title: Convergence of signaling by interleukin-3, granulocyte-macrophage colony-stimulating factor, and mast cell growth factor on JAK2 tyrosine kinase.
abstract: Mast cell growth factor (MGF) (also called stem cell factor) synergizes with several lymphokines, including interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF), to promote proliferation and differentiation of certain hemopoietic progenitor cells. Although similar patterns of tyrosine-phosphorylated proteins characterize cells stimulated by MGF, IL-3, and GM-CSF, only the MGF receptor is a tyrosine kinase, and the heterodimeric receptors for IL-3 and GM-CSF share a common beta subunit that is devoid of enzymatic activity. Here we show that signaling pathways utilized by all three cytokines include the cytoplasmic tyrosine kinase JAK2. Analysis of several factor-dependent myeloid cell lines indicated that JAK2 is physically associated with the common beta subunit and with MGF receptor (c-Kit) even prior to ligand binding. However, each of the ligands induced elevated tyrosine phosphorylation of JAK2 and a consequent increase in its catalytic activity. These results demonstrate for the first time the convergence within the same myeloid cells of signaling pathways originating in two distinct lymphokine receptors and a tyrosine kinase receptor on activation of a cytoplasmic tyrosine kinase.
authors.affiliation: Dipartimento di Scienze Biomediche e Oncologia Umana, Università di Torino, Italy.
authors.forename: M F
authors.initials: MF
authors.lastname: Brizzi
authors.forename: M G
authors.initials: MG
authors.lastname: Zini
authors.forename: M G
authors.initials: MG
authors.lastname: Aronica
authors.forename: J M
authors.initials: JM
authors.lastname: Blechman
authors.forename: Y
authors.initials: Y
authors.lastname: Yarden
authors.forename: L
authors.initials: L
authors.lastname: Pegoraro
mesh_terms: D000595:Amino Acid Sequence; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000502:physiology*; D016298:Hematopoietic Cell Growth Factors / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D007377:Interleukin-3 / Q000502:physiology*; D053614:Janus Kinase 2; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000276:immunology; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019009:Proto-Oncogene Proteins c-kit; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D016184:Receptors, Colony-Stimulating Factor / Q000378:metabolism*; D015398:Signal Transduction; D019089:Stem Cell Factor; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D016298:Hematopoietic Cell Growth Factors; D007377:Interleukin-3; D010455:Peptides; D011518:Proto-Oncogene Proteins; D016184:Receptors, Colony-Stimulating Factor; D019089:Stem Cell Factor; D019000:Phosphotyrosine; D014443:Tyrosine; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D011505:Protein-Tyrosine Kinases; D019009:Proto-Oncogene Proteins c-kit; D020794:Receptor Protein-Tyrosine Kinases; C507924:JAK2 protein, human; D053614:Janus Kinase 2