title: G-CSF stimulates Jak2-dependent Gab2 phosphorylation leading to Erk1/2 activation and cell proliferation.
abstract: Granulocyte colony-stimulating factor (G-CSF), the major cytokine regulator of neutrophilic granulopoiesis, stimulates both the proliferation and differentiation of myeloid precursors. A variety of signaling proteins have been identified as mediators of G-CSF signaling, but understanding of their specific interactions and organization into signaling pathways for particular cellular effects is incomplete. The present study examined the role of the scaffolding protein Grb2-associated binding protein-2 (Gab2) in G-CSF signaling. We found that a chemical inhibitor of Janus kinases inhibited G-CSF-stimulated Gab2 phosphorylation. Transfection with Jak2 antisense and dominant negative constructs also inhibited Gab2 phosphorylation in response to G-CSF. In addition, G-CSF enhanced the association of Jak2 with Gab2. In vitro, activated Jak2 directly phosphorylated specific Gab2 tyrosine residues. Mutagenesis studies revealed that Gab2 tyrosine 643 (Y643) was a major target of Jak2 in vitro, and a key residue for Jak2-dependent phosphorylation in intact cells. Mutation of Gab2 Y643 inhibited G-CSF-stimulated Erk1/2 activation and Shp2 binding to Gab2. Loss of Y643 also inhibited Gab2-mediated G-CSF-stimulated cell proliferation. Together, these results identify a novel signaling pathway involving Jak2-dependent Gab2 phosphorylation leading to Erk1/2 activation and cell proliferation in response to G-CSF.
authors.affiliation: Department of Pathology, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Lin
authors.initials: L
authors.lastname: Wang
authors.forename: Jia
authors.initials: J
authors.lastname: Xue
authors.forename: Eva V
authors.initials: EV
authors.lastname: Zadorozny
authors.forename: Lisa J
authors.initials: LJ
authors.lastname: Robinson
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002645:Chickens; D004789:Enzyme Activation / Q000187:drug effects; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology*; D006801:Humans; D053614:Janus Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D022423:Myeloid Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11 / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C490895:GAB2 protein, human; D047428:Protein Kinase Inhibitors; D016179:Granulocyte Colony-Stimulating Factor; D019000:Phosphotyrosine; D053614:Janus Kinase 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11