Opposing roles of Ras/Raf oncogenes and the MEK1/ERK signaling module in regulation of expression and adhesive function of surface transglutaminase
Opposing roles of Ras/Raf oncogenes and the MEK1/ERK signaling module in regulation of expression and adhesive function of surface transglutaminase
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DOI：
10.1074/jbc.m303488200
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发表时间：
2003-09-12
影响因子：
4.8
通讯作者：
Belkin, AM
中科院分区：
文献类型：
--
作者：
Akimov, SS;Belkin, AM
组织转氨酶（tTG）作为细胞表面上的纤连蛋白的有效且普遍存在的整合素相关粘附共受体，并影响几种关键的整合素功能。在这里，我们报告说，在成纤维细胞中，激活的H-Ras和Raf-1癌基因减少生物合成，与β（1）整合素，和表面表达的tTG，因为下调tTG mRNA。反过来，表面tTG的减少抑制了H-Ras和Raf-1转化的细胞在纤连蛋白上的粘附，特别是在其tTG结合片段I（6）II（1，2）I（7-9）上的粘附，该片段不直接与整联蛋白相互作用。Ras/Raf下游信号与特定的药理学抑制剂的分析表明，tTG表达的减少是由p38 MAPK，c-Jun NH 2-末端激酶和磷脂酰肌醇3-激酶途径介导的。相比之下，ERK通路的激活增加的组成型活性MEK 1刺激tTG mRNA的表达，生物合成，和表面表达的tTG，而MEK抑制剂或显性负MEK 1发挥相反的效果。ERK信号对表面tTG的调节改变了细胞在纤连蛋白及其结合tTG的片段上的粘附。此外，在未转化的成纤维细胞中，通过粘附在纤连蛋白或生长因子上的ERK信号传导的瞬时刺激提高了tTG的生物合成，增加了与β（1）整联蛋白的复合物形成，并提高了tTG的表面表达。最后，ERK激活是生长因子诱导的tTG在粘附成纤维细胞表面上的重新分布以及β 1整合素和tTG在细胞-基质粘附接触处的共聚集所必需的。总之，我们的数据表明，下调表面tTG的Ras和Raf癌基因的转化成纤维细胞的粘附缺陷，而刺激的生物合成和表面表达的tTG的MEK 1/ERK模块促进和维持未转化细胞的细胞-基质粘附。Ras/Raf癌基因及其直接下游信号传导模块MEK 1/ERK对tTG表达的对比效应与表面tTG的粘附功能一致。
Tissue transglutaminase (tTG) serves as a potent and ubiquitous integrin-associated adhesion co-receptor for fibronectin on the cell surface and affects several key integrin functions. Here we report that in fibroblasts, activated H-Ras and Raf-1 oncogenes decrease biosynthesis, association with beta(1) integrins, and surface expression of tTG because of down-regulation of tTG mRNA. In turn, the reduction of surface tTG inhibits adhesion of H-Ras- and Raf-1-transformed cells on fibronectin and, in particular, on its tTG-binding fragment I(6) II(1,2) I(7-9), which does not interact directly with integrins. Analysis of Ras/Raf downstream signaling with specific pharmacological inhibitors reveals that the decrease in tTG expression is mediated by the p38 MAPK, c-Jun NH2-terminal kinase, and phosphatidylinositol 3-kinase pathways. In contrast, increased activation of the ERK pathway by constitutively active MEK1 stimulates tTG mRNA expression, biosynthesis, and surface expression of tTG, whereas MEK inhibitors or dominant negative MEK1 exert an opposite effect. This modulation of surface tTG by ERK signaling alters adhesion of cells on fibronectin and its fragment that binds tTG. Furthermore, transient stimulation of ERK signaling in untransformed fibroblasts by adhesion on fibronectin or growth factors elevates tTG biosynthesis, increases complex formation with beta(1) integrins, and raises surface expression of tTG. Finally, ERK activation is required for growth factor-induced redistribution of tTG on the surface of adherent fibroblasts and co-clustering of beta(1) integrins and tTG at cell-matrix adhesion contacts. Together, our data indicate that down-regulation of surface tTG by Ras and Raf oncogenes contributes to adhesive deficiency of transformed fibroblasts, whereas stimulation of biosynthesis and surface expression of tTG by the MEK1/ERK module promotes and sustains cell-matrix adhesion of untransformed cells. Contrasting effects of Ras/Raf oncogenes and their immediate downstream signaling module, MEK1/ERK, on tTG expression are consistent with adhesive function of surface tTG.