Universität zu Köln

Di Giacomo, Bruna (2023). Regulation of metabolism by DNA-binding ability and acetylation of FOXO in Drosophila. PhD thesis, Universität zu Köln.

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Abstract

Population ageing is a major social problem, and researchers are exploring ways to promote healthy ageing. One area of investigation is the evolutionarily conserved insulin-insulin like growth factor signaling pathway (IIS), the reduced activity of which has been largely associated with improved health and longevity in different species. FOXO transcription factors are downstream effectors of this pathway and have been identified as mediators of the healthspan and lifespan benefits. Besides regulating ageing, FOXOs play a crucial role in the regulation of energy homeostasis and metabolism. In order to coordinate all the different functions associated with the protein, their action is specifically regulated by post-translational modifications and interactions with binding partners. However, the molecular mechanisms behind FOXO regulation in vivo have not been fully elucidated. In this PhD project, I used the model organism Drosophila melanogaster to investigate the specific contribution of DNA-binding ability and acetylation in the regulation of FOXO-related functions. In the first part of the study, I used previously generated mutant flies expressing constitutively acetylated or deacetylated dFOXO proteins to study the influence of this modification on lifespan and metabolism. We found that dFOXO acetylation plays a crucial role in the response to yeast starvation and, partially, cholesterol starvation. To have a deeper insight into the lysine residues whose acetylation regulates dFOXO function, I generated novel partial acetylation mutants and observed overlapping phenotypes with the complete acetylation mutants. Acetylation of FOXO also seemed to drive metabolism towards lipogenesis. Moreover, constitutively acetylated dFOXO protected flies from the detrimental effects of a high-sugar diet. Finally, we described a new role of dFOXO as potential mediator of methionine depletion. In the second part of the project, I used dFOXO mutant flies in which the DNA-binding ability of the protein was abolished to identify functions that are independent of its direct transcriptional ability. Our results indicate that dFOXO-mediated response to sugar starvation is completely dependent on its DNA-binding ability, whereas it promotes lipid usage under starvation independently of its transcriptional ability. Moreover, we observed that dFOXO-DBD mutants switch from carbohydrates to lipids as preferential energy source upon starvation. In conclusion, this PhD study sheds light on the specific metabolic functions associated with dFOXO and on its regulatory mechanisms in vivo.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Di Giacomo, Bruna ele_bruna@hotmail.it UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-716454
Date:	17 November 2023
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Außeruniversitäre Forschungseinrichtungen > MPI for Biology of Ageing
Subjects:	Generalities, Science Natural sciences and mathematics Life sciences
Uncontrolled Keywords:	Keywords Language metabolism, acetylation, FOXO, DNA-binding, Drosophila English
Date of oral exam:	7 June 2023
Referee:	Name Academic Title Partridge, Linda Prof. Dr. Roth, Siegfried Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/71645