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dc.contributor.author
Weber, Carmen A.
dc.contributor.supervisor
Weis, Karsten
dc.contributor.supervisor
Kaksonen, Marko
dc.contributor.supervisor
Picotti, Paola
dc.contributor.supervisor
Sauer, Uwe
dc.date.accessioned
2020-06-17T07:20:19Z
dc.date.available
2020-06-16T16:59:03Z
dc.date.available
2020-06-17T07:20:19Z
dc.date.issued
2020
dc.identifier.uri
http://hdl.handle.net/20.500.11850/420766
dc.identifier.doi
10.3929/ethz-b-000420766
dc.description.abstract
Cells such as the budding yeast Saccharomyces cerevisiae are frequently subjected to environmental changes in their natural habitat and have evolved elaborate stress responses to cope with changing conditions. For instance, starvation from carbon, and more specifically glucose, has been reported to drastically change cellular metabolism, protein expression programs, as well as the biophysical properties in the cytosol. The biophysical changes manifest as a decrease of cytosolic diffusion and an increase of cytoplasmic rigidity. One of the first and fastest layers to respond to starvation is cellular metabolism. An acute complete depletion of glucose will rapidly reduce cellular energy levels in yeast cells, which quickly reach a novel, though lower, equilibrium that can be maintained for hours. Since cells will need to keep investing energy to maintain homeostasis and survive starvation, an internal energy resource is needed to fuel the cell during starvation. We therefore performed an in-depth analysis of the metabolic state during starvation and provide a novel comprehensive overview of the kinetics of intracellular metabolite levels within seconds to hours of acute glucose depletion. Based on the insights from these metabolic maps, both β-oxidation and autophagy were found to contribute to ATP maintenance and survival, suggesting that these processes are major contributors to cellular energy balance during starvation. Besides metabolic re-programming, acute glucose starvation results in a decrease of cytosolic diffusion, an increase of the rigidity of the cytosol, and formation of biomolecular condensates in yeast cells. These changes in biophysical properties have raised great interest in the field due to their expected global consequences: for instance, cellular biochemistry relies on molecular interactions within the cell, and these could drastically change when biophysical properties such as cytosolic diffusion are modified. However, neither the exact biophysical response, its effect on the cell, nor its underlying molecular drivers are known. I characterized this response, which we termed SiROP (stress-induced re-organization and phase transition), and showed that SiROP can be induced within few minutes of glucose starvation. Electron microscopy (EM) studies indicated that the cytosol of starved cells is more crowded with macromolecules, which could explain the decrease in cytosolic movement, the increase in rigidity of the cytosol, as well as the propensity of proteins and RNA to form condensates. To assess the molecular mechanism of SiROP, a genetic screen was performed, with hits including β-oxidation mutants, which had previously been found to affect the cells’ ability to maintain ATP levels and survival during starvation. Furthermore, mutations in mitochondrial genes that lead to a loss of aerobic respiration were found to inhibit the cells’ ability to perform SiROP and showed increased cytosolic granules as well as reduced cell survival. Intriguingly, a short heat-shock prior to starvation could rescue survival, alleviate the strong granule formation in respiratory-deficient cells, and restore the SiROP response. To understand the molecular mechanism behind the rescue, a second genetic screen was performed, which indicated that the rescue depends on the stress-induced transcriptional activator Msn2. In sum, I have extensively characterized the cellular response to glucose starvation from different angles and identified molecular players that regulate metabolic responses as well as biophysical property changes in yeast cells. In the future, these correlations between metabolism, biophysical properties, and cellular stress could be furthermore tested in mammalian cells, a task which I have begun to study by testing several tools to assess the biophysical properties in mammalian cells.
en_US
dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.publisher
ETH Zurich
en_US
dc.subject
glucose
en_US
dc.subject
starvation
en_US
dc.subject
yeast
en_US
dc.subject
metabolism
en_US
dc.subject
autophagy
en_US
dc.subject
lipid metabolism
en_US
dc.subject
biophysical properties
en_US
dc.subject
cytosolic diffusion
en_US
dc.subject
mammalian cells
en_US
dc.subject
Macromolecular crowding
en_US
dc.subject
particle tracking
en_US
dc.title
SiROP - Regulation of the cytosolic and metabolic response to glucose starvation
en_US
dc.type
Doctoral Thesis
dc.date.published
2020-06-17
ethz.size
136 p.
en_US
ethz.code.ddc
DDC - DDC::5 - Science::570 - Life sciences
en_US
ethz.identifier.diss
26556
en_US
ethz.publication.place
Zurich
en_US
ethz.publication.status
published
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02030 - Dep. Biologie / Dep. of Biology::02517 - Institut für Biochemie / Institute of Biochemistry (IBC)::09464 - Weis, Karsten / Weis, Karsten
en_US
ethz.leitzahl.certified
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02030 - Dep. Biologie / Dep. of Biology::02517 - Institut für Biochemie / Institute of Biochemistry (IBC)::09464 - Weis, Karsten / Weis, Karsten
en_US
ethz.relation.hasPart
20.500.11850/419628
ethz.relation.hasPart
handle/20.500.11850/422296
ethz.date.deposited
2020-06-16T16:59:13Z
ethz.source
FORM
ethz.eth
yes
en_US
ethz.availability
Embargoed
en_US
ethz.date.embargoend
2023-06-17
ethz.rosetta.installDate
2020-06-17T07:21:12Z
ethz.rosetta.lastUpdated
2022-03-29T02:25:47Z
ethz.rosetta.versionExported
true
ethz.COinS
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