Mitochondrial nucleoid remodeling and biogenesis are regulated by the p53-p21(WAF1)-PKC zeta pathway in p16(INK4a)-silenced cells

Abstract

Mitochondrial dysfunction is linked to age-related senescence phenotypes. We report here the pathway increasing nucleoid remodeling and biogenesis in mitochondria during the senescence of foreskin human diploid fibroblasts (fs-HDF) and WI-38 cells. Replicative senescence in fs-HDF cells increased mitochondria! nucleoid remodeling as indicated by 5-bromo-2'-deoxyuridine (BrdU) incorporation and mitochondrial transcription factor A (TFAM) expression in enlarged and fused mitochondria. Mitochondrial nucleoid remodeling was accompanied by mitochondrial biogenesis in old cells, and the expression levels of OXPHOS complex-I, -IV and -V subunits, PGC1 alpha and NRF1 were greatly increased compared to young cells. Activated protein kinase C zeta (PKC zeta) increased mitochondrial activity and expressed phenotypes of delayed senescence in fs-HDF cells, but not in WI-38 cells. The findings were reproduced in the doxorubicin-induced senescence of young fs-HDF and WI-38 cells via the PKC zeta-LKB1-AMPK signaling pathway, which was regulated by the p53-p21(WAF1) pathway when p16(INK4a) was silenced. The signaling enhanced PGC-1 alpha-NRF1-TFAM axis in mitochondria, which was demonstrated by Ingenuity Pathway Analysis of young and old fs-HDF cells. Activation of the p53-p21(WAF1 )pathway and silencing of p16(INK4a) are responsible for mitochondrial reprogramming in senescent cells, which may be a compensatory mechanism to promote cell survival under senescence stress.