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Role of the Rab family small G proteins in synaptic and epithelial plasticity

Rab 家族小 G 蛋白在突触和上皮可塑性中的作用

基本信息

批准号：
15390096
负责人：
SASAKI Takuya
金额：
$ 9.92万
依托单位：
The University of Tokushima
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

项目摘要

The Rab family small G proteins, which consist of more than 60 family members in mammalian cells, play a crucial role in determining the specificity of vesicular transport pathways. Rab3A has been shown to be a modulatory component which regulates Ca^<2+>-dependent synaptic vesicle exocytosis. Rab3A cycles between the GDP-bound inactive form and the GTP-bound active form and translocates between the cytosol of the presynaptic nerve terminal and the membranes of synaptic vesicles and the presynaptic plasma membrane. The activation and the translocation are regulated by three regulators (Rab GDI, Rab3 GAP, Rab3 GEP). Our previous studies on Rab GDIα-deficient and Rab3 GEP-deficient mice revealed that these regulators are involved in modulating short-term synaptic plasticity. In this study, we have succeeded in generating Rab3 GAP-deficient mice and we are investigating the role of Rab3 GAP in synaptic plasticity. Rab13 localizes to tight junctions (TJs) in polarized epithelial cells, but its function is poorly understood. In the present study, we have examined the role of Rab13 in regulating the vesicular transport of TJ transmembrane proteins. In the exocytotic pathways, we found that Rab13 directs the cell-surface transport of claudin-1, but not a basolateral transmembrane protein, low-density lipoprotein receptor. We have also found that a pool of occludin was continuously endocytosed and recycled back to the cell-surface in epithelial cells. Our results indicated that Rab13 specifically regulated the endocytic recycling of occludin. Furthermore, we found that Rab13 did not affect the recycling of transferrin receptor, that was recycled to the basolateral plasma membrane domain. We isolated a protein that specifically interacted with the GTP-bound form of Rab13, but not its GDP-bound form. Our results suggest that Rab13 is a crucial regulator for the transport of occludin and claudins to TJs and for the epithelial plasticity.

Rab 家族小 G 蛋白由哺乳动物细胞中 60 多个家族成员组成，在确定囊泡转运途径的特异性方面发挥着至关重要的作用。 Rab3A已被证明是调节Ca 2+ 依赖性突触小泡胞吐作用的调节成分。 Rab3A 在 GDP 结合的非活性形式和 GTP 结合的活性形式之间循环，并在突触前神经末梢的胞质溶胶与突触小泡的膜和突触前质膜之间易位。激活和易位由三个调节因子（Rab GDI、Rab3 GAP、Rab3 GEP）调节。我们之前对 Rab GDIα 缺陷和 Rab3 GEP 缺陷小鼠的研究表明，这些调节因子参与调节短期突触可塑性。在这项研究中，我们成功培育了 Rab3 GAP 缺陷小鼠，并正在研究 Rab3 GAP 在突触可塑性中的作用。 Rab13 定位于极化上皮细胞中的紧密连接 (TJ)，但对其功能知之甚少。在本研究中，我们研究了 Rab13 在调节 TJ 跨膜蛋白囊泡运输中的作用。在胞吐途径中，我们发现Rab13指导claudin-1的细胞表面转运，但不指导基底外侧跨膜蛋白、低密度脂蛋白受体。我们还发现，上皮细胞中的一群occludin被不断地内吞并循环回到细胞表面。我们的结果表明 Rab13 特异性调节 occludin 的内吞再循环。此外，我们发现 Rab13 不影响转铁蛋白受体的回收，转铁蛋白受体被回收到基底外侧质膜结构域。我们分离出一种与 Rab13 的 GTP 结合形式特异性相互作用的蛋白质，但不与 GDP 结合形式相互作用。我们的结果表明，Rab13 是 occludin 和 claudins 转运至 TJ 以及上皮可塑性的关键调节因子。