Liu Chun-Yi, Lee Cheng-Feng, Wei Yau-Huei
Institute of Biochemistry and Molecular Biology, School of Life Sciences, National Yang-Ming University, 155 Li-Nong St., Sec. 2, Peitou, Taipei 112, Taiwan.
Biochim Biophys Acta. 2009 Aug;1792(8):783-90. doi: 10.1016/j.bbadis.2009.05.005. Epub 2009 May 27.
The 4977 bp deletion of mitochondrial DNA (mtDNA), often found in patients with chronic progressive external ophthalmoplegia (CPEO), has been demonstrated to increase the susceptibility to apoptosis of human cells. We investigated the mechanism underlying the apoptotic susceptibility of the Delta4977 cybrid harboring about 80% 4977 bp-deleted mtDNA. The production of hydrogen peroxide (H(2)O(2)) and phosphorylation of PKCdelta and ERK1/2 were increased in the Delta4977 cybrid, which was more susceptible to UV-induced apoptosis. Moreover, treatment with N-acetyl-l-cysteine (NAC) or blocking of activation of PKCdelta by rottlerin or PKCdelta-siRNA, and inhibition of ERK1/2 by PD98059 or ERK1/2-siRNA significantly attenuated the susceptibility of the Delta4977 cybrid to apoptosis. Furthermore, the increase of PKCdelta expression in the Delta4977 cybrid also amplified the apoptotic signal through caspase 3-mediated proteolytic activation of PKCdelta. In addition, PKCdelta and ERK1/2 were hyperphosphorylated in skin fibroblasts of CPEO patients harboring 4977 bp-deleted mtDNA. We suggest that the activation of PKCdelta and ERK1/2 elicited by 4977 bp-deleted mtDNA-induced oxidative stress plays a role in the susceptibility of the mutant cells to apoptosis. This may explain, at least in part, the degenerative manifestation of brain and muscle in patients with mitochondrial encephalomyopathies such as CPEO syndrome.
线粒体DNA（mtDNA）4977 bp的缺失常见于慢性进行性外眼肌麻痹（CPEO）患者，已被证明会增加人类细胞对凋亡的易感性。我们研究了携带约80% 4977 bp缺失mtDNA的Delta4977胞质杂种细胞凋亡易感性的潜在机制。Delta4977胞质杂种细胞中过氧化氢（H₂O₂）的产生以及PKCδ和ERK1/2的磷酸化增加，该细胞对紫外线诱导的凋亡更敏感。此外，用N - 乙酰 - l - 半胱氨酸（NAC）处理，或用rottlerin或PKCδ - siRNA阻断PKCδ的激活，以及用PD98059或ERK1/2 - siRNA抑制ERK1/2，均显著减弱了Delta4977胞质杂种细胞对凋亡的易感性。此外，Delta4977胞质杂种细胞中PKCδ表达的增加还通过caspase 3介导的PKCδ蛋白水解激活放大了凋亡信号。此外，在携带4977 bp缺失mtDNA的CPEO患者的皮肤成纤维细胞中，PKCδ和ERK1/2发生了过度磷酸化。我们认为，4977 bp缺失的mtDNA诱导的氧化应激引发的PKCδ和ERK1/2激活在突变细胞对凋亡的易感性中起作用。这可能至少部分解释了线粒体脑肌病如CPEO综合征患者脑和肌肉的退行性表现。
