Adhesion-associated and PKC-modulated changes in serine/threonine phosphorylation of p120-catenin.
Adhesion-associated and PKC-modulated changes in serine/threonine phosphorylation of p120-catenin.
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DOI：
10.1021/bi034597h
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发表时间：
2003-07
期刊：
影响因子：
2.9
通讯作者：
Xiaobo Xia;D. J. Mariner;A. Reynolds
中科院分区：
文献类型：
--
作者：
Xiaobo Xia;D. J. Mariner;A. Reynolds
p120-catenin （p120）最初被确定为酪氨酸激酶底物，随后被证明可以调节钙粘蛋白介导的细胞-细胞粘附。p120 Arm结构域与E-cadherin的结合似乎是维持足够的cadherin水平以实现强粘附所必需的。相反，到Arm结构域的序列氨基端具有负调控功能，可能由磷酸化调节。几种诱导细胞-细胞粘附快速变化的药物，包括PDBu、组胺、凝血酶和LPA，会导致p120s /T磷酸化的显著变化。在某些情况下，这些变化是PKC依赖性的，但粘附、PKC激活和p120磷酸化之间的关系尚不清楚，部分原因是相关的p120磷酸化位点尚不清楚。作为直接鉴定这些修饰在粘附中的功能的关键一步，我们使用二维色氨酸图谱和位点定向诱变来确定p120 S/T磷酸化的构成位点和pkc调节位点。在已确定的8个位点中，两个位点在体外被GSK3 β选择性磷酸化，但在体内用GSK3 β抑制剂处理细胞并没有消除这些位点。体内PKC刺激诱导了S268位点的有效去磷酸化，以及其他几个位点的部分去磷酸化。令人惊讶的是，PKC也强烈诱导了S873位点的磷酸化。这些数据直接将PKC激活与p120磷酸化的特异性变化联系起来，并确定了与组胺和PDBu等药物诱导的PKC依赖性粘附变化机制相关的靶点。
p120-catenin (p120) was originally identified as a tyrosine kinase substrate, and subsequently shown to regulate cadherin-mediated cell-cell adhesion. Binding of the p120 Arm domain to E-cadherin appears to be necessary to maintain adequate cadherin levels for strong adhesion. In contrast, the sequence amino-terminal to the Arm domain confers a negative regulatory function that is likely to be modulated by phosphorylation. Several agents that induce rapid changes in cell-cell adhesion, including PDBu, histamine, thrombin, and LPA, result in significant changes in p120 S/T phosphorylation. In some cases, these changes are PKC-dependent, but the relationship among adhesion, PKC activation, and p120 phosphorylation is unclear, in part because the relevant p120 phosphorylation sites are unknown. As a crucial step toward directly identifying the function of these modifications in adhesion, we have used two-dimensional tryptic mapping and site-directed mutagenesis to pinpoint the constitutive and PKC-modulated sites of p120 S/T phosphorylation. Of eight sites that have been identified, two were selectively phosphorylated in vitro by GSK3 beta, but in vivo treatment of cells with GSK3 beta inhibitors did not eliminate these sites. PKC stimulation in vivo induced potent dephosphorylation at S268, and partial dephosphorylation of several additional sites. Surprisingly, PKC also strongly induced phosphorylation at S873. These data directly link PKC activation to specific changes in p120 phosphorylation, and identify the target sites associated with the mechanism of PKC-dependent adhesive changes induced by agents such as histamine and PDBu.