USAG-1 aggravates renal ischemia‒reperfusion injury via promoting GPX4 degradation-induced ferroptosis.

Renal ischemia‒reperfusion injury (IRI) remains an inevitable complication in kidney transplantation and a leading cause of delayed graft function (DGF). Ferroptosis, a form of iron-dependent lipid peroxidation-driven cell death, has emerged as an important mechanism contributing to renal IRI. Although uterine sensitization-associated gene-1 (USAG-1) has been implicated in both acute and chronic kidney injury, its involvement in IRI-associated ferroptosis has not been elucidated. In this study, using murine renal ischemia-reperfusion models and human transplant kidney biopsies (from donation after circulatory death donors), we demonstrate that USAG-1 is significantly upregulated under ischemic stress. Importantly, higher USAG-1 expression in donor kidneys was associated with worse allograft function post-transplantation, suggesting that USAG-1 may serve as a promising biomarker for transplant injury and outcomes. In addition, genetic ablation of USAG-1 markedly attenuated both IRI- and folic acid-induced ferroptosis, accompanied by reduced acute kidney injury severity. Mechanistically, glutathione peroxidase 4 (GPX4) was a critical downstream effector of USAG-1 in mediating ferroptotic processes. HSP family A member 5 (HSPA5), a canonical molecular chaperone, stabilized GPX4 via direct interactions. Our findings revealed that overexpressed USAG-1 competitively binds to HSPA5, thereby disrupting the HSPA5-GPX4 interaction. This interference was abrogated by truncation mutants of USAG-1 that failed to interact with HSPA5. Notably, functional validation of the USAG-1/HSPA5/GPX4 axis confirmed that preserving HSPA5-GPX4 binding mitigated ferroptosis and alleviated renal injury. Overall, our study reveals a previously unrecognized mechanism by which USAG-1 promotes ferroptosis in renal IRI and highlights the therapeutic potential of targeting the USAG-1/HSPA5/GPX4 axis to improve graft outcomes post-transplantation.