title: Fundamentally different roles for LFA-1, Mac-1 and alpha4-integrin in neutrophil chemotaxis.
abstract: Although the LFA-1, Mac-1 and alpha(4) integrins are required for chemotaxis, it is unknown how they are regulated or what specific role they play. Previously we demonstrated that fMLP and IL-8 induce chemotaxis via the p38 MAPK and phosphoinositide 3-kinase (PI3K) pathways, respectively. Here we show that these chemoattractants also activate and use Mac-1 and LFA-1 in a differential manner during chemotaxis. Using integrin-specific substrata, we demonstrate that cell movement in response to IL-8 is mediated by Mac-1, whereas LFA-1 is required for directional migration. By contrast, chemotaxis to fMLP requires Mac-1 for cell movement, whereas LFA-1 and alpha(4)-integrin are required for directional migration. On serum protein, which contains ligands for LFA-1, Mac-1 and alpha(4)-integrin, chemotaxis to fMLP is dependent on Mac-1, whereas chemotaxis to IL-8 is dependent on LFA-1. These results suggest that Mac-1 is the dominant integrin involved in chemotaxis to fMLP, and LFA-1 is the dominant integrin involved in chemotaxis to IL-8. Consistent with these observations, higher quantities of high-affinity Mac-1 are found on cells chemotaxing to fMLP then on cells chemotaxing to IL-8. Moreover, a much larger quantity of clustered LFA-1 was found on cells migrating to IL-8 compared to cells moving towards fMLP. When cells are presented with competing gradients of fMLP and IL-8, they preferentially migrate towards fMLP and activate/utilize integrins in a manner identical to fMLP alone. Under the same conditions, p38 MAPK inhibition abolishes the preferential migration to fMLP; instead, the cells migrate preferentially towards IL-8. The activation and utilization of integrins under these conditions are consistent with patterns observed with IL-8 alone. Together, these data suggest that fMLP and IL-8 differentially activate integrins for use during chemotaxis, that p38 MAPK is a major mediator in the activation and utilization of integrins, and selective integrin activation occurs during chemotaxis between opposing gradients.
authors.affiliation: Immunology Research Group, Department of Physiology and Biophysics, Faculty of Medicine, University of Calgary, 3330 Hospital Drive, Alberta T2N 4N1, Canada.
authors.forename: Bryan
authors.initials: B
authors.lastname: Heit
authors.forename: Pina
authors.initials: P
authors.lastname: Colarusso
authors.forename: Paul
authors.initials: P
authors.lastname: Kubes
mesh_terms: D002634:Chemotaxis, Leukocyte / Q000187:drug effects / Q000502:physiology*; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D039441:Integrin alpha4 / Q000378:metabolism*; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D016209:Interleukin-8 / Q000494:pharmacology; D008024:Ligands; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism*; D016177:Macrophage-1 Antigen / Q000378:metabolism*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
chemical_list: D005353:Fibronectins; D007093:Imidazoles; D016209:Interleukin-8; D008024:Ligands; D016169:Lymphocyte Function-Associated Antigen-1; D016177:Macrophage-1 Antigen; D011725:Pyridines; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1; D039441:Integrin alpha4; D009240:N-Formylmethionine Leucyl-Phenylalanine; C093642:SB 203580