The mechanism of protection of apoptosis by the mitochondrial PHGPx

本课题旨在探讨磷脂氢过氧化物谷胱甘肽过氧化物酶（PHGPx）对细胞凋亡的保护机制。2-脱氧葡萄糖诱导的细胞凋亡完全被线粒体PHGPx的过表达所抑制。细胞色素c（cyt.c）的释放提供了细胞凋亡的不可逆信号。线粒体PHGPx的过表达抑制cyt.c从线粒体的释放。cyt的释放分两步进行。C来自线粒体。第一步是cyt.c从线粒体内膜上解离，第二步是游离的cyt通过。细胞色素C通过渗透性转换孔（PT孔）与线粒体膜上的特异性磷脂心磷脂结合，PT孔通过腺嘌呤核苷酸转运子（ANT）调节细胞色素C的开放。cyt.c与CL单层的结合显著降低CL的自氧化。结果表明，细胞色素c可从线粒体内膜释放，细胞凋亡诱导后ANT活性明显降低。ANT的失活与cyt的释放有很好的对应关系。C来自线粒体。与线粒体融合的CLOOH能明显抑制线粒体的ANT活性，提示CLOOH能抑制ANT活性。结果表明，CL作为线粒体特异性磷脂的过氧化作用可能是启动细胞凋亡的关键步骤。

In this project, we try to find out the mechanism of the protection of apoptosis mitochondrial type of phospholipid hydroperoxide glutathione peroxidase (PHGPx). Apoptosis caused by 2deoxyglucose was completely suppressed by the overexpression of mitochondrial PHGPx. The release of cytochrome c (cyt.c) provide the irreversible signal of apoptosis. Overexpression of mitochondrial PHGPx inhibit the release of cyt.c from mitochondria. There are two steps for the liberation of cyt. C from mitochondria. First step is the dissociation of cyt.c from inner membrane of mitochondria and second step is the passage of free cyt. C through the permeability transition pore (PT pore) which regulates the opening by adenine nucleotide translocator (ANT).Cyt.c preferentially binds to the monolayer of cardiolipin which is the specific phospholipid in mitochondria. Binding of cyt.c to CL monolayer significantly decreased by the autooxidation of CL. Cyt.c released from liposome containing CL by the peroxidation with radical initiator, these results suggest that cytc could release from inner membrane of mitochondoria.ANT activity was significantly decreased by the induction of apoptosis. Inactivation of ANT was well correspond to the liberation of cyt. C from mitochondria. ANT activity of mitochondria markedly inhibited by the fusion of CLOOH with isolated mitochondria suggesting that CLOOH could inhibit ANT activity. ANT activity of reconstituted proteoliposome was suppressed by the addition of CLOOH in proteoliposome.These results suggest that peroxidation of CL as a mitochondrial specific phospholipid might be a key step to initiate the apoptosis.