Differential Regulation of Synaptic Vesicle Tethering and Docking by UNC-18 and TOM-1.
Differential Regulation of Synaptic Vesicle Tethering and Docking by UNC-18 and TOM-1.
复制标题
DOI：
10.3389/fnsyn.2010.00141
复制
发表时间：
2010-01-01
影响因子：
3.7
通讯作者：
Richmond, Janet E
中科院分区：
文献类型：
--
作者：
Gracheva, Elena O;Maryon, Ed B;Richmond, Janet E
突触融合蛋白、SNAP-25和小突触泡蛋白之间的SNARE复合物的组装是引发突触囊泡融合所必需的。由于Munc 18和tomosyn竞争突触融合蛋白的相互作用，这些蛋白质之间的相互作用被预测在调节突触传递中是重要的。我们通过研究C.线虫unc-18（Munc 18）、unc-64（syntaxin）和tom-1（tomosyn）。我们以前已经证明unc-18突变体减少了突触传递，而tom-1突变体表现出增强的释放。在这里，我们发现unc-18突变体的释放缺陷与两种形态学上不同的囊泡池的丧失有关：那些束缚在质膜25 nm内的囊泡池和那些与质膜对接的囊泡池。相比之下，引发缺陷unc-13突变体积累拴系囊泡，而停靠囊泡大大减少，表明拴系是α-18依赖性的，并且在没有引发的情况下发生。C. elegans UNC-64突变体与UNC-18突变体表型相似，失去了束缚的和停靠的囊泡，而开放的突触融合蛋白的过表达优先增加囊泡对接，表明UNC-18/封闭的突触融合蛋白相互作用是囊泡束缚的原因。考虑到脊椎动物tomosyn和Munc 18之间对突触融合蛋白结合的竞争，我们假设C.线虫TOM-1可以抑制两个依赖于β 18的囊泡靶向步骤。与这一假设相一致，tom-1突变体表现出增强的p18质膜定位和随之而来的增加拴系和对接的突触囊泡。此外，在tom-1;unc-18双突变体中，对接的引发囊泡池相对于unc-18单突变体优先被拯救。总之，这些数据提供了证据的差异调节的两个囊泡靶向步骤，通过与突触融合蛋白的竞争性相互作用的ESTA-18和TOM-1。
The assembly of SNARE complexes between syntaxin, SNAP-25 and synaptobrevin is required to prime synaptic vesicles for fusion. Since Munc18 and tomosyn compete for syntaxin interactions, the interplay between these proteins is predicted to be important in regulating synaptic transmission. We explored this possibility, by examining genetic interactions between C. elegans unc-18(Munc18), unc-64(syntaxin) and tom-1(tomosyn). We have previously demonstrated that unc-18 mutants have reduced synaptic transmission, whereas tom-1 mutants exhibit enhanced release. Here we show that the unc-18 mutant release defect is associated with loss of two morphologically distinct vesicle pools; those tethered within 25nm of the plasma membrane and those docked with the plasma membrane. In contrast, priming defective unc-13 mutants accumulate tethered vesicles, while docked vesicles are greatly reduced, indicating tethering is UNC-18-dependent and occurs in the absence of priming. C. elegans unc-64 mutants phenocopy unc-18 mutants, losing both tethered and docked vesicles, whereas overexpression of open syntaxin preferentially increases vesicle docking, suggesting UNC-18/closed syntaxin interactions are responsible for vesicle tethering. Given the competition between vertebrate tomosyn and Munc18, for syntaxin binding, we hypothesized that C. elegans TOM-1 may inhibit both UNC-18-dependent vesicle targeting steps. Consistent with this hypothesis, tom-1 mutants exhibit enhanced UNC-18 plasma membrane localization and a concomitant increase in both tethered and docked synaptic vesicles. Furthermore, in tom-1;unc-18 double mutants the docked, primed vesicle pool is preferentially rescued relative to unc-18 single mutants. Together these data provide evidence for the differential regulation of two vesicle targeting steps by UNC-18 and TOM-1 through competitive interactions with syntaxin.