The glucose signal transduction pathway mediated by the Rgt2 and Snf3 glucose sensors in the budding yeast Saccharomyces cerevisiae
Open AccessSensing and signaling the presence of extracellular glucose is crucial for yeast Saccharomyces cerevisiae because of its fermentative metabolism, characterized by high glucose flux through glycolysis, mediated by expression of glucose transporter genes (HXTs). Yeast cells mediate aerobic glycolysis in part, by the crosstalk between two glucose signaling pathways: 1) the Rgt2/Snf3 glucose induction pathway and 2) the Snf1/Mig1 glucose repression pathway. The yeast Rgt1 repressor inhibits transcription of HXT genes in the absence of glucose by recruiting general transcription repressor Ssn6/Tup1 and the HXT corepressor Mth1. In response to glucose, Rgt1 is phosphorylated by the cAMP-activated protein kinase A (PKA) and dissociates from the HXT promoters and no longer interacts with Ssn6/Tup1, resulting in the HXT gene expression. Glucose regulates Rgt1 function by primarily modulating the Rgt1-Ssn6/Tup1 interaction and Rgt1 removal from DNA occurs but not necessary for expression of HXT genes. Ssn6/Tup1 interferes with Rgt1 DNA-binding activity in the absence of Mth1, and that Rgt1 function abrogated by Ssn6 overexpression is restored by cooverexpression of Mth1. Mth1 acts like a scaffold-like protein to facilitate interaction between Rgt1 and Ssn6/Tup1 by blocking PKA-dependent Rgt1 phosphorylation. The cell surface glucose receptors Rgt2 and Snf3 and the glucose transporter (Hxt1) are stable and functional only in the presence of glucose but are removed from the plasma membrane through ubiquitination and subsequent vacuolar degradation via endocytosis in the absence of glucose. In conclusion, this study provides a novel mechanism of eukaryotic gene regulation and a conceptual framework of ligand-receptor interaction at cell surface to explain distinctive fermentative lifestyle of Saccharomyces cerevisiae.
- All rights reserved
Notice to Authors
If you are the author of this work and you have any questions about the information on this page, please use the Contact form to get in touch with us.