Schmidt, Anna Mareike

MY PROJECT

Under high glucose conditions the yeast Saccharomyces cerevisae ferments glucose to ethanol regardless if oxygen is present or absent, a phenomenon called glucose repression. It is known that hexokinase (Hxk)2, which phosphorylates glucose, also participates in glucose repression. Its precise role in glucose repression, however, is still not understood. In a systems biology approach I try to elucidate how Hxk2 participates in glucose repression.

Student Projects

1) Effects of the glycolytic flux on the yeast's metabolome

Duration: 3 months

When the yeast Saccharomyces cerevisiae is grown at high glucose the glucose is fermented to ethanol regardless if oxygen is present or absent. This phenomenon is called glucose repression which is similar to the Warburg effect in many cancer cells. In yeast the glycolytic flux seems to determine the level of glucose repression. However, how the glycolytic flux is actually sensed is completely unknown. One option is that the flux is sensed through characteristic metabolite levels.
Using a set of yeast mutants showing different glucose transport characteristics you will determine how the glycolytic flux affects the yeast’s metabolome. As part of this, you will learn how to cultivate S. cerevisiae and determine the glycolytic fluxes in the mutants by 13C flux analysis and HPLC. Furthermore, you will apply several state-of-the-art analytical techniques, specifically GC-TOF and LC-MS/MS, for metabolome analysis.

This project will give you the opportunity to get to know both standard laboratory techniques as well as up-to-date techniques used in systems biology.

Interested? Then contact Mareike Schmidt (mareike.schmidt@imsb.biol.ethz.ch)

2) Elucidating the role of Hxk2 isoforms in yeast using fluorescence microscopy

Glucose is the preferred carbon and energy source of the yeast Saccharomyces cerevisae. After being taken up into the cell glucose is phosphorylated at its C6 atom: a reaction which can be catalyzed by three different enzymes: hexokinase (Hxk)1, Hxk2 and glucokinase (Glk)1. Besides its enzymatic activity Hxk2 was shown to mediate glucose repression, a phenomenon which is characterized by fermentation of glucose under high glucose conditions irrespective of the presence of oxygen.

Data indicate that Hxk1 and/or Glk1 may be able to substitute Hxk2 in mediating glucose repression. Hxk2 can be localized in the cytoplasm or the nucleus depending on glucose concentration of the medium. Hxk1 and Glk1 must show the same localization pattern as Hxk2 in order be able to substitute Hxk2. However, nothing is known about the cellular localization of Hxk1 and Glk1. Furthermore, expression data on the three enzymes during growth on glucose or ethanol are contradictory.

In this project you will determine the expression level of Hxk1, Hxk2 and Glk1 under different growth conditions observing gfp-tagged versions of these enzymes using fluorescence microscopy. Furthermore, you will examine the cellular localization of these enzymes under steady-state and dynamic conditions to see if Hxk1 and/or Glk1 show the same localization pattern as Hxk2. The obtained data will provide a clearer picture of the role of Hxk1 and Glk1 in the yeast cell apart from glucose phosphorylation.

During this project you will learn how to use both standard laboratory techniques as well as our up-to-date equipment such as a high-end microscope and microfluidic chips.

Interested? Then contact Mareike Schmidt (mareike.schmidt@imsb.biol.ethz.ch)