title: Parallel phosphatidylinositol 3-kinase (PI3K)-dependent and Src-dependent pathways lead to CXCL8-mediated Rac2 activation and chemotaxis.
abstract: The requirement for phosphatidylinositol 3-kinase (PI3K) in the establishment of cell polarity and motility in a number of cell types has recently come into question. In this study, we demonstrate that inhibition of PI3K by wortmannin in neutrophil-like differentiated HL60 cells expressing CXCR2 resulted in reduced cell motility but normal chemotaxis in response to a gradient of CXCL8. However, wortmannin inhibition of PI3K did impair the ability of cells to re-orient their polarity and respond quickly to a change in the direction of the CXCL8 gradient. We hypothesized that Src-regulated ELMO-Dock2-Rac2 activation mediates chemotaxis in the absence of PI3K activity. Inhibition of Src with the small molecule inhibitor, PP2, or inhibition of Dock2 by shRNA knockdown confirmed the functional role of Src and Dock2 in regulating chemotaxis when PI3K was inhibited. Moreover, neutrophils isolated from bone marrow of hck(-/-)fgr(-/-)lyn(-/-) mice exhibited much more severe inhibition of chemotaxis when PI3K was blocked with wortmannin as compared with neutrophils isolated from bone marrow of wild-type mice. Thus, PI3K and Src-ELMO-Dock2 pathways work in parallel to activate Rac2 and modulate chemotaxis in response to a CXCL8 gradient in neutrophils.
authors.affiliation: Department of Cancer Biology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232, USA.
authors.forename: Jiqing
authors.initials: J
authors.lastname: Sai
authors.forename: Dayanidhi
authors.initials: D
authors.lastname: Raman
authors.forename: Yuxin
authors.initials: Y
authors.lastname: Liu
authors.forename: John
authors.initials: J
authors.lastname: Wikswo
authors.forename: Ann
authors.initials: A
authors.lastname: Richmond
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D016764:Cell Polarity / Q000502:physiology; D002633:Chemotaxis / Q000187:drug effects / Q000502:physiology*; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009504:Neutrophils / Q000166:cytology / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051572:Proto-Oncogene Proteins c-hck / Q000235:genetics / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology; D023063:Receptors, Interleukin-8B / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D000077191:Wortmannin; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism*; D000097766:RAC2 GTP-Binding Protein
chemical_list: D000730:Androstadienes; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D016209:Interleukin-8; D009419:Nerve Tissue Proteins; D019869:Phosphatidylinositol 3-Kinases; D047428:Protein Kinase Inhibitors; D051572:Proto-Oncogene Proteins c-hck; D011743:Pyrimidines; D023063:Receptors, Interleukin-8B; D000077191:Wortmannin; D020744:rac GTP-Binding Proteins; D019061:src-Family Kinases; D000097766:RAC2 GTP-Binding Protein; C412373:AG 1879; C508606:CXCL8 protein, human; C402110:DOCK2 protein, human; C485840:DOCK3 protein, human; C477286:FGD1-related Cdc42-GEF protein, human; C496631:HCK protein, human; C496632:Hck protein, mouse; C060902:lyn protein-tyrosine kinase