Role of novel activity-associated postsynaptic proteins in synaptic function

For an animal to successfully navigate and adapt to its environment, effective communication between neurons at specialized sites called synapses is crucial. Impairments in synaptic transmission are frequently observed in various neurological and psychiatric disorders. The postsynaptic compartment of excitatory synapses, also known as the postsynaptic density (PSD), consists of complex protein networks that allow the transduction of neurotransmitter signals into electrical and chemical signals within the neuron. The PSD undergoes continuous, activity-dependent protein remodeling that directly impacts synapse function. Thus, profiling the proteomic landscape of active synapses is a powerful approach to uncover the molecular mechanisms of activity-driven synaptic remodeling. To study this, I utilized Cal-ID, a newly developed enzyme that biotinylates proximal proteins in a calcium-dependent manner. Given that synaptic activity triggers localized increases in Ca2+ level, I employed synaptic Cal-ID as a cutting-edge technique to investigate active synapses with unprecedented spatiotemporal resolution, enabling the targeted enrichment of proteins specifically associated with synaptic activity. First, I validated the ability of synaptic Cal-ID to respond to changes in synaptic activity. Next, I used synaptic Cal-ID to perform unbiased proteomic screens in cultured neurons and mouse brains. I identified two novel candidates, Anks1a and Ubash3b, that were not previously known to be in synapses. I found that Anks1a and Ubash3b are localized to excitatory synapses, show activity-dependent synaptic localization, and play important roles in basal synaptic function. This goal of the proposal is to study Anks1a and Ubash3b by 1) determining how activity leads to synaptic recruitment of Anks1a and Ubash3b, 2) determining whether Anks1a and Ubash3b regulates synapse function through EGFR signaling, and 3) determine whether Anks1a and Ubash3b are necessary for synaptic plasticity and learning and memory. This research is significant because it will 1) bring insight into activity-dependent remodeling in synapses, 2) help identify new mechanisms that can be targeted to treat neurological diseases, and 3) validate a novel tool for analysis of active synapses, which paves new and exciting paths for the synaptic field. The applicant has proposed this work in part to further their long-term goal of establishing an independent research career to understand synapse function and activity within different cell types across development, and how disruptions in synaptic function can lead to neurodevelopmental disorders. This proposal consists of various career development and transition plans, combined with extensive training in live-imaging, super-resolution microscopy, and quantitative analysis for proteomics under the guidance of an expert mentoring team, all of whom will mentor the applicant through the transition to a tenure track academic position.