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Updated: Sep 4, 2025

Visualizing the Conformational Dynamics of Membrane Receptors Using Single-Molecule FRET
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Structural insight into the activation mechanism of MrgD with heterotrimeric Gi-protein revealed by cryo-EM

Shota Suzuki1,2, Momoko Iida3, Yoko Hiroaki4,5

  • 1Department of Basic Medicinal Sciences, Graduate School of Pharmaceutical Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan.

Communications Biology
|July 15, 2022
PubMed

Insights

Mas-related G protein-coupled receptor D (MrgD) structures reveal its activation mechanism. Cryo-EM structures show beta-alanine binding and receptor conformational changes, aiding drug design for pain and itch signaling.

Area of Science:

  • Structural Biology
  • Neuroscience
  • Pharmacology

Background:

  • Mas-related G protein-coupled receptor D (MrgD) is implicated in pain and itch signaling.
  • MrgD exhibits high basal activity for Gi activation and recognizes ligands like beta-alanine.
  • Understanding MrgD's activation mechanism is crucial for therapeutic targeting, but high-resolution structures were lacking.

Purpose of the Study:

  • To determine the high-resolution structures of the MrgD-Gi complex.
  • To elucidate the structural basis of MrgD activation by its endogenous ligand, beta-alanine.
  • To provide insights for the rational design of MrgD-targeting drugs.

Main Methods:

  • Cryo-electron microscopy (cryo-EM) was employed to resolve the MrgD-Gi complex structures.
  • Structures were determined at 3.1 Å (beta-alanine bound) and 2.8 Å (apo) resolution.
  • Conformational changes associated with ligand binding and receptor activation were analyzed.

Main Results:

  • Two cryo-EM structures of the MrgD-Gi complex were obtained in the beta-alanine-bound and apo states.
  • Beta-alanine binds to a shallow pocket within the extracellular domains of MrgD.
  • Significant conformational changes in the extracellular portion of transmembrane helix 6 were observed, indicating an active receptor conformation.

Conclusions:

  • The study provides the first high-resolution structures of the MrgD-Gi complex, revealing its activation mechanism.
  • The findings demonstrate a structural basis for MrgD's ligand recognition and activation by beta-alanine.
  • These structural insights offer a framework for developing novel therapeutics targeting MrgD for pain and itch.

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