title: Isoproterenol is a positive regulator of the suppressor of cytokine signaling-3 gene expression in 3T3-L1 adipocytes.
abstract: SOCS (suppressor of cytokine signaling)-3 has recently been shown to be an insulin- and tumor necrosis factor (TNF)-alpha-induced negative regulator of insulin signaling. To further clarify a potential involvement of SOCS-3 in the development of insulin resistance, we measured differentiation-dependent SOCS-3 mRNA expression in 3T3-L1 adipocytes and studied its regulation by various hormones known to impair insulin signaling using quantitative real-time RT-PCR. There was a differentiation-dependent downregulation of SOCS-3 mRNA by 50% over the 9 day adipocyte differentiation course. Interestingly, besides insulin and TNF-alpha, chronic treatment of differentiated 3T3-L1 cells with 10 microM isoproterenol for 16 h stimulated SOCS-3 gene expression by about 3.5-fold. Furthermore, isoproterenol stimulated SOCS-3 mRNA expression in a dose-dependent manner with significant activation detectable at concentrations as low as 10 nM isoproterenol. Moreover, a strong 27- and 47-fold activation of SOCS-3 mRNA expression could be seen after 1 h of isoproterenol and GH treatment respectively. The stimulatory effect of isoproterenol could be almost completely reversed by pretreatment of 3T3-L1 cells with the beta-adrenergic antagonist propranolol. Finally, isoproterenol's action could be mimicked by stimulation of G(S)-proteins with cholera toxin and of adenylyl cyclase with forskolin and dibutyryl cAMP. Taken together, our results demonstrate a differentiation-dependent downregulation of SOCS-3 in adipocytes and suggest that SOCS-3 gene expression is stimulated by beta-adrenergic agents via activation of a G(S)-protein-adenylyl cyclase-dependent pathway. As SOCS-3 is a novel inhibitor of insulin signaling, the data support a possible role of this protein as a selectively regulated mediator of catecholamine-induced insulin resistance.
authors.affiliation: University of Leipzig, Department of Internal Medicine III, 04103 Leipzig, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Fasshauer
authors.forename: J
authors.initials: J
authors.lastname: Klein
authors.forename: U
authors.initials: U
authors.lastname: Lossner
authors.forename: R
authors.initials: R
authors.lastname: Paschke
mesh_terms: D016475:3T3 Cells; D000262:Adenylyl Cyclases / Q000378:metabolism; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000378:metabolism; D005786:Gene Expression Regulation; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance; D007545:Isoproterenol / Q000494:pharmacology*; D051379:Mice; D011433:Propranolol / Q000494:pharmacology; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012097:Repressor Proteins; D015398:Signal Transduction / Q000187:drug effects*; D013268:Stimulation, Chemical; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D014157:Transcription Factors
chemical_list: D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D007328:Insulin; D011506:Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; C491411:Socs3 protein, mouse; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D014157:Transcription Factors; D011433:Propranolol; D019205:GTP-Binding Protein alpha Subunits, Gs; D000262:Adenylyl Cyclases; D007545:Isoproterenol