Rac1 is deactivated at integrin activation sites through an IQGAP1-filamin-A-RacGAP1 pathway
Rac1 is deactivated at integrin activation sites through an IQGAP1-filamin-A-RacGAP1 pathway
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DOI：
10.1242/jcs.121988
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发表时间：
2013-09-15
影响因子：
4
通讯作者：
Humphries, Martin J.
中科院分区：
文献类型：
--
作者：
Jacquemet, Guillaume;Morgan, Mark R.;Humphries, Martin J.
细胞迁移对正常生理和疾病发病机制都有重要贡献。整合素与细胞外配体的接合通过小GTdR Rac 1的周期性激活和失活在空间上控制定向迁移所需的动态膜突起和细胞骨架重组事件。虽然控制整合素介导的Rac 1激活的途径是合理的定义，负责关闭活动的机制知之甚少。在这里，对活化的整联蛋白相关复合物的蛋白质组学分析表明，含有细丝蛋白A和IQ基序的GTPase-activating protein 1（IQGAP 1）是将β 1整联蛋白与Rac 1连接起来的候选蛋白。siRNA介导的细丝蛋白-A或IQGAP 1的敲低在细胞在纤连蛋白上铺展期间诱导高的失调的Rac 1活性。使用免疫沉淀和免疫细胞化学，细丝蛋白-A和IQGAP 1被证明是一个复杂的一部分，募集到活性β 1整合素。对单个细丝蛋白-A、IQGAP 1和Rac 1下拉的质谱分析和生化分析，将Rac GAP 1鉴定为新型IQGAP 1结合伴侣。进一步的免疫沉淀和免疫细胞化学分析表明，RacGAP 1被募集到IQGAP 1和活性β 1整合素中，并且在纤连蛋白上铺展期间，RacGAP 1表达的抑制引发Rac 1活性升高。与这些发现一致，细丝蛋白-A、IQGAP 1或RacGAP 1的表达减少触发了不受约束的膜突出并破坏了纤维状细胞外基质上的定向细胞迁移。这些发现表明了一种模型，其中整合素参与，随后是细丝蛋白A，IQGAP 1和RacGAP 1招募，使Rac 1失活，以限制其空间活性，从而协调定向细胞迁移。
Cell migration makes a fundamental contribution to both normal physiology and disease pathogenesis. Integrin engagement with extracellular ligands spatially controls, via the cyclical activation and deactivation of the small GTPase Rac1, the dynamic membrane protrusion and cytoskeletal reorganization events that are required for directional migration. Although the pathways that control integrin-mediated Rac1 activation are reasonably well defined, the mechanisms that are responsible for switching off activity are poorly understood. Here, proteomic analysis of activated integrin-associated complexes suggests filamin-A and IQ-motif-containing GTPase-activating protein 1 (IQGAP1) as candidates that link beta 1 integrin to Rac1. siRNA-mediated knockdown of either filamin-A or IQGAP1 induced high, dysregulated Rac1 activity during cell spreading on fibronectin. Using immunoprecipitation and immunocytochemistry, filamin-A and IQGAP1 were shown to be part of a complex that is recruited to active beta 1 integrin. Mass spectrometric analysis of individual filamin-A, IQGAP1 and Rac1 pull-downs and biochemical analysis, identified RacGAP1 as a novel IQGAP1 binding partner. Further immunoprecipitation and immunocytochemistry analyses demonstrated that RacGAP1 is recruited to IQGAP1 and active beta 1 integrin, and that suppression of RacGAP1 expression triggered elevated Rac1 activity during spreading on fibronectin. Consistent with these findings, reduced expression of filamin-A, IQGAP1 or RacGAP1 triggered unconstrained membrane protrusion and disrupted directional cell migration on fibrillar extracellular matrices. These findings suggest a model whereby integrin engagement, followed by filamin-A, IQGAP1 and RacGAP1 recruitment, deactivates Rac1 to constrain its activity spatially and thereby coordinate directional cell migration.