Martin Angel G, Nguyen Jack, Wells James A, Fearnhead Howard O
Apoptosis Section, Laboratory of Protein Dynamics and Signaling, NCI-Frederick, Frederick, MD 21702, USA.
Biochem Biophys Res Commun. 2004 Jul 2;319(3):944-50. doi: 10.1016/j.bbrc.2004.05.084.
Caspases are cysteine proteases and potent inducers of apoptosis. Their activation and activity is therefore tightly regulated. There are several mechanisms by which caspases can be activated but one key pathway involves release of holo cytochrome c from mitochondria into the cytoplasm. Cytoplasmic holo cytochrome c binds to apoptotic protease activating factor-1 (Apaf-1), driving the formation of an Apaf-1 oligomer (the apoptosome) which in turn binds and activates caspase-9. Previously we showed that the apo form of cytochrome c (lacking heme) can bind Apaf-1 and block both holo-dependent caspase activation in cell extracts and Bax-induced apoptosis in cells. Here we tested the ability of apo cytochrome c to inhibit caspase-9 activation induced by recombinant Apaf-1. Furthermore, using purified proteins and size exclusion chromatography we show that apo cytochrome c prevents holo cytochrome c-dependent apoptosome formation.
半胱天冬酶是半胱氨酸蛋白酶,也是细胞凋亡的强效诱导剂。因此,它们的激活和活性受到严格调控。半胱天冬酶的激活有多种机制,但一个关键途径涉及全细胞色素c从线粒体释放到细胞质中。细胞质中的全细胞色素c与凋亡蛋白酶激活因子-1(Apaf-1)结合,促使Apaf-1寡聚体(凋亡小体)形成,而凋亡小体又会结合并激活半胱天冬酶-9。此前我们发现,细胞色素c的脱辅基形式(不含血红素)能够结合Apaf-1,并阻断细胞提取物中依赖全细胞色素c的半胱天冬酶激活以及细胞中Bax诱导的细胞凋亡。在此,我们测试了脱辅基细胞色素c抑制重组Apaf-1诱导的半胱天冬酶-9激活的能力。此外,我们使用纯化蛋白和尺寸排阻色谱法表明,脱辅基细胞色素c可阻止依赖全细胞色素c的凋亡小体形成。