Mechanisms of Membrane Fusion

项目摘要/摘要 膜融合对细胞生长、激素分泌、神经传递、 以及病原体对细胞的入侵。膜融合机制是保守的 酵母传给人类。我们已经开发了酵母空泡融合作为一个模型系统， 鉴定膜融合基因，建立纯化的体外融合实验 空泡，并提纯每种相关的蛋白质和脂肪以重组为 蛋白质脂质体，忠实地重建融合的各个方面。这些研究已经 揭示了最新的元素：1.一系列令人眼花缭乱的蛋白质和脂类， 配合有序的脂质双层拉伸和重排，给予融合而不溶解。 2.膜结合蛋白之间的复合体的组装，称为“陷阱” 并不是像之前认为的那样是自发的。它们的组装实际上是由一种 大型六角体复合体，称为HOP，它识别每个个体 诱捕并将它们组装成活性中间体，准备进行快速融合。3. 圈套的监护人，命名为NSF/Sec18和aSNAP/Sec17，这是 据信，融合后只起到分解陷阱复合体的作用，还能促进 核聚变。4.脂质在融合中起着重要和积极的作用。每一种机械式的 我们将追求洞察力；我们未来5年的目标是了解 啤酒花催化的圈套组装的中间体，它们的结构，作用 分子伴侣Sec17/Sec18，以及这些蛋白是如何触发脂质重排的 核聚变。核心作用强调了理解这一途径的重要性 啤酒花在致病病毒和细菌入侵人类细胞中的作用。

Project Summary/Abstract Membrane fusion is essential for cell growth, hormone secretion, neurotransmission, and cell invasion by pathogens. Membrane fusion mechanisms are conserved from yeast to humans. We have developed yeast vacuole fusion as a model system, identifying genes for membrane fusion, establishing an in vitro fusion assay with purified vacuoles, and purifying each relevant protein and lipid for reconstitution into proteoliposomes which faithfully reconstitute each aspect of fusion. These studies have revealed novel elements, most recently: 1. A dazzling array of proteins and lipids which cooperate for orderly lipid bilayer strain and rearrangement, giving fusion without lysis. 2. The assembly of complexes among membrane-bound proteins termed "SNAREs" isn't spontaneous, as heretofore believed. Their assembly is actually catalyzed by a large hexameric complex termed HOPS, which recognizes each of the individual SNAREs and assembles them in active intermediates, poised for rapid fusion. 3. Chaperones to the SNAREs, termed NSF/Sec18 and aSNAP/Sec17, which had been believed to only function to disassemble SNARE complexes after fusion, also promote fusion. 4. Lipids have a vital and active role in fusion. Each of these mechanistic insights will be pursued; our goals for the next 5 years are to understand the intermediates of HOPS-catalyzed SNARE assembly, their structures, the roles of chaperones Sec17/Sec18, and how these proteins trigger the lipid rearrangements of fusion. The importance of understanding this pathway is underscored by the central role of HOPS in the invasion of human cells by pathogenic viruses and bacteria.