UBR4 attenuates cisplatin-induced acute kidney injury by regulating the HRI-ISR axis.

Cisplatin is widely used in treating solid tumors, but its dose-limiting nephrotoxicity, which manifests as acute kidney injury (AKI), remains a major clinical challenge. The molecular pathways determining proximal tubular epithelial cell (PTEC) susceptibility during cisplatin-induced injury are not fully elucidated. Here, we identify ubiquitin protein ligase E3 component n-recognin 4 (UBR4) as a key regulator of the integrated stress response (ISR), which plays an important role in regulating reactive oxygen species (ROS) accumulation and mitophagy in the kidney. UBR4 expression was markedly upregulated in PTECs of mice with cisplatin-induced AKI. Tubule-specific Ubr4 deficiency exacerbated kidney dysfunction, tubular damage, and cell death. Mechanistically, UBR4 promoted ubiquitination and degradation of the kinase HRI, thereby constraining ISR overactivation and alleviating its inhibitory effect on mitophagy. Consistent with this mechanism, both genetic enhancement of UBR4 and pharmacological inhibition of the ISR with ISRIB significantly mitigated cisplatin-induced nephrotoxicity. Together, our findings uncover a previously unrecognized UBR4-HRI-ISR regulatory axis that serves as an intrinsic protective mechanism in the kidney and highlight UBR4 as a promising therapeutic target for preventing cisplatin-induced tubular injury.