Membrane Mimetic-Dependence of GPCR Energy Landscapes

Summary Protein function strongly depends on temperature, which is related to temperature-dependent changes in the equilibria of protein conformational states. We leveraged variable-temperature 19 F-NMR spectroscopy to interrogate the temperature dependence of the conformational landscape of the human A 2A adenosine receptor (A 2A AR), a class A GPCR. Temperature-induced changes in the conformational equilibria of A 2A AR in lipid nanodiscs were markedly dependent on the efficacy of bound drugs. While antagonist complexes displayed only modest changes as the temperature rose, both full and partial agonist complexes exhibited substantial increases in the active state population. Importantly, the temperature-dependent response of complexes with both full and partial agonists exhibited a pronounced sensitivity to the specific membrane mimetic employed. In striking contrast to observations within lipid nanodiscs, in detergent micelles the active state population exhibited different behavior for A 2A AR complexes with both full and partial agonists. This underscores the importance of the protein environment in understanding the thermodynamics of GPCR activation. Highlights Active A 2A AR population increases with increasing temperature in lipid nanodiscs Active A 2A AR population exhibits different temperature dependence in detergents Partial agonist complexes present a unique conformational state in nanodiscs Temperature dependence of partial agonist equilibria depends on membrane mimetic