Protein engineering approaches to determine adenosine receptor-G protein interactions.

Abstract

The adenosine receptor subfamily of G protein-coupled receptors is an important family of membrane receptors that modulate blood pressure and more recently have been implicated in cancer, neurodegenerative diseases, and diabetes, making them a significant fraction of drug discovery efforts. Adenosine A2A receptor (A2AR), one of four subfamily members, has a longer C-terminus than the other adenosine receptor subtypes, which may contribute to its exceptional trafficking to the plasma membrane, but its flexibility has been attributed to protein-protein interactions. Chimeric A1 and A3 receptors with A2AR C-termini showed improved localization to the plasma membrane and are functionally active, with greater than three-fold higher yields than previously reported from other heterologous expression systems. Interestingly, these chimeras are able to bind to their native G proteins, suggesting the specificity of interaction does not rely on the C-terminus. To investigate this further using purified A2AR and Gαs, we determined the affinity and binding rates via surface plasmon resonance (SPR). Together with in vivo signaling data, our results suggest that loss of downstream signaling for the truncation may result from a reduced GPCR-G protein complex interaction, which may be important for interpretation of structure-based drug discovery screening. Current studies are focused on the effect of lipid nanodiscs on A2AR-G protein interactions.