FIG. 9.

Model for glucose sensing in C. albicans. The Hgt4 glucose sensor resides in the plasma membrane of cells. The C-terminal tail of Hgt4 associates with Std1, a transcriptional corepressor that also associates with the Rgt1 DNA-binding protein. Std1, together with Rgt1, represses expression of the HGT genes. Upon stimulation of the sensor by physiologic levels of glucose, Std1 is phosphorylated by Yck1, then ubiquitinated by SCF^Grr1, and finally degraded by the proteasome. Without Std1, Rgt1 is unable to repress transcription, leading to derepression of target genes such as those identified in Table 2.