The effect of suppressor of cytokine signaling 3 on GH signaling in beta-cells.
GH is an important regulator of cell growth and metabolism. In the pancreas, GH stimulates mitogenesis as well as insulin production in beta-cells. The cellular effects of GH are exerted mainly through activation of the Janus kinase-signal transducer and activator of transcription (STAT) pathway. Recently it has been found that suppressors of cytokine signaling (SOCS) proteins are able to inhibit GH-induced signal transduction. In the present study, the role of SOCS-3 in GH signaling was investigated in the pancreatic beta-cell lines RIN-5AH and INS-1 by means of inducible expression systems. Via stable transfection of the beta-cell lines with plasmids expressing SOCS-3 under the control of an inducible promoter, a time- and dose-dependent expression of SOCS-3 in the cells was obtained. EMSA showed that SOCS-3 is able to inhibit GH-induced DNA binding of both STAT3 and STAT5 in RIN-5AH cells. Furthermore, using Northern blot analysis it was shown that SOCS-3 can completely inhibit GH-induced insulin production in these cells. Finally, 5-bromodeoxyuridine incorporation followed by fluorescence-activated cell sorting analysis showed that SOCS-3 inhibits GH-induced proliferation of INS-1 cells. These findings support the hypothesis that SOCS-3 is a major regulator of GH signaling in insulin-producing cells.
Steno Diabetes Center, DK-2820 Gentofte, Denmark.
Sif G
SG
Rønn
Johnny A
JA
Hansen
Karen
K
Lindberg
Allan E
AE
Karlsen
Nils
N
Billestrup
D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D005434:Flow Cytometry; D013006:Growth Hormone / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D006801:Humans; D007328:Insulin / Q000235:genetics / Q000378:metabolism; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D008894:Milk Proteins; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects*; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors
D004268:DNA-Binding Proteins; D007328:Insulin; D008894:Milk Proteins; D011506:Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; C106644:SOCS3 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D050799:STAT5 Transcription Factor; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D013006:Growth Hormone