Trafficking regulator of GLUT4-1, TRARG1, positively regulates insulin-stimulated GLUT4 trafficking and insulin sensitivity. However, the mechanism(s) by which this occurs remain(s) unclear. Using biochemical and mass spectrometry analyses we found that TRARG1 is dephosphorylated in response to insulin in a PI3K/Akt-dependent manner and is a novel substrate for GSK3. Priming phosphorylation of murine TRARG1 at serine 84 allows for GSK3-directed phosphorylation at serines 72, 76 and 80. A similar pattern of phosphorylation was observed in human TRARG1, suggesting that our findings are translatable to human TRARG1. Pharmacological inhibition of GSK3 increased cell surface GLUT4 in cells stimulated with a submaximal insulin dose, and this was impaired following Trarg1 knockdown, suggesting that TRARG1 acts as a GSK3-mediated regulator in GLUT4 trafficking. These data place TRARG1 within the insulin signaling network and provide insights into how GSK3 regulates GLUT4 trafficking in adipocytes.

中文翻译：

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GLUT4-1 (TRARG1) 的运输监管机构是 GSK3 底物

GLUT4-1 的运输调节剂 TRARG1 正向调节胰岛素刺激的 GLUT4 运输和胰岛素敏感性。然而，发生这种情况的机制仍不清楚。使用生化和质谱分析，我们发现 TRARG1 以 PI3K/Akt 依赖性方式响应胰岛素而去磷酸化，并且是 GSK3 的新型底物。鼠 TRARG1 在丝氨酸 84 处的启动磷酸化允许 GSK3 定向磷酸化在丝氨酸 72、76 和 80 处。在人类 TRARG1 中观察到类似的磷酸化模式，表明我们的发现可转化为人类 TRARG1。GSK3 的药理学抑制增加了用次最大胰岛素剂量刺激的细胞中的细胞表面 GLUT4，并且这在 Trarg1 敲低后受损，表明 TRARG1 在 GLUT4 运输中充当 GSK3 介导的调节剂。这些数据将 TRARG1 置于胰岛素信号网络中，并深入了解 GSK3 如何调节脂肪细胞中的 GLUT4 运输。