Title : Structural and functional analysis of neuronal PSD-93 as a target for calmodulin – effects on learning and memory
Abstract:
MAGUKs (Membrane Associated Guanylate Kinase) proteins are an essential component of the PSD (Post-synaptic density), a protein rich region associated with the post synaptic membrane in the neurons. MAGUKs act as scaffolding proteins for receptors and thus play critical roles in synaptic plasticity and signaling. Discrepancies in the function and structure of these scaffolding MAGUKs have been recently found to be responsible for neurodegenerative diseases like Alzheimer’s and Parkinson’s. Two closely similar proteins from the MAGUK family, PSD-93 and PSD-95, are known to bind, anchor, and stabilize receptors such as AMPARs and NMDARs. Palmitoylation, a post-translational modification that takes place on the N-terminus of these proteins, has a significant impact on their appropriate membrane localization and function at postsynapses. According to recent research, Calmodulin (CaM) activated by Ca2+, binds to PSD-95's N-terminus, blocking this scaffolding protein palmitoylation and causing it to be released from the postsynaptic membrane resulting in drastic changes in the organization of PSD. This study is to investigate that CaM/Ca2+ interacts with the N-terminus of PSD-93, and its effect in inducing PSD-93 postsynaptic functional changes by using Nuclear Magnetic Resonance spectroscopy (NMR) structural biology, other biochemical and cellular biology approaches. Our NMR HSQC titration showed that the N-terminal peptide of PSD-93 induced structural changes of CaM/Ca2+ indicating the interaction. Recombinant DNA plasmid pET24b-PSD93NT(1-68) was constructed and used to overexpress the protein with a His tag in E. coli expression system. The expressed PSD93-NT is being purified using affinity and size exclusion chromatography methods and confirmed using SDS-PAGE. Purified protein will be used to perform structural and binding studies. These research results will provide structural insights into how plasticity is mediated in the neuron by different protein interactions, which may open a pathway to understanding neurodegenerative diseases like Parkinson’s and Alzheimer’s.
