ApoE Mass Spec study

This proposal includes the study of ApoE4 cleavage products and ApoE4/E3 proteome signatures using the LC-MS/MS platform for E-scape Bio, Inc. There are three goals in this proposal: Goal 1) Determine ApoE4 cleavage products to identify selective proteolytic fragments of neuronal human ApoE4 and ApoE3 immuno-affinity enriched from NSE-E4 and NSE-E3 mouse cortices. In order to maximize our analytical coverage of the amino sequence of ApoE, we will analyze the intact fragments without further digestion, after digestion with trypsin, and if necessary additional enzymes (Arg-C, Asp-N. Elastase, etc.). If needed we will also use a combination of enzymes to localize cleavage sites on APOE. We will then correlate LC-MS/MS peptides sequences and observed endogenous proteolytic sites, that are unique for ApoE4. Goal 2) LC-MS/MS analysis to identify of cytosolic and synaptosomal co-immunoprecipiated (co-IP) ApoE4 and ApoE3 protein complexes enriched from NSE-E4 and NSE-E3 mouse cortices, respectively. Goal 3) Characterize proteome signatures of ApoE4 and ApoE3 iPSC derived cortical neuron cultures to understand the functional differences between these genotypes and determine if we can pharmacologically convert the ApoE4 proteome signatures into an ApoE3-like.