8-Dehydrosterols induce v-atpase dysfunction in yeast. Protective effect of an alternative H+-PUMP

Abstract

Toxic sterol precursors, such as 8-dehydrosterols, are present in a wide range of biologically relevant situations, from human rare diseases such as Conradi-Hünnermann-Happle Syndrome to amine fungicide-treated fungi and crops. However, the molecular and cellular bases of their toxicity are still obscure. Here we show that 8-dehydrosterols affect vacuole acidification producing Vma--like phenotypes in Saccharomyces cerevisiae. Upon expression of a gene construct of the proton-pumping membrane-embedded pyrophosphatase AVP1 from the plant Arabidopsis thaliana as an alternative proton pump, erg2 -derived strains revert their Vma--like phenotypes and wild-type cells can proliferate in the presence of lethal concentrations of tridemorph. Also, endo- and exocytotic defects in erg2 mutants are alleviated by the presence of a plant H+-pyrophosphatase. Despite their effect on endo/exocytic traffic, 8-dehydrosterols do not induce endoplasmic reticulum stress or assembly defects on the V-ATPase. On the contrary, they exert their influence directly at the vacuole level by inducing PEP4-dependent proteolytic degradation of V0 components, like a subunit Vph1p. These results can help to understand the etiology of sterol-related diseases, the fungicidal effect of amine compounds and the tolerance to this type of compounds observed in certain field fungi isolates and, in general, in plants.