Proteasome dysfunction in retinal pigment epithelium during aging contributes to the pathogenesis of Age-Macular related Degeneration

Purpose Age-related Macular Degeneration (AMD) is the leading cause of blindness in people older than 50 in developed countries, and is associated with formation of subretinal deposits (drusen) and damage to Bruch’s membrane (BM) basal to the retinal pigment epithelium (RPE). It has been reported that activities of the ubiquitin-proteasome pathway (UPP) in retinal pigment epithelium decrease upon aging. Previous studies demonstrated that expression of ubiquitin in which lysine 6 is replaced by tryptophan (K6W-Ub) impairs the function of UPP. The main objective of this work was to investigate the hypothesis that chronically impairment of UPP in RPE contributes to some of the cardinal features of AMD, including drusens. Methods To address this question ARPE-19 cells were infected with empty vector, K6W Ubiquitin mutant and Wild Type Ubiquitin. The drusen formation and accumulation in basal matrix was evaluated by confocal microscopy, using specific drusen markers such as APOE, while exosome realease was determined by western blot (such as CD63 and Tsg101) and flow cytometry following exosomes isolation by ultracentrifugation. Results The results obtained showed that expression of K6W mutant Ub leads to an impairment of proteasome activity and an increased amount of exosomes release and drusen accumulation. Conclusion In this study the data might provide a vaulable tool to eluciadte the biological determinats of age-related proteolytic stress and its impacts on proteostasis in the retina.