Desagher S, Osen-Sand A, Nichols A, Eskes R, Montessuit S, Lauper S, Maundrell K, Antonsson B, Martinou J C
Serono Pharmaceutical Research Institute, Ares-Serono International S.A., CH-1228 Plan-les-Ouates, Geneva, Switzerland.
J Cell Biol. 1999 Mar 8;144(5):891-901. doi: 10.1083/jcb.144.5.891.
Here we report that in staurosporine-induced apoptosis of HeLa cells, Bid, a BH3 domain containing protein, translocates from the cytosol to mitochondria. This event is associated with a change in conformation of Bax which leads to the unmasking of its NH2-terminal domain and is accompanied by the release of cytochrome c from mitochondria. A similar finding is reported for cerebellar granule cells undergoing apoptosis induced by serum and potassium deprivation. The Bax-conformational change is prevented by Bcl-2 and Bcl-xL but not by caspase inhibitors. Using isolated mitochondria and various BH3 mutants of Bid, we demonstrate that direct binding of Bid to Bax is a prerequisite for Bax structural change and cytochrome c release. Bcl-xL can inhibit the effect of Bid by interacting directly with Bax. Moreover, using mitochondria from Bax-deficient tumor cell lines, we show that Bid- induced release of cytochrome c is negligible when Bid is added alone, but dramatically increased when Bid and Bax are added together. Taken together, our results suggest that, during certain types of apoptosis, Bid translocates to mitochondria and binds to Bax, leading to a change in conformation of Bax and to cytochrome c release from mitochondria.
我们在此报告，在星形孢菌素诱导的HeLa细胞凋亡过程中，含BH3结构域的蛋白质Bid从胞质溶胶转位至线粒体。此事件与Bax构象的改变相关，这导致其氨基末端结构域暴露，并伴随着细胞色素c从线粒体释放。对于血清和钾缺乏诱导凋亡的小脑颗粒细胞，也有类似发现。Bcl-2和Bcl-xL可阻止Bax构象改变，但半胱天冬酶抑制剂则不能。使用分离的线粒体和Bid的各种BH3突变体，我们证明Bid与Bax的直接结合是Bax结构改变和细胞色素c释放的先决条件。Bcl-xL可通过直接与Bax相互作用来抑制Bid的作用。此外，使用来自Bax缺陷肿瘤细胞系的线粒体，我们发现单独添加Bid时，Bid诱导的细胞色素c释放可忽略不计，但Bid和Bax一起添加时则显著增加。综上所述，我们的结果表明，在某些类型的凋亡过程中，Bid转位至线粒体并与Bax结合，导致Bax构象改变以及细胞色素c从线粒体释放。
