PDF(Pubmed)
Abstract：
Tethering factors play a critical role in deciphering the correct combination of vesicle and target membrane, before SNARE complex formation and membrane fusion. The exocyst plays a central role in tethering post-Golgi vesicles to the plasma membrane, although the mechanism by which this occurs is poorly understood. We recently established an assay for measuring exocyst-mediated vesicle tethering in vitro and we have adapted this assay to examine the ability of exocyst to tether vesicles in an asymmetric manner. We demonstrate that exocyst differs from another post-Golgi vesicle tethering protein, Sro7, in that it is fully capable of tethering vesicles with a functional Rab GTPase, Sec4, to vesicles lacking a functional Rab GTPase. Using this assay, we show that exocyst requires both the Rab and R-SNARE, Snc1, to be present on the same membrane surface. Using Sac1 phosphatase treatment, we demonstrate a likely role for phosphoinositides on the opposing Rab-deficient membrane. This suggests a specific model for exocyst orientation and its points of contact between membranes during heterotypic tethering of post-Golgi vesicles with the plasma membrane.
摘要：
束缚因子在破译囊泡和靶膜的正确组合中起着关键作用，在SNARE复合物形成和膜融合之前。外囊在将后高尔基囊泡连接到质膜中起着核心作用，尽管这种情况发生的机制知之甚少。我们最近建立了一种用于在体外测量外囊介导的囊泡束缚的测定法，并且我们已对该测定法进行了调整，以检查外囊以不对称方式对束缚囊泡的能力。我们证明外囊不同于另一种后高尔基囊泡连接蛋白，Sro7，因为它完全能够将囊泡与功能性RabGTP酶束缚在一起，Sec4，至缺乏功能性RabGTP酶的囊泡。使用这种方法，我们显示出胞囊需要Rab和R-SNARE，Snc1,存在于相同的膜表面上。使用Sac1磷酸酶处理，我们证明了磷酸肌醇在相反的Rab缺陷膜上的可能作用。这表明在高尔基体囊泡与质膜的异型连接过程中，胞囊取向及其膜之间接触点的特定模型。
