Nitrate and Phosphate Transporters Rescue Fluoride Toxicity in Yeast

Chem Res Toxicol. 2019 Nov 18;32(11):2305-2319. doi: 10.1021/acs.chemrestox.9b00315. Epub 2019 Oct 16.

Abstract

Organisms are exposed to fluoride in the air, water, and soil. Yeast and other microbes utilize fluoride channels as a method to prevent intracellular fluoride accumulation and mediate fluoride toxicity. Consequently, deletion of fluoride exporter genes (FEX) in S. cerevisiae resulted in over 1000-fold increased fluoride sensitivity. We used this FEX knockout strain to identify genes, that when overexpressed, are able to partially relieve the toxicity of fluoride exposure. Overexpression of five genes, SSU1, YHB1, IPP1, PHO87, and PHO90, increase fluoride tolerance by 2- to 10-fold. Overexpression of these genes did not provide improved fluoride resistance in wild-type yeast, suggesting that the mechanism is specific to low fluoride toxicity in yeast. Ssu1p and Yhb1p both function in nitrosative stress response, which is induced upon fluoride exposure along with metal influx. Ipp1p, Pho87p, and Pho90p increase intracellular orthophosphate. Consistent with this observation, fluoride toxicity is also partially mitigated by the addition of high levels of phosphate to the growth media. Fluoride inhibits phosphate import upon stress induction and causes nutrient starvation and organelle disruption, as supported by gene induction monitored through RNA-Seq. The combination of observations suggests that transmembrane nutrient transporters are among the most sensitized proteins during fluoride-instigated stress.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Anion Transport Proteins / genetics
  • Calcium / metabolism
  • Dioxygenases / genetics
  • Gene Expression Regulation, Fungal / drug effects*
  • Hemeproteins / genetics
  • Inorganic Pyrophosphatase / genetics
  • Mitochondria / drug effects
  • Mitochondria / metabolism
  • Nitrate Transporters
  • Nitrates / metabolism*
  • Nitrosative Stress
  • Phosphates / metabolism*
  • RNA-Seq
  • Saccharomyces cerevisiae / drug effects*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / genetics
  • Sodium Fluoride / toxicity*

Substances

  • Anion Transport Proteins
  • Hemeproteins
  • Nitrate Transporters
  • Nitrates
  • Phosphates
  • Saccharomyces cerevisiae Proteins
  • Ssu1 protein, S cerevisiae
  • Sodium Fluoride
  • Dioxygenases
  • YHB1 protein, S cerevisiae
  • IPP1 protein, S cerevisiae
  • Inorganic Pyrophosphatase
  • Calcium