title: Genetic evidence for convergence of c-Kit- and alpha4 integrin-mediated signals on class IA PI-3kinase and the Rac pathway in regulating integrin-directed migration in mast cells.
abstract: Mast cells play a critical role in host defense against a number of pathogens. Increased mast cell infiltration has been described in allergic asthma, in rheumatoid arthritis, and during helminthes infection. Despite the importance of mast cells in allergic disease and defense against infection, little is known about the mechanisms by which mast cells migrate to various tissues under steady state conditions or during infection or inflammation. Here, we show that activation of c-Kit by its ligand, stem cell factor (SCF), cooperates with alpha4 integrin in inducing directed migration of mast cells on fibronectin. A reduction in migration and activation of a small G protein, Rac, was observed in mast cells derived from class IA phosphoinositide-3 kinase (PI-3kinase)-deficient mice in response to SCF stimulation and in mast cells expressing the dominant-negative Rac (RacN17), as well as in mast cells deficient in the hematopoietic-specific small G protein, Rac2. In addition, a PI-3kinase inhibitor inhibited alpha4- as well as SCF-induced migration in a dose-dependent fashion. In contrast, a mitogen-activated protein kinase (MAPK) inhibitor had little effect. Consistent with the pharmacologic results, abrogating the binding of the p85alpha subunit of class IA PI-3kinase to c-Kit also resulted in inhibition of SCF-induced migration on fibronectin. These genetic and biochemical data demonstrate that both c-Kit and alpha4 integrin signaling are linked to class IA PI-3kinase and Rac pathways and regulate integrin-directed (haptotactic) migration in mast cells.
authors.affiliation: Section of Neonatal-Perinatal Medicine, Department of Pediatrics, Indiana University School of Medicine, Indianapolis 46202, USA.
authors.forename: Bai Lin
authors.initials: BL
authors.lastname: Tan
authors.forename: Mustafa N
authors.initials: MN
authors.lastname: Yazicioglu
authors.forename: David
authors.initials: D
authors.lastname: Ingram
authors.forename: Jennifer
authors.initials: J
authors.lastname: McCarthy
authors.forename: Jovencio
authors.initials: J
authors.lastname: Borneo
authors.forename: David A
authors.initials: DA
authors.lastname: Williams
authors.forename: Reuben
authors.initials: R
authors.lastname: Kapur
mesh_terms: D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001665:Binding Sites; D002633:Chemotaxis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005353:Fibronectins; D015870:Gene Expression; D039441:Integrin alpha4 / Q000502:physiology*; D039041:Integrin alpha4beta1 / Q000276:immunology / Q000378:metabolism; D039081:Integrin alpha5beta1 / Q000378:metabolism; D008407:Mast Cells / Q000737:chemistry / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019869:Phosphatidylinositol 3-Kinases / Q000172:deficiency / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019009:Proto-Oncogene Proteins c-kit / Q000276:immunology / Q000502:physiology*; D015398:Signal Transduction; D019089:Stem Cell Factor / Q000494:pharmacology; D020744:rac GTP-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D000097766:RAC2 GTP-Binding Protein
chemical_list: D000906:Antibodies; D004791:Enzyme Inhibitors; D005353:Fibronectins; D039441:Integrin alpha4; D039041:Integrin alpha4beta1; D039081:Integrin alpha5beta1; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019009:Proto-Oncogene Proteins c-kit; D019089:Stem Cell Factor; D020744:rac GTP-Binding Proteins; D000097766:RAC2 GTP-Binding Protein