Sastry Sarita K, Lyons Patrick D, Schaller Michael D, Burridge Keith
Department of Cell and Developmental Biology and Lineberger Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA.
J Cell Sci. 2002 Nov 15;115(Pt 22):4305-16. doi: 10.1242/jcs.00105.
The cytoplasmic protein tyrosine phosphatase, PTP-PEST, associates with the focal adhesion proteins p130cas and paxillin and has recently been implicated in cell migration. In this study, we investigated the mechanism by which PTP-PEST regulates this phenomenon. We find that PTP-PEST is activated in an adhesion-dependent manner and localizes to the tips of membrane protrusions in spreading fibroblasts. We show that the catalytic activity of PTP-PEST is a key determinant for its effects on motility. Overexpression of PTP-PEST, but not a catalytically inactive form, impairs haptotaxis, cell spreading and formation of membrane protrusions in CHOK1 cells. In addition, overexpression of PTP-PEST in Rat1 fibroblasts perturbs membrane ruffling and motility in response to PDGF stimulation. The expression level of PTP-PEST modulates the activity of the small GTPase, Rac1. PTP-PEST overexpression suppresses activation of Rac1 in response to both integrin-mediated adhesion or growth factor stimulation. In contrast, fibroblasts that lack PTP-PEST expression show enhanced Rac1 activity. Co-expression of constitutively active Rac1 with PTP-PEST overcomes the inhibition of cell spreading and migration indicating that PTP-PEST acts by antagonizing Rac1 activation. Our data suggest a model in which PTP-PEST is activated by integrins and localized to regions where it can control motile events at the leading edge through inhibition of the small GTPase Rac1.
细胞质蛋白酪氨酸磷酸酶PTP - PEST与粘着斑蛋白p130cas和桩蛋白相关联，并且最近被认为与细胞迁移有关。在本研究中，我们调查了PTP - PEST调节这一现象的机制。我们发现PTP - PEST以粘着依赖性方式被激活，并定位于铺展的成纤维细胞中膜突出物的尖端。我们表明，PTP - PEST的催化活性是其对运动性产生影响的关键决定因素。PTP - PEST的过表达，而不是催化失活形式，会损害CHOK1细胞中的趋触性、细胞铺展和膜突出物的形成。此外，在大鼠1成纤维细胞中过表达PTP - PEST会扰乱对血小板衍生生长因子（PDGF）刺激的膜 ruffling和运动性。PTP - PEST的表达水平调节小GTP酶Rac1的活性。PTP - PEST过表达抑制Rac1对整合素介导的粘着或生长因子刺激的激活。相反，缺乏PTP - PEST表达的成纤维细胞显示出增强的Rac1活性。组成型活性Rac1与PTP - PEST的共表达克服了对细胞铺展和迁移的抑制，表明PTP - PEST通过拮抗Rac1激活起作用。我们的数据提出了一个模型，其中PTP - PEST被整合素激活并定位于可以通过抑制小GTP酶Rac1来控制前沿运动事件的区域。
