POUGNET Johan-Till

Johan-Till POUGNET

ATP P2X receptors down-regulate AMPA receptor trafficking and postsynaptic efficacy in hippocampal neurons

décembre 2013 Directeur(s) de thèse : Eric BOUE-GRABOT Résumé de thèse

Ionotropic AMPA receptors (AMPAR) activated by glutamate are the main actors of the fast excitatory synaptic transmission in the mammalian brain. They also play a crucial role in the process of synaptic plasticity that are widely recognized to be the basis of key cognitive functions such as learning and memory.

P2X receptors are ATP-gated cation channels widely expressed in the brain where they mediate action of extracellular adenosine-5’-triphosphate (ATP) released by neurons or glia. P2X receptors are located et the periphery of glutamatergic synapses and although purinergic signaling has multiple effects on synaptic transmission and plasticity, the function of P2X receptors at brain synapses remains to be established.

Here, we show in cultured hippocampal neurons that activation of postsynaptic P2X receptors by exogenous ATP or glial release of endogenous ATP decreases the amplitude of miniature excitatory postsynaptic currents and AMPA-evoked currents. Using a combination of electrophysiology, surface or internalization assays and real time imaging, we demonstrate that the calcium influx through the ATP-gated channels triggers AMPA receptor internalization through clathrin-mediated dynamin-dependent endocytosis leading to reduced surface AMPA receptors and therefore, altered AMPA-mediated current. We also identified by molecular and pharmacological approaches the signaling cascade involved in the P2X-mediated alteration of surface AMPAR trafficking. P2X-mediated AMPAR internalization is dependent on the activation of protein kinase CamKII and protein phosphatases which regulate the phosphorylation level of AMPARs..

Our finding indicates that postsynaptic P2X receptors play a critical role in regulating the surface expression of AMPAR and thereby regulate the synaptic strength.