title: A novel SHP-1/Grb2-dependent mechanism of negative regulation of cytokine-receptor signaling: contribution of SHP-1 C-terminal tyrosines in cytokine signaling.
abstract: SHP-1, an src homology 2 (SH2) domain containing protein tyrosine phosphatase, functions as a negative regulator of signaling downstream of cytokine receptors, receptor tyrosine kinases and receptor complexes of the immune system. Dephosphorylation of receptors and/or receptor-associated kinases has been described as the mechanism for the function of SHP-1. Here we demonstrate a novel mechanism by which SHP-1 down-regulates the Janus kinase-2 (Jak2)/signal transducer and activator of transcription-5 (Stat5) pathway downstream of the prolactin receptor (PRLR) and the erythropoietin receptor (EPOR) in a catalytic activity-independent manner. Structural/functional analysis of SHP-1 defined the C-terminal tyrosine residues (Y278, Y303, Y538, Y566) within growth factor receptor-bound protein 2 (Grb-2) binding motif to be responsible for delivering the inhibitory effects. Our results further indicate that these tyrosine residues, via recruitment of the adaptor protein Grb-2, are required for targeting the inhibitory protein suppressor of cytokine signaling-1 (SOCS-1) to Jak2 kinase. Finally, loss of SOCS-1 expression in SOCS-1(-/-) mouse embryonic fibroblast (MEF) cells led to attenuation in SHP-1 function to down-regulate PRL-induced Stat5 activation. All together, our results indicate that SHP-1 inhibits PRLR and EPOR signaling by recruitment and targeting of SOCS-1 to Jak2, highlighting a new mechanism of SHP-1 regulation of cytokine-receptor signaling.
authors.affiliation: Department of Medicine, Royal Victoria Hospital, McGill University, 687 Pine Ave West, Montreal, QC H3A 1A1, Canada.
authors.forename: Parham
authors.initials: P
authors.lastname: Minoo
authors.forename: Maryam Mohsen
authors.initials: MM
authors.lastname: Zadeh
authors.forename: Robert
authors.initials: R
authors.lastname: Rottapel
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Lebrun
authors.forename: Suhad
authors.initials: S
authors.lastname: Ali
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002384:Catalysis; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology; D051380:GRB2 Adaptor Protein; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D053614:Janus Kinase 2; D007668:Kidney / Q000166:cytology; D008156:Luciferases / Q000235:genetics; D016399:Lymphoma, T-Cell; D051379:Mice; D008894:Milk Proteins; D017434:Protein Structure, Tertiary; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D051381:Rats; D018121:Receptors, Cytokine / Q000378:metabolism*; D017467:Receptors, Erythropoietin / Q000378:metabolism; D011981:Receptors, Prolactin / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D050799:STAT5 Transcription Factor; D015398:Signal Transduction / Q000502:physiology*; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C495949:Grb2 protein, mouse; C495950:Grb2 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D008894:Milk Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D018121:Receptors, Cytokine; D017467:Receptors, Erythropoietin; D011981:Receptors, Prolactin; D012097:Repressor Proteins; C108944:SOCS1 protein, human; D050799:STAT5 Transcription Factor; C491590:Socs1 protein, mouse; C491589:Socs1 protein, rat; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators; D014443:Tyrosine; D008156:Luciferases; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; C507926:Jak2 protein, mouse; C507927:Jak2 protein, rat; D053614:Janus Kinase 2; C509249:PTPN6 protein, human; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C509248:Ptpn6 protein, mouse; C509250:Ptpn6 protein, rat