PROJECT SUMMARY Alzheimer’s disease (AD) is a devastating neurodegenerative disorder with no definitive treatment that reverses the course of the disease, and we still lack a firm grasp on how older people develop AD. Bridging Integrator 1 (BIN1) is the second-largest genetic risk factor for late-onset AD. At least 12 different alternatively spliced BIN1 isoforms are expressed in the brain, including the neuron-specific BIN1 isoform 1 (BIN1iso1) and the ubiquitously expressed BIN1 isoform 9 (BIN1iso9). In the brain gray matter of patients with AD, there is a decrease in neuronal BIN1iso1 and an increase in BIN1iso9 compared to healthy controls. Thus far, evidence has shown that neuronal BIN1 isoforms participate in clathrin-mediated endocytosis, endocytic recycling, and synaptic vesicle release and retrieval. However, the mechanisms by which BIN1 contributes to these functions and the neighborhood of proteins that BIN1 interacts with to accomplish these cellular tasks remain largely undefined. Therefore, a fundamental gap in the field is an unbiased characterization of BIN1iso1 interacting proteins and proximal neighbors. Closing this gap will help define BIN1’s biological functions in healthy and diseased brain neurons. Utilizing the highly innovative proximity biotin ligase, TurboID, fused to BIN1iso1, will allow the identification of all proteins within a 10-nm radius. TurboID-based proximity labeling coupled with the most recent advanced quantitative mass spectrometry and data analysis methods represents a powerful strategy for discovery research. My preliminary in vitro studies using this approach in mouse N2a neuroblastoma cells resulted in the discovery of 234 proteins as BIN1-associated (proximal) or interacting proteins. These results identified several known BIN1 interactors such as tau, dynamin, synaptojanin, and many previously unknown proximal proteins. The following Specific Aims will translate these findings in vivo and dramatically advance the field. Aim 1. Identify neuronal BIN1iso1 interacting proteins in vivo using wild-type mice under homeostatic conditions. Aim 2. Establish neuronal BIN1iso interactome in mouse models of AD (5XFAD and PS19) before and after the onset of pathology. This project will not only advance the field by providing those studying AD and BIN1 with a list of BIN1iso1 proximal proteins to generate novel hypotheses but will also support the applicant’s pre-doctoral research training in AD pathophysiology, advanced methods such as in vivo AAV transduction, proximity-based labeling in the context of AD pathology, large-scale proteomics data analysis, and bioinformatics analysis of BIN1 functional pathways. The dynamic and highly collaborative research environment at the USF Health Byrd Alzheimer’s Institute will enhance the learning opportunities in cell biology and molecular pathology within an established AD laboratory led by a committed mentor. Furthermore, research training in proteomics approaches offered by the collaborator’s lab and the Proteomics Core facilities will complement the applicant’s interdisciplinary research training in age-related neurodegenerative disease.

Project Narrative Alzheimer’s disease is a devastating neurodegenerative disease affecting ~6.5 million Americans aged 65 and older with no currently available treatment that reverses the course of the disease. BIN1 is the second most significant locus according to genome-wide associate studies for the development of late onset Alzheimer’s disease, only behind ApoE4, and we have very little idea of how BIN1 may confer increased risk for Alzheimer’s disease. I will use a novel discovery approach coupled to the latest advancements in quantitative mass spectrometry to define the BIN1 protein interaction network, which will lead to the discovery of new BIN1 functional pathways that may increase Alzheimer’s disease risk.