Huang C, Liu J, Haudenschild C C, Zhan X
Department of Experimental Pathology, The Holland Laboratory, American Red Cross, Rockville, Maryland 20855, USA.
J Biol Chem. 1998 Oct 2;273(40):25770-6. doi: 10.1074/jbc.273.40.25770.
Cortactin, a filamentous actin cross-linking protein and a substrate of Src protein tyrosine kinase, is phosphorylated at tyrosine residues upon stimulation by extracellular signals. We have previously demonstrated that the filamentous actin cross-linking activity of cortactin is attenuated by Src (Huang, C., Ni, Y., Gao, Y., Haudenschild, C. C., and Zhan, X. (1997) J. Biol. Chem. 272, 13911-13915). In vitro, tyrosine phosphorylation of cortactin occurs specifically within the region between the proline-rich sequence and the Src homology 3 domain. Among the nine tyrosine residues in this region, mutations at Tyr421, Tyr466, and Tyr482 significantly reduced Src-meditated tyrosine phosphorylation both in vitro and in vivo. Ectopic expression of wild-type cortactin in ECV304, a spontaneously transformed human umbilical endothelial cell line, resulted in an enhanced cell migration. In contrast, overexpression of a cortactin mutant deficient in tyrosine phosphorylation impaired the migration of endothelial cells. These findings reveal an intracellular signaling mechanism whereby the motility of endothelial cells is regulated by a Src-mediated tyrosine phosphorylation of cortactin.
皮层肌动蛋白是一种丝状肌动蛋白交联蛋白，也是Src蛋白酪氨酸激酶的底物，在受到细胞外信号刺激时，其酪氨酸残基会发生磷酸化。我们之前已经证明，Src会减弱皮层肌动蛋白的丝状肌动蛋白交联活性（黄，C.，倪，Y.，高，Y.，豪登施尔德，C.C.，和詹，X.（1997年）《生物化学杂志》272，13911 - 13915）。在体外，皮层肌动蛋白的酪氨酸磷酸化特异性地发生在富含脯氨酸序列和Src同源3结构域之间的区域内。在该区域的九个酪氨酸残基中，Tyr421、Tyr466和Tyr482处的突变在体外和体内均显著降低了Src介导的酪氨酸磷酸化。在ECV304（一种自发转化的人脐静脉内皮细胞系）中异位表达野生型皮层肌动蛋白会导致细胞迁移增强。相反，过表达缺乏酪氨酸磷酸化的皮层肌动蛋白突变体则会损害内皮细胞的迁移。这些发现揭示了一种细胞内信号传导机制，即内皮细胞的运动性由Src介导的皮层肌动蛋白酪氨酸磷酸化调节。
