Max Planck Institute of Biochemistry, Department for Molecular Medicine, 82152 Martinsried, Germany.
J Cell Sci. 2012 Nov 1;125(Pt 21):5233-40. doi: 10.1242/jcs.112029. Epub 2012 Sep 3.
The focal adhesion (FA) protein PINCH-1 is required for the survival of primitive endoderm (PrE) cells. How PINCH-1 regulates this fundamental process is not known. Here, we use embryoid bodies (EBs) and isolated EB-derived PrE cells to investigate the mechanisms by which PINCH-1 promotes PrE survival. We report that loss of PINCH-1 in PrE cells leads to a sustained activity of JNK and the pro-apoptotic factor Bax. Mechanistically, the sustained JNK activation was due to diminished levels of the JNK inhibitory factor Ras suppressor protein-1 (RSU-1), whose stability was severely reduced upon loss of PINCH-1. Chemical inhibition of JNK attenuated apoptosis of PrE cells but failed to reduce Bax activity. The increased Bax activity was associated with reduced integrin signalling and diminished Bcl-2 levels, which were shown to inhibit Bax. Altogether our findings show that PINCH-1 is a pro-survival factor that prevents apoptosis of PrE cells by modulating two independent signalling pathways; PINCH-1 inhibits JNK-mediated apoptosis by stabilising the PINCH-1 binding protein RSU-1 and promotes Bcl-2-dependent pro-survival signalling downstream of integrins.
黏着斑蛋白 PINCH-1 对于原始内胚层(PrE)细胞的存活是必需的。然而,PINCH-1 如何调节这一基本过程尚不清楚。在这里,我们使用胚状体(EBs)和分离的 EB 来源的 PrE 细胞来研究 PINCH-1 促进 PrE 细胞存活的机制。我们报告说,PrE 细胞中 PINCH-1 的缺失会导致 JNK 的持续激活和促凋亡因子 Bax。从机制上讲,持续的 JNK 激活是由于 JNK 抑制因子 Ras 抑制蛋白-1(RSU-1)水平降低所致,而 PINCH-1 的缺失严重降低了 RSU-1 的稳定性。JNK 的化学抑制减弱了 PrE 细胞的凋亡,但未能降低 Bax 的活性。Bax 活性的增加与整合素信号的减少和 Bcl-2 水平的降低有关,Bcl-2 被证明可以抑制 Bax。总之,我们的研究结果表明,PINCH-1 是一种促存活因子,通过调节两条独立的信号通路来防止 PrE 细胞凋亡;PINCH-1 通过稳定其结合蛋白 RSU-1 来抑制 JNK 介导的细胞凋亡,并促进整合素下游 Bcl-2 依赖性的促存活信号。