TRIM21 ubiquitylates GPX4 and promotes ferroptosis to aggravate ischemia/reperfusion-induced acute kidney injury

Aims: This study aims to verify the molecular mechanism that Tripartite motif containing 21 (TRIM21) promotes ubiquitination degradation of glutathione peroxidase 4 (GPX4) by regulating ferroptosis, and to discuss the feasibility of TRIM21 as a new therapeutic target for acute kidney injury (AKI). Materials and methods: Ischemia-reperfusion (I/R)-AKI model was constructed using Trim21^+/+ and Trim21^−/− mice, and the expression of markers associated with kidney injury and ferroptosis were evaluated. HK-2 cells were treated by RSL3 and Erastin, and a hypoxia/reoxygenation (H/R) model was constructed to simulate I/R injury in vivo. Key findings: In vivo, TRIM21 is highly expressed in I/R kidney tissues. Loss of TRIM21 alleviated I/R-AKI and improved renal function. The upregulation of GPX4, a key ferroptosis regulator, and the mild mitochondrial damage suggested that loss of TRIM21 had a negative regulation of ferroptosis. In vitro, TRIM21 was highly expressed in H/R models, and overexpression of TRIM21 in HK-2 cells increased ROS production, promoted intracellular iron accumulation, and boosted cellular sensitivity to RSL3 and Erastin. Mechanistically, we confirmed that GPX4 is a substrate of TRIM21 and can be degraded by TRIM21-mediated ubiquitination, suggesting that inhibiting TRIM21 attenuates ferroptosis. A JAK2 inhibitor Fedratinib downregulated TRIM21 expression and reduced damage both in vivo and in vitro, which is correlated with the upregulation of GPX4. Significance: Our study showed that loss of TRIM21 could alleviate ferroptosis induced by I/R, revealed the mechanism of ubiquitination degradation of GPX4 by TRIM21 and suggested TRIM21 is a potential target for the treatment of AKI.