A Novel Approach to Study Synaptic Plasticity in Isolated Synaptosomes using Flow Cytometry

University Of California-Irvine, Irvine CA

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Abstract

? DESCRIPTION (provided by applicant): Learning depends on the integrity of synaptic plasticity, and it is hypothesized that the decline in cognitive function with age and Alzheimer's disease (AD) is due to impaired synaptic plasticity. One of the most widely used models for studying molecular mechanisms of hippocampal synaptic plasticity is NMDA-receptor dependent long term potentiation (LTP), a cellular analogue of learning and memory. We propose that isolated synaptosomes, which consist of a presynaptic terminal attached to a postsynaptic unit, can provide a powerful system for the study of synaptic plasticity at a biochemical level. Our approach involves isolating synaptosomes from the hippocampus and chemically inducing long-term potentiation (cLTP) to drive activity-dependent changes at the synapse. We identify activity-induced changes by immunostaining for key markers of plasticity, such as the glutamate receptor subunit GluR1, followed by fluorescence cytometry (flow cytometry) to select synaptosomes with positive GluR1 surface staining, a method we refer to as `Fluorescent Assessment of Chemically-Stimulated Long-Term Potentiation' (FACS-LTP). In this proposal, our goal is to build on our initial data that FACS-LTP can be applied to synaptosomes to investigate activity-dependent biochemical modifications in normal animals, and how these change in aging and with Alzheimer's Disease (AD). In this proposal, we aim to: 1) evaluate if cLTP treatment of synaptosomes engages similar biochemical pathways as occurs in slices and cultures with electrophysiological induction, 2) evaluate if the synaptosome-FACS-LTP approach detects declines in synaptic plasticity with age, AD and in the presence of pathology (specifically focusing on IL-1? driven inflammation), and can be used for drug-screening to identify agents that facilitate or impair synaptic plasticity. Overall, our model system, which uses synaptosomes in combination with LTP to study plasticity, introduces a new functional assay for behavioral studies, mechanistic studies, and screening of pharmaceuticals.