Renal chronic inflammation is an important hallmark of diabetic renal fibrosis. Casein kinase 2 interacting protein 1 (CKIP-1) performs a nephroprotective role in the pathogenesis of diabetic nephropathy (DN), which is dramatically decreased in diabetic kidneys. However, whether CKIP-1 regulates inflammation to ameliorate renal fibrosis remains unclear and it is interesting to clarify the degradation mechanism of CKIP-1. Here, we identified CKIP-1 expression was down-regulated in diabetic kidneys and knockout (KO) of CKIP-1 increased c-Jun expression and extra cellular matrix (ECM) in kidneys of normal mice, and knockout (KO) of CKIP-1 further exacerbated renal inflammatory fibrosis in diabetic mice. Moreover, the activated Src kinase interacted with CKIP-1 at Lys252 and increased K48 linked polyubiquitination and proteasome degradation of CKIP-1 in HG induced GMCs and diabetic kidneys. Mechanistically, Src facilitating the binding of c-Cbl with CKIP-1 by promoting the phosphorylation of c-Cbl, thereby increasing Cbl-mediated ubiquitination of CKIP-1 to down-regulate CKIP-1 protein expression. Thus, our study highlighted the anti-inflammation role of CKIP-1 and clarified the mechanism of CKIP-1 degradation in DN.
Keywords: CKIP-1; Diabetic nephropathy; Phosphorylation; Src kinase; Ubiquitination; c-Cbl.
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