Coincidence of actin filaments and talin is required to activate vinculin
Coincidence of actin filaments and talin is required to activate vinculin
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DOI：
10.1074/jbc.m607324200
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发表时间：
2006-12-29
影响因子：
4.8
通讯作者：
Craig, Susan W.
中科院分区：
文献类型：
--
作者：
Chen, Hui;Choudhury, Dilshad M.;Craig, Susan W.
白藜芦醇通过加强细胞外基质和细胞骨架之间的接触来调节细胞粘附。整联蛋白配体，塔林，到黏着斑蛋白的头部结构域和F-肌动蛋白到其尾部结构域的结合是这种功能的潜在机制，但是黏着斑蛋白通过其头部和尾部结构域之间的分子内相互作用而被自身抑制，并且必须被激活以结合塔林和肌动蛋白。由于黏着斑蛋白的自身抑制是通过两个头部和尾部界面之间的协同作用发生的，因此一种假设是激活可能通过协调破坏两个界面的两个配体发生。为了验证这个想法，我们使用了荧光共振能量转移探针，直接报告黏着斑蛋白的激活。无论是talin棒，VBS 3（一种talin肽，模拟一个假定的激活状态的talin），也不是F-肌动蛋白单独可以激活黏着斑蛋白。但在F-actin存在下，talin rod或VBS 3诱导黏着斑蛋白的剂量依赖性激活。活化数据得到溶液相结合研究的支持，其显示talin棒或VBS 3不能结合粘着斑蛋白，而相同的两个配体紧密结合粘着斑蛋白头部结构域（Kd类似于100 nM）。这些数据强烈支持黏着斑蛋白激活的组合机制，此外，他们是不一致的模型，其中塔林或活化塔林是足以激活黏着斑蛋白。组合激活意味着在细胞粘附位点，黏着斑蛋白是一个巧合检测器，等待同时信号从塔林和肌动蛋白聚合释放其支架活性。
Vinculin regulates cell adhesion by strengthening contacts between extracellular matrix and the cytoskeleton. Binding of the integrin ligand, talin, to the head domain of vinculin and F-actin to its tail domain is a potential mechanism for this function, but vinculin is autoinhibited by intramolecular interactions between its head and tail domain and must be activated to bind talin and actin. Because autoinhibition of vinculin occurs by synergism between two head and tail interfaces, one hypothesis is that activation could occur by two ligands that coordinately disrupt both interfaces. To test this idea we use a fluorescence resonance energy transfer probe that reports directly on activation of vinculin. Neither talin rod, VBS3 ( a talin peptide that mimics a postulated activated state of talin), nor F-actin alone can activate vinculin. But in the presence of F-actin either talin rod or VBS3 induces dose-dependent activation of vinculin. The activation data are supported by solution phase binding studies, which show that talin rod or VBS3 fails to bind vinculin, whereas the same two ligands bind tightly to vinculin head domain ( Kd similar to 100 nM). These data strongly support a combinatorial mechanism of vinculin activation; moreover, they are inconsistent with a model in which talin or activated talin is sufficient to activate vinculin. Combinatorial activation implies that at cell adhesion sites vinculin is a coincidence detector awaiting simultaneous signals from talin and actin polymerization to unleash its scaffolding activity.