Department of Gastrointestinal Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
Division of Endocrinology, Diabetes and Nutrition, Department of Medicine, University of Maryland School of Medicine, Baltimore, USA.
Adipocyte. 2021 Dec;10(1):524-531. doi: 10.1080/21623945.2021.1980257.
Peroxisome proliferator-activated receptor-γ (PPARγ) is the master regulator of adipogenesis, but knowledge about how PPARγ is regulated at the protein level is very limited. We aimed to identify PPARγ-interacting proteins which modulate PPARγ's protein levels and transactivating activities in human adipocytes. We expressed Flag-tagged PPARγ in human preadipocytes as bait to capture PPARγ-associated proteins, followed by mass spectroscopy and proteomics analysis, which identified serine/threonine kinase 38 (STK38) as a major PPARγ-associated protein. Protein pulldown studies confirmed this protein-protein interaction in transfected cells, and reporter assays demonstrated that STK38 enhanced PPARγ's transactivating activities without requiring STK38's kinase activity. In cell-based assays, STK38 increased PPARγ protein stability, extending PPARγ's half-life from ~1.08 to 1.95 h. Notably, in human preadipocytes, the overexpression of STK38 enhanced adipogenesis, whereas knockdown impaired the process in a PPARγ-dependent manner. Thus, we discovered that STK38 is a novel PPARγ-cofactor promoting adipogenesis, likely through stabilization of PPARγ.
过氧化物酶体增殖物激活受体-γ（PPARγ）是脂肪生成的主调控因子，但关于 PPARγ 在蛋白质水平上如何被调控的知识非常有限。我们旨在鉴定出调节人脂肪细胞中 PPARγ 蛋白水平和转录激活活性的 PPARγ 相互作用蛋白。我们将 Flag 标记的 PPARγ 表达于人前体脂肪细胞中作为诱饵，以捕获与 PPARγ 相关的蛋白，然后进行质谱和蛋白质组学分析，鉴定出丝氨酸/苏氨酸激酶 38（STK38）是主要的 PPARγ 相关蛋白。蛋白pulldown 研究在转染细胞中证实了这种蛋白-蛋白相互作用，报告基因检测表明 STK38 增强了 PPARγ 的转录激活活性，而不需要 STK38 的激酶活性。在细胞水平的测定中，STK38 增加了 PPARγ 蛋白的稳定性，将 PPARγ 的半衰期从约 1.08 小时延长至 1.95 小时。值得注意的是，在人前体脂肪细胞中，STK38 的过表达增强了脂肪生成，而敲低则以依赖 PPARγ 的方式损害了这一过程。因此，我们发现 STK38 是一种促进脂肪生成的新型 PPARγ 共激活因子，可能通过稳定 PPARγ 来实现。
