Figure 8.

Regulation of osmotic stress response by two-component system. Sln1p acts as an osmotic sensor protein to regulate the Hog1-MAPK signal transduction system in C. albicans. When the cells are in an isoosmotic or hypoosmotic environment, phosphorylation of Ssk1p inhibits activation of the Hog1-MAPK cascade, but in hyperosmotic cells, unphosphorylated Ssk1p activates the Ssk2/22 MAPKKK and subsequent phosphorylation of Pbs2p and Hog1p. Finally, the phosphorylated Hog1p is transferred to the nucleus, which activates transcription factors to induce the expression of GPD1, increasing the intracellular glycerol content to adapt to hyperosmotic stress