Activation of PKCdelta and ERK1/2 in the sensitivity to UV-induced apoptosis of human cells harboring 4977 bp deletion of mitochondrial DNA.
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.
Liu
Chun-Yi
CY
Institute of Biochemistry and Molecular Biology, School of Life Sciences, National Yang-Ming University, 155 Li-Nong St., Sec. 2, Peitou, Taipei 112, Taiwan.
Lee
Cheng-Feng
CF
Wei
Yau-Huei
YH
D000098:Acetophenones / Q000378:metabolism; D000111:Acetylcysteine / Q000378:metabolism; D017209:Apoptosis / Q000528:radiation effects*; D001578:Benzopyrans / Q000378:metabolism; D002478:Cells, Cultured; D004272:DNA, Mitochondrial / Q000235:genetics*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D017353:Gene Deletion; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism*; D017246:Ophthalmoplegia, Chronic Progressive External / Q000235:genetics; D051745:Protein Kinase C-delta / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D014466:Ultraviolet Rays
D000098:Acetophenones; D001578:Benzopyrans; D004272:DNA, Mitochondrial; D004791:Enzyme Inhibitors; D017382:Reactive Oxygen Species; C085746:rottlerin; D051745:Protein Kinase C-delta; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D000111:Acetylcysteine