Issad T, Combettes M, Ferre P
Institut National de la Santé et de la Recherche Médicale Unité 342, Université René Descartes, Paris, France.
Eur J Biochem. 1995 Nov 15;234(1):108-15. doi: 10.1111/j.1432-1033.1995.108_c.x.
The effect of a beta-adrenergic agonist (isoproterenol) on the tyrosine kinase activity of the insulin receptor was studied in intact adipocytes. Isoproterenol treatment rapidly (5 min) inhibited the insulin-induced autophosphorylation of the insulin receptor on tyrosine residues in intact adipocytes. The effect of insulin on the phosphorylation of cellular proteins on tyrosine residues was also inhibited by isoproterenol. In order to understand the mechanism responsible for this inhibition, two-dimensional phosphopeptide mapping of the insulin receptor was performed. The pattern of phosphorylation of the insulin receptor in freshly isolated adipocytes showed marked differences from that previously observed in cultured cells overexpressing insulin receptors. These differences include a larger proportion of receptors being phosphorylated on the three tyrosines from the kinase domain and no apparent phosphorylation of the two tyrosines close to the C-terminus after insulin stimulation. Isoproterenol markedly inhibited the effect of insulin on the phosphorylation of the three tyrosines from the kinase domain. However, this inhibition was not associated with an increase in the phosphorylation of serine/threonine peptides. Thus, this direct analysis of insulin receptor phosphorylation sites in intact adipocytes does no support the idea that beta-adrenegic agents inhibit the tyrosine kinase activity of the receptor through a serine/threonine phosphorylation-dependent mechanism.
在完整的脂肪细胞中研究了β-肾上腺素能激动剂（异丙肾上腺素）对胰岛素受体酪氨酸激酶活性的影响。异丙肾上腺素处理可迅速（5分钟）抑制完整脂肪细胞中胰岛素诱导的胰岛素受体酪氨酸残基的自磷酸化。异丙肾上腺素还抑制了胰岛素对细胞蛋白质酪氨酸残基磷酸化的作用。为了了解这种抑制作用的机制，对胰岛素受体进行了二维磷酸肽图谱分析。新鲜分离的脂肪细胞中胰岛素受体的磷酸化模式与先前在过表达胰岛素受体的培养细胞中观察到的模式有明显差异。这些差异包括激酶结构域中三个酪氨酸磷酸化的受体比例更大，以及胰岛素刺激后靠近C末端的两个酪氨酸没有明显的磷酸化。异丙肾上腺素显著抑制胰岛素对激酶结构域中三个酪氨酸磷酸化的作用。然而，这种抑制作用与丝氨酸/苏氨酸肽磷酸化的增加无关。因此，对完整脂肪细胞中胰岛素受体磷酸化位点的直接分析不支持β-肾上腺素能药物通过丝氨酸/苏氨酸磷酸化依赖性机制抑制受体酪氨酸激酶活性的观点。
