Localization of Rab3A-binding site on C2A domain of synaptotagmin I to reveal its regulatory mechanism.
Localization of Rab3A-binding site on C2A domain of synaptotagmin I to reveal its regulatory mechanism.
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DOI：
10.1016/j.ijbiomac.2016.12.074
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发表时间：
2017-03
影响因子：
8.2
通讯作者：
Xiaochao Tang;C. Xie;Ying Wang;Xianchun Wang
中科院分区：
文献类型：
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作者：
Xiaochao Tang;C. Xie;Ying Wang;Xianchun Wang
突触结合蛋白I（Synaptotagmin I，Syt I）通过其C2结构域与其他分子结合来调节神经递质释放和多种其他细胞过程。我们的前期研究表明Rab 3A是一个新的与Syt I相互作用的小GTP结合蛋白，可以与Syt I的两个C2结构域结合; C2B的多聚赖氨酸基序是Rab 3A结合的关键位点，但C2 A上的结合位点尚不清楚。为了定位C2 A上Rab 3的结合位点并揭示其调控机制，本研究考察了重组Rab 3A与不同C2 A突变体之间的相互作用。结果表明，C2 A上Rab 3A的一个关键结合位点位于结构域柔性环2的R199 K200处，该位点与大多数已知的功能位点或残基不重叠。推测Rab 3A与C2 A之间的相互作用并非简单地基于静电力，Rab 3A主要通过影响C2 A与突触前膜磷脂的结合来调节C2 A介导的囊泡-突触前膜融合。这些结果有助于理解Rab 3和synaptotagmin在突触囊泡胞吐调控中的作用机制。
Synaptotagmin I (Syt I) functions in the regulation of neurotransmitter release and multiple other cellular processes through its C2 domain binding to other molecules. Our previous study demonstrated that Rab3A, a small GTP-binding protein, is a new interacting partner of Syt I and could bind to both of the C2 domains; the polylysine motif in C2B is a key site for Rab3A binding, but the binding site on C2A is not clear. In order to localize Rab3-binding site on C2A and reveal the relevant regulatory mechanism, in the present study we investigated the interaction between recombinant Rab3A and various C2A mutants. The results showed that a key Rab3A-binding site on C2A is located at R199K200 in the flexible loop 2 of the domain, and the site does not overlap with most of the known functional sites or residues. It was speculated that the interaction between Rab3A and C2A is not simply based on electrostatic force, and Rab3A regulates C2A-mediated vesicle-presynaptic membrane fusion mainly through affecting the C2A binding to phospholipids in the presynaptic membrane. These results have contributed to the comprehension of action mechanism of Rab3 and synaptotagmin in the regulation of synaptic vesicle exocytosis.