Article | Published:

Mechanism of N-terminal modulation of activity at the melanocortin-4 receptor GPCR

Nature Chemical Biology volume 8, pages 725730 (2012) | Download Citation

Abstract

Most of our understanding of G protein–coupled receptor (GPCR) activation has been focused on the direct interaction between diffusible ligands and their seven-transmembrane domains. However, a number of these receptors depend on their extracellular N-terminal domain for ligand recognition and activation. To dissect the molecular interactions underlying both modes of activation at a single receptor, we used the unique properties of the melanocortin-4 receptor (MC4R), a GPCR that shows constitutive activity maintained by its N-terminal domain and is physiologically activated by the peptide α-melanocyte stimulating hormone (αMSH). We find that activation by the N-terminal domain and αMSH relies on different key residues in the transmembrane region. We also demonstrate that agouti-related protein, a physiological antagonist of MC4R, acts as an inverse agonist by inhibiting N terminus–mediated activation, leading to the speculation that a number of constitutively active orphan GPCRs could have physiological inverse agonists as sole regulators.

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Acknowledgements

This work was supported by US National Institutes of Health (NIH) grant DK60540 and an American Heart Association Established Investigator Award to C.V., NIH DK064265 to G.M., an American Heart Association Predoctoral Fellowship and NIH National Research Service Award Endocrinology Training Grant to B.A.E. and a Spanish Ministry of Science and Innovation Award (SAF2010-22198-C02-02) to L.P. C.G. is funded as a Chercheur Qualifié by the Fonds National de la Recherche Scientifique. We would like to thank H. Bourne, B. Conklin and G. Vassart for reviewing the initial version of the manuscript and providing insightful comments.

Author information

Author notes

    • Baran A Ersoy
    •  & Darren A Thompson

    Present addresses: Department of Medicine, Brigham and Women′s Hospital and Harvard Medical School, Boston, Massachusetts, USA (B.A.E.) and Department of Chemistry, The Scripps Research Institute, La Jolla, California, USA (D.A.T.).

Affiliations

  1. Department of Medicine, University of California–San Francisco, San Francisco, California, USA.

    • Baran A Ersoy
    • , Sumei Zhang
    •  & Christian Vaisse
  2. The Diabetes Center, University of California–San Francisco, San Francisco, California, USA.

    • Baran A Ersoy
    • , Sumei Zhang
    •  & Christian Vaisse
  3. Laboratori de Medicina Computacional, Unitat de Bioestadística, Facultat de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain.

    • Leonardo Pardo
  4. Department of Chemistry and Biochemistry, University of California–Santa Cruz, Santa Cruz, California, USA.

    • Darren A Thompson
    •  & Glenn Millhauser
  5. Structure et Fonction des Membranes Biologiques, Université Libre de Bruxelles, Brussels, Belgium.

    • Cedric Govaerts

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Contributions

B.A.E. contributed to the hypothesis, designed and performed experiments, analyzed data and wrote the manuscript. L.P. designed and performed computational experiments, analyzed data and wrote the manuscript. S.Z. performed experiments. D.A.T. contributed to the hypothesis, and designed and performed experiments. G.M. contributed to the hypothesis, and provided reagents and expertise. C.G. contributed to the hypothesis, designed experiments and wrote the manuscript, and C.V. contributed to the hypothesis, directed the work, designed experiments and wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Christian Vaisse.

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DOI

https://doi.org/10.1038/nchembio.1008

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