Elucidating Novel Regulators of Microglial Phagocytosis in Alzheimer’s Disease - Project Summary Over 6 million Americans aged 65 and above currently suffer from Alzheimer's Disease (AD). This substantial prevalence among the elderly underscores aging as one of the most prominent risk factors contributing to the onset of AD. Microglia are cells that facilitate the clearance of cellular debris including protein aggregates through the process of phagocytosis. Notably, microglial phagocytic function is impaired in both aging and AD, however, the molecular mechanism that drives this dysfunction is not well characterized. My F99 work will delineate how the loss of the RNA-binding protein, Quaking (Qki), drives phagocytic dysfunction in AD. My K00 work will follow a similar path by focusing on how the dysregulation of an important phagocytic lipid, Phosphatidylinositol-3- phosphate (PI3P), can lead to impairment in microglial membrane dynamics in the context of AD. My sponsor's (Dr. Jian Hu) previous work has established the foundation to support the novel hypothesis that Qki promotes microglial phagocytosis to attenuate AD progression. For Aim 1 (F99), I will be utilizing the conditional deletion of Qki in microglia in an AD mouse model to 1) Assess the impact of Qki loss on the development of AD pathology. 2) Isolate primary microglia to directly test phagocytic activity. 3) Perform a rescue experiment with the agonist treatment of the Qki downstream transcription factor PPARβ. Published work indicating the downregulation of PI3P in AD and PI3P enrichment in the phagocytic cup along with data from Dr. Hu's lab indicating that PI3P synthesis is indirectly regulated by Qki has established the framework for my K00 research. My K00 work (Aim 2), will address the role of PI3P in the regulation of phagocytic membrane dynamic and eventual contribution to AD progression through 1) Validating the expression of the PI3P and its synthesizing enzyme Vps34 on the phagosome. 2) Utilizing conditional deletion of the Vps34 in microglia within AD mouse models to characterize the impact of PI3P loss on AD progression. Overall, this work will directly contribute to the NIA's priority of understanding the molecular mechanisms that contribute to AD which is one of the most prevalent age-related neurodegenerative diseases. To successfully complete my proposed aims, I will receive thorough training guided by an expert mentoring team in microglia culture, transcriptomic analysis, lipidomic analysis, and AD mouse pathology characterization. Together, this training will provide me with a well-equipped platform to succeed as an aging researcher with the establishment of an independent research laboratory focused on delineating microglial dysfunction in AD.
