Ampk-dependent Repression Of Hepatic Gluconeogenesis Via Disruption Of Creb Center Dot Crtc2 Complex By Orphan Nuclear Receptor Small Heterodimer Partner
activated protein-kinase; binding-protein; Biochemistry & Molecular Biology; creb coactivator crtc2; gene-expression; insulin; metformin; phosphorylation; shp; torc2; transcriptional activity
Orphan nuclear receptor small heterodimer partner (SHP) plays a key role in transcriptional repression of gluconeogenic enzyme gene expression. Here, we show that SHP inhibited protein kinase A-mediated transcriptional activity of cAMP-response element-binding protein (CREB), a major regulator of glucose metabolism, to modulate hepatic gluconeogenic gene expression. Deletion analysis of phosphoenolpyruvate carboxykinase (PEPCK) promoter demonstrated that SHP inhibited forskolin-mediated induction of PEPCK gene transcription via inhibition of CREB transcriptional activity. In vivo imaging demonstrated that SHP inhibited CREB-regulated transcription coactivator 2 (CRTC2)-mediated cAMP-response element-driven promoter activity. Furthermore, overexpression of SHP using adenovirus SHP decreased CRTC2-dependent elevations in blood glucose levels and PEPCK or glucose-6-phosphatase (G6Pase) expression in mice. SHP and CREB physically interacted and were co-localized in vivo. Importantly, SHP inhibited both wild type CRTC2 and S171A (constitutively active form of CRTC2) coactivator activity and disrupted CRTC2 recruitment on the PEPCK gene promoter. In addition, metformin or overexpression of a constitutively active form of AMPK (Ad-CA-AMPK) inhibited S171A-mediated PEPCK and G6Pase gene expression, and hepatic glucose production and knockdown of SHP partially relieved the metformin- and Ad-CA-AMPK-mediated repression of hepatic gluconeogenic enzyme gene expression in primary rat hepatocytes. In conclusion, our results suggest that a delayed effect of metformin-mediated induction of SHP gene expression inhibits CREB-dependent hepatic gluconeogenesis.
Lee J M; Seo W Y; Song K H; Chanda D; Kim Y D; Kim D K; Lee M W; Ryu D; Kim Y H; Noh J R; Lee C H; Chiang J Y L; Koo S H; Choi H S
Journal of Biological Chemistry
2010
2010-10
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1074/jbc.M110.134890" target="_blank" rel="noreferrer noopener">10.1074/jbc.M110.134890</a>
Orphan Nuclear Receptor Small Heterodimer Partner Negatively Regulates Growth Hormone-mediated Induction Of Hepatic Gluconeogenesis Through Inhibition Of Signal Transducer And Activator Of Transcription 5 (stat5) Transactivation
ampk; ataxia-telangiectasia; atm; Biochemistry & Molecular Biology; expression; Glucose; glucose-6-phosphatase gene; involvement; metformin; protein kinase; shp
Growth hormone (GH) is a key metabolic regulator mediating glucose and lipid metabolism. Ataxia telangiectasia mutated (ATM) is a member of the phosphatidylinositol 3-kinase superfamily and regulates cell cycle progression. The orphan nuclear receptor small heterodimer partner (SHP: NR0B2) plays a pivotal role in regulating metabolic processes. Here, we studied the role of ATM on GH-dependent regulation of hepatic gluconeogenesis in the liver. GH induced phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6-phosphatase gene expression in primary hepatocytes. GH treatment and adenovirus-mediated STAT5 overexpression in hepatocytes increased glucose production, which was blocked by a JAK2 inhibitor, AG490, dominant negative STAT5, and STAT5 knockdown. We identified a STAT5 binding site on the PEPCK gene promoter using reporter assays and point mutation analysis. Up-regulation of SHP by metformin-mediated activation of the ATM-AMP-activated protein kinase pathway led to inhibition of GH-mediated induction of hepatic gluconeogenesis, which was abolished by an ATM inhibitor, KU-55933. Immunoprecipitation studies showed that SHP physically interacted with STAT5 and inhibited STAT5 recruitment on the PEPCK gene promoter. GH-induced hepatic gluconeogenesis was decreased by either metformin or Ad-SHP, whereas the inhibition by metformin was abolished by SHP knockdown. Finally, the increase of hepatic gluconeogenesis following GH treatment was significantly higher in the liver of SHP null mice compared with that of wildtype mice. Overall, our results suggest that the ATM-AMP-activated protein kinase-SHP network, as a novel mechanism for regulating hepatic glucose homeostasis via a GH-dependent pathway, may be a potential therapeutic target for insulin resistance.
Kim Y D; Li T G; Ahn S W; Kim D K; Lee J M; Hwang S L; Kim Y H; Lee C H; Lee I K; Chiang J Y L; Choi H S
Journal of Biological Chemistry
2012
2012-10
Journal Article or Conference Abstract Publication
<a href="http://doi.org/10.1074/jbc.M112.339887" target="_blank" rel="noreferrer noopener">10.1074/jbc.M112.339887</a>