Universität zu Köln

de Alcantara Fernandes, Stephanie ORCID: 0000-0001-8625-8747 (2024). Regulation of mTOR signaling by nutrients and post-translational modifications. PhD thesis, Universität zu Köln.

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Abstract

The mTOR (mechanistic target of Rapamycin) signaling pathways are at the center of cellular physiology. As such, their dysregulation is a common characteristic of many conditions, such as cancer, neurodegeneration and aging. mTORC1 (mTOR complex 1) regulates cellular growth by controlling protein synthesis, autophagy and lysosomal biogenesis. On the other hand, mTORC2 (mTOR complex 2) is involved in the regulation of cell survival and proliferation. mTOR responds to upstream cues that control its function via the activity of key GTPases that regulate its localization, and via alterations in PTMs (post-translational modifications) on several signaling components. In particular, AAs (amino acids) regulate mTORC1 via changes in its subcellular localization, promoting mTORC1 recruitment to lysosomes. However, the reasoning for the lysosomal localization of mTORC1 and whether mTORC1 is active in different subcellular locations is an open question. Here, using multiple approaches to disrupt lysosomal function, I show that mTORC1 localization to lysosomes is linked to lysosomal activity. This observation indicates that mTORC1 is found at lysosomes likely due to basal protein degradation in the lysosomal lumen and subsequent nutrient release. Unexpectedly, under AA sufficiency, delocalization of mTORC1 from lysosomes led to a complete loss of TFEB phosphorylation, with very mild effects on the canonical substrates S6K1 and 4E-BP1. PTMs primarily include phosphorylation and ubiquitination events. Although the former is well-described in the control of mTOR complexes, the latter is less well-understood. Nonetheless, work over the recent years established that ubiquitination of several components of the mTORC1 and mTORC2 pathways is also an important part of their regulation. mTOR, the catalytic component of both mTORC1 and mTORC2, is itself heavily ubiquitinated. Hence, the identification of proteins able to modulate mTOR ubiquitination is of great importance to understand mTOR regulation. In this thesis, I identified the DUB (deubiquitinase) CYLD as an interacting partner of mTOR. Strikingly, CYLD is able to modulate mTOR ubiquitination and activity. Overall, my work expanded the knowledge on mTOR signaling regulation by uncovering the spatial separation of mTORC1 functions and a novel DUB for mTOR.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code de Alcantara Fernandes, Stephanie sfernandes@age.mpg.de orcid.org/0000-0001-8625-8747 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-721497
Date:	2024
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Außeruniversitäre Forschungseinrichtungen > MPI for Biology of Ageing
Subjects:	Life sciences
Uncontrolled Keywords:	Keywords Language mTOR English signaling English lysosomes English amino acids English ubiquitin English
Date of oral exam:	26 May 2023
Referee:	Name Academic Title Demetriades, Constantinos Dr. Lemberg, Marius Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/72149