SNARE and regulatory proteins induce local membrane protrusions to prime docked vesicles for fast calcium-triggered fusion
SNARE and regulatory proteins induce local membrane protrusions to prime docked vesicles for fast calcium-triggered fusion
复制标题
DOI：
10.1002/embr.201337807
复制
发表时间：
2014-03-01
期刊：
影响因子：
7.7
通讯作者：
Briggs, John A. G.
中科院分区：
文献类型：
--
作者：
Bharat, Tanmay A. M.;Malsam, Joerg;Briggs, John A. G.
突触囊泡与质膜融合，从而释放神经递质进入突触间隙。介导这一过程的蛋白质机制由可溶性N-乙基马来酰亚胺敏感因子附着蛋白受体（SNARE）和调节蛋白组成，这是众所周知的，但这些蛋白质引发突触膜融合的机制仍有争议。在这项研究中，我们应用大规模，自动冷冻电子断层扫描成像在体外系统，重建突触融合。我们的研究结果表明，在对接和启动囊泡快速Ca-2（+）触发的融合，SNARE蛋白与调节蛋白协同作用，诱导质膜局部突起，直接向启动囊泡。因此，SNARE和调节蛋白将膜稳定在高能状态，从该状态开始，融合的活化能大大降低，在释放复合蛋白钳时允许同步和瞬时融合。SynopsiimageCryo-electron tomography of regulated SNARE-介导的膜融合表明，突触囊泡诱导靶膜的突起，这可能引发它们的融合。突起的高局部膜曲率可以代表高能量状态，在Ca 2+激活时，从该高能量状态可以发生快速、协调的融合。
AbstractSynaptic vesicles fuse with the plasma membrane in response to Ca2+ influx, thereby releasing neurotransmitters into the synaptic cleft. The protein machinery that mediates this process, consisting of soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) and regulatory proteins, is well known, but the mechanisms by which these proteins prime synaptic membranes for fusion are debated. In this study, we applied large-scale, automated cryo-electron tomography to image an in vitro system that reconstitutes synaptic fusion. Our findings suggest that upon docking and priming of vesicles for fast Ca-2(+)-triggered fusion, SNARE proteins act in concert with regulatory proteins to induce a local protrusion in the plasma membrane, directed towards the primed vesicle. The SNAREs and regulatory proteins thereby stabilize the membrane in a high-energy state from which the activation energy for fusion is profoundly reduced, allowing synchronous and instantaneous fusion upon release of the complexin clamp.SynopsisimageCryo-electron tomography of regulated SNARE-mediated membrane fusion shows that synaptic vesicles induce a protrusion in the target membrane that may prime them for fusion.Vesicles that are docked and primed for fusion in vitro are shown in an intermediate state characterized by a protrusion in the target membrane.High local membrane curvature of the protrusion may represent a high-energy state from which fast, coordinated fusion can occur upon Ca2+ activation.