title: Enterostatin affects cyclic AMP and ERK signaling pathways to regulate Agouti-related protein (AgRP) expression.
abstract: Enterostatin, a gut-brain peptide, inhibits dietary fat intake in rats. The purpose of this study was to identify the intracellular signaling pathways that are responsive to enterostatin and that modulate the effects of enterostatin on the expression of Agouti-related protein (AgRP). We used the hypothalamic GT1-7 neuronal cell line to identify the effects of enterostatin on cyclic AMP and ERK signaling using conventional immunoassays or Western blots to assay the activity of these pathways. Enterostatin enhanced the level of cyclic AMP, PKA(RIIbeta) and phospho-CREB and increased pERK levels in GT 1-7 cells. The effects on pERK were rapid (7.5 min) and dose-dependent. These signaling responses were blocked by an antibody to the enterostatin receptor (beta subunit of F1-ATPase), by the pERK inhibitor U0126 and by the P2Y receptor antagonist Suramin. Enterostatin showed a biphasic effect on AgRP mRNA, initially increasing but subsequently decreasing the levels. The cyclic AMP activator Sp-cAMP increased AgRP mRNA expression. Transfection of a wild type ERK construct reduced AgRP mRNA levels. Enterostatin inhibited expression of Krüppel-like factor 4 (KLF4), a transcriptional regulator of AgRP. KLF4 gene expression was increased by Sp-cAMP but decreased by wild-type ERK expression. U0126 blocked the effect of enterostatin on KLF4 expression. We conclude that enterostatin binding to its receptor activates the pERK pathway to inhibit AgRP gene expression but may enhance AgRP expression through activation of the cyclic AMP pathway. These pathways probably mediate the enterostatin inhibition of dietary fat intake.
authors.affiliation: Center for Advanced Nutrition, Utah State University, 4715 Old Main Hill, Logan, UT 84322-4715, USA.
authors.forename: Miejung
authors.initials: M
authors.lastname: Park
authors.forename: Hyoungil
authors.initials: H
authors.lastname: Oh
authors.forename: David A
authors.initials: DA
authors.lastname: York
mesh_terms: D000263:Adenylate Kinase / Q000378:metabolism; D054369:Agouti-Related Protein / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003089:Colipases / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism*; D004792:Enzyme Precursors / Q000494:pharmacology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009474:Neurons / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection
chemical_list: D054369:Agouti-Related Protein; D003089:Colipases; D004792:Enzyme Precursors; C000715468:Klf4 protein, mouse; C000715469:Klf4 protein, rat; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; C037107:procolipase; D000242:Cyclic AMP; D048049:Extracellular Signal-Regulated MAP Kinases; D000263:Adenylate Kinase