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Jean-Pierre Vilardaga"Nouvelles pistes pour l'exploration des récepteurs couplés aux proteines G".

Abstract :

Hormones and neurotransmitters transduce signals via G-protein-coupled receptors as key switches in order to change cellular functions. Despite utilizing common signalling pathways, hormone and neurotransmitter responses exhibit different temporal pattern. To reveal the molecular basis for such differences we developed a generally applicable fluorescence-based technique for real-time monitoring of the activation switch for G protein-coupled receptors in single cells. We used such direct measurements to investigate the activation of the alpha2Aadrenergic (neurotransmitter) and the parathyroid hormone (PTH, hormone) receptors and observed kinetics that were much faster than previously thought: 40 ms for the alpha2Aadrenergic receptor and 1 s for the PTH receptor. The different switch times are in agreement with the distinct biological functions of these receptors. Agonist, partial agonist and antagonist could rapidly switch on and off the receptor in proportion to their respective intrinsic activities. These measurements permit the comparison of agonist, partial agonist and inverse agonist intrinsic activities at the receptor itself and provide evidence for millisecond activation times of G-protein coupled receptors. This FRET-based approach also allows to follow many aspects of receptor behaviour like 1) the simultaneous recording of receptor (alpha2A-adrenergic receptor) and effectors (GIRK: G proteinactivated Inwardly Rectifying K+ channel) activities, 2) the comparison of receptor (PTH receptor) activation and desensitisation (interaction with ß-arrestin), 3) the imaging of receptor (alpha2A-adrenergic receptor) activation in neuron cells (PC-12).