Biochemical and pharmacological studies with KT7692 and LY294002 on the role of phosphatidylinositol 3-kinase in Fc epsilon RI-mediated signal transduction.
Wortmannin inhibited phosphatidylinositol 3-kinase (P13-kinase) and Fc epsilon RI-mediated histamine secretion in RBL-2H3 cells to a similar degree, with IC50 values of 3 and 2 nM, respectively. Although P13-kinase is an acknowledged regulator of intracellular trafficking and secretion, wortmannin has proved to be a difficult drug to use in assessing the role of P13-kinase because it inhibits another important enzyme, myosin light-chain kinase (MLCK; IC50 = 200 nM). In the present study we synthesized a unique derivative of wortmannin, O-acetyl-delta 16-wortmannin-17-ol (KT7692), that has an inhibitory potency against PI3-kinase one-hundredth that of wortmannin, but retains a similar potency to wortmannin against MLCK. Histamine secretion was influenced 100-fold more by wortmannin than by KT7692.2-(4-Morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002), a structurally different PI3-kinase inhibitor from wortmannin, inhibited PI3-kinase with an IC50 of 2 microM but had little effect on MLCK activity in this concentration range. LY294002 also inhibited histamine secretion in RBL-2H3 cells with an IC50 of 5 microM. These results provide further evidence that PI3-kinase is involved in the signal transduction pathway responsible for histamine secretion after stimulation of Fc epsilon RI. Furthermore KT7692 in combination with wortmannin and LY294002 would be a powerful tool for clarifying the involvement of PI3-kinase as distinct from that of MLCK in signal transduction systems of various cellular responses.
D000730:Androstadienes / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000201:enzymology; D002867:Chromones / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006633:Histamine Antagonists / Q000494:pharmacology; D006636:Histamine Release / Q000187:drug effects*; D015471:Leukemia, Basophilic, Acute; D009025:Morpholines / Q000494:pharmacology*; D018994:Myosin Light Chains / Q000378:metabolism; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017455:Receptors, IgE / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D014407:Tumor Cells, Cultured; D000077191:Wortmannin
D000730:Androstadienes; D002867:Chromones; D004791:Enzyme Inhibitors; D006633:Histamine Antagonists; D009025:Morpholines; D018994:Myosin Light Chains; D018129:Phosphatidylinositol Phosphates; D017455:Receptors, IgE; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D009219:Myosin-Light-Chain Kinase; D000077191:Wortmannin