Inflammation and plaque formation downstream of disrupted autophagy in Alzheimer's disease

Alzheimer’s disease and related dementias (AD/ADRD) are devastating diseases to those diagnosed and come with a high cost to society. Reliable early identification and improved intervention is vital to treat patients before neuronal loss is irreversible. Autophagy is strongly implicated in the progression of AD, and thus has been an attractive therapeutic target for many years, but to reach a successful autophagy-targeting drug requires better understanding of the molecular consequences of disrupted autophagy. I propose to investigate how disrupted autophagy contributes to the chronic inflammation and plaque formation associated with the progression of AD. Using two of the most common AD risk variants as models to disrupt specific aspects of autophagy, I will investigate how the misregulation of mitochondrial DNA (mtDNA) and amyloid precursor protein (APP), autophagy cargos I identified in my postdoc, contribute to neuroinflammation, synapse loss, and plaque deposition observed in AD. AD initiation and progression involves multiple cell types, therefore I will use innovative iPSC models and cutting-edge techniques to model and manipulate complex interactions between neurons and microglia in a simplified system. In the K99 phase of this award, I will confirm that the ApoE4 AD risk variant disrupts mitochondria-endoplasmic reticulum contacts, which I predict will impair the clearance of mtDNA. I expect accumulation of mtDNA will sensitize neurons to release inflammatory factors, resulting in sustained microglia activation, release of complement and synapse loss. In the R00 phase, I will apply similar approaches mastered in the K99 phase to investigate the contribution of autophagy to plaque deposition. First, based off preliminary data, I will determine whether APP is an autophagy cargo in neurons or microglia, and whether it is normally transferred between the cell types. Second, as dysregulated Tau is a major disruptor of microtubules and organelle trafficking, I will investigate the sensitivity of TauR317W neurons to disruptions to autophagosome trafficking. I have found in my postdoctoral work that impaired autophagosome trafficking decreases degradation and increases secretion of autophagy cargo, thus I expect TauR317W sensitizes neurons to increase secretion and transfer of APP to microglia. I will then investigate the role of microglial autophagy to prevent plaque formation, and how this may be perturbed by the accumulation of Tau aggregrates and neurofibrillary tangles in TauR317W microglia. Completion of the independent aims will highlight the multifaceted role of autophagy in disease progression, identify specific molecular consequences of disrupted autophagy, and ultimately help to identify novel biomarkers and therapeutic targets for AD/ADRD.