USP24 inhibits autophagy in diabetic myocardial disorder by regulating TRAF6-mediated ubiquitination of Beclin-1

Aims: Although Autophagy inhibition is implicated in the onset and progression of diabetic myocardial disorder (DMD), its molecular mechanisms remain poorly understood. Herein, we assessed the regulatory role of the USP24-TRAF6-Beclin-1 pathway in Autophagy and its potential therapeutic value in DMD.

Materials and methods: A diabetic mouse model was established using a high-fat diet combined with streptozotocin injection. Primary neonatal mouse cardiomyocytes and H9c2 cells were cultured in vitro under high-glucose and palmitate conditions to mimic DMD. Autophagic flux was assessed by transmission electron microscopy, the mRFP-GFP-LC3 reporter assay, and Western blot analysis of LC3, p62, and Beclin-1. Molecular mechanisms were explored using Co-immunoprecipitation, Western blotting, lentiviral-mediated knockdown or overexpression, and Cell Counting Kit-8 assays.

Key findings: USP24 and TRAF6 were upregulated in DMD both in vivo and in vitro, accompanied by decreased Beclin-1, an elevated LC3-II/LC3-I ratio, increased p62, and impaired autophagolysosomal formation. USP24 directly interacted with and deubiquitinated TRAF6, thereby stabilizing its protein. TRAF6 bound to and ubiquitinated Beclin-1, promoting its degradation. Silencing USP24 reduced TRAF6, restored Beclin-1, enhanced autophagic flux, increased Bcl-2, and improved cardiomyocyte viability in DMD. Overexpression of TRAF6 reversed the effects induced by USP24 knockdown.

Significance: USP24 inhibits Autophagy in DMD, specifically by deubiquitinating TRAF6 and stabilizing its expression, while TRAF6 promotes Beclin-1 ubiquitination and degradation. Targeting the USP24 may offer a novel therapeutic strategy for DMD.

Autophagy; Beclin-1; Diabetic cardiomyopathy; Diabetic myocardial disorder; TRAF6; USP24; Ubiquitination.