Hog1MAPK
Hog1 MAPK is a serine/threonine protein kinase in the budding yeast Saccharomyces cerevisiae. It is the central effector of the High Osmolarity Glycerol (HOG) pathway and coordinates cellular adaptation to hyperosmotic stress. Upon osmotic shock, two upstream osmosensors transmit signals to Hog1 via the MAP kinase kinase Pbs2. The Sln1-Ypd1-Ssk1 branch and the Sho1 branch converge on Pbs2, which directly phosphorylates Hog1 at a conserved TXY activation motif. Phosphorylated Hog1 translocates to the nucleus and orchestrates transcriptional and metabolic changes necessary for osmotic tolerance.
Transcriptional responses include induction of glycerol biosynthesis and transport genes, notably GPD1 and GPP2, enabling accumulation
Regulation and termination: Hog1 activity is reversed by dual-specificity phosphatases Ptp2 and Ptp3, which dephosphorylate Hog1
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