title: PUFA-induced cell death is mediated by Yca1p-dependent and -independent pathways, and is reduced by vitamin C in yeast.
abstract: Polyunsaturated fatty acids (PUFA) such as linoleic acid (LA, n-6, C18:2) and γ-linolenic acid (GLA, n-6, C18:3) are essential and must be obtained from the diet. There has been a growing interest in establishing a bio-sustainable production of PUFA in several microorganisms, e.g. in yeast Saccharomyces cerevisiae. However, PUFAs can also be toxic to cells because of their susceptibility to peroxidation. Here we investigated the negative effects of LA and GLA production on S. cerevisiae by characterizing a strain expressing active Δ6 and Δ12 desaturases from the fungus Mucor rouxii. Previously, we showed that the PUFA-producing strain has low viability, down-regulated genes for oxidative stress response, and decreased proteasome activity. Here we show that the PUFA strain accumulates high levels of reactive oxygen species (ROS) and lipid peroxides, and accumulates damaged proteins. The PUFA strain also showed great increase in metacaspase Yca1p activity, suggesting cells could die by caspase-mediated cell death. When treated with antioxidant vitamin C, ROS, lipid peroxidation and protein carbonylation were greatly reduced, and the activity of the metacaspase was significantly decreased too, ultimately doubling the lifespan of the PUFA strain. When deleting YCA1, the caspase-like activity and the oxidative stress decreased and although the lifespan was slightly prolonged, the phenotype could not be fully reversed, pointing that Yca1p was not the main executor of cell death.
authors.affiliation: Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, SE-412 96, Gothenburg, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Johansson
authors.affiliation: Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, SE-412 96, Gothenburg, Sweden.
authors.forename: Xin
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, SE-412 96, Gothenburg, Sweden.
authors.forename: Stefina
authors.initials: S
authors.lastname: Milanova
authors.affiliation: Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, SE-412 96, Gothenburg, Sweden.
authors.forename: Cristiano
authors.initials: C
authors.lastname: Santos
authors.affiliation: Department of Biology and Biological Engineering, Chalmers University of Technology, Kemivägen 10, SE-412 96, Gothenburg, Sweden dina.petranovic@chalmers.se.
authors.forename: Dina
authors.initials: D
authors.lastname: Petranovic
mesh_terms: D001205:Ascorbic Acid; D020169:Caspases / Q000378:metabolism*; D016923:Cell Death; D003600:Cytosol / Q000737:chemistry; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism; D005227:Fatty Acids / Q000032:analysis; D005231:Fatty Acids, Unsaturated / Q000633:toxicity*; D053263:Gene Regulatory Networks; D050296:Microbial Viability / Q000187:drug effects; D009090:Mucorales / Q000201:enzymology / Q000235:genetics; D018384:Oxidative Stress; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D044943:Fatty Acid Desaturases; D020169:Caspases; C456272:MCA1 protein, S cerevisiae; D001205:Ascorbic Acid
keywords: Saccharomyces cerevisiae; caspase activation; lipid peroxidation; oxidative stress; polyunsaturated fatty acids; protein carbonylation