A cell-free system based on the cytosol of normally growing cells, which reproduces measurable aspects of the apoptotic program, is provided. The apoptotic program is initiated by addition of dATP in the specific exemplification of the HeLa 100,000×g supernatant. Fractionation of the cytosol yielded a 15 kDa protein, identified by absorption spectrum and protein sequence as cytochrome c, that is required for in vitro apoptosis. Elimination of cytochrome c from cytosol by immunodepletion or inclusion of sucrose to stabilize mitochondria during cytosol preparation, diminished the apoptotic activity. Addition of exogenous cytochrome c to cytochrome c-depleted extracts restored apoptotic activity. Cells undergoing apoptosis in vivo showed increased release of cytochrome c to their cytosol, suggesting that mitochondria may function in apoptosis by releasing cytochrome c.
本研究提供了一种基于正常生长细胞的细胞液的无
细胞系统,它能重现细胞凋亡程序的可测量方面。在 HeLa 100,000×g 上清液的特定示例中加入 d
ATP 即可启动细胞凋亡程序。通过吸收光谱和蛋白质序列鉴定,细胞色素 c 是体外细胞凋亡所必需的。在细胞液制备过程中,通过免疫耗竭或加入
蔗糖稳定线粒体来消除细胞色素 c,都会降低细胞凋亡活性。在细胞色素 c 贫化的
提取物中加入外源性细胞色素 c 可恢复细胞凋亡活性。体内发生凋亡的细胞显示细胞色素 c 向细胞膜的释放增加,这表明线粒体可能通过释放细胞色素 c 在细胞凋亡中发挥作用。