Scheid M P, Duronio V
Department of Medicine, University of British Columbia, Jack Bell Research Centre, Vancouver, British Columbia, Canada V6H 3Z6.
J Biol Chem. 1996 Jul 26;271(30):18134-9. doi: 10.1074/jbc.271.30.18134.
Hemopoietic cells respond to cytokines by initiating tyrosine phosphorylation of receptors and receptor-associated proteins, leading to the activation of numerous cytosolic and membrane associated enzymes, including phosphatidylinositol 3-OH kinase (PI 3-kinase). Recent reports have suggested that PI 3-kinase may serve as an upstream activator of mitogen-activated protein (MAP) kinase. After stimulation with interleukin-3 and granulocyte-macrophage colony-stimulating factor, we show here that inhibition of MAP kinase activity by two inhibitors of PI 3-kinase, wortmannin and LY-294002, does not correlate with their ability to inhibit PI 3-kinase or p70 S6 kinase phosphorylation. Complete inhibition of phosphatidylinositol 3,4,5-trisphosphate production occurred at approximately 100 nM WM or 25 microM LY-294002, but at these concentrations, WM significantly inhibited MAP kinase activation, while LY-294002 had virtually no effect on MAP kinase activity. Furthermore, WM does not inhibit phorbol ester-mediated MAP kinase activation, but LY-294002 does. Together these results suggest WM and LY-294002 are differentially inhibiting enzymes other than PI 3-kinase that function upstream of MAP kinase.
造血细胞通过启动受体及受体相关蛋白的酪氨酸磷酸化对细胞因子作出反应，从而激活众多胞质和膜相关酶，包括磷脂酰肌醇3-羟基激酶（PI 3-激酶）。最近的报道表明，PI 3-激酶可能作为丝裂原活化蛋白（MAP）激酶的上游激活剂。在用白细胞介素-3和粒细胞-巨噬细胞集落刺激因子刺激后，我们在此表明，两种PI 3-激酶抑制剂渥曼青霉素和LY-294002对MAP激酶活性的抑制与其抑制PI 3-激酶或p70 S6激酶磷酸化的能力不相关。在约100 nM渥曼青霉素或25 μM LY-294002时，磷脂酰肌醇3,4,5-三磷酸的产生完全受到抑制，但在这些浓度下，渥曼青霉素显著抑制MAP激酶激活，而LY-294002对MAP激酶活性几乎没有影响。此外，渥曼青霉素不抑制佛波酯介导的MAP激酶激活，但LY-294002可以。这些结果共同表明，渥曼青霉素和LY-294002对MAP激酶上游发挥作用的PI 3-激酶以外的酶有不同的抑制作用。
