title: Novel pathways of F-actin polymerization in the human neutrophil.
abstract: Recently we demonstrated the existence of a phosphatidylinositol 3-kinase (PI3K)-independent F-actin polymerization during neutrophil pseudopod extension. Here we examine the use of the PI3K-dependent and PI3K-independent pathways of activation by the N-formyl peptide receptor and the chemokine receptors, and the priming of the 2 pathways by granulocyte-macrophage colony-stimulating factor (GM-CSF) and insulin. The inhibition of PI3K activity with wortmannin showed that rate of pseudopod extension stimulated with N-formyl-Met-Leu-Phe (fMLP was mostly dependent on PI3K, while the rate of interleukin-8 (IL-8)-stimulated pseudopod extension was less dependent on PI3K. The incubation of cells with either GM-CSF or insulin increased the rate of pseudopod extension by 50% when the cells were stimulated with IL-8 but not with fMLP. The stimulation with IL-8 phosphorylated the PI3K regulatory subunit. This phosphorylation was enhanced by GM-CSF, which increased PI3K activity and total phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3) production. The effect of GM-CSF was blocked with wortmannin. In contrast, insulin did not increase p85 phosphorylation and did not enhance PI3K activity or PtdIns(3,4,5)P3 production. The effect of insulin was insensitive to wortmannin; however, it was blocked by an Src homology 2 (SH2)-binding peptide. These data indicate that priming of IL-8 activation with GM-CSF was mediated via the PI3Ks of class IA, while priming with insulin used a PI3K-independent pathway.
authors.affiliation: Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708-0300, USA.
authors.forename: David
authors.initials: D
authors.lastname: Chodniewicz
authors.forename: Doncho V
authors.initials: DV
authors.lastname: Zhelev
mesh_terms: D000199:Actins / Q000378:metabolism*; D000328:Adult; D000730:Androstadienes / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D002630:Chemotactic Factors / Q000494:pharmacology; D002633:Chemotaxis / Q000187:drug effects / Q000276:immunology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D019869:Phosphatidylinositol 3-Kinases / Q000494:pharmacology; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D011108:Polymers / Q000378:metabolism; D011554:Pseudopodia / Q000187:drug effects / Q000378:metabolism; D000077191:Wortmannin
chemical_list: D000199:Actins; D000730:Androstadienes; D002352:Carrier Proteins; D002630:Chemotactic Factors; D004791:Enzyme Inhibitors; D007004:Hypoglycemic Agents; D007328:Insulin; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D011108:Polymers; C060974:phosphatidylinositol 3,4,5-triphosphate; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D019869:Phosphatidylinositol 3-Kinases; D000077191:Wortmannin