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The melanocortin-4 receptor (MC4R), a hypothalamic master regulator of energy homeostasis and appetite, is a class A G-protein-coupled receptor and a prime target for the pharmacological treatment of obesity. Here, we present cryo-electron microscopy structures of MC4R-Gs-protein complexes with two drugs recently approved by the FDA, the peptide agonists NDP-α-MSH and setmelanotide, with 2.9 Å and 2.6 Å resolution. Together with signaling data from structure-derived MC4R mutants, the complex structures reveal the agonist-induced origin of transmembrane helix (TM) 6-regulated receptor activation. The ligand-binding modes of NDP-α-MSH, a high-affinity linear variant of the endogenous agonist α-MSH, and setmelanotide, a cyclic anti-obesity drug with biased signaling toward Gq/11, underline the key role of TM3 in ligand-specific interactions and of calcium ion as a ligand-adaptable cofactor. The agonist-specific TM3 interplay subsequently impacts receptor-Gs-protein interfaces at intracellular loop 2, which also regulates the G-protein coupling profile of this promiscuous receptor. Finally, our structures reveal mechanistic details of MC4R activation/inhibition, and provide important insights into the regulation of the receptor signaling profile which will facilitate the development of tailored anti-obesity drugs. © 2021. The Author(s).


Nicolas A Heyder, Gunnar Kleinau, David Speck, Andrea Schmidt, Sarah Paisdzior, Michal Szczepek, Brian Bauer, Anja Koch, Monique Gallandi, Dennis Kwiatkowski, Jörg Bürger, Thorsten Mielke, Annette G Beck-Sickinger, Peter W Hildebrand, Christian M T Spahn, Daniel Hilger, Magdalena Schacherl, Heike Biebermann, Tarek Hilal, Peter Kühnen, Brian K Kobilka, Patrick Scheerer. Structures of active melanocortin-4 receptor-Gs-protein complexes with NDP-α-MSH and setmelanotide. Cell research. 2021 Nov;31(11):1176-1189

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PMID: 34561620

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