡和质膜的融合。囊泡SNARE突触泡蛋白2（syb 2）和两个质膜SNARE突触融合蛋白（syx）和SNAP-25形成的SNARE复合物将两个膜拉在一起，但膜并置之后的事件以及SNARE重塑脂质膜的方式仍然知之甚少。SNARE syx和syb 2具有跨膜结构域（TMD），其可以直接对脂质双层施加力。的TMD的syx影响融合孔通量的方式，表明它线的新生融合孔通过质膜。syb 2的TMD穿过囊泡膜，并且是syx最有可能完成穿过囊泡膜的蛋白质融合孔的伴侣，但这种囊泡陷阱在融合孔中的作用尚未得到测试。在这里，进行电流分析和电导测量，以探测在小鼠嗜铬细胞中的儿茶酚胺胞吐过程中形成的融合孔中syb 2 TMD的功能。融合孔通量是敏感的N末端附近的TMD残基的大小和电荷，融合孔电导改变在这些网站的取代。与syx不同，影响融合孔渗透的syb 2残基沿着TMD的两个α-螺旋面而不是一个面下降沿着。这些结果表明syb 2 TMD在新生融合孔中的作用，但与syx TMD的结构排列非常不同。
Ca2+-triggered release of neurotransmitters and hormones depends on soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) to drive the fusion of the vesicle and plasma membranes. The formation of the SNARE complex by the vesicle SNARE synaptobrevin 2 (syb2) and the two plasma membrane SNAREs syntaxin (syx) and SNAP-25 draws the two membranes together, but the events that follow membrane juxtaposition, and the ways that SNAREs remodel lipid membranes remain poorly understood. The SNAREs syx and syb2 have transmembrane domains (TMDs) that can exert force directly on the lipid bilayers. The TMD of syx influences fusion pore flux in a manner that suggests it lines the nascent fusion pore through the plasma membrane. The TMD of syb2 traverses the vesicle membrane and is the most likely partner to syx in completing a proteinaceous fusion pore through the vesicle membrane, but the role of this vesicle SNARE in fusion pores has yet to be tested. Here amperometry and conductance measurements were performed to probe the function of the syb2 TMD in fusion pores formed during catecholamine exocytosis in mouse chromaffin cells. Fusion pore flux was sensitive to the size and charge of TMD residues near the N terminus; fusion pore conductance was altered by substitutions at these sites. Unlike syx, the syb2 residues that influence fusion pore permeation fell along two alpha-helical faces of its TMD, rather than one. These results indicate a role for the syb2 TMD in nascent fusion pores, but in a very different structural arrangement from that of the syx TMD.