Symmetrical organization of proteins under docked synaptic vesicles
Symmetrical organization of proteins under docked synaptic vesicles
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DOI：
10.1002/1873-3468.13316
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发表时间：
2019-01-01
期刊：
影响因子：
3.5
通讯作者：
Rothman, James E.
中科院分区：
文献类型：
--
作者：
Li, Xia;Radhakrishnan, Abhijith;Rothman, James E.
在钙调节的胞吐过程中，构成的融合机制在部分组装状态下被‘夹住’，直到被钙同步释放。参与这一过程的蛋白质机制是已知的，但超分子结构和潜在的机制尚不清楚。在这里，我们使用冷冻电子断层扫描分析神经生长因子分化的神经内分泌(PC12)细胞来描绘停靠的小泡下释放机制的组织。我们发现，恰好有六个胞吐模块，每个模块都可能由一个SNAREpin及其结合的突触素、复合蛋白和Munc18蛋白组成，对称地排列在囊泡-PM界面上。突变分析表明，这种对称的组织是以突触素的环状寡聚体为模板的。观测到的排列，包括其精确的径向定位，与最近提出的“扶壁环假说”是一致的。
During calcium-regulated exocytosis, the constitutive fusion machinery is 'clamped' in a partially assembled state until synchronously released by calcium. The protein machinery involved in this process is known, but the supra-molecular architecture and underlying mechanisms are unclear. Here, we use cryo-electron tomography analysis in nerve growth factor-differentiated neuro-endocrine (PC12) cells to delineate the organization of the release machinery under the docked vesicles. We find that exactly six exocytosis modules, each likely consisting of a single SNAREpin with its bound Synaptotagmins, Complexin, and Munc18 proteins, are symmetrically arranged at the vesicle-PM interface. Mutational analysis suggests that the symmetrical organization is templated by circular oligomers of Synaptotagmin. The observed arrangement, including its precise radial positioning, is in-line with the recently proposed 'buttressed ring hypothesis'.