Project Summary Alzheimer’s disease (AD) represents one of the foremost healthcare challenges of our times and is a leading cause of death worldwide. AD accounts for the overwhelming majority of dementias, which affect over 35 million people worldwide. This number is expected to double every twenty years. Dysfunction of the Adenosine triphosphate (ATP) Binding Cassette Subfamily A member 7 (ABCA7) transporter has been linked to both early and late onset AD through alterations in lipid homeostasis, Amyloid-Beta (Aβ) homeostasis, and phagocytosis. ABCA7 single nucleotide polymorphisms have been associated with late onset AD, suggesting that targeting ABCA7 could pave the way forward for new therapeutic AD strategies. The long-term objectives of this project are to gain mechanistic insight into human ABCA7 (hABCA7). We will use a combination of high-resolution structural analysis, in vitro functional characterization, and discovery of antibody and small molecule binders for hABCA7. The latter will aid in diagnostics and targeting, or function as potentiators and/or correctors of hABCA7 dysfunction. Specific Aim 1 deals the functional characterization of ABCA7 ATPase activity and the establishment of an in vitro transport assay to assay the lipid specificities and transport properties of the transporter and probe its interaction with different apolipoproteins. Specific Aim 2 deals with the detailed cryo- EM analysis of hABCA7 alone and in combination with nucleotides, different lipid environments, and small molecule and antibody based binders. Our results will shed light on the physiological functioning of human ABCA7, which is as of yet poorly understood, and validate its potential utilization as a therapeutic target for which future antibody and drug discovery efforts can be directed, thereby bridging basic and translational research for this relatively unexplored area of AD research.