Kaplan D D, Meigs T E, Casey P J
Department of Pharmacology, Duke University Medical Center, Durham, North Carolina 27710, USA.
J Biol Chem. 2001 Nov 23;276(47):44037-43. doi: 10.1074/jbc.M106121200. Epub 2001 Sep 6.
Heterotrimeric G proteins of the G(12) subfamily mediate cellular signals leading to events such as cytoskeletal rearrangements, cell proliferation, and oncogenic transformation. Several recent studies have revealed direct effector proteins through which G(12) subfamily members may transmit signals leading to various cellular responses. Our laboratory recently demonstrated that Galpha(12) and Galpha(13) specifically interact with the cytoplasmic domains of several members of the cadherin family of cell adhesion molecules (Meigs, T. E., Fields, T. A., McKee, D. D., and Casey, P. J. (2001) Proc. Natl. Acad. Sci. U. S. A. 98, 519-524). This interaction causes beta-catenin to release from cadherin and relocalize to the cytoplasm and nucleus, where it participates in transcriptional activation. Here we report that two distinct regions of the epithelial cadherin (E-cadherin) tail are required for interaction with beta-catenin and Galpha(12), respectively. Deletion of an acidic, 19-amino acid region of E-cadherin abolishes its ability to bind beta-catenin in vitro, to inhibit beta-catenin-mediated transactivation, or to stabilize beta-catenin; causes subcellular mislocalization of beta-catenin; and disrupts cadherin-mediated cell adhesion. On the other hand, deletion of a distinct 11-amino acid region of E-cadherin dramatically attenuates interaction with Galpha(12); furthermore, Galpha(12) is ineffective in stimulating beta-catenin release from an E-cadherin cytoplasmic domain lacking this putative Galpha(12)-binding region. These findings indicate that Galpha(12) and beta-catenin do not compete for the same binding site on cadherin and provide molecular targets for selectively disrupting the interaction of these proteins with cadherin.
G(12)亚家族的异源三聚体G蛋白介导细胞信号，引发细胞骨架重排、细胞增殖和致癌转化等事件。最近的几项研究揭示了一些直接效应蛋白，G(12)亚家族成员可能通过这些蛋白传递导致各种细胞反应的信号。我们实验室最近证明，Gα(12)和Gα(13)与细胞粘附分子钙粘蛋白家族的几个成员的胞质结构域特异性相互作用（梅格斯，T.E.，菲尔兹，T.A.，麦基，D.D.，和凯西，P.J.（2001年）美国国家科学院院刊98，519 - 524）。这种相互作用导致β-连环蛋白从钙粘蛋白释放并重新定位到细胞质和细胞核，在那里它参与转录激活。在此我们报告，上皮钙粘蛋白（E-钙粘蛋白）尾部的两个不同区域分别是与β-连环蛋白和Gα(12)相互作用所必需的。删除E-钙粘蛋白的一个含19个氨基酸的酸性区域会消除其在体外结合β-连环蛋白、抑制β-连环蛋白介导的反式激活或稳定β-连环蛋白的能力；导致β-连环蛋白在亚细胞水平上定位错误；并破坏钙粘蛋白介导的细胞粘附。另一方面，删除E-钙粘蛋白一个不同的含11个氨基酸的区域会显著减弱与Gα(12)的相互作用；此外，Gα(12)在从缺乏这个假定的Gα(12)结合区域的E-钙粘蛋白胞质结构域刺激β-连环蛋白释放方面无效。这些发现表明，Gα(12)和β-连环蛋白不会竞争钙粘蛋白上的相同结合位点，并为选择性破坏这些蛋白质与钙粘蛋白的相互作用提供了分子靶点。
