| 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.identifier.uri | http://dx.doi.org/10.53846/goediss-5869 | |
| dc.language.iso | eng | de |
| dc.rights.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 | |