Project summary Alzheimer’s disease (AD) afflicts over 6.5 million Americans and is the sixth leading cause of death in the US. Despite more than a decade of clinical research to uncover biologic drugs to resolve negative sequelae that accrete due to AD, no disease-modifying agents have been shown to reverse AD-related neurodegeneration for long durations. Rather, available therapeutics aim to counter neurotransmitter imbalances that account for a subset of AD symptoms, and more recent immunotherapies are of controversial utility that is accompanied by severe risks of edema. While deaths from stroke, HIV, and heart disease have decreased over the last two decades, reported deaths from AD have more than doubled over the same period, reflecting a need for innovations in AD treatment. Genetic engineering strategies and cell-based therapies aim to supply or stimulate neural precursors, enhance structural neuroplasticity, and combat neuronal death, and therefore offer an avenue to potentially turn the tide of neurodegeneration and resolve aspects of AD. However, to date, none of these therapies has proven effective and have instead highlighted the need to find methods to dynamically control behaviors of cells in the central nervous system (CNS) in accordance with signatures of pathology. Here, we propose to investigate engineered astrocytes and microglia as programmable agents for disease-dependent coordination of neuro-protective behaviors. Microglia and astrocytes play central roles in the CNS response to amyloid-b (Ab) and hyperphosphorylated tau – the biochemical hallmarks of AD – making them attractive candidates to selectively train for pre-defined functions in response to pathologic AD features. Thus, we aim to develop a synthetic biology tool that allows astrocytes and microglia to produce biologic drugs in targeted CNS sites displaying Ab-related signatures of AD pathology. In Aim 1, we will investigate whether our receptor platform programs astrocytes within an organotypic slice culture to respond to Ab with engineered outputs that can support neuronal health. In Aim 2, we will test whether our synthetic signaling module enables engineered astrocytes and microglia to protect neurons and counteract Ab-driven degeneration in an in vitro stem cell model of AD. Collectively, these experiments will establish the utility of an orthogonal signaling channel that governs responses of either in situ engineered cells or stem cell-derived CNS cell replacements to pathogenic Ab.