Ethanolamine phospholipid synthesis in Leishmania

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The goal of this application is to determine how Leishmania parasites acquire ethanolamine phospholipids (EPL), an abundant class of lipids with vital functions in membrane- and non-membrane processes. This is significant because a better understanding of EPL acquisition will shed new light on the unique biochemistry of Leishmania parasites and the results may lead to novel drug targets. In many eukaryotes, EPL are generated through the ethanolamine branch of the Kennedy pathway, the uptake and remodeling of exogenous lipids, and the interconversion between phosphatidylserine and phosphatidylethanolamine. During their life cycle, Leishmania parasites alternate between extracellular promastigotes in sandflies and intracellular amastigotes in mammals. Preliminary studies demonstrate that the enzyme ethanolamine-phosphate cytidylyltransferase (EPCT) is absolutely essential for the promastigote AND amastigote stages of Leishmania major. EPCT is required for the de novo synthesis of EPL via the Kennedy pathway. In contrast, the de novo synthesis of choline phospholipids, which are far more abundant than EPL, is fully dispensable for L. major amastigotes, the pathogenic form to humans. Based on these and other findings, the central hypothesis is that while Leishmania amastigotes can acquire most of their lipids through salvage and remodeling, they must synthesize a specific subset of EPL that cannot be sufficiently scavenged from the host. Three specific aims will be undertaken concurrently to test this hypothesis and explore the roles of EPL synthesis in Leishmania. Aim 1 is to determine why EPCT is indispensable for amastigotes. The plan is to elucidate the lipidome of intracellular amastigotes, identify those amastigote specific EPL, and reveal the types of host lipids that are selectively salvaged by amastigotes. Aim 2 is to assess the essentiality of EPCT in Leishmania donovani and Leishmania amazonensis. This is important because different Leishmania species may have distinct requirements for lipid uptake and synthesis. This aim will determine whether EPCT is a pan- Leishmania target and identify the types of EPL that are synthesized via EPCT. Aim 3 is to investigate the roles of phosphatidylserine decarboxylase and phosphatidylserine synthase. These enzymes have never been studied in Leishmania and their impact on in EPL synthesis, mitochondria functions, and virulence will be determined. Successful completion of these aims will reveal how Leishmania acquire EPL through different pathways and elucidate the crucial functions of EPL. The findings may lead to the identification of new drug targets (e.g. EPCT) or new strategies to block the essential lipid transfer from host to Leishmania. This project is well within the principle investigator’s area of expertise and its scope is appropriate for a research team mainly made of undergraduate and graduate students. In summary, this AREA grant is expected to improve our understanding of Leishmania biology and expand the undergraduate research capacity at Texas Tech University.