ARAP3 is essential for formation of lamellipodia after growth factor stimulation
ARAP3 is essential for formation of lamellipodia after growth factor stimulation
复制标题
DOI：
10.1242/jcs.02755
复制
发表时间：
2006-02-01
影响因子：
4
通讯作者：
Hawkins, PT
中科院分区：
文献类型：
--
作者：
Krugmann, S;Andrews, S;Hawkins, PT
Rho和Arf家族的小GTP酶控制着肌动蛋白的动态重排和囊泡运输事件。ARAP3是RhoA和Arf6的双重缺口，受磷脂酰肌醇(3，4，5)-三磷酸[PtdIns(3，4，5)P-3]调节，磷脂酰肌醇(3，4，5)是磷脂酰肌醇3-激酶(PI3K)信号通路的产物。为了研究ARAP3的生理功能，我们在内皮细胞模型中使用了基于RNAi的方法。ARAP3缺陷细胞表现出RhoA和Arf6活性增强。从表型上看，它们比对照组更圆，并显示出非常细小的应力纤维。ARAP3缺失的细胞不能在生长因子刺激下产生片状脂血症，这一过程依赖于PI3K和RAC的活性。在受刺激的ARAP3 RNAi细胞中，RAC被瞬时激活，尽管其细胞定位发生了变化，这可能是Arf6活性增加的结果。我们得出结论，ARAP3募集到PtdIns(3，4，5)P-3升高的位点对于允许RhoA的局部失活和Arf6的循环是至关重要的，这两者都是允许生长因子刺激的片状脂蛋白形成所必需的。
Rho and Arf family small GTPases control dynamic actin rearrangements and vesicular trafficking events. ARAP3 is a dual GAP for RhoA and Arf6 that is regulated by phosphatidylinositol (3,4,5)-trisphosphate [PtdIns(3,4,5)P-3], a product of the phosphoinositide 3-kinase (PI3K) signalling pathway. To investigate the physiological function of ARAP3, we used an RNAi-based approach in an endothelial cell model. ARAP3-deficient cells showed increased activities of RhoA and Arf6. Phenotypically, they were more rounded than control counterparts and displayed very fine stress fibres. ARAP3-deficient cells were not capable of producing lamellipodia upon growth factor stimulation, a process known to depend on PI3K and Rac activities. Rac was transiently activated in stimulated ARAP3 RNAi cells although its cellular localisation was altered, a likely consequence of increased Arf6 activity. We conclude that ARAP3 recruitment to sites of elevated PtdIns(3,4,5)P-3 is crucial to allow localised inactivation of RhoA and cycling of Arf6, both of which are necessary to allow growth factor-stimulated formation of lamellipodia.