Exchange factors directly activated by cAMP mediate melanocortin 4 receptor-induced gene expression.
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.
Walther-Straub-Institut für Pharmakologie und Toxikologie, Ludwig-Maximilians-Universität., München, 80336 München, Germany.
Evi
E
Glas
Walther-Straub-Institut für Pharmakologie und Toxikologie, Ludwig-Maximilians-Universität., München, 80336 München, Germany.
Harald
H
Mückter
Walther-Straub-Institut für Pharmakologie und Toxikologie, Ludwig-Maximilians-Universität., München, 80336 München, Germany.
Thomas
T
Gudermann
Walther-Straub-Institut für Pharmakologie und Toxikologie, Ludwig-Maximilians-Universität., München, 80336 München, Germany.
Andreas
A
Breit
D000818:Animals; D002460:Cell Line; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004435:Eating; D015870:Gene Expression; D005786:Gene Expression Regulation; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D007031:Hypothalamus / Q000166:cytology / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D051379:Mice; D010766:Phosphorylation; D044105:Receptor, Melanocortin, Type 4 / Q000235:genetics* / Q000378:metabolism
C115163:CREB1 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; D020662:Guanine Nucleotide Exchange Factors; C470072:MC4R protein, human; C116122:RAPGEF3 protein, human; C442864:RAPGEF4 protein, human; D044105:Receptor, Melanocortin, Type 4; D017868:Cyclic AMP-Dependent Protein Kinases