Webb Donna J, Kovalenko Mykola, Whitmore Leanna, Horwitz Alan F
Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA.
Biochem Biophys Res Commun. 2006 Aug 11;346(4):1284-8. doi: 10.1016/j.bbrc.2006.06.036. Epub 2006 Jun 14.
G protein-coupled receptor kinase-interacting protein (GIT)1 is a multidomain, adaptor protein that regulates cellular processes, such as migration and protrusive activity, by bringing together various signaling molecules, including PIX, PAK, and paxillin. Mutants of GIT1, which lack the C-terminal paxillin binding domain, fail to mediate its effects on migration and protrusions, suggesting that sites within this domain are critical to GIT1 function. In this study, we show that serine 709, which is located within the paxillin binding domain, regulates GIT1 function. Phosphorylation of serine 709 is necessary for GIT1-induced effects on protrusions. Phosphorylation of this site also regulates GIT1 interaction with paxillin, which could serve to target GIT1 to the leading edge of cells. As shown by an in vitro kinase assay, PAK phosphorylates GIT1 on serine 709. Taken together, our results indicate that GIT1 phosphorylation on serine 709 increases its binding to paxillin and regulates protrusive activity in cells.
G蛋白偶联受体激酶相互作用蛋白（GIT）1是一种多结构域衔接蛋白，它通过聚集包括PIX、PAK和桩蛋白在内的各种信号分子来调节细胞过程，如迁移和突出活动。缺乏C末端桩蛋白结合结构域的GIT1突变体无法介导其对迁移和突出的影响，这表明该结构域内的位点对GIT1功能至关重要。在本研究中，我们表明位于桩蛋白结合结构域内的丝氨酸709调节GIT1功能。丝氨酸709的磷酸化对于GIT1诱导的突出效应是必需的。该位点的磷酸化还调节GIT1与桩蛋白的相互作用，这可能有助于将GIT1靶向细胞前沿。如体外激酶测定所示，PAK使GIT1的丝氨酸709磷酸化。综上所述，我们的结果表明，GIT1丝氨酸709的磷酸化增加了其与桩蛋白的结合，并调节细胞中的突出活动。
