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  • 1
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    G-protein-independent coupling of MC4R to Kir7.1 in hypothalamic neurons (2015)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2015-01-21
    Description: The regulated release of anorexigenic alpha-melanocyte stimulating hormone (alpha-MSH) and orexigenic Agouti-related protein (AgRP) from discrete hypothalamic arcuate neurons onto common target sites in the central nervous system has a fundamental role in the regulation of energy homeostasis. Both peptides bind with high affinity to the melanocortin-4 receptor (MC4R); existing data show that alpha-MSH is an agonist that couples the receptor to the Galphas signalling pathway, while AgRP binds competitively to block alpha-MSH binding and blocks the constitutive activity mediated by the ligand-mimetic amino-terminal domain of the receptor. Here we show that, in mice, regulation of firing activity of neurons from the paraventricular nucleus of the hypothalamus (PVN) by alpha-MSH and AgRP can be mediated independently of Galphas signalling by ligand-induced coupling of MC4R to closure of inwardly rectifying potassium channel, Kir7.1. Furthermore, AgRP is a biased agonist that hyperpolarizes neurons by binding to MC4R and opening Kir7.1, independently of its inhibition of alpha-MSH binding. Consequently, Kir7.1 signalling appears to be central to melanocortin-mediated regulation of energy homeostasis within the PVN. Coupling of MC4R to Kir7.1 may explain unusual aspects of the control of energy homeostasis by melanocortin signalling, including the gene dosage effect of MC4R and the sustained effects of AgRP on food intake.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4383680/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4383680/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ghamari-Langroudi, Masoud -- Digby, Gregory J -- Sebag, Julien A -- Millhauser, Glenn L -- Palomino, Rafael -- Matthews, Robert -- Gillyard, Taneisha -- Panaro, Brandon L -- Tough, Iain R -- Cox, Helen M -- Denton, Jerod S -- Cone, Roger D -- 5R01 DK082884-03/DK/NIDDK NIH HHS/ -- DK020593/DK/NIDDK NIH HHS/ -- F31 DK102343/DK/NIDDK NIH HHS/ -- P30 DK020593/DK/NIDDK NIH HHS/ -- R01 DK064265/DK/NIDDK NIH HHS/ -- R01 DK070332/DK/NIDDK NIH HHS/ -- R01DK064265/DK/NIDDK NIH HHS/ -- R01DK070332/DK/NIDDK NIH HHS/ -- R25 GM059994/GM/NIGMS NIH HHS/ -- England -- Nature. 2015 Apr 2;520(7545):94-8. doi: 10.1038/nature14051. Epub 2015 Jan 19.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Physiology &Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA. ; Department of Chemistry &Biochemistry, University of California, Santa Cruz, California 95064, USA. ; 1] Department of Molecular Physiology &Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA [2] Department of Pharmacology, Meharry Medical College, Nashville, Tennessee 37208, USA. ; King's College London, Wolfson Centre for Age-Related Diseases, Guy's Campus, London SE1 1UL, UK. ; 1] Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA [2] Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25600267" target="_blank"〉PubMed〈/a〉
    Keywords: Action Potentials ; Agouti-Related Protein/metabolism ; Animals ; Eating/genetics ; Energy Metabolism ; Female ; *GTP-Binding Protein alpha Subunits, Gs ; HEK293 Cells ; Homeostasis/genetics ; Humans ; Ligands ; Male ; Melanocortins/metabolism ; Mice ; Neurons/*metabolism ; Paraventricular Hypothalamic Nucleus/*cytology ; Potassium Channels, Inwardly Rectifying/*metabolism ; Receptor, Melanocortin, Type 4/genetics/*metabolism ; Signal Transduction/genetics ; alpha-MSH/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 2
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    Multinodal regulation of the arcuate/paraventricular nucleus circuit by leptin [Neuroscience] (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-01-05
    Description: Melanocortin-4 receptor (MC4R) is critical for energy homeostasis, and the paraventricular nucleus of the hypothalamus (PVN) is a key site of MC4R action. Most studies suggest that leptin regulates PVN neurons indirectly, by binding to receptors in the arcuate nucleus or ventromedial hypothalamus and regulating release of products like α-melanocyte-stimulating hormone (α-MSH), neuropeptide Y (NPY), glutamate, and GABA from first-order neurons onto the MC4R PVN cells. Here, we investigate mechanisms underlying regulation of activity of these neurons under various metabolic states by using hypothalamic slices from a transgenic MC4R-GFP mouse to record directly from MC4R neurons. First, we show that in vivo leptin levels regulate the tonic firing rate of second-order MC4R PVN neurons, with fasting increasing firing frequency in a leptin-dependent manner. We also show that, although leptin inhibits these neurons directly at the postsynaptic membrane, α-MSH and NPY potently stimulate and inhibit the cells, respectively. Thus, in contrast with the conventional model of leptin action, the primary control of MC4R PVN neurons is unlikely to be mediated by leptin action on arcuate NPY/agouti-related protein and proopiomelanocortin neurons. We also show that the activity of MC4R PVN neurons is controlled by the constitutive activity of the MC4R and that expression of the receptor mRNA and α-MSH sensitivity are both stimulated by leptin. Thus, leptin acts multinodally on arcuate nucleus/PVN circuits to regulate energy homeostasis, with prominent mechanisms involving direct control of both membrane conductances and gene expression in the MC4R PVN neuron.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 3
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    Regulation of energy rheostasis by the melanocortin-3 receptor (2018)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2018-08-23
    Description: Like most homeostatic systems, adiposity in mammals is defended between upper and lower boundary conditions. While leptin and melanocortin-4 receptor (MC4R) signaling are required for defending energy set point, mechanisms controlling upper and lower homeostatic boundaries are less well understood. In contrast to the MC4R, deletion of the MC3R does not produce measurable hyperphagia or hypometabolism under normal conditions. However, we demonstrate that MC3R is required bidirectionally for controlling responses to external homeostatic challenges, such as caloric restriction or calorie-rich diet. MC3R is also required for regulated excursion from set point, or rheostasis, during pregnancy. Further, we demonstrate a molecular mechanism: MC3R provides regulatory inputs to melanocortin signaling, acting presynaptically on agouti-related protein neurons to regulate -aminobutyric acid release onto anorexigenic MC4R neurons, exerting boundary control on the activity of MC4R neurons. Thus, the MC3R is a critical regulator of boundary controls on melanocortin signaling, providing rheostatic control on energy storage.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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