KLF5 Alleviates Excessive Autophagy-Induced Podocyte Injury by Enhancing ITCH-Mediated Ubiquitination of ACTR2.

ACTR2 is highly expressed and autophagy is enhanced in adriamycin (ADR)-induced nephropathic rats, and KLF5/ITCH is predicted to be the upstream axis of ACTR2. Accordingly, we investigated the regulation of excessive autophagy by KLF5/ITCH/ACTR2 in inflammatory ADR-induced podocytes and preliminarily elucidated the molecular mechanisms of podocyte injury. ADR was used to establish a rat model of nephropathy as well as a model of podocyte injury. Proteinuria, albumin, serum creatinine, triglyceride and total cholesterol levels, histopathologic staining were assessed. Transmission electron microscopy was applied to observe autophagy, and Western blot to detect protein levels in vivo. Quantitative real-time polymerase chain reaction, Western blot, flow cytometry, Co-immunoprecipitation, chromatin immunoprecipitation, dual luciferase reporter genes, and bioinformatics analyses were performed for in vitro mechanistic and functional exploration. ADR rat model was successfully constructed, showing abnormal biochemical indices, pathological damage and autophagic vesicle formation, increased expressions of autophagy-related proteins and ACTR2 protein, and decreased expressions of KLF5 and ITCH. ACTR2 silencing reversed ADR-induced apoptosis and inflammatory factors, decreased LC3 II/LC3 I, Beclin 1, Bax and C-caspase 3 levels, and elevated Bcl-2 level in vitro. KLF5 activated ITCH to promote ubiquitinated degradation of ACTR2. KLF5 overexpression attenuated the promoting effects of ACTR2 on autophagy, apoptosis, and inflammation in podocytes. The mechanism by which KLF5 protects podocytes from injury is to promote ITCH transcription, thereby facilitating ITCH-mediated ubiquitination of ACTR2 and inhibiting podocyte autophagy.