Figure 7.
Models of Fe trafficking in WT, Δccc1, and CCC1-up cells. In WT cells, Fe import is regulated by the concentration of cytosolic Fe C. Mitochondria and vacuoles compete to import C. The majority of C enters the vacuoles via Ccc1p. Once in the vacuole, vacuolar iron F2 is oxidized to HS FeIII (F3); at high pH, a portion of this Fe is converted into nanoparticles P. In Δccc1 cells, there is no Ccc1p-dependent Fe influx into vacuoles, so cytosolic Fe increases in concentration. This concentration exceeds a threshold value such that further import into the cell is inhibited. In CCC1-up cells, overexpression of CCC1 increases the flux of Fe into the vacuole, thereby decreasing the concentration of cytosolic Fe below a threshold value, such that Fe import into the cell is upregulated.