Starvation-induced degradation of yeast hexose transporter Hxt7p is dependent on endocytosis, autophagy and the terminal sequences of the permease.
The yeast high-affinity glucose transporters Hxt6p and Hxt7p are rapidly degraded during nitrogen starvation in the presence of high concentrations of fermentable carbon sources. Our results suggest that degradation is mainly due to the stimulation of general protein turnover and not caused by a mechanism specifically triggered by glucose. Analysis of Hxt6p/7p stability and cellular distribution in end4, aut2 and apg1 mutants indicates that Hxt7p is internalized by endocytosis, and autophagy is involved in the final delivery of Hxt7p to the vacuole for proteolytic degradation. Internalization and degradation of Hxt7p were blocked after truncation of its N-terminal hydrophilic domain. Nevertheless, this fully functional and stabilized hexose transporter could not maintain fermentation capacity of the yeast cells under starvation conditions, indicating a regulatory constraint on glucose uptake.
Krampe
Stefanie
S
Institut für Mikrobiologie, Heinrich-Heine-Universität, Universitätsstr. 1, Geb. 26.12.01, D-40225, Düsseldorf, Germany.
Boles
Eckhard
E
D000071187:Autophagy-Related Protein 5; D004705:Endocytosis / Q000502:physiology*; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D009584:Nitrogen / Q000172:deficiency / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D013217:Starvation / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases
C102268:ATG5 protein, S cerevisiae; D000071187:Autophagy-Related Protein 5; D005656:Fungal Proteins; C095258:HXT7 protein, S cerevisiae; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D044767:Ubiquitin-Protein Ligases; D009584:Nitrogen