Engineering Inorganic Pyrophosphate Metabolism as a Strategy to Generate a Fluoride-Resistant Saccharomyces cerevisiae Strain

TL;DR

This paper shows how engineering pyrophosphatase metabolism in yeast can make it resistant to fluoride, a toxic anion found in the environment.

Contribution

The study introduces new genetic strategies to enhance fluoride resistance in yeast by modifying pyrophosphatase activity.

Findings

Overexpression of IPP1 or its human ortholog increases fluoride tolerance in yeast.

Substituting IPP1 with a fluoride-insensitive PPase from Streptococcus mutans also enhances resistance.

Maintaining PPase activity is crucial for yeast adaptation to high fluoride concentrations.

Abstract

Fluorine accounts for 0.3 g/kg of the Earth’s crust, being widely distributed in the environment as fluoride. The toxic effects of this anion in humans and other organisms have been known for a long time. Fluoride has been reported to alter several cellular processes although the mechanisms involved are largely unknown. Inorganic pyrophosphatases (PPases) are ubiquitous enzymes that hydrolyze inorganic pyrophosphate (PPi), a metabolite generated from ATP. In Saccharomyces cerevisiae, the enzyme responsible for PPi hydrolysis in the cytosol (IPP1) is strongly inhibited by fluoride in vitro. The essentiality of IPP1 for growth has been previously demonstrated using YPC3, a yeast mutant with conditional expression of the corresponding gene. Here, YPC3 was used to generate cells that tolerate high concentrations of fluoride by (a) the overexpression of IPP1 or its human ortholog, or (b) the substitution of IPP1 by the fluoride-insensitive PPase from Streptococcus mutans. The results obtained suggest that maintaining appropriate levels of PPase activity in the cytosol is essential for the adaptation of S. cerevisiae to high fluoride concentrations. The increase in fluoride tolerance allows YPC3 cells transformed with suitable plasmids to be selected on rich non-selective medium supplemented with this anion.

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