Vacuolar H+-ATPase works in parallel with the HOG pathway to adapt Saccharomyces cerevisiae cells to osmotic stress.
Hyperosmotic stress activates an array of cellular detoxification mechanisms, including the high-osmolarity glycerol (HOG) pathway. We report here that vacuolar H(+)-ATPase (V-ATPase) activity helps provide osmotic tolerance in Saccharomyces cerevisiae. 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-green fluorescent protein localization, transcriptional activation of a subset of HOG pathway effectors, and transcriptional inhibition of parallel mitogen-activated protein kinase pathway targets. vma2Δ hog1Δ and vma3Δ pbs2Δ double mutants have a synthetic growth phenotype, poor salt tolerance, and an aberrant, hyper-elongated morphology on solid media, accompanied by activation of a filamentous response element-LacZ construct, indicating cross talk 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.
Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA.
Sheena Claire
SC
Li
Theodore T
TT
Diakov
Jason M
JM
Rizzo
Patricia M
PM
Kane
D000222:Adaptation, Physiological; D015966:Gene Expression Regulation, Fungal; D017930:Genes, Reporter; D005990:Glycerol / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D009994:Osmolar Concentration; D009997:Osmotic Pressure; D010766:Phosphorylation; D012441:Saccharomyces cerevisiae / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D055049:Salt Tolerance / Q000235:genetics; D015398:Signal Transduction / Q000502:physiology*; D014158:Transcription, Genetic; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*
D029701:Saccharomyces cerevisiae Proteins; D020928:Mitogen-Activated Protein Kinases; D025262:Vacuolar Proton-Translocating ATPases; D005990:Glycerol