Final Activity Report Summary - GLUR TRAFFICKING (High resolution single molecule imaging to determine the spatio-temporal rules of glutamate receptor trafficking during synaptic plasticity)
The regulation of neurotransmitter receptors localisation at synaptic sites plays a crucial role for efficient neuronal transmission and plasticity. The molecular mechanisms that regulate receptor trafficking in and out synapses just begin to be unravelled. They include the processes of exo and endocytosis to insert and remove receptors form the plasma membrane, as well as receptor surface trafficking through lateral diffusion between the synaptic and extrasynaptic membrane. These processes are highly regulated by neuronal activity, adaptor proteins and phosphorylation.
The recent development of high resolution single molecule imaging of live neurons by the host laboratory has allowed to attain unprecedented precision in the determination of individual receptor movements in and out synapses. This has allowed to show that 1) receptor diffusion in the plane of the membrane is a key process in regulating receptor numbers at synapses, and 2) that the different types of glutamate receptors display differential activity dependent regulation of mobility. At excitatory synapses, endocytic zones (EZs) allow clathrin-mediated internalisation of surface AMPA Receptors (AMPAR). EZs are mostly located adjacent to the postsynaptic density (PSD) by dynamin-3. Displacement of EZs away from the PSD leads to a loss of synaptic AMPAR and reduces excitatory synaptic transmission by impairing receptor recycling.
During the course of this work, Enrica Petrini investigated the impact of EZ location on the lateral mobility of surface AMPAR in resting conditions and during synaptic potentiation. During basal activity, EZs adjacent to the PSD maintain a pool of mobile AMPAR at synapses. Displacement of EZs and impairment of receptor recycling deplete synapses of AMPAR mobile pool. Chemical stimulation, that potentiates glutamatergic synapses, induces mobile synaptic receptor stabilisation and AMPAR lateral recruitment to synapses. Displacement of EZs occludes these effects. Thus mobile AMPAR, maintained at synapses by the presence of EZs close to the PSD, are crucial for accumulating and stabilising AMPAR at synapses during synaptic potentiation.
The recent development of high resolution single molecule imaging of live neurons by the host laboratory has allowed to attain unprecedented precision in the determination of individual receptor movements in and out synapses. This has allowed to show that 1) receptor diffusion in the plane of the membrane is a key process in regulating receptor numbers at synapses, and 2) that the different types of glutamate receptors display differential activity dependent regulation of mobility. At excitatory synapses, endocytic zones (EZs) allow clathrin-mediated internalisation of surface AMPA Receptors (AMPAR). EZs are mostly located adjacent to the postsynaptic density (PSD) by dynamin-3. Displacement of EZs away from the PSD leads to a loss of synaptic AMPAR and reduces excitatory synaptic transmission by impairing receptor recycling.
During the course of this work, Enrica Petrini investigated the impact of EZ location on the lateral mobility of surface AMPAR in resting conditions and during synaptic potentiation. During basal activity, EZs adjacent to the PSD maintain a pool of mobile AMPAR at synapses. Displacement of EZs and impairment of receptor recycling deplete synapses of AMPAR mobile pool. Chemical stimulation, that potentiates glutamatergic synapses, induces mobile synaptic receptor stabilisation and AMPAR lateral recruitment to synapses. Displacement of EZs occludes these effects. Thus mobile AMPAR, maintained at synapses by the presence of EZs close to the PSD, are crucial for accumulating and stabilising AMPAR at synapses during synaptic potentiation.