MECHANISMS OF MEMBRANE FUSION

我们建议研究控制胞吐的分子因子， 通过简化的（亚细胞）体外内吞融合事件 这些过程的模型。 我们将确定单个脂质的作用， 物种以及低pH和渗透梯度对膜融合的影响 通过脂质体融合测定。 我们还建议确定 细胞质因子和膜蛋白参与融合 分离的包被囊泡与溶酶体的相互作用 嗜铬颗粒与嗜铬细胞质膜。 个人 项目可分类如下： (1)通过单个脂质种类控制膜融合：（i）脂质 参与刺激相关的“磷脂效应“，即：三，二， 和单磷脂酰肌醇及其代谢副产物， 磷脂酸、甘油二酯和花生四烯酸;（ii）酰基链 （iii）特定磷脂物质内的组成（流动性）; 凝胶-液晶和层状-六方HII相变;（iv） 糖脂猪和凝集素。 (2)低pH和渗透性颗粒在膜融合中的作用：（i） 低pH值（4.5-6.5）诱导的膜融合的分子要求，作为一种 脂质包膜病毒的融合模型和分选， 再循环的内吞囊泡;和（ii）的贡献，渗透 脂质体融合的动力学和Ca++需求的梯度 不同的组成和大小。 (3)介导胞吐作用的细胞质和膜蛋白： 突触蛋白和其他细胞质因子和颗粒膜蛋白 Ca ~（++）介导的嗜铬颗粒与血浆的相互作用 膜。 (4)与包被囊泡融合有关的分子因子 溶酶体：有荧光的包被囊泡与溶酶体融合 测定和细胞质因子和膜蛋白介导的 包被囊泡的去包被以及它们与溶酶体的融合。

We propose to study the molecular factors which control exocytotic and endocytotic fusion events by means of simplified (sub-cellular) in vitro models for these processes. We will determine the role of individual lipid species and the effects of low pH and osmotic gradients on membrane fusion by means of liposome fusion assays. We also propose to identify the cytoplasmic factors and membrane proteins involved by following the fusion of isolated coated vesicles with lysosomes and the interaction of chromaffin granules with chromaffin cell plasma membranes. The individual projects can be categorized as follows: (1) Control of membrane fusion by individual lipid species: (i) the lipids involved in the stimulus-linked "phospholipid effect, "ie: the tri-, di-, and monophosphatidylinositols and their metabolic byproducts, phosphatidate, diglycerides and arachindonic acids; (ii) acyl chain composition (fluidity) within a particular phospholipid species; (iii) the gel-liquid crystalline and lamellar-hexagonal HII phase transitions; (iv) glycolipigs and lectins. (2) The role of low pH and osmotic grandients in membrane fusion: (i) molecular requirements of low pH (4.5-6.5)-induced membrane fusion, as a model for the fusion of lipid-enveloped viruses and the sorting-out and recycling of endocytotic vesicles; and (ii) the contribution of osmotic gradients to the kinetics and Ca++ requirements of the fusion of liposomes of varying composition and size. (3) Cytoplasmic and membrane proteins which mediate exocytosis: the role synexin and other cytoplasmic factors and granule membrane proteins in the Ca++ mediated interaction of isolated chromaffin granules with plasma membranes. (4) Molecular factors involved in the fusion of coated vesicles with lysosomes: fusion of coated vesicles with lysosomes with a fluorescence assay and the cytoplasmic factors and membrane proteins which mediate the uncoating of the coated vesicles and their fusion with the lysosomes.