Signal transduction in neutrophil activation Phosphatidylinositol 3-kinase is stimulated without tyrosine phosphorylation

• Published in: FEBS letters 1992-09, Vol.309 (3), p.242-248
• Main Authors: Vlahos, Chris J., Matter, William F.
• Format: Article
• Language: English
• Subjects: 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; activation; Biological and medical sciences; Blotting, Western; Cell physiology; Chromatography, High Pressure Liquid; Enzyme Activation; FMLP; Fundamental and applied biological sciences. Psychology; glycerophosphatidylinositol; gPtdIns; HEPES; leukocyte (neutrophilic); man; Molecular and cellular biology; N-formyl-Met-Leu-Phe; N-Formylmethionine Leucyl-Phenylalanine - pharmacology; Neutrophil activation; Neutrophils - enzymology; PBS; PDGF; phosphate-buffered saline; phosphatidylinositol; Phosphatidylinositol 3-kinase; Phosphatidylinositol 3-Kinases; Phosphorylation; Phosphotransferases - metabolism; platelet-derived growth factor; PtdIns; Signal Transduction; stimulation; tyrosine; Tyrosine - metabolism; Tyrosine phosphorylation
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(92)80781-B

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-P 3 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 85kDa 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.