Department of Pathology, Shanghai Medical College, Fudan University, Shanghai, China.
J Cell Biochem. 2010 Nov 1;111(4):1010-9. doi: 10.1002/jcb.22789.
Decorin (DCN) is a member of small leucine-rich proteoglycan family that neutralizes the bioactivity of transforming growth factor-beta1 (TGF-β1). It has been proven to be a promising anti-fibrotic agent to treat glomerulonephritis. But the underlining mechanism for regulating and degrading intracellular DCN is still not fully understood. In this study, we investigated the roles of ubiquitination in the regulation of cytoplasmic DCN metabolism in rat mesangial cells (MC) by immunoprecipitation and Western blot. The results showed that a proportion of cytoplasmic DCN was ubiquitinated in normal MC and was enhanced in N-glycosylation inhibitor (tunicamycin)-treated MC. After being treated with the proteasome inhibitor MG132, ubiquitinated DCN accumulated and displayed a prolonged half-life, accompanied by decreased TGF-β1 expression and reduced collagen IV mRNA level in MC. This study demonstrated that the stability and function of cytoplasmic DCN can be regulated by ubiquitin-proteasome system (UPS) in MC, which implies that regulating the ubiquitination and degradation of DCN might be a novel approach for modulating MC bioactivity.
核心蛋白聚糖（DCN）是小富含亮氨酸的蛋白聚糖家族的成员，可中和转化生长因子-β1（TGF-β1）的生物活性。它已被证明是一种有前途的抗纤维化药物，可用于治疗肾小球肾炎。但是，调节和降解细胞内 DCN 的潜在机制仍未完全阐明。在这项研究中，我们通过免疫沉淀和 Western blot 研究了泛素化在调节大鼠肾小球系膜细胞（MC）细胞质 DCN 代谢中的作用。结果表明，在正常 MC 中，一部分细胞质 DCN 发生泛素化，并且在 N-糖基化抑制剂（衣霉素）处理的 MC 中增强。用蛋白酶体抑制剂 MG132 处理后，泛素化的 DCN 积累并表现出延长的半衰期，同时 MC 中的 TGF-β1 表达减少，胶原 IV mRNA 水平降低。这项研究表明，UPS 可调节 MC 中的细胞质 DCN 的稳定性和功能，这表明调节 DCN 的泛素化和降解可能是调节 MC 生物活性的一种新方法。
