Rap1 GTPase-activating protein SPA-1 negatively regulates cell adhesion
Rap1 GTPase-activating protein SPA-1 negatively regulates cell adhesion
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DOI：
10.1074/jbc.274.26.18463
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发表时间：
1999-06-25
影响因子：
4.8
通讯作者：
Minato, N
中科院分区：
文献类型：
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作者：
Tsukamoto, N;Hattori, M;Minato, N
Rap1 GTP酶在多种类型的细胞中被多种刺激激活，但其确切功能尚不清楚。在这项研究中，我们已经证明SPA-1通过GTP酶激活蛋白(GAP)活性来干扰膜靶向C3G、C3G-F在293T细胞中对Rap1的激活。在HeLa细胞中瞬时表达的SpA-1主要定位于皮质细胞骨架，并诱导细胞聚集，而C3G-F则相反地诱导细胞广泛扩散。四环素调控系统在HeLa细胞中条件性过表达SPA-1抑制了纤维连接蛋白包裹的培养皿上RAP1的激活，导致粘附性降低。当在建立细胞黏附后有条件地诱导SPA-1时，细胞逐渐聚集并从培养皿中脱离。外源性纤维连接蛋白以剂量依赖的方式抵消这两种作用。逆转录病毒过表达SPA-1在早幼粒细胞32D细胞中也可抑制RAP1的激活和粒细胞集落刺激因子诱导的细胞黏附，但不影响分化。这些结果表明，RAP1 GTP是细胞外基质和可溶性因子诱导的细胞黏附所必需的，而SPA-1负调控细胞黏附。
Rap1 GTPase is activated by a variety of stimulations in many types of cells, but its exact functions remain unknown. In this study we have shown that SPA-1 interferes with Rap1 activation by membrane-targeted C3G, C3G-F, in 293T cells through the GTPase activating protein (GAP) activity. SPA-1 transiently expressed in HeLa cells was mostly localized at the cortical cytoskeleton and induced rounding up of the cells, whereas C3G-F conversely induced extensive cell spreading. Conditional SPA-1 overexpression in HeLa cells by tetracycline-regulative system suppressed Rap1 activation upon plating on dishes coated with fibronectin and resulted in the reduced adhesion. When SPA-1 was conditionally induced after the established cell adhesion, the cells gradually rounded up and detached from the dish. Both effects were counteracted by exogenous fibronectin in a dose-dependent manner. Retroviral overexpression of SPA-1 in promyelocytic 32D cells also inhibited both activation of Rap1 and induction of cell adhesion by granulocyte colony stimulating factor without affecting differentiation. These results have indicated that Rap1 GTP is required for the cell adhesion induced by both extracellular matrix and soluble factors, which is negatively regulated by SPA-1.