Asymmetric conformational changes in a GPCR dimer controlled by G-proteins

Area of Science:

• Molecular biology
• Cell signaling
• Biophysics

Background:

• G-protein-coupled receptors (GPCRs) are crucial for cellular communication.
• Traditionally viewed as monomers, GPCRs are now understood to form homo- or heterodimers.
• Understanding GPCR dimer function is key to deciphering complex cell signaling pathways.

Purpose of the Study:

• To investigate the conformational changes within GPCR dimers upon agonist binding.
• To determine if a single occupied subunit in a GPCR dimer can initiate signaling.
• To explore the role of G-protein interaction in the symmetry of GPCR dimer function.

Main Methods:

• Utilized a leukotriene B(4) receptor dimer model.
• Incorporated a single 5-hydroxytryptophan-labeled protomer for fluorescence measurements.
• Analyzed conformational changes in response to varying agonist occupancy and G-protein coupling.

Main Results:

• A GPCR dimer with only one agonist-bound subunit can activate G-protein signaling.
• Liganded subunits within a G-protein-coupled dimer exhibit distinct conformations.
• Asymmetric conformational changes were only observed in the presence of G-protein interaction.

Conclusions:

• GPCR dimer function is not always symmetric, particularly upon G-protein engagement.
• G-protein interaction imposes constraints that lead to asymmetric conformational states in GPCR dimers.
• These findings suggest novel possibilities for differential signaling by GPCR dimers.