Trans-homophilic interaction of CADM1 activates PI3K by forming a complex with MAGuK-family proteins MPP3 and Dlg.
Trans-homophilic interaction of CADM1 activates PI3K by forming a complex with MAGuK-family proteins MPP3 and Dlg.
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DOI：
10.1371/journal.pone.0082894
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发表时间：
2014
期刊：
影响因子：
3.7
通讯作者：
Murakami Y
中科院分区：
文献类型：
--
作者：
Murakami S;Sakurai-Yageta M;Maruyama T;Murakami Y
CADM1（细胞粘附分子1）是一种属于免疫球蛋白超家族的细胞粘附分子，参与细胞间相互作用以及上皮结构的形成和维持。 CADM1 的表达在各种源自上皮细胞的肿瘤中经常下调。然而，由 CADM1 介导的细胞粘附激活的细胞内信号通路仍然未知。在这里，我们建立了一种基于细胞的扩散测定法来分析由 CADM1 的跨同质相互作用特异性激活的信号通路。在该测定中，表达外源CADM1的MDCK细胞在涂有CADM1重组胞外片段的玻璃上孵育，并通过测量其表面积来量化细胞铺展程度。对 104 种已知功能的化学抑制剂的分析筛选表明，磷酸肌醇 3-激酶 (PI3K) 抑制剂 LY294002 能够以剂量依赖性方式有效抑制细胞扩散。 Akt 和 Rac1 抑制剂（PI3K 的下游效应器）也部分抑制细胞扩散，而添加两种抑制剂阻止细胞扩散的程度与 LY294002 相同。此外，MPP3 和 Dlg（膜相关鸟苷酸激酶同源物 (MAGuK) 蛋白）通过在细胞外周形成多蛋白复合物，将 CADM1 与 PI3K 的 p85 连接起来。这些结果表明CADM1介导的反式同质相互作用激活PI3K途径以重组肌动蛋白细胞骨架并形成上皮细胞结构。
CADM1 (Cell adhesion molecule 1), a cell adhesion molecule belonging to the immunoglobulin superfamily, is involved in cell-cell interaction and the formation and maintenance of epithelial structure. Expression of CADM1 is frequently down-regulated in various tumors derived from epithelial cells. However, the intracellular signaling pathways activated by CADM1-mediated cell adhesion remain unknown. Here, we established a cell-based spreading assay to analyze the signaling pathway specifically activated by the trans-homophilic interaction of CADM1. In the assay, MDCK cells expressing exogenous CADM1 were incubated on the glass coated with a recombinant extracellular fragment of CADM1, and the degree of cell spreading was quantified by measuring their surface area. Assay screening of 104 chemical inhibitors with known functions revealed that LY294002, an inhibitor of phosphoinositide 3-kinase (PI3K), efficiently suppressed cell spreading in a dose-dependent manner. Inhibitors of Akt and Rac1, downstream effectors of PI3K, also partially suppressed cell spreading, while the addition of both inhibitors blocked cell spreading to the same extent as did LY294002. Furthermore, MPP3 and Dlg, membrane-associated guanylate kinase homologs (MAGuK) proteins, connect CADM1 with p85 of PI3K by forming a multi-protein complex at the periphery of cells. These results suggest that trans-homophilic interaction mediated by CADM1 activates the PI3K pathway to reorganize the actin cytoskeleton and form epithelial cell structure.
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