Abstract: Alzheimer's disease (AD) is characterized by the loss of memory accompanied by neuronal cell death and metabolic dysfunction. Numerous studies have reported a dysregulation in neuronal intracellular calcium (iCa2+) signaling as an early event in AD pathogenesis. It is thought that a prolonged elevation in neuronal iCa2+ promotes excessive mitochondrial calcium (mCa2+) uptake, yet to date no study has examined the contribution of mCa2+ uptake to disease progression. Since mCa2+ flux is an important regulator of cellular respiration and cell death, both of which are involved in AD pathogenesis, we hypothesize that mCa2+ overload is a key contributor to AD pathology and may contribute to metabolic deficits and neuronal demise. To define the role of mCa2+ exchange in AD we have generated 3xTg-AD mutant mice with neuronal-specific deletion of Mitochondrial Calcium Uniporter (MCU), which is required for mCa2+ uptake. In addition, we have generated a gain-of-function mutant mouse expressing the recently identified mitochondrial calcium uniporter beta subunit (MCUb). MCUb was recently reported as a negative regulator of mCa2+ uptake and we have observed substantial changes in its expression in AD. These models will allow causative experimentation to test if mCa2+ uptake drives AD progression. Mice will be examined for alterations in memory, amyloidosis, tau-pathology, oxidative stress, synaptic and metabolic function. Preliminary data suggest that mCa2+ uptake overload impairs the clearance of misfolded proteins and dysfunctional mitochondria. Therefore, we will mechanistically examine the link between mCa2+ exchange and autophagic and mitophagic pathways. Optimally, the proposed studies will discover new therapeutic targets for AD and associated mitochondrial dysfunction and provide a training and research platform to promote the PIs independent research career.