CHEMOTAXIS OF CHINESE-HAMSTER OVARY CELLS EXPRESSING THE HUMAN NEUTROPHIL FORMYL PEPTIDE RECEPTOR - ROLE OF SIGNAL-TRANSDUCTION MOLECULES AND ALPHA(5)BETA(1) INTEGRIN

Activation of the N-formyl peptide receptor (FPR) of human neutrophils by ligands such as N-formylmethionine-leucine-phenylalanine (fMLP) in duces mobilization of intracellular calcium, cell adhesion, chemotaxis , superoxide production and degranulation, Chinese hamster ovary (CHO) cells are normally devoid of FPR and unresponsive to fMLP, but when s tably transfected with a human FPR cDNA, exhibited some of these same responses, Specifically, stimulation with fMLP resulted in release of intracellular calcium and chemotactic migration toward a gradient of f MLP. As in neutrophils, both processes were inhibited through receptor desensitization by prior exposure to a higher or equal concentration of ligand or by treatment with pertussis toxin, Soluble and membrane-b ound fibronectin greatly increased fMLP-induced chemotaxis of CHO cell s expressing FPR, but not of wild-type CHO cells, suggesting a role fo r FPR in activation of integrin function. Evidence for this hypothesis was obtained by demonstrating that CHO cells expressing FPR rapidly i ncreased their adhesion to a fibronectin-coated surface after stimulat ion with fMLP. Both chemotaxis and adhesion were largely inhibited by RGDS peptide and a function-blocking antibody against as integrin, FPR -mediated chemotaxis of the CHO transfectants was partly inhibited by a tyrosine kinase inhibitor, herbimycin A, and blocked by a phosphoino sitide 3-kinase inhibitor, wortmannin. These data suggest that stimula tion of CHO FPR transfectants with a gradient of JMLP results in phosp hoinositide 3-kinase-dependent chemotactic migration, which is enhance d by binding of activated alpha(5)beta(1) to fibronectin. This non-mye loid, non-lymphoid fibroblastic cell line will thus serve as a useful model to investigate additional requirements of signal transduction mo lecules, adhesion molecules and cytoskeletal elements in FPR-mediated chemotaxis.