Direct interactions between C. elegans RAB-3 and Rim provide a mechanism to target vesicles to the presynaptic density.
Direct interactions between C. elegans RAB-3 and Rim provide a mechanism to target vesicles to the presynaptic density.
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DOI：
10.1016/j.neulet.2008.08.026
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发表时间：
2008-10-24
影响因子：
2.5
通讯作者：
Richmond JE
中科院分区：
文献类型：
--
作者：
Gracheva EO;Hadwiger G;Nonet ML;Richmond JE
Rim是一种多结构域的活性区蛋白，调节胞吐作用，并参与囊泡启动和突触前可塑性。我们最近证实了与C. elegans Rim（称为EST-10）伴随着邻近突触前密度的停靠囊泡的减少。由于Rim已知与囊泡相关的GTrib 3A相互作用，因此我们在此询问是否通过β-10/Rab-3相互作用将突触囊泡募集到突触前密度的β-10依赖性。我们首先确定了C。秀丽线虫Rab-3（称为RAB-3）在其GTP结合状态而非GDP结合状态下与β-10相互作用。然后，我们通过EM分析证明，RAB-3突变突触表现出与UNC-10突变体相同的囊泡靶向缺陷。此外，UNC-10; rab-3双突变体表型复制了单突变体的靶向缺陷，表明RAb-10和RAB-3在突触前密度下以相同的途径靶向囊泡。unc-10;rab-3双突变体的内源性释放与unc-10单突变体相似，但比rab-3突变体更严重，表明较温和的rab-3释放缺陷反映了常见的靶向缺陷。Rim最近被证明通过与钙通道的直接相互作用积极调节钙内流。与这一观点一致，我们发现在C区，钙离子通道和钙离子通道共存，钙离子通道和钙离子通道共存。在UNC-10和RAB-3突变体中，线虫突触前密度和突触释放表现出降低的钙敏感性。总之，这些结果表明，通过RAB-3/RAB-10相互作用靶向突触前密度的囊泡理想地定位于有效的钙依赖性释放。
Rim is a multi-domain, active zone protein that regulates exocytosis and is implicated in vesicle priming and presynaptic plasticity. We recently demonstrated that synaptic defects associated with loss of C. elegans Rim (termed UNC-10) are accompanied by a reduction in docked vesicles adjacent to the presynaptic density. Since Rim is known to interact with the vesicle-associated GTPase Rab3A, here we asked whether UNC-10-dependent recruitment of synaptic vesicles to the presynaptic density was through an UNC-10/Rab-3 interaction. We first established that C. elegans Rab-3 (termed RAB-3) in its GTP but not GDP-bound state interacts with UNC-10. We then demonstrated by EM analysis that rab-3 mutant synapses exhibit the same vesicle-targeting defect as unc-10 mutants. Furthermore, unc-10;rab-3 double mutants phenocopy the targeting defects of the single mutants, suggesting UNC-10 and RAB-3 act in the same pathway to target vesicles at the presynaptic density. Endogenous release of unc-10;rab-3 double mutants was similar to that of unc-10 single mutants, but more severe than rab-3 mutants, suggesting the common targeting defects are reflected by the milder rab-3 release defect. Rim has recently been shown to positively regulate calcium influx through direct interactions with calcium channels. Consistent with this notion we found UNC-10 colocalized with the calcium channel, UNC-2 at C. elegans presynaptic densities and synaptic release in unc-10 and rab-3 mutants exhibit reduced calcium-sensitivity. Together these results suggest that vesicles targeted to the presynaptic density by RAB-3/UNC-10 interactions are ideally positioned for efficient calcium-dependent release.
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