title: ER stress induced by the OCH1 mutation triggers changes in lipid homeostasis in Kluyveromyces lactis.
abstract: In Kluyveromyces lactis yeast, OCH1 encodes for the α-1,6-mannosyltrasferase that adds the initial α-1,6-mannose to the outer-chains of N-glycoproteins. Kloch1-1 mutant cells showed altered calcium homeostasis and endoplasmic reticulum (ER) stress. Since ER plays a major role in lipid biosynthesis and lipid droplet (LD) formation, herein the impact of Och1p depletion on lipid homeostasis was investigated. Transcriptional profiles of genes involved in biosynthesis of fatty acids, their amount and composition changed in mutant cells. An increased amount of ergosterol was determined in these cells. Enhanced transcription of genes involved in both synthesis and mobilization of LDs was also found in Kloch1-1 cells, accompanied by a reduced amount of LDs. We provide evidence that ER alterations, determined by protein misfolding as a result of reduced N-glycosylation, induced altered lipid homeostasis in Kloch1-1 cells. Chemical chaperone 4-phenyl butyrate (4-PBA) slightly alleviated the LD phenotype in cells depleted of Och1p. Remarkably, complete suppression of ER stress, via increased expression of plasma membrane calcium channel subunit Mid1, fully restored lipid homeostasis in mutant cells. To further reinforce this finding, low numbers of LDs were observed in wild type cells when ER stress was triggered by DTT treatment.
authors.affiliation: Department of Biology and Biotechnology, Sapienza-University of Rome, Rome, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Zanni
authors.affiliation: Institute of Physics, University Cattolica del Sacro Cuore, Rome, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Maulucci
authors.affiliation: INAIL, Research, Certification and Control Division, DIT, Monteporzio Catone, Rome, Italy.
authors.forename: Donatella
authors.initials: D
authors.lastname: Pomata
authors.affiliation: Department of Chemistry, Sapienza-University of Rome, Rome, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Buiarelli
authors.affiliation: Institute of Translational Pharmacology, CNR, Rome, Italy.
authors.forename: Ewa K
authors.initials: EK
authors.lastname: Krasnowska
authors.affiliation: Institute of Translational Pharmacology, CNR, Rome, Italy.
authors.forename: Tiziana
authors.initials: T
authors.lastname: Parasassi
authors.affiliation: Institute of Physics, University Cattolica del Sacro Cuore, Rome, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: De Spirito
authors.affiliation: Department of Environmental Biotechnology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany.
authors.forename: Hermann J
authors.initials: HJ
authors.lastname: Heipieper
authors.affiliation: Department of Biology and Biotechnology, Sapienza-University of Rome, Rome, Italy. Electronic address: daniela.uccelletti@uniroma1.it.
authors.forename: Daniela
authors.initials: D
authors.lastname: Uccelletti
mesh_terms: D059865:Endoplasmic Reticulum Stress; D004875:Ergosterol; D005227:Fatty Acids / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D006031:Glycosylation; D006706:Homeostasis / Q000235:genetics; D007716:Kluyveromyces / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D050356:Lipid Metabolism / Q000235:genetics; D008364:Mannosyltransferases / Q000235:genetics* / Q000378:metabolism*; D009154:Mutation
chemical_list: D005227:Fatty Acids; D005656:Fungal Proteins; D008364:Mannosyltransferases; D004875:Ergosterol
keywords: 4-PBA; ER stress; Fatty acids; Lipid droplets; N-glycosylation