SOCS-1, -2, -3: selective targets and functions downstream of the prolactin receptor.
Suppressors of cytokine signaling, SOCS-1, SOCS-2 and SOCS-3, are non-transmembrane proteins with Src-homology-2 (SH2) domain, involved in negative regulation of the Janus kinase (Jak)/signal transducer and activator of transcription (Stat) pathway. Using transient overexpression system the role of SOCS proteins in regulating prolactin receptor intracellular mediators leading to gene activation was analyzed. Overexpression of SOCS-1 led to a significant reduction in PRLR-mediated tyrosyl phosphorylation of Jak2, PRLR, Stat5 and the cytoplasmic protein tyrosine phosphatase SHP2. Overexpression of SOCS-3 however, led to selective inhibition in PRLR-mediated tyrosyl phosphorylation of Jak2, the PRLR as well as SHP2. On the other hand, overexpression of SOCS-2 had no inhibitory effects on the tyrosyl phosphorylation status of the PRLR, Jak2, Stat5 or SHP2 in response to PRLR activation. Finally, the role of SOCS proteins in regulating the biological activity of the PRLR was investigated. Unlike SOCS-2, both SOCS-1 and SOCS-3 abolished the ability of the PRLR to induce beta-casein gene promoter activation. These results demonstrate that SOCS-1, SOCS-2 and SOCS-3 are differentially implicated in PRLR signaling to gene activation.
Tomic
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Department of Medicine, McGill University Health Center, Royal Victoria Hospital, Montréal, Qué., Canada.
Chughtai
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N
Ali
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D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D053614:Janus Kinase 2; D008894:Milk Proteins; D010766:Phosphorylation; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism / Q000502:physiology*; D011518:Proto-Oncogene Proteins; D051381:Rats; D011981:Receptors, Prolactin / Q000378:metabolism*; D012097:Repressor Proteins; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D050799:STAT5 Transcription Factor; D015398:Signal Transduction; D000071222:Suppressor of Cytokine Signaling 1 Protein; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors; D014162:Transfection
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008894:Milk Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011981:Receptors, Prolactin; D012097:Repressor Proteins; D050799:STAT5 Transcription Factor; C491589:Socs1 protein, rat; C491408:Socs2 protein, rat; C491410:Socs3 protein, rat; D000071222:Suppressor of Cytokine Signaling 1 Protein; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D011505:Protein-Tyrosine Kinases; C507927:Jak2 protein, rat; D053614:Janus Kinase 2; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516727:Ptpn11 protein, rat; C509250:Ptpn6 protein, rat; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases