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dc.contributor.advisor Kühnlein, Ronald P. Dr.
dc.contributor.author Hehlert, Philip
dc.date.accessioned 2016-09-30T08:29:47Z
dc.date.available 2016-09-30T08:29:47Z
dc.date.issued 2016-09-30
dc.identifier.uri http://hdl.handle.net/11858/00-1735-0000-002B-7C12-C
dc.language.iso eng de
dc.relation.uri http://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subject.ddc 570 de
dc.title Function of the α/β-hydrolase fold family proteins Pummelig (CG1882) and Hormone-sensitive lipase in the Drosophila melanogaster lipid metabolism de
dc.type doctoralThesis de
dc.contributor.referee Wimmer, Ernst A. Prof. Dr.
dc.date.examination 2016-08-03
dc.description.abstracteng To maintain energy homeostasis, all organisms need to adjust the generation and mobilization of their energy stores. The key molecules for energy storage are neutral lipids, mainly triacylglycerides (TAGs), which accumulate in specialized tissues like the mammalian adipose tissue or the fat body of the fruit fly Drosophila melanogaster. Inside the cell neutral lipids are wrapped by phospholipid monolayer to form a unique organelle called lipid droplet (LD). A set of LD proteins act on the surface of these organelles to manage fundamental lipid homeostasis functions like lipid mobilization at this compartment border. Remarkably, central mammalian LD proteins involved in storage fat mobilization like Perilipins or the Adipose triglyceride lipase (ATGL) have functional homologues in fruit flies (namely Plin1 and Brummer) suggesting an evolutionary conservation of factors and mechanisms of lipid mobilization between flies and men. In mammals the α/β-hydrolase fold family proteins Hormone-sensitive lipase (HSL) and α/β-hydrolase domain containing 5 (ABHD5 or CGI-58) are core components of the lipid mobilization module. ABHD5 acts as an activator of ATGL and HSL represents the main diacylglyceride (DAG) lipase. In this work I characterized the functions of the related genes for mammalian HSL (Hsl) and ABHD5 (CG1882, pummelig) in D. melanogaster. Most findings for Hsl, are consistent with the published data for its mammalian homolog indicating an evolutionary conservation of its function. DmHsl1 mutant flies have no altered body fat storage, as also observed in HSL deficient mice. A DmHsl::GFP fusion protein is conditionally localized on LDs and the substrate spectrum is very similar to mammalian HSL. However, whereas diacylglyceride amounts are increased in HSL deficient mice, this could not be observed in DmHsl1 mutant flies. Also neither lipid mobilization nor fecundity were impaired in DmHsl deficient flies, leaving it open to identify a biological phenotype in DmHsl1 flies. pummelig mutant (puml1) larvae had normal body fat storage but body fat stores (mainly TAGs) in adult puml1 flies were increased in comparison to control flies. At the same time Glycogen stores in puml1 flies were decreased by ~40% compared to control flies which was accompanied by a higher desiccation sensitivity. puml1 flies survived significantly longer under starvation and surprisingly mobilized storage lipids faster than controls. In vitro assays using recombinantly expressed pummelig identified Puml as an active phospholipase with substrate affinities for Phosphatidic acid (PA), Phosphatidylglycerol (PG), N-Arachidonoyl-phosphatidylethanolamine (NAPE), Ethyl palmitate and Bis(monoacylglycero)phosphate (BMP[R,R]). However, Puml cannot activate the main triglyceride lipase Brummer in flies. Besides increased body fat storage, massive lipid accumulations in Malpighian tubules (the renal organs of the fly) could be observed in puml1 flies. Further experiments indicated a tissue autonomous control of lipid storage in Malpighian tubules. Additionally, metabolic rate in puml1 flies was similar to control flies. Interestingly, food intake of puml1 flies was comparable to controls but the rate of lipogenesis was drastically increased. Localization studies using Puml::mCherry fusion protein confirmed the LD localization in adult fat body tissue and additionally could show that Puml::mCherry co-localized with peroxisome-targeted eYFP. As peroxisomes are important for the breakdown of long-chain fatty acids (LCFAs) a lipidomics analysis was performed with Malpighian tubule samples that revealed increased TAG storage with a shift towards longer fatty acid sidechains and increased un-saturation grade of the esterified fatty acids. An extended working model is provided which explains the observed phenotypes in puml1 flies. My findings contribute to a broader understanding of the complex network which controls lipid metabolism. de
dc.contributor.coReferee Kühnlein, Ronald P. Dr.
dc.contributor.thirdReferee Mansouri, Ahmed Prof. Dr.
dc.contributor.thirdReferee Zimmermann, Robert PD Dr.
dc.contributor.thirdReferee Feußner, Ivo Prof. Dr.
dc.subject.eng Drosophila melanogaster de
dc.subject.eng Metabolism de
dc.subject.eng Lipid Metabolism de
dc.subject.eng Pummelig de
dc.subject.eng Puml de
dc.subject.eng DmABHD4 de
dc.subject.eng DmABHD5 de
dc.subject.eng DmABHD4/5 de
dc.subject.eng Hormone-sensitive lipase de
dc.subject.eng Hsl de
dc.subject.eng DmHsl de
dc.subject.eng CG1882 de
dc.subject.eng CG11055 de
dc.subject.eng Lipolysis de
dc.identifier.urn urn:nbn:de:gbv:7-11858/00-1735-0000-002B-7C12-C-0
dc.affiliation.institute Göttinger Graduiertenschule für Neurowissenschaften, Biophysik und molekulare Biowissenschaften (GGNB) de
dc.subject.gokfull Biologie (PPN619462639) de
dc.identifier.ppn 869470329

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