PROJECT SUMMARY The diversity of acyl chain composition in membrane phospholipids suggests a variety of specific cellular and physiological roles. Indeed, the identification of numerous phospholipid metabolites that can act as lipid mediators has highlighted the many important signaling pathways that are influenced by phospholipid metabolism. However, despite the myriad physiological and pathological implications, including in inflammatory diseases like multiple sclerosis and rheumatoid arthritis, neurodegeneration, cancer, metabolic syndrome, and fertility, there is still much to be discovered about phospholipid remodeling and regulation in vivo. Phospholipase A2 (PLA2) enzymes are critical regulators of phospholipid acyl chain distribution and also are essential for generating lipid mediators. Calcium dependent cytosolic PLA2s (cPLA2s) have been strongly linked to lipid mediator signaling, while the calcium independent PLA2s (iPLA2s) were initially believed to be the ?housekeeping? enzymes, important mostly for membrane homeostasis. For this reason, comparatively less is known about iPLA2s. However, recent studies implicate them in lipid mediator signaling as well, and suggest that they are key players in metabolic syndrome and neurodegeneration via cellular effects on ER stress, apoptosis, mitochondrial integrity, and nutrient sensing. Because of these new revelations, iPLA2s represent important emerging drug targets, making it imperative to understand better how iPLA2s are regulated in vivo and how their cellular functions underlie their physiological effects. This proposal will investigate iPLA2? in Drosophila melanogaster, making use of the first fly null mutant in this gene. This mutant has revealed two novel physiological roles of iPLA2?, in female fertility and aging. Aim 1 will analyze the mechanism of iPLA2? function in female fertility using cytological analysis of actin dynamics, cell death, and molecular markers of nutrient sensing. Genetic interaction and epistasis tests with other genes active in these processes will provide molecular context for iPLA2? activity in this milieu. Aim 2 will localize the somatic activity of iPLA2? in aging to specific cell type(s), and Aim 3 will investigate the regulation of iPLA2? by in vivo structure-function analysis. Drosophila provides a simple and genetically tractable model system for linking physiology with cell biology, creating and analyzing transgenes in vivo, and examining lifespan in a short-lived organism. The many invaluable insights gained from Drosophila into numerous cellular processes and molecular pathways provide ample precedent for using this model. Aim 1 is being conducted in the Steinhauer lab, while Aim 2 is structured as the laboratory component of the undergraduate genetics course at Yeshiva University, making it the first Course-based Undergraduate Research Experience (CURE) at YU. Aim 3 will involve both the Steinhauer lab and the course. Thus, this proposal strongly addresses the directives of the R15 AREA program: to enhance the research experience of undergraduates, to strengthen the research environment on undergraduate campuses, and to expose undergraduates to developmental model organisms.