Oxidative regulation mechanisms in the mitochondrial intermembrane space

Manganas, Phanee (2017) Oxidative regulation mechanisms in the mitochondrial intermembrane space. PhD thesis, University of Glasgow.

Abstract

Oxidative stress occurs when cells are unable to cope with the levels of various reactive
oxygen species (ROS) that arise as part of regular cellular metabolism or in response to
ionising radiation (H2O2, O2-, OH-). The most well studied ROS is H2O2, due to its dual
role as a mediator of oxidative stress and a signalling molecule for many cellular pathways.
Cells possess a number of different mechanisms to combat ROS, in order to prevent their
levels from becoming toxic.
In this thesis, we studied three different aspects of the antioxidant defence in
Saccharomyces cerevisiae. In the first part, we explored the role of erythroascorbic acid –
the yeast analogue of ascorbic acid (vitamin C) – and attempted to determine its role as an
antioxidant in yeast. Our results were inconclusive, though there were indications that the
presence of erythroascorbic acid may have a protective effect on the mitochondrial inner
membrane potential (ΔΨ), protecting it from depolarisation.
The second part focused on elucidating the mitochondrial targeting of the main H2O2
sensor Gpx3 and, more specifically, whether the Yap1-binding proteins, Ybp1 and Ybp2,
have an effect on the import of Gpx3 in yeast mitochondria. Our results show a slight
effect of Ybp1 (but not Ybp2) on the import of Gpx3, indicating that Ybp1 may act as a
chaperone for the more efficient targeting of Gpx3 from the cytosol to the outer
mitochondrial membrane and, as a result, its eventual translocation into the IMS.
The final part of this thesis focused on elucidating the import of Trx1 and Trr1 in the
mitochondrial IMS, as well as their function in this particular subcompartment. The
discovery of two members of the thioredoxin system in the IMS is important, due to the
absence of a known reducing mechanism in this oxidising compartment. Our results
determined that several well-known import factors are dispensable for the import of either
Trx1 or Trr1, indicating that they follow a yet unknown pathway for their translocation
into the IMS. Importantly, we showed that Trx1 is reduced (and thus, active) in the IMS
and that it can interact in vitro with both components of the MIA machinery (Mia40 and
Erv1), while in organello experiments showed that Trx1 most probably interacts with a
large number of Mia40 substrates.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: mitochondria, intermembrane space, import, oxidation, oxidative stress response, reductive pathways, thioredoxin.
• Subjects: Q Science > Q Science (General); Q Science > QH Natural history > QH301 Biology; Q Science > QH Natural history > QH345 Biochemistry
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Molecular Biosciences
• Supervisor's Name: Tokatlidis, Professor Kostas
• Date of Award: 2017
• Depositing User: Phanee Manganas
• Unique ID: glathesis:2017-8568
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 03 Nov 2017 16:35
• Last Modified: 15 Nov 2017 14:50
• URI: https://theses.gla.ac.uk/id/eprint/8568

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