The role of trehalose synthesis for the acquisition of thermotolerance in yeast

Abstract

In baker's yeast (Saccharomyces cerevisiae), accumulation of the non‐reducing disaccharide, trehalose, is triggered by stimuli that activate the heat‐shock response. Previously, trehalose levels have been shown to be closely correlated with thermotolerance, suggesting a protective function of this substance. Genetic evidence in support of this view is presented in an accompanying paper [De Virgilio, C., Hottiger, T., Dominguez, J., Boller, T. & Wiemken, A. (1993) Eur. J. Biochem. 219, 179–186]. In this study, we have examined the effect of trehalose on the thermal stability of proteins, a parameter thought to be a major determinant of thermotolerance. Physiological concentrations of trehalose (up to 0.5 M) were found to efficiently protect enzymes of yeast (glucose‐6P‐dehydrogenase, phosphoglucose‐isomerase) as well as enzymes of non‐yeast origin (bovine glutamic dehydrogenase, EcoRI) against heat inactivation in vitro. Trehalose also reduced the heat‐induced formation of protein aggregates. The disaccharide proved to be a compatible solute, as even at very high concentrations (up to 1 M) it did not significantly interfere with the activity of test enzymes. Trehalose was at least as good or better a protein stabilizer than any of a number of other compatible solutes (including sugars, polyalcohols and amino acids), while the structurally related trehalose‐6P was devoid of any protective effect. Thermoprotection of enzymes by trehalose was evident even in solutions containing high concentrations of yeast protein or substrate. The data indicate that trehalose accumulation may increase the thermotolerance of yeast by enhancing protein stability in intact cells.

The role of trehalose synthesis for the acquisition of thermotolerance in yeast

“…Similar restrictions may, in principle, apply to the experiments involving the izthl mutant strain. Finally, although trehalose synthesis is shown to be an important element of thermotolerance, our results suggest that trehalose accumulation is not the only mechanism by which yeast cells acquire thermotolerance and indeed a large number of alternatives have been suggested (Hottiger et al, 1993).…”

“…These data indicate an important role for the TPS2 gene in thermotolerance induction and suggest that accumulation of Tre6P instead of trehalose reduces thermotolerance. A possible explanation for this is provided by the fact that trehalose, but not Tre6P, is able to protect proteins against thermal denaturation (Hottiger et al, 1993). Thermotolerance and accumulation of trehalose in a stationary tps2 disruption mutant While wild-type cells (RH144-3 A) entering the stationary phase accumulated up to 1.0 g trehalose/g protein, cells of a tps2 disruption mutant (CDV64) accumulated up to 1.4 g Tre6Plg protein but almost no trehalose upon initiation of the stationary phase (data not shown).…”

Structural analysis of the subunits of the trehalose‐6‐phosphate synthase/phosphatase complex in Saccharomyces cerevisiae and their function during heat shock

“…It has been suggested, therefore, that trehalose plays a role as a stabiliser of cellular structures under stress conditions (Keller et al, 1982;Crowe et al, 1984). In accordance with this suggestion, in vitro studies have revealed the exceptional capability of trehalose in protecting biological membranes and enzymes from freezing-or drying-induced dehydration (for a review see Crowe et al, 1992) and heat stress (Hottiger et al, 1994).…”

Yeast metabolic and signaling genes are required for heat-shock survival and have little overlap with the heat-induced genes

“…Trehalose metabolism has been well described as a determinant for stress survival, including heat (20,(26)(27)(28). However, multiple roles have been ascribed to trehalose in mediating heat protection, and a detailed mechanistic role has not been completely determined.…”