Distinct mechanisms of α5β1 integrin activation by Ha-Ras and R-Ras
Distinct mechanisms of α5β1 integrin activation by Ha-Ras and R-Ras
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DOI：
10.1074/jbc.m000633200
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发表时间：
2000-07-21
影响因子：
4.8
通讯作者：
Takatsu, K
中科院分区：
文献类型：
--
作者：
Kinashi, T;Katagiri, K;Takatsu, K
为了研究Ras/Rho家族成员在内向外信号激活整合素中的可能作用，我们检测了Ras/Rho小gtpase在骨髓源性肥大细胞中刺激α (5) β (1) （vla5）对纤维连接蛋白的亲和力的能力。我们发现，Ha-Ras（Val-12）和R-Ras（Val-38）对VLA-5与纤维连接蛋白的粘附和配体结合活性均有较强的刺激作用，但wortmannin仅抑制Ha-Ras(Val-12)-而不抑制R-Ras(Val-38)-诱导的粘附，这表明Ha-Ras（Val-12）依赖于磷脂酰肌醇（PI） 3-激酶诱导粘附，而R-Ras（Val-38）有另一个独立于PI 3-激酶诱导粘附的途径。效应环突变体Ha-Ras(Val-12)E37G保留了刺激肥大细胞对纤维连接蛋白粘附的能力，而Y40C则没有。与此一致的是，主要表达于肥大细胞的PI 3-激酶p110 δ与Ha-Ras(Val-12) E37G相互作用，而与Y40C不相互作用，这也与肥大细胞中Akt磷酸化水平相关。这些结果表明，Ha-Ras（Val-12）通过PI 3-激酶p110 δ激活了VLA-B。R-Ras效应环区域对粘附的突变效应与PI 3-激酶活性无关，这与我们的观点一致，即R-Ras有一个独特的途径来调节VLA-5的亲和力。
To investigate the possible roles of the Ras/Rho family members in the inside-out signals to activate integrins, we examined the ability of Ras/Rho small GTPases to stimulate avidity of alpha(5)beta(1) (VLA-5) to fibronectin in bone marrow-derived mast cells. We found that both Ha-Ras(Val-12) and R-Ras(Val-38) had strong stimulatory effects on adhesion and ligand binding activity of VLA-5 to fibronectin, However, only Ha-Ras(Val-12)-, but not R-Ras(Val-38)-induced adhesion was inhibited by wortmannin, which suggests that Ha-Ras(Val-12) is dependent on phosphatidylinositol (PI) 3-kinase on adhesion whereas R-Ras(Val-38) has another PI 3-kinase independent pathway to induce adhesion. The effector loop mutant Ha-Ras(Val-12)E37G, but not Y40C retained the ability to stimulate adhesion of mast cells to fibronectin. Consistently, PI 3-kinase p110 delta, predominantly expressed in mast cells, interacted with Ha-Ras(Val-12) E37G, but not Y40C, which was also correlated with the levels of Akt phosphorylation in mast cells. Furthermore, marked adhesion was induced by a membrane-targeted version of p110 delta, These results indicate that Ha-Ras(Val-12) activated VLA-B through PI 3-kinase p110 delta. The mutational effects of the R-Ras effector loop region on adhesion were not correlated with PI 3-kinase activities, consistent with our contention that R-Ras has a distinct pathway to modulate avidity of VLA-5.