Wortmannin inhibits mitogen-activated protein kinase activation by platelet-activating factor through a mechanism independent of p85/p110-type phosphatidylinositol 3-kinase.
We have shown previously that wortmannin partially inhibits mitogen-activated protein kinase (MAPK) activated by platelet-activating factor (PAF) in guinea pig neutrophils (Ferby, M. I., Waga, I., Sakanaka, C., Kume, K., and Shimizu, T. (1994) J. Biol. Chem. 269, 30485-30488). To identify whether p85-dependent phosphatidylinositol 3-kinase is a target molecule of wortmannin in this inhibitory process, we established a murine macrophage cell line (P388D1), inducibly expressing a dominant-negative p85, delta p85. Upon induction of delta p85 by isopropyl-beta-D-thiogalactopyranoside, PAF still induced unaltered activation of MAPK, which was inhibited completely by wortmannin and 1,2-bis-(O-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester in an additive manner. Thus, PAF activates MAPK in P388D1 cells via two distinct pathways, one calcium-dependent and another calcium-independent, but wortmannin-sensitive. The inhibition of calcium-independent activation of MAPK by wortmannin does not involve p85-dependent phosphatidylinositol 3-kinase.
Ferby
I M
IM
Department of Biochemistry, Faculty of Medicine, University of Tokyo, Japan.
Waga
I
I
Hoshino
M
M
Kume
K
K
Shimizu
T
T
D000730:Androstadienes / Q000494:pharmacology*; D000818:Animals; D001381:Azepines / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002417:Cattle; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D051379:Mice; D009281:Naphthalenes / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000502:physiology*; D010972:Platelet Activating Factor / Q000494:pharmacology*; D014162:Transfection; D000077191:Wortmannin
D000730:Androstadienes; D001381:Azepines; D004791:Enzyme Inhibitors; D009281:Naphthalenes; D010972:Platelet Activating Factor; C070571:ML 7; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D017871:Calcium-Calmodulin-Dependent Protein Kinases; D000077191:Wortmannin