title: Melanocortin potentiates leptin-induced STAT3 signaling via MAPK pathway.
abstract: The co-existence of receptors for leptin and melanocortin in cerebral microvessels suggests possible interactions between leptin and alpha-melanocyte stimulating hormone (MSH) signaling. In this study, we showed that ObRb and melanocortin receptor MC3R and MC4R were present in enriched cerebral microvessels. To test the interactions between ObRb and MC3R or MC4R-mediated cellular signaling, we over-expressed these plasmids in RBE4 cerebral microvascular endothelial cells and HEK293 cells in culture. Activation of signal transducers and activators of transcription-3 (STAT3) in response to leptin was determined by western blotting and luciferase reporter assays. Production of cAMP downstream to melanocortin receptors was determined with a chemiluminescent ELISA kit. alphaMSH, which increased intracellular cAMP, also potentiated leptin-induced STAT3 activation. This potentiation was abolished by a specific MEK inhibitor, indicating the involvement of the mitogen-activated kinase pathway. Reversely, the effect of leptin on alphaMSH-induced cAMP production was minimal. Thus, melanocortin specifically potentiated STAT3 signaling downstream to ObRb by cross-talk with mitogen-activated kinase. The cooperation of ObRb and G protein-coupled receptors in cellular signaling may have considerable biological implications not restricted to feeding and obesity.
authors.affiliation: Pennington Biomedical Research Center, Baton Rouge, Louisiana 70808, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Wu
authors.forename: Yi
authors.initials: Y
authors.lastname: He
authors.forename: Abba J
authors.initials: AJ
authors.lastname: Kastin
authors.forename: Hung
authors.initials: H
authors.lastname: Hsuchou
authors.forename: Charles I
authors.initials: CI
authors.lastname: Rosenblum
authors.forename: Weihong
authors.initials: W
authors.lastname: Pan
mesh_terms: D000818:Animals; D002460:Cell Line; D002536:Cerebral Arteries / Q000187:drug effects / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D006801:Humans; D020738:Leptin / Q000378:metabolism* / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D053486:Melanocortins / Q000378:metabolism* / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008833:Microcirculation / Q000187:drug effects / Q000502:physiology; D020239:Receptor Cross-Talk / Q000187:drug effects / Q000502:physiology; D044104:Receptor, Melanocortin, Type 3 / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D044105:Receptor, Melanocortin, Type 4 / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000187:drug effects / Q000378:metabolism; D054411:Receptors, Leptin / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D000521:alpha-MSH / Q000378:metabolism / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D020738:Leptin; C470053:Mc3r protein, mouse; D053486:Melanocortins; D044104:Receptor, Melanocortin, Type 3; D044105:Receptor, Melanocortin, Type 4; D043562:Receptors, G-Protein-Coupled; D054411:Receptors, Leptin; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D000521:alpha-MSH; D000242:Cyclic AMP