title: Functional and biochemical consequences of abrogating the activation of multiple diverse early signaling pathways in Kit. Role for Src kinase pathway in Kit-induced cooperation with erythropoietin receptor.
abstract: Kit receptor tyrosine kinase and erythropoietin receptor (Epo-R) cooperate in regulating blood cell development. Mice that lack the expression of Kit or Epo-R die in utero of severe anemia. Stimulation of Kit by its ligand, stem cell factor activates several distinct early signaling pathways, including phospholipase C gamma, phosphatidylinositol 3-kinase, Src kinase, Grb2, and Grb7. The role of these pathways in Kit-induced growth, proliferation, or cooperation with Epo-R is not known. We demonstrate that inactivation of any one of these early signaling pathways in Kit significantly impairs growth and proliferation. However, inactivation of the Src pathway demonstrated the most profound defect. Combined stimulation with Epo also resulted in impaired cooperation between Src-defective Kit mutant and Epo-R and, to a lesser extent, with Kit mutants defective in the activation of phosphatidylinositol 3-kinase or Grb2. The impaired cooperation between the Src-defective Kit mutant and Epo-R was associated with reduced transphosphorylation of Epo-R and expression of c-Myc. Remarkably, restoration of only the Src pathway in a Kit receptor defective in the activation of all early signaling pathways demonstrated a 50% correction in proliferation in response to Kit stimulation and completely restored the cooperation with Epo-R. These data demonstrate an essential role for Src pathway in regulating growth, proliferation, and cooperation with Epo-R downstream from Kit.
authors.affiliation: Section of Neonatal-Perinatal Medicine, Department of Pediatrics, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
authors.forename: Bai Lin
authors.initials: BL
authors.lastname: Tan
authors.forename: Li
authors.initials: L
authors.lastname: Hong
authors.forename: Veerendra
authors.initials: V
authors.lastname: Munugalavadla
authors.forename: Reuben
authors.initials: R
authors.lastname: Kapur
mesh_terms: D000818:Animals; D001773:Blood Cells / Q000166:cytology*; D002460:Cell Line; D051379:Mice; D015513:Oncogene Proteins / Q000378:metabolism*; D019009:Proto-Oncogene Proteins c-kit; D017467:Receptors, Erythropoietin / Q000378:metabolism*; D015398:Signal Transduction; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D015513:Oncogene Proteins; D017467:Receptors, Erythropoietin; D019009:Proto-Oncogene Proteins c-kit; D019061:src-Family Kinases