title: Niche anchorage and signaling through membrane-bound Kit-ligand/c-kit receptor are kinase independent and imatinib insensitive.
abstract: Kit ligand (KitL) and its tyrosine kinase receptor c-kit are critical for germ cells, melanocytes, mastocytes, and hematopoietic stem cells. Alternative splicing of KitL generates membrane-bound KitL (mb-KitL) or soluble KitL, providing survival or cell migration, respectively. Here we analyzed whether c-kit can function both as an adhesion and signaling receptor to mb-KitL presented by the environmental niche. At contacts between fibroblasts and MC/9 mast cells, mb-KitL, and c-kit formed ligand/receptor clusters that formed stable complexes, which resisted dissociation by c-kit blocking mAbs and provided cell anchorage under physiological shear stresses. Clusters recruited tyrosine-phosphorylated proteins and induced spatially restricted F-actin polymerization. Mutational analysis of c-kit demonstrated kinase-independent mb-KitL/c-kit clustering, anchorage, F-actin polymerization, and Tyr567-dependent cluster phosphorylation. Kinase inhibition of c-kit by imatinib reduced cluster coalescence, but allowed cluster phosphorylation and F-actin polymerization, which required PI3K recruitment and a newly identified juxtamembrane residue. Synergies between integrin and c-kit-mediated spreading and adhesion of MC/9 cells were studied in vitro on immobilized-KitL/fibronectin surfaces. While c-kit blocking antibodies prevented spreading, imatinib blocked spreading induced by soluble- but not immobilized KitL. Thus, "mechanical" activation of c-kit provides signaling, niche-anchorage, and synergies with integrin-mediated adhesion, which is independent of kinase function and resistant to c-kit kinase inhibitors.-
authors.affiliation: Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire, Geneva, Switzerland; and.
authors.forename: Séverine
authors.initials: S
authors.lastname: Tabone-Eglinger
authors.affiliation: Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire, Geneva, Switzerland; and.
authors.forename: Zuleika
authors.initials: Z
authors.lastname: Calderin-Sollet
authors.affiliation: Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire, Geneva, Switzerland; and.
authors.forename: Perrine
authors.initials: P
authors.lastname: Pinon
authors.affiliation: Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire, Geneva, Switzerland; and.
authors.forename: Nicole
authors.initials: N
authors.lastname: Aebischer
authors.affiliation: Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire, Geneva, Switzerland; and.
authors.forename: Monique
authors.initials: M
authors.lastname: Wehrle-Haller
authors.affiliation: Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire, Geneva, Switzerland; and.
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Jacquier
authors.affiliation: Department of Microbiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: David
authors.initials: D
authors.lastname: Boettiger
authors.affiliation: Department of Cell Physiology and Metabolism, University of Geneva, Centre Médical Universitaire, Geneva, Switzerland; and bernhard.wehrle-haller@unige.ch.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Wehrle-Haller
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001549:Benzamides / Q000494:pharmacology*; D019556:COS Cells; D002448:Cell Adhesion; D002465:Cell Movement; D060833:Cellular Microenvironment; D002522:Chlorocebus aethiops; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D000068877:Imatinib Mesylate; D016023:Integrins / Q000378:metabolism; D008407:Mast Cells / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D051379:Mice; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology*; D011485:Protein Binding; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D019009:Proto-Oncogene Proteins c-kit / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology*; D015398:Signal Transduction
chemical_list: D000199:Actins; D001549:Benzamides; D016023:Integrins; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D000068877:Imatinib Mesylate; D019009:Proto-Oncogene Proteins c-kit
keywords: adhesion and spreading; fibronectin; integrin; mast cells; stem cell factor