The Dynamic AMPA Receptor Interactome During Plasticity and Learning

Summary AMPA receptors (AMPARs) are the major excitatory neurotransmitter receptors in the brain and their dynamic trafficking is essential for synaptic plasticity that underlies memory. AMPARs participate in vast postsynaptic protein complexes that impact their properties and trafficking. We hypothesize that dynamic rearrangements in postsynaptic protein-protein interactions (PPIs) tune AMPAR levels in response to stimuli, giving rise to synaptic plasticity and memory. We previously identified GRIP1/GRIP2, PICK1 and others as key synaptic proteins that regulate AMPAR trafficking and plasticity through dynamic and selective interactions with the cytoplasmic domains of the receptor. Recent evidence suggests that AMPARs might also regulated by yet unidentified interactions with their extracellular N-terminal domain. Advances in proximity-dependent biotinylation with miniTurbo has recently enabled identification of in vivo protein interactions, occurring both extracellularly and intracellularly, by quantitative mass spectrometry. This technology has been pioneered to map synapse composition in vivo, but has never been used to study PPIs or synaptic plasticity in this capacity. We will extend our characterization of AMPAR trafficking during plasticity in vivo by fusing the genetically encodable biotin ligase, miniTurbo, to either the extracellular N- or intracellular C-termini of GluA1/2-AMPARs and deliver them to the hippocampus of mice using viruses. We will then observe how AMPAR PPIs change in two complementary models of plasticity – the inhibitory avoidance model of rodent memory and its direct electrophysiological correlate, LTP of the CA3→CA1 synapse. Identification of PPIs that are common to these two models of plasticity will not only further our model of AMPAR trafficking during plasticity but will also identify common biochemical processes between LTP and learning and memory. Moreover, synaptic proteins that impact AMPAR trafficking have recently been associated with various neuropsychiatric disorders such as intellectual disability, autism, and schizophrenia and thus understanding these processes may have impact on potential therapeutic approaches to these disorders.