Insight into the molecular structure of an appetite-regulating cell receptor

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New joint Publication by subproject A01, A05, Z03, B02 and C01/Z04:

 

Activation of the G-protein-coupled MC4R receptor by the drug setmelanotide. The image shows how the hormone combines with the receptor to activate the G-protein. The receptor then causes the GDP nucleotide to split from the G-protein. GDP is replaced by the nucleotide GTP, which is present at high concentrations inside the cell. This in turn causes the G-protein to uncouple from the receptor, triggering an explosion of signals inside the cell. An activated receptor results in appetite reduction, a blocked receptor in increased hunger. © Charité l Patrick Scheerer.

Heyder NA, Kleinau G, Speck D, Schmidt A, Paisdzior S, Szczepek M, Bauer B, Koch A, Gallandi M, Kwiatkowski D, Bürger J, Mielke T, Beck-Sickinger AG, Hildebrand PW, Spahn CMT, Hilger D, Schacherl M, Biebermann H, Hilal T, Kühnen P, Kobilka BK, Scheerer P. Structures of active melanocortin-4 receptor-Gs-protein complexes with NDP-α-MSH and setmelanotide. Cell Res. 2021 Sep 24. doi: 10.1038/s41422-021-00569-8. Epub ahead of print. PMID: 34561620.

 

Abstract: 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.

>> Press Release by Charité- Universitätsmedizin Berlin (27.09.2021):
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Insight into the molecular structure of an appetite-regulating cell receptor