Myers M G, Grammer T C, Brooks J, Glasheen E M, Wang L M, Sun X J, Blenis J, Pierce J H, White M F
Research Division, Joslin Diabetes Center, Bethesda, Maryland, USA.
J Biol Chem. 1995 May 19;270(20):11715-8. doi: 10.1074/jbc.270.20.11715.
The NH2 terminus of insulin receptor substrate-1 (IRS-1) contains a pleckstrin homology (PH) domain. We deleted the PH domain in IRS-1 (IRS-1 delta PH) and expressed the mutant in Chinese hamster ovary and 32D cells. During insulin stimulation, IRS-1 delta PH is poorly tyrosine-phosphorylated in CHO cells, but undergoes serine/threonine phosphorylation. Similarly, IRS-1 delta PH fails to undergo insulin-stimulated tyrosine phosphorylation in 32D cells, which uncouples the activation of phosphatidylinositol 3'-kinase and p70s6k from the endogenous insulin receptors. Overexpression of the insulin receptor in 32DIR cells, however, restores tyrosine phosphorylation of IRS-1 delta PH and rescues insulin responses including mitogenesis. Thus, while the PH domain is not required for the engagement of downstream signals, it is one of the elements in the NH2 terminus of IRS-1 that is needed for a sensitive coupling to insulin receptors, especially at ordinary receptor levels found in most cells and tissues.
胰岛素受体底物-1（IRS-1）的氨基末端含有一个普列克底物蛋白同源（PH）结构域。我们删除了IRS-1中的PH结构域（IRS-1ΔPH），并在中国仓鼠卵巢细胞和32D细胞中表达该突变体。在胰岛素刺激过程中，IRS-1ΔPH在中国仓鼠卵巢细胞中酪氨酸磷酸化水平较低，但会发生丝氨酸/苏氨酸磷酸化。同样，IRS-1ΔPH在32D细胞中也不能进行胰岛素刺激的酪氨酸磷酸化，这使得磷脂酰肌醇3'-激酶和p70s6k的激活与内源性胰岛素受体解偶联。然而，在32DIR细胞中过表达胰岛素受体可恢复IRS-1ΔPH的酪氨酸磷酸化，并挽救包括有丝分裂在内的胰岛素反应。因此，虽然PH结构域对于下游信号的传导不是必需的，但它是IRS-1氨基末端中一个对与胰岛素受体敏感偶联所必需的元件，尤其是在大多数细胞和组织中发现的普通受体水平。
