title: Negative regulation of growth hormone receptor/JAK2 signaling by signal regulatory protein alpha.
abstract: Signal regulatory proteins (SIRPs) are receptor-like transmembrane proteins, the majority of which contain a cytoplasmic proline-rich region and four cytoplasmic tyrosines that, when phosphorylated, bind SH2 domain-containing protein tyrosine phosphatases (SHP). We demonstrated previously that growth hormone (GH) induces tyrosyl phosphorylation of SIRPalpha and association of SIRPalpha with SHP-2. The GH-activated tyrosine kinase JAK2 associates with and tyrosyl-phosphorylates SIRPalpha1. Here we show that JAK2-SIRPalpha1 association does not require phosphotyrosines in SIRPalpha1 or JAK2 or the proline-rich region of SIRPalpha1. However, when the C-terminal 30 amino acids of SIRPalpha1 containing the proline-rich region and tyrosine 495 are deleted, tyrosyl phosphorylation of SIRPalpha1 by JAK2 and association of SHP-2 with SIRPalpha1 are reduced. GH-dependent tyrosyl phosphorylation of JAK2 is reduced when wild-type SIRPalpha1 compared with SIRPalpha1 lacking the four cytoplasmic tyrosines (SIRP 4YF) is expressed in cells, suggesting that SIRPalpha1 negatively regulates GHR/JAK2 signaling. Consistent with reduced JAK2 activity, overexpression of wild-type SIRPalpha1 but not SIRP 4YF reduces GH-induced phosphorylation of ERKs 1 and 2, STAT3, and STAT5B. These results suggest that SIRPalpha1 is a negative regulator of GH signaling and that the ability of SIRPalpha1 mutants to negatively regulate GHR-JAK2 signaling correlates with their ability to bind SHP-2.
authors.affiliation: Department of Microbiology and Immunology and Department of Physiology, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA.
authors.forename: M R
authors.initials: MR
authors.lastname: Stofega
authors.forename: L S
authors.initials: LS
authors.lastname: Argetsinger
authors.forename: H
authors.initials: H
authors.lastname: Wang
authors.forename: A
authors.initials: A
authors.lastname: Ullrich
authors.forename: C
authors.initials: C
authors.lastname: Carter-Su
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000943:Antigens, Differentiation; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D019382:Human Growth Hormone / Q000494:pharmacology*; D006801:Humans; D053614:Janus Kinase 2; D053616:Janus Kinase 3; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D039842:Neural Cell Adhesion Molecule L1; D019006:Neural Cell Adhesion Molecules / Q000378:metabolism*; D010766:Phosphorylation; D011392:Proline; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D011971:Receptors, Immunologic; D011986:Receptors, Somatotropin / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D050796:STAT3 Transcription Factor; D017384:Sequence Deletion; D015398:Signal Transduction / Q000502:physiology*; D015534:Trans-Activators / Q000378:metabolism; D014162:Transfection; D014443:Tyrosine; D018909:src Homology Domains
chemical_list: D000943:Antigens, Differentiation; D004268:DNA-Binding Proteins; D008562:Membrane Glycoproteins; D039842:Neural Cell Adhesion Molecule L1; D019006:Neural Cell Adhesion Molecules; D011518:Proto-Oncogene Proteins; D011971:Receptors, Immunologic; D011986:Receptors, Somatotropin; D011994:Recombinant Proteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C494087:Stat3 protein, mouse; D015534:Trans-Activators; D019382:Human Growth Hormone; D014443:Tyrosine; D011392:Proline; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; C507933:JAK3 protein, human; C507926:Jak2 protein, mouse; C507935:Jak3 protein, mouse; D053614:Janus Kinase 2; D053616:Janus Kinase 3; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D017027:Protein Tyrosine Phosphatases