Atg5-mediated autophagy controls apoptosis/anoikis via p53/Rb pathway in naked mole-rat fibroblasts

Abstract

The naked mole-rat (NMR, Heterocephalus glaber) is the longest-living known rodent species, with a maximum lifespan of over 30 years. NMRs exhibit negligible senescence, exceptional resistance to cancer, and high basal autophagy activity compared with mouse. The molecular mechanisms and physiological roles underlying the high basal autophagy activity in NMRs remain to be elucidated. We identified that the Atg12-Atg5 conjugate, a critical component of autophagosome formation, was highly expressed in NMR skin fibroblasts (NSFs) compared with that in mouse skin fibroblasts. Phenotypic analysis of Atg5 knockdown NSFs revealed that high basal autophagy activity in NSFs was associated with abundant expression of the Atg12-Atg5 conjugate. Atg5 knockdown in NSFs led to accumulation of dysfunctional mitochondria, and suppressed cell proliferation and cell adhesion ability, promoting apoptosis/anoikis accompanied by upregulation of the apoptosis-related genes, Bax and Noxa. Furthermore, inhibition of the p53/Rb pro-apoptotic pathway with SV40 large T antigen abolished Atg5 knockdown-induced increases in apoptosis/anoikis. Taken together, these findings suggest that high basal autophagy activity in NMR cells, mediated by Atg5, contributes to suppression of p53/Rb-induced apoptosis, which could benefit the longevity of NMR cells.

Keywords: Aging; Anoikis; Apoptosis; Atg5; Autophagy; Longevity; Naked mole-rat.