An ARF6/Rab35 GTPase Cascade for Endocytic Recycling and Successful Cytokinesis
An ARF6/Rab35 GTPase Cascade for Endocytic Recycling and Successful Cytokinesis
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DOI：
10.1016/j.cub.2011.11.058
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发表时间：
2012-01-24
期刊：
影响因子：
9.2
通讯作者：
Echard, Arnaud
中科院分区：
文献类型：
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作者：
Chesneau, Laurent;Dambournet, Daphne;Echard, Arnaud
细胞分裂桥不稳定导致双核细胞，可促进体内肿瘤的发生。膜运输对动物细胞的胞质分裂至关重要[2-8]，由不同的gtpase （Rab11, Rab21, Rab35, ARF6, RalA/B）调节的几种内吞途径[9-16]有助于胞质分裂的后沟步骤。然而，对于这些途径如何协调成功的细胞分裂，我们知之甚少。Rab35 GTPase控制着一个快速的内吞循环途径，必须激活Rab35 GTPase才能在细胞间桥定位SEPTIN细胞骨架，从而完成细胞分裂[12]。在这里，我们报道了ARF6 GTPase[17,18]负调控Rab35的激活，从而调控Rab35通路。表达组成激活的、gtp结合的ARF6突变体的人类细胞与过表达灭活的、gtp结合的Rab35突变体的细胞表现出相同的内吞循环和细胞分裂缺陷。作为分子机制，我们发现Rab35 GAP EP164B是ARF6负性调节Rab35激活的效应因子。出乎意料的是，这种调控发生在网格蛋白包覆的凹处，激活的ARF6减少了Rab35进入内吞途径的负荷。因此，ARF蛋白的一个效应是下游Rab蛋白的GAP，我们认为这种分层的ARF/Rab GTPase级联控制了细胞分裂所必需的共同内吞途径的适当激活。
Cytokinesis bridge instability leads to binucleated cells that can promote tumorigenesis in vivo [1]. Membrane trafficking is crucial for animal cell cytokinesis [2-8], and several endocytic pathways regulated by distinct GTPases (Rab11, Rab21, Rab35, ARF6, RalA/B) [9-16] contribute to the post-furrowing steps of cytokinesis. However, little is known about how these pathways are coordinated for successful cytokinesis. The Rab35 GTPase controls a fast endocytic recycling pathway and must be activated for SEPTIN cytoskeleton localization at the intercellular bridge, and thus for completion of cytokinesis [12]. Here, we report that the ARF6 GTPase [17,18] negatively regulates Rab35 activation and hence the Rab35 pathway. Human cells expressing a constitutively activated, GTP-bound ARF6 mutant display identical endocytic recycling and cytokinesis defects as those observed upon overexpression of the inactivated, GDP-bound Rab35 mutant. As a molecular mechanism, we identified the Rab35 GAP EP164B as an effector of ARF6 in negatively regulating Rab35 activation. Unexpectedly, this regulation takes place at clathrin-coated pits, and activated ARF6 reduces Rab35 loading into the endocytic pathway. Thus, an effector of an ARF protein is a GAP for a downstream Rab protein, and we propose that this hierarchical ARF/Rab GTPase cascade controls the proper activation of a common endocytic pathway essential for cytokinesis.