Lysine 63 ubiquitination is involved in the progression of tubular damage in diabetic nephropathy

The purpose of our study was to evaluate how hyperglycemia (HG) influences Lys63 protein ubiquitinationand its involvement in tubular damage and fibrosis in diabetic nephropathy (DN). Gene and protein expression of UBE2v1, a ubiquitin-conjugating E2-enzyme variant that mediates Lys63-linked ubiquitination, and Lys63- ubiquitinatedproteins increased in HK2 tubular cells under HG. Matrix-assisted laser desorption/ionization–time of flight/ tandem mass spectrometryidentified 30 Lys63- ubiquitinatedproteins, mainly involved in cellular organization, such as β-actin, whose Lys63 ubiquitinationincreased under HG, leading to cytoskeleton disorganization. This effect was reversed by the inhibitor of the Ubc13/UBE2v1 complex NSC697923. Western blot analysis confirmed that UBE2v1 silencing in HK2 under HG, restored Lys63-β-actin ubiquitinationlevels to the basal condition. Immunohistochemistry on patients with type 2 diabetic (T2D) revealed an increase in UBE2v1- and Lys63- ubiquitinatedproteins, particularly in...