Ortiz-Ferrón G, Tait S W, Robledo G, de Vries E, Borst J, López-Rivas A
Instituto de Parasitología y Biomedicina, CSIC, Granada, Spain.
Cell Death Differ. 2006 Nov;13(11):1857-65. doi: 10.1038/sj.cdd.4401875. Epub 2006 Feb 17.
Breast cancer cells often show increased activity of the mitogen-activated protein kinase (MAPK) pathway. We report here that this pathway reduces their sensitivity to death ligand tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and present the underlying mechanism. Activation of protein kinase C (PKC) inhibited TRAIL-induced apoptosis in a protein synthesis-independent manner. Deliberate activation of MAPK was also inhibitory. In digitonin-permeabilized cells, PKC activation interfered with the capacity of recombinant truncated (t)Bid to release cytochrome c from mitochondria. MAPK activation did not affect TRAIL or tumor necrosis factor (TNF)alpha-induced Bid cleavage. However, it did inhibit translocation of (t)Bid to mitochondria as determined both by subcellular fractionation analysis and confocal microscopy. Steady state tBid mitochondrial localization was prohibited by activation of the MAPK pathway, also when the Bcl-2 homology domain 3 (BH3) domain of tBid was disrupted. We conclude that the MAPK pathway inhibits TRAIL-induced apoptosis in MCF-7 cells by prohibiting anchoring of tBid to the mitochondrial membrane. This anchoring is independent of its interaction with resident Bcl-2 family members.
乳腺癌细胞通常表现出丝裂原活化蛋白激酶（MAPK）信号通路活性增强。我们在此报告，该信号通路会降低乳腺癌细胞对死亡配体肿瘤坏死因子相关凋亡诱导配体（TRAIL）的敏感性，并揭示其潜在机制。蛋白激酶C（PKC）的激活以不依赖蛋白质合成的方式抑制TRAIL诱导的细胞凋亡。刻意激活MAPK也具有抑制作用。在洋地黄皂苷通透的细胞中，PKC激活会干扰重组截短型（t）Bid从线粒体释放细胞色素c的能力。MAPK激活并不影响TRAIL或肿瘤坏死因子（TNF）α诱导的Bid裂解。然而，通过亚细胞分级分析和共聚焦显微镜检测发现，它确实抑制了（t）Bid向线粒体的转位。即使tBid的Bcl-2同源结构域3（BH3）结构域被破坏，MAPK信号通路的激活也会阻止tBid在稳态时定位于线粒体。我们得出结论，MAPK信号通路通过阻止tBid锚定到线粒体膜上，从而抑制MCF-7细胞中TRAIL诱导的细胞凋亡。这种锚定与其与驻留Bcl-2家族成员的相互作用无关。
