CAPS drives trans-SNARE complex formation and membrane fusion through syntaxin interactions
CAPS drives trans-SNARE complex formation and membrane fusion through syntaxin interactions
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DOI：
10.1073/pnas.0900755106
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发表时间：
2009-10-13
影响因子：
11.1
通讯作者：
Martin, Thomas F. J.
中科院分区：
文献类型：
--
作者：
James, Declan J.;Kowalchyk, Judith;Martin, Thomas F. J.
Ca2+ 依赖性分泌激活蛋白 (CAPS) 是调节囊泡胞吐作用的重要因素，在 Ca2+ 触发囊泡与质膜融合之前的启动反应中发挥作用。然而，CAPS 调节促进囊泡融合的确切事件尚不清楚。在当前的工作中，我们使用包含 VAMP2 的供体和包含 Syntaxin-1/SNAP-25 的受体脂质体在 SNARE 依赖性脂质体融合测定中重建了 CAPS 功能。 CAPS 融合刺激需要受体脂质体中的 PI(4,5)P-2，并且不依赖于 Ca2+，但通过包含突触结合蛋白可恢复 Ca2+ 依赖性。 CAPS 刺激反式 SNARE 复合物形成，同时在生理 SNARE 密度下刺激全膜融合。 CAPS 结合 syntaxin-1，竞争性抑制 syntaxin-1 结合的 CAPS 截短也会抑制 CAPS 依赖性融合。结果揭示了引发蛋白具有意想不到的活性，可以通过有效促进反式-SNARE复合物的形成来加速融合。 CAPS 可能通过在质膜上组织 SNARE 复合物来发挥启动作用。
Ca2+-dependent activator protein for secretion (CAPS) is an essential factor for regulated vesicle exocytosis that functions in priming reactions before Ca2+-triggered fusion of vesicles with the plasma membrane. However, the precise events that CAPS regulates to promote vesicle fusion are unclear. In the current work, we reconstituted CAPS function in a SNARE-dependent liposome fusion assay using VAMP2-containing donor and syntaxin-1/SNAP-25-containing acceptor liposomes. The CAPS stimulation of fusion required PI(4,5)P-2 in acceptor liposomes and was independent of Ca2+, but Ca2+ dependence was restored by inclusion of synaptotagmin. CAPS stimulated trans-SNARE complex formation concomitant with the stimulation of full membrane fusion at physiological SNARE densities. CAPS bound syntaxin-1, and CAPS truncations that competitively inhibited syntaxin-1 binding also inhibited CAPS-dependent fusion. The results revealed an unexpected activity of a priming protein to accelerate fusion by efficiently promoting trans-SNARE complex formation. CAPS may function in priming by organizing SNARE complexes on the plasma membrane.