Role of Prion protein in premature senescence of human fibroblasts

Prion protein (PrP) is essentially known for its capacity to induce neurodegenerative prion diseases in mammals caused by a conformational change in its normal cellular isoform (PrPc) into an infectious and disease-associated misfolded form, called scrapie isofoms (PrPSc). Although its sequence is highly conserved, less information is available on its physiological role under normal conditions. However, increasing evidence supports a role for PrPc in the cellular response to oxidative stress. In the present study, a new link between PrP and senescence is highlighted. The role of PrP in premature senescence induced by copper was investigated. WI-38 human fibroblasts were incubated with copper sulfate (CuSO4) to trigger premature senescence. This induced an increase of PrP mRNA level, an increase of protein abundance of the normal form of PrP and a nuclear localization of the protein. Knockdown of PrP expression using specific small interfering RNA (siRNA) gave rise to appearance of several biomarkers of senescence as a senescent morphology, an increase of senescence associated beta-galactosidase activity and a decrease of the cellular proliferative potential. Overall these data suggest that PrP protects cells against premature senescence induced by copper.