v-SNARE actions during Ca2+-triggered exocytosis
v-SNARE actions during Ca2+-triggered exocytosis
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DOI：
10.1016/j.cell.2007.09.025
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发表时间：
2007-10-19
期刊：
影响因子：
64.5
通讯作者：
Bruns, Dieter
中科院分区：
文献类型：
--
作者：
Kesavan, Jaideep;Borisovska, Maria;Bruns, Dieter
SNARE蛋白在对立膜之间的组装介导合成脂质体的融合，但尚不清楚在Ca2+增加的时刻，SNAREs是否在胞分泌过程中起作用，为分泌囊泡的融合提供分子力。本研究表明，染色质颗粒胞外分泌过程中融合前和融合后步骤的执行关键取决于形成SNARE基序的复合物和囊泡SNARE蛋白synaptobrevin II的跨膜锚点之间的短分子距离。通过插入柔性的“连接物”来延长突触短缩蛋白的近膜区域，减少颗粒的启动，延迟细胞内钙逐步升高时胞外分泌的开始，减弱早期融合孔的波动，并以连接物长度依赖的方式减缓孔的快速扩张。这些观察结果提供了证据，证明v-SNARE蛋白在毫秒时间尺度上驱动Ca2+触发的膜融合，并支持一个模型，其中SNAREs的连续分子牵拉引导囊泡在连续的胞外作用阶段。
Assembly of SNARE proteins between opposing membranes mediates fusion of synthetic liposomes, but it is unknown whether SNAREs act during exocytosis at the moment of Ca2+ increase, providing the molecular force for fusion of secretory vesicles. Here, we show that execution of pre- and postfusional steps during chromaffin granule exocytosis depends crucially on a short molecular distance between the complex forming SNARE motif and the transmembrane anchor of the vesicular SNARE protein synaptobrevin II. Extending the juxtamembrane region of synaptobrevin by insertion of flexible `` linkers'' reduces priming of granules, delays initiation of exocytosis upon stepwise elevation of intracellular calcium, attenuates fluctuations of early fusion pores, and slows rapid expansion of the pore in a linker-length dependent fashion. These observations provide evidence that v-SNARE proteins drive Ca2+- triggered membrane fusion at millisecond time scale and support a model wherein continuous molecular pulling by SNAREs guides the vesicle throughout the consecutive stages of exocytosis.