Are neuronal SNARE proteins Ca2+ sensors?
Are neuronal SNARE proteins Ca2+ sensors?
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DOI：
10.1016/j.jmb.2005.01.024
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发表时间：
2005-03-18
影响因子：
5.6
通讯作者：
Rizo, J
中科院分区：
文献类型：
--
作者：
Chen, XC;Tang, J;Rizo, J
由突触素、突触素和SNAP-25形成的神经元SNAR复合体在钙离子触发的神经递质释放中起核心作用。SNARE复合体表面含有几个潜在的钙结合部位，提示SNARs可能直接参与了细胞释放过程中的钙结合。事实上，SNAP-25在两个可能的钙配体(E170A/Q177A)上过表达携带突变的SNAP-25会导致嗜铬细胞胞吐的钙协同降低。为了测试SNARE络合物是否可能在钙敏感中发挥作用，我们使用基于横向弛豫优化谱(TROSY)的核磁共振方法分析了它与Cat(2+)的结合特性。在SNARE复合体表面发现了几个钙结合位点，但大多数都不是钙专一性的，亲和力都很低。此外，我们发现，E170A/Q177A SNAP-25突变不会改变SNARE与钙离子感受器突触素1之间的相互作用，但会严重损害SNARE复合体的组装。这些结果表明，在神经递质释放的过程中，SNARE不直接作为钙受体发挥作用，但SNARE复合体组装与钙感受紧密相连。(C)2005爱思唯尔有限公司。保留所有权利。
The neuronal SNARE complex formed by synaptobrevin, syntaxin and SNAP-25 plays a central role in Ca2+-triggered neurotransmitter release. The SNARE complex contains several potential Ca2+-binding sites on the surface, suggesting that the SNAREs may be involved directly in Ca2+-binding during release. Indeed, overexpression of SNAP-25 bearing mutations in two putative Ca2+ ligands (E170A/Q177A) causes a decrease whether in the Ca2+-cooperativity of exocytosis in chromaffin cells. To test whether the SNARE complex might function in Ca2+-sensing, we analyzed its Cat(2+)-binding properties using transverse relaxation optimized spectroscopy (TROSY)-based NMR methods. Several Ca2+-binding sites are found on the surface of the SNARE complex, but most of them are not specific for Ca2+ and all have very low affinity. Moreover, we find that the E170A/Q177A SNAP-25 mutation does not alter interactions between the SNARES and the Ca2+ sensor synaptotagmin 1, but severely impairs SNARE complex assembly. These results suggest that the SNAREs do not act directly as Ca2+ receptors but SNARE complex assembly is coupled tightly to Ca2+-sensing during neurotransmitter release. (C) 2005 Elsevier Ltd. All rights reserved.