Ohkubo T, Ozawa M
Department of Biochemistry, Faculty of Medicine, Kagoshima University, Kagoshima 890-8520, Japan.
J Biol Chem. 1999 Jul 23;274(30):21409-15. doi: 10.1074/jbc.274.30.21409.
Cadherins are transmembrane glycoproteins involved in Ca(2+)-dependent cell-cell adhesion. Previously, we showed that the conserved membrane-proximal region of the E-cadherin cytoplasmic domain negatively regulates adhesion activity. In this report, we provide several lines of evidence that p120(ctn) is involved in this negative regulation. p120(ctn) binds to the membrane-proximal region of the nonfunctional carboxyl-terminally deleted E-cadherin protein. An additional internal deletion in this region prevented the association with p120(ctn) and activated the protein, as seen in an aggregation assay. Furthermore, the nonfunctional E-cadherin can be activated through coexpression of p120(ctn) proteins with amino-terminal deletions, which eliminate several potential serine/threonine phosphorylation sites but do not affect the ability to bind to cadherins. Finally, we show that staurosporine, a kinase inhibitor, induces an increased electrophoretic mobility of p120(ctn) bound to E-cadherin polypeptides, activates the nonfunctional E-cadherin protein, and converts the wild-type E-cadherin and an E-cadherin-alpha-catenin chimeric protein from a cytochalasin D-sensitive to a cytochalasin D-insensitive state. Together, these results indicate that p120(ctn) is a modulator of E-cadherin-mediated cell adhesion.
钙黏蛋白是参与钙离子依赖性细胞间黏附的跨膜糖蛋白。此前，我们发现E-钙黏蛋白细胞质结构域保守的膜近端区域对黏附活性起负调控作用。在本报告中，我们提供了多条证据表明p120（连环蛋白）参与了这一负调控过程。p120（连环蛋白）与无功能的羧基末端缺失型E-钙黏蛋白的膜近端区域结合。该区域的另一个内部缺失阻止了与p120（连环蛋白）的结合并激活了该蛋白，这在聚集试验中可见。此外，无功能的E-钙黏蛋白可通过共表达氨基末端缺失的p120（连环蛋白）蛋白而被激活，这些缺失消除了几个潜在的丝氨酸/苏氨酸磷酸化位点，但不影响与钙黏蛋白结合的能力。最后，我们发现激酶抑制剂星形孢菌素可诱导与E-钙黏蛋白多肽结合的p120（连环蛋白）的电泳迁移率增加，激活无功能的E-钙黏蛋白蛋白，并将野生型E-钙黏蛋白和E-钙黏蛋白-α-连环蛋白嵌合蛋白从细胞松弛素D敏感状态转变为细胞松弛素D不敏感状态。这些结果共同表明，p120（连环蛋白）是E-钙黏蛋白介导的细胞黏附的调节因子。
