XRCC5 downregulated by TRIM25 is susceptible for lens epithelial cell apoptosis

Exposure of the lens to UVB can lead to oxidative stress, which would result in age-related cataract (ARC) formation. In this study, we investigate the regulatory mechanism of tripartite motif containing 25 (TRIM25) in ARC. The protein level of TRIM25 was elevated in ARC specimens and UVB-exposed SRA01/04 cells. Bioinformatic analysis indicated that X-ray repair cross complementing 5 (XRCC5) might interact with TRIM25, and the interaction was validated via immunoprecipitation. TRIM25 interacted with XRCC5 and ubiquitinated it for degradation. Further studies showed that XRCC5 overexpression notably repressed UVB-induced apoptosis, while XRCC5 knockdown promoted apoptosis. Of note, ubiquitination of XRCC5 mediated by TRIM25 overexpression facilitated apoptosis. Attenuation of XRCC5 ubiquitination by mutant with substitution of lysine residues with arginine residues rescued its anti-apoptosis effect. Moreover, we observed that TRIM25-mediated XRCC5 degradation was reversed by proteasome inhibitor MG-132 or lysosome inhibitor 3-MA. In conclusion, TRIM25 mediates ubiquitination of XRCC5 to regulate the function and degradation of XRCC5, suggesting that interventions targeting TRIM25 might be a promising therapeutic strategy for ARC.