Journal Article

Conformational rearrangement during activation of a metabotropic glutamate receptor

Liauw, Brandon Wey-Hung, Afsari, Hamid Samareh, Vafabakhsh, Reza

2021

Overview

G protein-coupled receptors (GPCRs) relay information across cell membranes through conformational coupling between the ligand-binding domain and cytoplasmic signaling domain. In dimeric class C GPCRs, the mechanism of this process, which involves propagation of local ligand-induced conformational changes over 12 nm through three distinct structural domains, is unknown. Here, we used single-molecule FRET and live-cell imaging and found that metabotropic glutamate receptor 2 (mGluR2) interconverts between four conformational states, two of which were previously unknown, and activation proceeds through the conformational selection mechanism. Furthermore, the conformation of the ligand-binding domains and downstream domains are weakly coupled. We show that the intermediate states act as conformational checkpoints for activation and control allosteric modulation of signaling. Our results demonstrate a mechanism for activation of mGluRs where ligand binding controls the proximity of signaling domains, analogous to some receptor kinases. This design principle may be generalizable to other biological allosteric sensors. Single-molecule FRET of mGluR2 shows that the conformations of the ligand-binding domain and the linked cysteine-rich domain are loosely coupled during ligand-induced activation and defines two pre-active states linking inactive and active states.

• Publisher: Nature Publishing Group US,Nature Publishing Group
• Subject: 631/45/612/194 / 631/57/2265 / 631/92/609 / Allosteric properties / Allosteric Regulation / Amino Acids - pharmacology / Binding / Binding Sites / Biochemical Engineering / Biochemistry / Bioorganic Chemistry / Biosensing Techniques / Bridged Bicyclo Compounds, Heterocyclic - pharmacology / Cell Biology / Cell membranes / Chemistry / Chemistry and Materials Science / Chemistry/Food Science / Coupling (molecular) / Cyclopropanes - pharmacology / Domains / Fluorescence Resonance Energy Transfer / G protein-coupled receptors / Gene Expression / Genetic Vectors - chemistry / Genetic Vectors - metabolism / Glutamate receptors / Glutamic Acid - chemistry / Glutamic Acid - pharmacology / Glutamic acid receptors (metabotropic) / Glycine - analogs & derivatives / Glycine - pharmacology / HEK293 Cells / Humans / Kinases / Ligands / Models, Molecular / Protein Binding / Protein Conformation, alpha-Helical / Protein Conformation, beta-Strand / Protein Interaction Domains and Motifs / Protein Multimerization - drug effects / Receptors / Receptors, Metabotropic Glutamate - agonists / Receptors, Metabotropic Glutamate - chemistry / Receptors, Metabotropic Glutamate - genetics / Receptors, Metabotropic Glutamate - metabolism / Signaling / Single Molecule Imaging