Taylor D, Uhing R J, Blackmore P F, Prpić V, Exton J H
J Biol Chem. 1985 Feb 25;260(4):2011-4.
Recent studies with viral oncogene tyrosine kinases have suggested that these kinases may phosphorylate phosphoinositides and diacylglycerol. Since the receptors for insulin and epidermal growth factor (EGF) also possess tyrosine kinase activity, we have investigated possible effects of insulin and EGF on phosphoinositide metabolism in rat liver plasma membranes and rat hepatocytes. In plasma membranes prepared from rats injected 18 h prior with [3H]myo-inositol or incubated with [gamma-32P]ATP, phosphatidylinositol-4-P and phosphatidylinositol-4,5-P2 were formed, but there were no effects of either insulin or EGF although these agents stimulated protein tyrosine phosphorylation. In hepatocytes incubated with [3H]myo-inositol, label was incorporated into phosphatidylinositol, phosphatidylinositol-4-P, and phosphatidylinositol-4,5-P2, but there was no effect of insulin. Incubation of hepatocytes with [3H]myo-inositol plus insulin or EGF for 2 h also did not alter the formation of [3H]myo-inositol-1,4,5-P3 from [3H]phosphatidylinositol-4,5-P2 induced by vasopressin. These findings suggest that the tyrosine kinase activity of liver insulin and EGF receptors is not important in phosphoinositide formation.
最近对病毒癌基因酪氨酸激酶的研究表明，这些激酶可能使磷酸肌醇和二酰基甘油磷酸化。由于胰岛素和表皮生长因子（EGF）的受体也具有酪氨酸激酶活性，我们研究了胰岛素和EGF对大鼠肝细胞膜及大鼠肝细胞中磷酸肌醇代谢的可能影响。在用[3H]肌醇预先注射18小时的大鼠制备的细胞膜中，或与[γ-32P]ATP一起孵育时，会形成磷脂酰肌醇-4-磷酸和磷脂酰肌醇-4,5-二磷酸，但胰岛素和EGF均无影响，尽管这些试剂能刺激蛋白质酪氨酸磷酸化。在用[3H]肌醇孵育的肝细胞中，标记物掺入了磷脂酰肌醇、磷脂酰肌醇-4-磷酸和磷脂酰肌醇-4,5-二磷酸中，但胰岛素无影响。用[3H]肌醇加胰岛素或EGF孵育肝细胞2小时，也未改变血管加压素诱导的由[3H]磷脂酰肌醇-4,5-二磷酸形成[3H]肌醇-1,4,5-三磷酸的过程。这些发现表明，肝胰岛素和EGF受体的酪氨酸激酶活性在磷酸肌醇形成中并不重要。
