title: Granulocyte colony-stimulating factor receptor signaling involves the formation of a three-component complex with Lyn and Syk protein-tyrosine kinases.
abstract: Granulocyte colony-stimulating factor (G-CSF) is a glycoprotein that critically regulates the viability, proliferation, and differentiation of granulocytic precursors and the function of neutrophils by signaling through its receptor. Cloning of the human G-CSF receptor (G-CSFR) cDNA has demonstrated sequence homology with other members of the hematopoietic/cytokine receptor superfamily. G-CSF stimulates the appearance of phosphotyrosine proteins in several types of human and murine myeloid cells. Since the receptor does not possess intrinsic tyrosine kinase activity, we hypothesized that G-CSFR interacts with and activates cytosolic protein-tyrosine kinases (PTKs). In vitro protein kinase assay of human G-CSFR immunoprecipitates demonstrated at least two tyrosine phosphoproteins, pp55 and pp70. We observed that G-CSF activated p53/p56lyn, a Src-related PTK, and p72syk, a non-Src-related PTK. Lyn and Syk were recovered in anti-G-CSFR immunoprecipitates; Lyn was detected in the absence of ligand. In addition, upon G-CSF stimulation, Lyn coimmunoprecipitated with Syk. Analysis of the G-CSFR amino acid sequence revealed a potential receptor activation motif for Syk. On the basis of immunoprecipitation and sequence analysis data, we propose that the human G-CSFR forms a three-component signaling complex with Lyn and Syk. Their sequential recruitment into the G-CSFR signaling complex demonstrates the coordinated involvement of two PTKs with a member of the hematopoietic/cytokine receptor superfamily.
authors.affiliation: Department of Pediatrics, University of Pittsburgh School of Medicine, PA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Corey
authors.forename: A L
authors.initials: AL
authors.lastname: Burkhardt
authors.forename: J B
authors.initials: JB
authors.lastname: Bolen
authors.forename: R L
authors.initials: RL
authors.lastname: Geahlen
authors.forename: L S
authors.initials: LS
authors.lastname: Tkatch
authors.forename: D J
authors.initials: DJ
authors.lastname: Tweardy
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D004792:Enzyme Precursors / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008969:Molecular Sequence Data; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D016188:Receptors, Granulocyte Colony-Stimulating Factor / Q000378:metabolism*; D015398:Signal Transduction; D000072377:Syk Kinase; D019061:src-Family Kinases
chemical_list: D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D016188:Receptors, Granulocyte Colony-Stimulating Factor; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; C000606897:Syk protein, mouse; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases