Signal transduction in neutrophil activation. Phosphatidylinositol 3-kinase is stimulated without tyrosine phosphorylation.
Treatment of human neutrophils with the peptide f-Met-Leu-Phe (FMLP) results in neutrophil activation concomitant with stimulation of phosphatidylinositol (PtdIns) 3-kinase activity as measured by production of PtdIns-3,4,5-P3 in [32P]orthophosphate labeled cells. Antiphosphotyrosine immunoprecipitates were assayed for PtdIns 3-kinase activity; essentially no activity was present in lysates from either stimulated or unstimulated cells. The 85 kDa regulatory subunit of PtdIns 3-kinase, which normally serves as a substrate for tyrosine kinases, was not detected by SDS-PAGE or Western blot analysis in antiphosphotyrosine immunoprecipitates. In addition, no radioactive band corresponding to PtdIns 3-kinase was observed by SDS-PAGE following antiPtdIns 3-kinase immunoprecipitations. However, immunoprecipitates using polyclonal antibodies against PtdIns 3-kinase showed high PtdIns 3-kinase activity in neutrophil lysates and the 85 kDa subunit of PtdIns 3-kinase was detected in Western blots; no differences in activity were observed in FMLP-stimulated and unstimulated cells. These results suggest that, in contrast to polypeptide growth factor signal transduction systems, the activation of PtdIns 3-kinase by FMLP does not require tyrosine phosphorylation.
Vlahos
C J
CJ
Cardiovascular Research, Lilly Research Laboratories, Indianapolis IN 46285-0403.
Matter
W F
WF
D015153:Blotting, Western; D002851:Chromatography, High Pressure Liquid; D004789:Enzyme Activation; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000201:enzymology*; D019869:Phosphatidylinositol 3-Kinases; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism*; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism
D014443:Tyrosine; D009240:N-Formylmethionine Leucyl-Phenylalanine; D010770:Phosphotransferases; D019869:Phosphatidylinositol 3-Kinases