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

[摘要]

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 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.

[学科分类] 生物化学/生物物理

[关键词] Neutrophil activation;Tyrosine phosphorylation;Phosphatidylinositol 3-kinase;Signal transduction;FMLP;N-formyl-Met-Leu-Phe;PtdIns;phosphatidylinositol;PDGF;platelet-derived growth factor;PBS;phosphate-buffered saline;HEPES;4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid;gPtdIns;glycerophosphatidylinositol