Ruest P J, Roy S, Shi E, Mernaugh R L, Hanks S K
Department of Cell Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
Cell Growth Differ. 2000 Jan;11(1):41-8.
Focal adhesion kinase (FAK) is a key signaling molecule regulating cellular responses to integrin-mediated adhesion. Integrin engagement promotes FAK phosphorylation at multiple sites to achieve full FAK activation. Phosphorylation of FAK Tyr-397 creates a binding site for Src-family kinases, and phosphorylation of FAK Tyr-576/Tyr-577 in the kinase domain activation loop enhances catalytic activity. Using novel phosphospecific antibody reagents, we show that FAK activation loop phosphorylation is significantly elevated in cells expressing activated Src and is an early event following cell adhesion to fibronectin. In both cases, this regulation is largely dependent on Tyr-397. We also show that the FAK activation loop tyrosines are required for maximal Tyr-397 phosphorylation. Finally, immunostaining analyses revealed that tyrosine-phosphorylated forms of FAK are present in both newly forming and mature focal adhesions. Our findings support a model for reciprocal activation of FAK and Src-family kinases and suggest that FAK/Src signaling may occur during both focal adhesion assembly and turnover.
粘着斑激酶（FAK）是一种关键的信号分子，可调节细胞对整合素介导的粘附的反应。整合素的结合促进FAK在多个位点的磷酸化，以实现FAK的完全激活。FAK酪氨酸397位点的磷酸化产生了一个与Src家族激酶结合的位点，激酶结构域激活环中FAK酪氨酸576/酪氨酸577位点的磷酸化增强了催化活性。使用新型磷酸特异性抗体试剂，我们发现，在表达活化Src的细胞中，FAK激活环的磷酸化显著升高，并且是细胞粘附于纤连蛋白后的早期事件。在这两种情况下，这种调节在很大程度上依赖于酪氨酸397位点。我们还表明，FAK激活环酪氨酸对于酪氨酸397位点的最大磷酸化是必需的。最后，免疫染色分析显示，FAK的酪氨酸磷酸化形式存在于新形成的和成熟的粘着斑中。我们的研究结果支持FAK和Src家族激酶相互激活的模型，并表明FAK/Src信号可能在粘着斑组装和周转过程中发生。
