Kinetics of G-protein-coupled receptor signalling and desensitization.

The kinetics of G-protein-coupled receptor activation and deactivation has, so far, been measured only indirectly, most frequently by assessing the production of various second messengers. We have developed methods based on fluorescence resonance energy transfer to quantify the kinetics of receptor activation by agonist (measured as conformational change in the receptor), the kinetics of G-protein activation (measured as G-protein subunit rearrangement) and the kinetics of receptor inactivation by arrestins (measured as receptor-arrestin interaction). Using these methods, we show that receptor activation by agonists and signalling to G-proteins occur on the subsecond time scale, whereas receptor desensitization is limited by receptor phosphorylation and proceeds more slowly.