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A characterization of the lipid biosynthetic interactome in Saccharomyces cerevisiae
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- Author / Creator
- Greenwood, Brianna L.
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Lipids are integral components of all cells. Lipid molecules form the membrane and control membrane integrity while storage lipids act as a source of energy for the cell. The chemical properties of lipids are determined by the composition of the molecule’s acyl chain moieties. Incorporation of unsaturated acyl chains into phospholipids destined for the membrane generates a more fluid membrane, while a more unsaturated acyl chain profile in storage lipids permits lipid droplet biogenesis from the endoplasmic reticulum. In Saccharomyces cerevisiae, acyl-CoA is desaturated by the sole ∆9-desaturase Ole1. Ole1 plays an important role in S. cerevisiae, as up to 80% of the acyl chains are unsaturated. However, unsaturated acyl-CoA is distributed unevenly within the cell. Certain phospholipids, like phosphatidylethanolamine and phosphatidylcholine, are enriched for unsaturated acyl chains, while other phospholipids like phosphatidylinositol contain more saturated moieties. This indicates that the unsaturated acyl-CoA generated by Ole1 is more available to specific lipid biosynthetic enzymes. The mechanism controlling this specificity has not yet been characterized, but interactions between enzymes in lipid biosynthesis have been identified in other organisms. We propose that interactions between Ole1 and lipid biosynthetic enzymes exist in S. cerevisiae, and that these interactions control the incorporation of unsaturated acyl chains into certain lipids and thus regulate the chemical properties of phospholipid and storage lipid. We present herein a set of coimmunoprecipitation and membrane yeast two-hybrid studies that identified novel protein-protein interactions between Ole1 and lipid biosynthetic enzymes. Interactions with the main lysophosphatidic acid acyltransferase in S. cerevisiae, Slc1, and the essential CDP-DAG synthase, Cds1, were also discovered, further determining
the composition of the complex we have called the desaturasome. We have more deeply characterized the interaction between Ole1 and the diacylglycerol acyltransferase Dga1 and performed functional studies that suggest a role for the Ole1-Dga1 interaction in control over lipid droplet formation. Finally, we present evidence for the contention that the interaction between Ole1 and Dga1 controls the subcellular localization of the acyltransferase. This research has revealed the composition of a lipid biosynthetic interaction network that may serve to control the incorporation of unsaturated acyl-CoA into phospholipid and storage lipid and thus regulate the membrane fluidity and generation of lipid droplets from the endoplasmic reticulum. Future work should aim to determine whether the composition of the desaturasome differs between subcellular compartments and if these interactions channel lipid. Investigating the role of this lipid synthesizing supercomplex may have implications in metabolic engineering and treatment of lipid dysregulatory disorders in humans. -
- Graduation date
- Fall 2023
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.