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Feasting, Fasting and Fermenting: Glucose sensing in yeasts
Author(s) -
Johnston Mark
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.249.1
Subject(s) - snf3 , yeast , glucose transporter , nutrient sensing , repressor , fermentation , biochemistry , saccharomyces cerevisiae , biology , chemistry , signal transduction , gene , microbiology and biotechnology , insulin , transcription factor
Glucose fuels life. Most cells prefer it as a food source, and have sophisticated mechanisms for sensing it for efficient use. Yeast and tumor cells metabolize glucose in a seemingly foolish way: they eschew its oxidation (forgoing up to 38 ATPs), and choose to ferment it (settling for 2 ATPs). Yeast cells must sense glucose to know when they must utilize it efficiently because levels are low, and when it is plentiful and can be wasted in fermentation. Yeast throttles glucose utilization at the rate‐limiting step: transport. We discovered a novel glucose sensing system that adjusts this throttle by deploying the appropriate glucose transporters through regulation of their HXT genes. This pathway begins with glucose sensors in the membrane (Snf3 and Rgt2), founding members of a novel class of nutrient receptor related to nutrient transporters. The sensors are coupled to a casein kinase I (Yck), that transduces the glucose signal to a transcriptional repressor (Rgt1) of HXT genes, and its regulators (Mth1 and Std1). The fateful step in the pathway is glucose‐induced degradation of Mth1 and Std1, which relieves repression of HXT genes. This glucose sensing pathway enables yeasts’ profligate lifestyle by ensuring efficient glucose transport.