The V-ATPase works in parallel with the HOG pathway to adapt yeast cells to osmotic stress.

Hyperosmotic stress activates an array of cellular detoxification mechanisms, including the high osmolarity glycerol (HOG) pathway. We report that vacuolar H(+)-ATPase (V-ATPase) activity helps provide osmotic tolerance in yeast. V-ATPase subunit genes exhibit complex haploinsufficiency interactions with HOG pathway components. vma mutants lacking V-ATPase function are sensitive to high concentrations ...
of salt and exhibit Hog1p activation even at low salt concentrations, as demonstrated by phosphorylation of Hog1p, a shift in Hog1-GFP localization, transcriptional activation of a subset of HOG pathway effectors, and transcriptional inhibition of parallel MAPK pathway targets. vma2Δhog1Δ and vma3Δpbs2Δ double mutants have a synthetic growth phenotype, poor salt tolerance, and an aberrant, hyper-elongated morphology on solid media, accompanied by activation of a FRE-LacZ construct, indicating crosstalk into the filamentous growth pathway. Vacuoles isolated from wild-type cells briefly exposed to salt show higher levels of V-ATPase activity, and Na(+)/H(+) exchange in isolated vacuolar vesicles suggests a biochemical basis for the genetic interactions observed. V-ATPase activity is upregulated during salt stress by increasing assembly of the catalytic V(1) sector with the membrane-bound V(o) sector. Together, these data suggest that the V-ATPase acts in parallel with the HOG pathway in order to mediate salt detoxification.
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Date: Dec. 30, 2011
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