Exchange factors directly activated by cAMP mediate melanocortin 4 receptor-induced gene expression

Sci Rep. 2016 Sep 9:6:32776. doi: 10.1038/srep32776.

Abstract

Gs protein-coupled receptors regulate many vital body functions by activation of cAMP response elements (CRE) via cAMP-dependent kinase A (PKA)-mediated phosphorylation of the CRE binding protein (CREB). Melanocortin 4 receptors (MC4R) are prototypical Gs-coupled receptors that orchestrate the hypothalamic control of food-intake and metabolism. Remarkably, the significance of PKA for MC4R-induced CRE-dependent transcription in hypothalamic cells has not been rigorously interrogated yet. In two hypothalamic cell lines, we observed that blocking PKA activity had only weak or no effects on reporter gene expression. In contrast, inhibitors of exchange factors directly activated by cAMP-1/2 (EPAC-1/2) mitigated MC4R-induced CRE reporter activation and mRNA induction of the CREB-dependent genes c-fos and thyrotropin-releasing hormone. Furthermore, we provide first evidence that extracellular-regulated kinases-1/2 (ERK-1/2) activated by EPACs and not PKA are the elusive CREB kinases responsible for MC4R-induced CREB/CRE activation in hypothalamic cells. Overall, these data emphasize the pivotal role of EPACs rather than PKA in hypothalamic gene expression elicited by a prototypical Gs-coupled receptor.

MeSH terms

  • Animals
  • Cell Line
  • Cyclic AMP Response Element-Binding Protein / metabolism*
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • Eating
  • Gene Expression Regulation
  • Gene Expression*
  • Guanine Nucleotide Exchange Factors / metabolism*
  • HEK293 Cells
  • Humans
  • Hypothalamus / cytology
  • Hypothalamus / metabolism*
  • MAP Kinase Signaling System
  • Mice
  • Phosphorylation
  • Receptor, Melanocortin, Type 4 / genetics*
  • Receptor, Melanocortin, Type 4 / metabolism

Substances

  • CREB1 protein, human
  • Cyclic AMP Response Element-Binding Protein
  • Guanine Nucleotide Exchange Factors
  • MC4R protein, human
  • RAPGEF3 protein, human
  • RAPGEF4 protein, human
  • Receptor, Melanocortin, Type 4
  • Cyclic AMP-Dependent Protein Kinases