Insulin/IGF-1 and TNF-α stimulate phosphorylation of IRS-1 at inhibitory Ser307 via distinct pathways
Insulin/IGF-1 and TNF-α stimulate phosphorylation of IRS-1 at inhibitory Ser307 via distinct pathways
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DOI：
10.1172/jci10934
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发表时间：
2001-01-01
影响因子：
15.9
通讯作者：
White, MF
中科院分区：
文献类型：
--
作者：
Rui, LY;Aguirre, V;White, MF
IRS-1的丝氨酸/苏氨酸磷酸化可能抑制胰岛素信号传导，但相关的磷酸化位点难以在培养细胞中鉴定，也难以在分离的组织中验证。最近，我们发现重组NH 2-末端Jun激酶磷酸化IRS-1的Ser（307），这抑制胰岛素刺激的IRS-1的酪氨酸磷酸化。为了监测不同细胞和组织背景中Ser（307）的磷酸化，我们制备了磷酸化特异性多克隆抗体，命名为α pSer（307）。该抗体显示TNF-α、IGF-1或胰岛素刺激3 T3-L1前脂肪细胞和脂肪细胞中IRS-1在Ser（307）处的磷酸化。注射胰岛素到小鼠或大鼠中也刺激从肌肉免疫沉淀的IRS-1上的Ser（307）的磷酸化;此外，在高胰岛素血症正葡萄糖钳夹过程中，人肌肉中的Ser（307）被磷酸化。3 T3-L1前脂肪细胞和脂肪细胞的实验表明，LY 294002或渥曼青霉素抑制胰岛素刺激的Ser 307磷酸化，而PD 98059抑制TNF-α刺激的磷酸化。因此，不同的激酶途径可能在Ser（307）处会聚，以介导IRS-1信号传导的反馈或异源抑制，从而反调节胰岛素反应。
Serine/threonine phosphorylation of IRS-1 might inhibit insulin signaling, but the relevant phosphorylation sites are difficult to identify in cultured cells and to validate in isolated tissues. Recently, we discovered that recombinant NH2-terminal Jun kinase phosphorylates IRS-1 at Ser(307), which inhibits insulin-stimulated tyrosine phosphorylation of IRS-1. To monitor phosphorylation of Ser(307) in various cell and tissue backgrounds, we prepared a phosphospecific polyclonal antibody designated alpha pSer(307). This antibody revealed that TNF-alpha, IGF-1, or insulin stimulated phosphorylation of IRS-1 at Ser(307) in 3T3-L1 preadipocytes and adipocytes. Insulin injected into mice or rats also stimulated phosphorylation of Ser(307) on IRS-1 immunoprecipitated from muscle; moreover, Ser(307) was phosphorylated in human muscle during the hyperinsulinemic euglycemic clamp. Experiments in 3T3-L1 preadipocytes and adipocytes revealed that insulin-stimulated phosphorylation of Ser(307) was inhibited by LY294002 or wortmannin, whereas TNF-alpha -stimulated phosphorylation was inhibited by PD98059. Thus, distinct kinase pathways might converge at Ser(307) to mediate feedback or heterologous inhibition of IRS-1 signaling to counterregulate the insulin response.