R-AMPAR-T

Fast glutamatergic synaptic transmission is based on a precise and complex molecular organization which requires the control of AMPA receptor number and their alignment with respect to the presynaptic release site. Recent experimental evidence suggests that amongst the hundreds of synaptic proteins, a framework comprising less than ten postsynaptic proteins could compose the central core of AMPAR organization namely PSD95, synGAP, neuroligin and the TARPs. All of them are connected via specific proteinprotein interaction domains called PDZ domains. In the basal state, this organization mediates probabilistic synaptic transmission with a stable release probability and postsynaptic response. But as a function of pre- and postsynaptic activation history, it is now well described that synapses can change their short and long term response properties through biochemical mechanisms of synaptic plasticity. The project will be divided into three Objectives. In Objective 1 we will implement in an existing model three main modifications regarding newly available knowledge on AMPAR properties: (i) in situ constraints for the activation/inactivation kinetic rate constants of the tetrameric, multi-conductance, concerted opening model of AMPAR including the effect of AMPAR/TARP interaction on AMPAR gating properties; (ii) the tight organization of AMPAR in nanoclusters as reported recently by using super-resolution techniques; (iii) Finally the lateral diffusion of AMPAR which has been measured with live single particle techniques. In Objective 2 we will biochemically measure the on/ off rate and crossaffinity of the three main proteins responsible for AMPAR organization: PSD95, the TARPs and synGAP. At the end of this Objective, the model should be able to perfectly simulate synaptic transmission recorded at a neuron, both in term of kinetics, amplitude and variability, by taking into account the lateral mobility of AMPAR complex and PSD95 slot occupancy as a function of the determined affinity. Finally in Objective 3, we will validate the model and the hypothesis by modifying either the expression level of synGAP or the relative affinity of synGAP or TARP for PSD95, and then compare effect of such changes on AMPAR organization and dynamic properties and on synaptic transmission properties with the model predictions.