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Peroxisomal Components Function to Regulate Lipolysis at the Lipid Droplet Surface
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- Author / Creator
- Anderson-Baron, Matthew N
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Organelles serve to compartmentalize biochemical functions within the eukaryotic cell. However, to collectively maintain cellular homeostasis, organelles must communicate in some way in order to coordinate these functions. Two such organelles,the peroxisome and the lipid droplet, are both involved in the metabolism of cellular lipids. Therefore, it is likely that they communicate in order to coordinate their metabolic activity.Peroxisomes are small, ubiquitous organelles that produce and decompose hydrogen peroxide and metabolize particular species of lipid. Lipid droplets serve as the main storage reservoir for excess fatty acids and cholesterol within the cell. Studies haverevealed intimate physical connections between peroxisomes and lipid droplets; however, little is known about the mechanisms that regulate their communication. This thesis outlines the characterization of genes involved in peroxisome biogenesis in Drosophila and previously undocumented functions of peroxisomal components Pex13 and Pex14 at the lipid droplet surface. The subcellular localization of predicted peroxisome proteins was examined in Drosophila melanogaster. PEX genes encoding proteins called peroxins control the biogenesis and maintenance of the peroxisome population. The majority of the peroxins localized to peroxisomes in S2 cells, a cell line derived from Drosophila embryos. In addition, proteins expressing a canonical peroxisomal targeting signal, -SKL, at their Cterminusare likewise localized to peroxisomes in S2 cells. A comprehensive analysis of the various peroxisomal protein targeting pathways revealed that overall peroxisomebiogenesis and function are well conserved in Drosophila, validating the use as a model system to further investigate peroxisome activities, such as peroxisome-lipid dropletinteractions.S2 cells cultured in the presence of oleate exhibit changes in peroxisome phenotype and upregulation of Pex14. Furthermore, knockdown of Pex14 in both S2 cells and Drosophila larvae resulted in increased lipolysis and decreased triglyceride stores.Analysis of the subcellular localization of the various confirmed peroxins revealed that Pex3, Pex13, and Pex14 localized to the lipid droplet surface in S2 cells and normal rat kidney cells when cultures were supplemented with excess oleate. In addition, increased levels of Pex14 at the lipid droplet surface affected the localization of Hormone-sensitive lipase. Further, expression of the Drosophila homologue of CGI-58 was reduced in cellstreated with dsRNA targeting Pex14. In contrast, the localization of Pex14 to the lipid droplet surface was perturbed by the overexpression of Lipid storage droplet-1. Collectively, a subset of the peroxisome biogenesis proteins are diverted to thelipid droplet surface during periods of elevated lipid droplet metabolism, where they modulate the localization and expression of other proteins at the lipid droplet. It isproposed that peroxisomal components influence the metabolism of lipid droplets by gating the mobilization of free fatty acids from triglyceride stores.
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- Subjects / Keywords
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- Graduation date
- Spring 2019
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.