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Structures in G proteins important for subtype selective receptor binding and subsequent activation
Volker Jelinek1, Nadja Mösslein1, Moritz Bünemann2
1Institute of Pharmacology and Clinical Pharmacy, Philipps-University Marburg, Marburg, Germany.
Communications Biology
|May 28, 2021
Summary
Researchers identified key Gα subunit regions, including the N-terminus, β2/β3-loop, and α5 helix, that dictate selective G protein-coupled receptor (GPCR) binding and activation. These findings clarify GPCR-G protein interaction mechanisms.
Area of Science:
- Molecular pharmacology
- Cellular signaling
- Structural biology
Background:
- G protein-coupled receptors (GPCRs) mediate diverse physiological responses by coupling to specific heterotrimeric G proteins.
- Understanding the structural basis for selective GPCR-G protein recognition is crucial, as determinants within Gα subunits remain largely elusive.
- Approximately 800 human GPCRs exhibit remarkable selectivity in their G protein coupling.
Purpose of the Study:
- To directly compare how subtype-specific Gα structures influence GPCR-G protein complex stability and activation.
- To identify key structural determinants in Gα subunits responsible for selective coupling to distinct GPCRs.
- To elucidate the molecular mechanisms underlying G protein coupling selectivity.
Main Methods:
- Utilized Förster Resonance Energy Transfer (FRET) assays to distinguish between different Gα chimeras.
- Assessed the selective binding and activation capabilities of Gα chimeras by muscarinic M3 and histamine H1 receptors.
- Employed subtype-specific Gα constructs to probe structural influences on receptor interactions.
Main Results:
- Identified the Gα N-terminus (including αN/β1-hinge), β2/β3-loop, and α5 helix as critical determinants of G protein coupling selectivity.
- Demonstrated that these determinants differentially impact selective binding and subsequent activation depending on the specific GPCR.
- Showcased varying contributions of these regions to the stability of GPCR-G protein complexes.
Conclusions:
- The N-terminus, β2/β3-loop, and α5 helix of Gα subunits are key structural determinants for selective GPCR recognition and activation.
- The impact of these determinants is context-dependent, varying with the specific GPCR and its signaling pathway.
- These findings offer novel insights into the molecular basis of G protein coupling selectivity, extending beyond previously known C-terminal interactions.
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