Functional and structural insights into interactions between β-Arrestin 1 and Gαs or Gαi1.

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Signaling

Background:

• G proteins and arrestins are crucial for G protein-coupled receptor (GPCR) signaling.
• Their direct or functional interactions are increasingly recognized but poorly understood at a molecular level.

Purpose of the Study:

• To investigate the molecular details and functional consequences of Gα-βarrestin interactions.
• To quantify binding affinities and characterize conformational changes and functional outcomes.

Main Methods:

• Microscale thermophoresis (MST) to measure binding affinities between β-arrestin 1 (βarr1) and Gαs or Gαi1.
• Hydrogen/deuterium exchange mass spectrometry (HDX-MS) to analyze conformational changes.
• BODIPY-FL-GTPγS and β-strand XX (βXX) release assays for functional characterization.

Main Results:

• βarr1 preferentially binds to the active conformational ensemble of Gα subunits.
• Distinct conformational changes occur in Gαs versus Gαi1 upon βarr1 binding, indicating differential mechanisms.
• Gαs, but not Gαi1, enhances βarr1 C-tail release, while βarr1 binding does not affect Gα GDP/GTP turnover.

Conclusions:

• The study proposes a molecular mechanism for Gα-βarrestin interactions, highlighting asymmetric functional coupling.
• These findings reveal an underappreciated layer of GPCR signal transduction regulation.