Phosphatidylinositol 3-OH kinase activity is not required for activation of mitogen-activated protein kinase by cytokines.
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.
Scheid
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MP
Department of Medicine, University of British Columbia, Jack Bell Research Centre, Vancouver, British Columbia, Canada V6H 3Z6.
Duronio
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D000730:Androstadienes / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002460:Cell Line; D002867:Chromones / Q000494:pharmacology; D003115:Colony-Stimulating Factors / Q000494:pharmacology*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000502:physiology*; D007295:Inositol Phosphates / Q000378:metabolism; D007377:Interleukin-3 / Q000494:pharmacology; D009025:Morpholines / Q000494:pharmacology; D004676:Myelin Basic Protein / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases; D015398:Signal Transduction; D000077191:Wortmannin
D000730:Androstadienes; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002867:Chromones; D003115:Colony-Stimulating Factors; D004791:Enzyme Inhibitors; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D007295:Inositol Phosphates; D007377:Interleukin-3; D009025:Morpholines; D004676:Myelin Basic Protein; D019869:Phosphatidylinositol 3-Kinases; D010744:Phosphoric Monoester Hydrolases; D017853:Phosphotransferases (Alcohol Group Acceptor); D017346:Protein Serine-Threonine Kinases; D019893:Ribosomal Protein S6 Kinases; D000077191:Wortmannin; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C096024:phosphatidylinositol-3,4,5-trisphosphate 5-phosphatase