Complex sphingolipid profiling and identification of an inositol phosphorylceramide synthase in Dictyostelium discoideum

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Title: Complex sphingolipid profiling and identification of an inositol phosphorylceramide synthase in Dictyostelium discoideum
Authors: Listian, Stevanus Aditya
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Thesis advisor: Prof. Dr. Caroline Barisch
Thesis referee: Prof. Dr. Joost Holthuis
Abstract: Dictyostelium discoideum is a free-living social amoeba at the crossroads between uni- and multicellular life. It is often used as a model organism to investigate cellular processes related to the recognition, engulfment and infection course of intracellular pathogens. Sphingolipids are found in high abundance in the plasma membrane. They are cholesterol-binding lipids that control membrane properties, mediate signaling and act as adhesion molecules in recognition mechanisms essential to infection and immunity. In plants, animals and fungi, the sphingolipid pathway is largely established. However, in D. discoideum, neither the identity of the sphingolipids nor the biosynthesis pathway are well characterised. Using lipidomics, I observed that D. discoideum generates inositol-phosphorylceramide (IPC) with predominantly phytoceramide backbones. The candidates for IPC synthase were narrowed down using a bio-IT-based cloning strategy, and the activity of each candidate was analysed using a cell-free expression (CFE) system within defined lipid environments, which takes into account the selectivity of headgroup transfer from phosphatidylinositol (PI) to Ceramide (Cer). This led to the identification of DdIPCS1, a protein sharing multiple sequence motifs with yeast IPC and human sphingomyelin (SM) synthases. DdIPCS1 is localised at the Golgi apparatus and the contractile vacuole (CV) of D. discoideum. These ground-breaking findings pave the way for further research into the role of sphingolipids in phagocytosis and infection, bridging a large evolutionary gap.
Subject Keywords: Inositol phosphorylceramide; Sphingolipids; Lipidomics; Dictyostelium discoideum; Complex sphingolipids; Cell-free expression; Complex sphingolipids synthase
Issue Date: 18-Oct-2023
License name: Attribution 3.0 Germany
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Type of publication: Dissertation oder Habilitation [doctoralThesis]
Appears in Collections:FB05 - E-Dissertationen

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