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Li D, Rocha-Roa C, Schilling MA, Reinisch KM, Vanni S. Lipid scrambling is a general feature of protein insertases. Proc Natl Acad Sci U S A 2024; 121:e2319476121. [PMID: 38621120 PMCID: PMC11047089 DOI: 10.1073/pnas.2319476121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 03/13/2024] [Indexed: 04/17/2024] Open
Abstract
Glycerophospholipids are synthesized primarily in the cytosolic leaflet of the endoplasmic reticulum (ER) membrane and must be equilibrated between bilayer leaflets to allow the ER and membranes derived from it to grow. Lipid equilibration is facilitated by integral membrane proteins called "scramblases." These proteins feature a hydrophilic groove allowing the polar heads of lipids to traverse the hydrophobic membrane interior, similar to a credit card moving through a reader. Nevertheless, despite their fundamental role in membrane expansion and dynamics, the identity of most scramblases has remained elusive. Here, combining biochemical reconstitution and molecular dynamics simulations, we show that lipid scrambling is a general feature of protein insertases, integral membrane proteins which insert polypeptide chains into membranes of the ER and organelles disconnected from vesicle trafficking. Our data indicate that lipid scrambling occurs in the same hydrophilic channel through which protein insertion takes place and that scrambling is abolished in the presence of nascent polypeptide chains. We propose that protein insertases could have a so-far-overlooked role in membrane dynamics as scramblases.
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Affiliation(s)
- Dazhi Li
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT06520
| | - Cristian Rocha-Roa
- Department of Biology, University of Fribourg, FribourgCH-1700, Switzerland
| | - Matthew A. Schilling
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT06520
| | - Karin M. Reinisch
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT06520
| | - Stefano Vanni
- Department of Biology, University of Fribourg, FribourgCH-1700, Switzerland
- Swiss National Center for Competence in Research Bio-Inspired Materials, University of Fribourg, FribourgCH-1700, Switzerland
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2
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Li D, Rocha-Roa C, Schilling MA, Reinisch KM, Vanni S. Lipid scrambling is a general feature of protein insertases. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.01.555937. [PMID: 37693532 PMCID: PMC10491306 DOI: 10.1101/2023.09.01.555937] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Glycerophospholipids are synthesized primarily in the cytosolic leaflet of the endoplasmic reticulum (ER) membrane and must be equilibrated between bilayer leaflets to allow the ER and membranes derived from it to grow. Lipid equilibration is facilitated by integral membrane proteins called "scramblases". These proteins feature a hydrophilic groove allowing the polar heads of lipids to traverse the hydrophobic membrane interior, similar to a credit-card moving through a reader. Nevertheless, despite their fundamental role in membrane expansion and dynamics, the identity of most scramblases has remained elusive. Here, combining biochemical reconstitution and molecular dynamics simulations, we show that lipid scrambling is a general feature of protein insertases, integral membrane proteins which insert polypeptide chains into membranes of the ER and organelles disconnected from vesicle trafficking. Our data indicate that lipid scrambling occurs in the same hydrophilic channel through which protein insertion takes place, and that scrambling is abolished in the presence of nascent polypeptide chains. We propose that protein insertases could have a so-far overlooked role in membrane dynamics as scramblases.
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Affiliation(s)
- Dazhi Li
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | | | - Matthew A Schilling
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Karin M Reinisch
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Stefano Vanni
- Department of Biology, University of Fribourg, Switzerland
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3
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Farkas Á, Urlaub H, Bohnsack KE, Schwappach B. Regulated targeting of the monotopic hairpin membrane protein Erg1 requires the GET pathway. J Biophys Biochem Cytol 2022; 221:213228. [PMID: 35587358 PMCID: PMC9123286 DOI: 10.1083/jcb.202201036] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 03/27/2022] [Accepted: 04/12/2022] [Indexed: 02/08/2023] Open
Abstract
The guided entry of tail-anchored proteins (GET) pathway targets C-terminally anchored transmembrane proteins and protects cells from lipotoxicity. Here, we reveal perturbed ergosterol production in ∆get3 cells and demonstrate the sensitivity of GET pathway mutants to the sterol synthesis inhibiting drug terbinafine. Our data uncover a key enzyme of sterol synthesis, the hairpin membrane protein squalene monooxygenase (Erg1), as a non-canonical GET pathway client, thus rationalizing the lipotoxicity phenotypes of GET pathway mutants. Get3 recognizes the hairpin targeting element of Erg1 via its classical client-binding pocket. Intriguingly, we find that the GET pathway is especially important for the acute upregulation of Erg1 induced by low sterol conditions. We further identify several other proteins anchored to the endoplasmic reticulum (ER) membrane exclusively via a hairpin as putative clients of the GET pathway. Our findings emphasize the necessity of dedicated targeting pathways for high-efficiency targeting of particular clients during dynamic cellular adaptation and highlight hairpin proteins as a potential novel class of GET clients.
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Affiliation(s)
- Ákos Farkas
- Department of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany
| | - Henning Urlaub
- Bioanalytic Mass Spectrometry, Max-Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Bioanalytics, Institute of Clinical Chemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Katherine E Bohnsack
- Department of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany
| | - Blanche Schwappach
- Department of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany
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4
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Loss of SNORA73 reprograms cellular metabolism and protects against steatohepatitis. Nat Commun 2021; 12:5214. [PMID: 34471131 PMCID: PMC8410784 DOI: 10.1038/s41467-021-25457-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Accepted: 08/06/2021] [Indexed: 02/07/2023] Open
Abstract
Dyslipidemia and resulting lipotoxicity are pathologic signatures of metabolic syndrome and type 2 diabetes. Excess lipid causes cell dysfunction and induces cell death through pleiotropic mechanisms that link to oxidative stress. However, pathways that regulate the response to metabolic stress are not well understood. Herein, we show that disruption of the box H/ACA SNORA73 small nucleolar RNAs encoded within the small nucleolar RNA hosting gene 3 (Snhg3) causes resistance to lipid-induced cell death and general oxidative stress in cultured cells. This protection from metabolic stress is associated with broad reprogramming of oxidative metabolism that is dependent on the mammalian target of rapamycin signaling axis. Furthermore, we show that knockdown of SNORA73 in vivo protects against hepatic steatosis and lipid-induced oxidative stress and inflammation. Our findings demonstrate a role for SNORA73 in the regulation of metabolism and lipotoxicity.
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5
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Pačnik K, Ogrizović M, Diepold M, Eisenberg T, Žganjar M, Žun G, Kužnik B, Gostinčar C, Curk T, Petrovič U, Natter K. Identification of novel genes involved in neutral lipid storage by quantitative trait loci analysis of Saccharomyces cerevisiae. BMC Genomics 2021; 22:110. [PMID: 33563210 PMCID: PMC7871550 DOI: 10.1186/s12864-021-07417-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 01/31/2021] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND The accumulation of intracellular fat depots is a polygenic trait. Therefore, the extent of lipid storage in the individuals of a species covers a broad range and is determined by many genetic factors. Quantitative trait loci analysis can be used to identify those genetic differences between two strains of the same species that are responsible for the differences in a given phenotype. We used this method and complementary approaches to identify genes in the yeast Saccharomyces cerevisiae that are involved in neutral lipid storage. RESULTS We selected two yeast strains, the laboratory strain BY4741 and the wine yeast AWRI1631, with a more than two-fold difference in neutral lipid content. After crossing, sporulation and germination, we used fluorescence activated cell sorting to isolate a subpopulation of cells with the highest neutral lipid content from the pool of segregants. Whole genome sequencing of this subpopulation and of the unsorted pool of segregants implicated several loci that are involved in lipid accumulation. Three of the identified genes, PIG1, PHO23 and RML2, were investigated in more detail. Deletions of these genes and the exchange of the alleles between the two parental strains confirmed that the encoded proteins contribute to neutral lipid storage in S. cerevisiae and that PIG1, PHO23 and RML2 are the major causative genes. Backcrossing of one of the segregants with the parental strains for seven generations revealed additional regions in the genomes of both strains with potential causative genes for the high lipid accumulation phenotype. CONCLUSIONS We identified several genes that contribute to the phenotype of lipid accumulation in an allele-specific manner. Surprisingly, no allelic variations of genes with known functions in lipid metabolism were found, indicating that the level of storage lipid accumulation is determined by many cellular processes that are not directly related to lipid metabolism.
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Affiliation(s)
- Klavdija Pačnik
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
| | - Mojca Ogrizović
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Matthias Diepold
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
| | - Tobias Eisenberg
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
- BioTechMed-Graz, Graz, Austria
- Field of Excellence BioHealth - University of Graz, Graz, Austria
| | - Mia Žganjar
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia
| | - Gašper Žun
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia
| | - Beti Kužnik
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Cene Gostinčar
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
- Department of Biology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Tomaž Curk
- Faculty of Computer and Information Science, University of Ljubljana, Ljubljana, Slovenia
| | - Uroš Petrovič
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Ljubljana, Slovenia.
- Department of Biology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.
| | - Klaus Natter
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria.
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Wickramatunga PGTS, Gunawardene YINS, Wijesinghe KJ, Ellepola ANB, Dassanayake RS. RNAi-mediated silencing of ARV1 in Setaria digitata impairs in-vitro microfilariae release, embryogenesis and adult parasite viability. Vet Parasitol 2020; 284:109189. [PMID: 32739751 DOI: 10.1016/j.vetpar.2020.109189] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Revised: 07/15/2020] [Accepted: 07/16/2020] [Indexed: 02/01/2023]
Abstract
Setaria digitata is a nematode that resides in the peritoneal cavity of ruminants causing cerebrospinal nematodiasis disease affecting livestock and inflicting significant economic forfeitures in Asia. Further, this nematode can infect humans, causing abscesses, allergic reactions, enlarged lymph nodes, eye lesions and inflammation of the lungs. The 'ARE2 required for viability1' (ARV1) encodes for putative lipid transporter localized in the endoplasmic reticulum (ER) and Golgi complex membrane in humans and yeast. In the present study, the functional role of S. digitata ARV1 (SD-ARV1) was investigated using RNA interference (RNAi) reverse genetic tool. The targeted silencing SD-ARV1 transcripts by siRNA mediated RNAi resulted in a dramatic reduction of SD-ARV1 gene and protein expressions in S. digitata, which in turn modulated the parasitic motility, its production of eggs and microfilaria viability. Further, the same silencing caused severe phenotypic deformities such as distortion of eggs and embryonic development arrest in the intrauterine stages of adult female S. digitata. These results suggest that SD-ARV1 plays a pivotal role in worm embryogenesis, adult parasite motility and microfilariae viability. Finally, the ubiquitous presence of ARV1 in human filarial nematodes, its crucial functional roles in nematode biology and its remarkable diversity in primary protein structure compared to homologues in their hosts warrants further investigations to ascertain its candidacy in anthelmintic drug development.
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Affiliation(s)
| | | | - Kaveesha Jayani Wijesinghe
- Department of Chemistry, Faculty of Science, University of Colombo, PO 1490, Kumaratunga Munidasa Mawatha, Colombo, 00300, Sri Lanka
| | - Arjuna N B Ellepola
- Division of Oral Microbiology, Faculty of Dentistry, Health Sciences Center, Kuwait University, Kuwait
| | - Ranil Samantha Dassanayake
- Department of Chemistry, Faculty of Science, University of Colombo, PO 1490, Kumaratunga Munidasa Mawatha, Colombo, 00300, Sri Lanka.
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7
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An Erg11 lanosterol 14-α-demethylase-Arv1 complex is required for Candida albicans virulence. PLoS One 2020; 15:e0235746. [PMID: 32678853 PMCID: PMC7367482 DOI: 10.1371/journal.pone.0235746] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 06/23/2020] [Indexed: 02/07/2023] Open
Abstract
Azole resistant fungal infections remain a health problem for the immune compromised. Current therapies are limited due to rises in new resistance mechanisms. Therefore, it is important to identify new drug targets for drug discovery and novel therapeutics. Arv1 (are1 are2required for viability 1) function is highly conserved between multiple pathogenic fungal species. Candida albicans (C. albicans) cells lacking CaArv1 are azole hypersusceptible and lack virulence. Saccharomyces cerevisiae (S. cerevisiae) Scarv1 cells are also azole hypersusceptible, a phenotype reversed by expression of CaArv1, indicating conservation in the molecular mechanism for azole susceptibility. To define the relationship between Arv1 function and azole susceptibility, we undertook a structure/function analysis of ScArv1. We identified several conserved amino acids within the ScArv1 homology domain (ScAhd) required for maintaining normal azole susceptibility. Erg11 lanosterol 14-α-demethylase is the rate-limiting enzyme in sterol biosynthesis and is the direct target of azole antifungals, so we used our ScArv1 mutants in order to explore the relationship between ScArv1 and ScErg11. Specific ScArv1 mutants ectopically expressed from a low copy plasmid were unable to restore normal azole susceptibility to Scarv1 cells and had reduced Erg11 protein levels. Erg11 protein stability depended on its ability to form a heterodimeric complex with Arv1. Complex formation was required for maintaining normal azole susceptibility. Scarv1 cells expressing orthologous CaArv1 mutants also had reduced CaErg11 levels, were unable to form a CaArv1-CaErg11 complex, and were azole hypersusceptible. Scarv1 cells expressing CaArv1 mutants unable to interact with CaErg11 could not sustain proper levels of the azole resistant CaErg11Y132F F145L protein. Caarv1/Caarv1 cells expressing CaArv1 mutants unable to interact with CaErg11 were found to lack virulence using a disseminated candidiasis mouse model. Expressing CaErg11Y132F F145L did not reverse the lack of virulence. We hypothesize that the role of Arv1 in Erg11-dependent azole resistance is to stabilize Erg11 protein level. Arv1 inhibition may represent an avenue for treating azole resistance.
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8
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Okai H, Ikema R, Nakamura H, Kato M, Araki M, Mizuno A, Ikeda A, Renbaum P, Segel R, Funato K. Cold‐sensitive phenotypes of a yeast null mutant of ARV1 support its role as a GPI flippase. FEBS Lett 2020; 594:2431-2439. [DOI: 10.1002/1873-3468.13843] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 05/11/2020] [Accepted: 05/11/2020] [Indexed: 11/10/2022]
Affiliation(s)
- Haruka Okai
- School of Applied Biological Science Hiroshima University Higashi‐Hiroshima Japan
| | - Ryoko Ikema
- Graduate School of Integrated Sciences for Life Hiroshima University Higashi‐Hiroshima Japan
| | - Hiroki Nakamura
- Graduate School of Biosphere Science Hiroshima University Higashi‐Hiroshima Japan
| | - Mei Kato
- Graduate School of Integrated Sciences for Life Hiroshima University Higashi‐Hiroshima Japan
| | - Misako Araki
- Graduate School of Integrated Sciences for Life Hiroshima University Higashi‐Hiroshima Japan
| | - Ayumi Mizuno
- School of Applied Biological Science Hiroshima University Higashi‐Hiroshima Japan
| | - Atsuko Ikeda
- Graduate School of Biosphere Science Hiroshima University Higashi‐Hiroshima Japan
| | - Paul Renbaum
- Medical Genetics Institute Shaare Zedek Medical Center Jerusalem Israel
| | - Reeval Segel
- Medical Genetics Institute Shaare Zedek Medical Center Jerusalem Israel
| | - Kouichi Funato
- School of Applied Biological Science Hiroshima University Higashi‐Hiroshima Japan
- Graduate School of Integrated Sciences for Life Hiroshima University Higashi‐Hiroshima Japan
- Graduate School of Biosphere Science Hiroshima University Higashi‐Hiroshima Japan
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9
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Mokhtari M, Jackson MD, Brown AS, Ackerley DF, Ritson NJ, Keyzers RA, Munkacsi AB. Bioactivity-Guided Metabolite Profiling of Feijoa ( Acca sellowiana) Cultivars Identifies 4-Cyclopentene-1,3-dione as a Potent Antifungal Inhibitor of Chitin Synthesis. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2018; 66:5531-5539. [PMID: 29546758 DOI: 10.1021/acs.jafc.7b06154] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Pathogenic fungi continue to develop resistance against current antifungal drugs. To explore the potential of agricultural waste products as a source of novel antifungal compounds, we obtained an unbiased GC-MS profile of 151 compounds from 16 commercial and experimental cultivars of feijoa peels. Multivariate analysis correlated 93% of the compound profiles with antifungal bioactivities. Of the 18 compounds that significantly correlated with antifungal activity, 5 had not previously been described from feijoa. Two novel cultivars were the most bioactive, and the compound 4-cyclopentene-1,3-dione, detected in these cultivars, was potently antifungal (IC50 = 1-2 μM) against human-pathogenic Candida species. Haploinsufficiency and fluorescence microscopy analyses determined that the synthesis of chitin, a fungal-cell-wall polysaccharide, was the target of 4-cyclopentene-1,3-dione. This fungal-specific mechanism was consistent with a 22-70-fold reduction in antibacterial activity. Overall, we identified the agricultural waste product of specific cultivars of feijoa peels as a source of potential high-value antifungal compounds.
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Affiliation(s)
- Mona Mokhtari
- School of Biological Sciences , Victoria University of Wellington , Wellington 6012 , New Zealand
| | - Michael D Jackson
- School of Biological Sciences , Victoria University of Wellington , Wellington 6012 , New Zealand
| | - Alistair S Brown
- School of Biological Sciences , Victoria University of Wellington , Wellington 6012 , New Zealand
| | - David F Ackerley
- School of Biological Sciences , Victoria University of Wellington , Wellington 6012 , New Zealand
- Centre for Biodiscovery , Victoria University of Wellington , Wellington 6012 , New Zealand
| | | | - Robert A Keyzers
- Centre for Biodiscovery , Victoria University of Wellington , Wellington 6012 , New Zealand
- School of Chemical and Physical Sciences , Victoria University of Wellington , Wellington 6012 , New Zealand
| | - Andrew B Munkacsi
- School of Biological Sciences , Victoria University of Wellington , Wellington 6012 , New Zealand
- Centre for Biodiscovery , Victoria University of Wellington , Wellington 6012 , New Zealand
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10
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Chuartzman SG, Schuldiner M. Database for High Throughput Screening Hits (dHITS): a simple tool to retrieve gene specific phenotypes from systematic screens done in yeast. Yeast 2018; 35:477-483. [PMID: 29574976 PMCID: PMC6055851 DOI: 10.1002/yea.3312] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 03/04/2018] [Accepted: 03/07/2018] [Indexed: 12/21/2022] Open
Abstract
In the last decade several collections of Saccharomyces cerevisiae yeast strains have been created. In these collections every gene is modified in a similar manner such as by a deletion or the addition of a protein tag. Such libraries have enabled a diversity of systematic screens, giving rise to large amounts of information regarding gene functions. However, often papers describing such screens focus on a single gene or a small set of genes and all other loci affecting the phenotype of choice (‘hits’) are only mentioned in tables that are provided as supplementary material and are often hard to retrieve or search. To help unify and make such data accessible, we have created a Database of High Throughput Screening Hits (dHITS). The dHITS database enables information to be obtained about screens in which genes of interest were found as well as the other genes that came up in that screen – all in a readily accessible and downloadable format. The ability to query large lists of genes at the same time provides a platform to easily analyse hits obtained from transcriptional analyses or other screens. We hope that this platform will serve as a tool to facilitate investigation of protein functions to the yeast community.
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Affiliation(s)
- Silvia G Chuartzman
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, 7610001, Israel
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11
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Gallo-Ebert C, Francisco J, Liu HY, Draper R, Modi K, Hayward MD, Jones BK, Buiakova O, McDonough V, Nickels JT. Mice lacking ARV1 have reduced signs of metabolic syndrome and non-alcoholic fatty liver disease. J Biol Chem 2018; 293:5956-5974. [PMID: 29491146 DOI: 10.1074/jbc.ra117.000800] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2017] [Revised: 02/27/2018] [Indexed: 12/13/2022] Open
Abstract
Metabolic syndrome (MetS) is a term used to characterize individuals having at least three of the following diseases: obesity, dyslipidemia, hyperglycemia, insulin resistance, hypertension, and nonalcoholic fatty liver disease (NAFLD). It is widespread, and the number of individuals with MetS is increasing. However, the events leading to the manifestation of MetS are not well-understood. Here, we show that loss of murine ARV1 (mARV1) results in resistance to acquiring diseases associated with MetS. Arv1-/- animals fed a high-fat diet were resistant to diet-induced obesity, had lower blood cholesterol and triglyceride levels, and retained glucose tolerance and insulin sensitivity. Livers showed no gross morphological changes, contained lower levels of cholesterol, triglycerides, and fatty acids, and showed fewer signs of NAFLD. Knockout animals had elevated levels of liver farnesol X receptor (FXR) protein and its target, small heterodimer protein (SHP). They also had decreased levels of CYP7α1, CYP8β1, and mature SREBP1 protein, evidence suggesting that liver FXR signaling was activated. Strengthening this hypothesis was the fact that peroxisome proliferator-activating receptor α (PPARα) protein was elevated, along with its target, fibroblast growth factor 21 (FGF21). Arv1-/- animals excreted more fecal cholesterol, free fatty acids, and bile acids. Their small intestines had 1) changes in bile acid composition, 2) an increase in the level of the intestinal FXR antagonist, tauromuricholic acid, and 3) showed signs of attenuated FXR signaling. Overall, we believe that ARV1 function is deleterious when consuming a high-fat diet. We further hypothesize that ARV1 is critical for initiating events required for the progression of diseases associated with MetS and NAFLD.
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Affiliation(s)
- Christina Gallo-Ebert
- From the Institute of Metabolic Disorders, Genesis Biotechnology Group, Hamilton, New Jersey 08691
| | - Jamie Francisco
- From the Institute of Metabolic Disorders, Genesis Biotechnology Group, Hamilton, New Jersey 08691
| | - Hsing-Yin Liu
- From the Institute of Metabolic Disorders, Genesis Biotechnology Group, Hamilton, New Jersey 08691
| | | | - Kinnari Modi
- From the Institute of Metabolic Disorders, Genesis Biotechnology Group, Hamilton, New Jersey 08691
| | - Michael D Hayward
- Invivotek, Genesis Biotechnology Group, Hamilton, New Jersey 08691, and
| | - Beverly K Jones
- Invivotek, Genesis Biotechnology Group, Hamilton, New Jersey 08691, and
| | - Olesia Buiakova
- Invivotek, Genesis Biotechnology Group, Hamilton, New Jersey 08691, and
| | | | - Joseph T Nickels
- From the Institute of Metabolic Disorders, Genesis Biotechnology Group, Hamilton, New Jersey 08691, .,the Rutgers Center for Lipid Research, New Jersey Institute for Food, Nutrition, and Health, Rutgers University, New Brunswick, New Jersey 08901
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12
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Coradetti ST, Pinel D, Geiselman GM, Ito M, Mondo SJ, Reilly MC, Cheng YF, Bauer S, Grigoriev IV, Gladden JM, Simmons BA, Brem RB, Arkin AP, Skerker JM. Functional genomics of lipid metabolism in the oleaginous yeast Rhodosporidium toruloides. eLife 2018. [PMID: 29521624 PMCID: PMC5922974 DOI: 10.7554/elife.32110] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The basidiomycete yeast Rhodosporidium toruloides (also known as Rhodotorula toruloides) accumulates high concentrations of lipids and carotenoids from diverse carbon sources. It has great potential as a model for the cellular biology of lipid droplets and for sustainable chemical production. We developed a method for high-throughput genetics (RB-TDNAseq), using sequence-barcoded Agrobacterium tumefaciens T-DNA insertions. We identified 1,337 putative essential genes with low T-DNA insertion rates. We functionally profiled genes required for fatty acid catabolism and lipid accumulation, validating results with 35 targeted deletion strains. We identified a high-confidence set of 150 genes affecting lipid accumulation, including genes with predicted function in signaling cascades, gene expression, protein modification and vesicular trafficking, autophagy, amino acid synthesis and tRNA modification, and genes of unknown function. These results greatly advance our understanding of lipid metabolism in this oleaginous species and demonstrate a general approach for barcoded mutagenesis that should enable functional genomics in diverse fungi. The fungus Rhodosporidium toruloides can grow on substances extracted from plant matter that is inedible to humans such as corn stalks, wood pulp, and grasses. Under some growth conditions, the fungus can accumulate massive stores of hydrocarbon-rich fats and pigments. A community of scientists and engineers has begun genetically modifying R. toruloides to convert these naturally produced fats and pigments into fuels, chemicals and medicines. These could form sustainable replacements for products made from petroleum or harvested from threatened animal and plant species. Fungi, plants, animals and other eukaryotes store fat in specialized compartments called lipid droplets. The genes that control the metabolism – the production, use and storage – of fat in lipid bodies have been studied in certain eukaryotes, including species of yeast. However, R. toruloides is only distantly related to the most well-studied of these species. This means that we cannot be certain that a gene will play the same role in R. toruloides as in those species. To assemble the most comprehensive list possible of the genes in R. toruloides that affect the production, use, or storage of fat in lipid bodies, Coradetti, Pinel et al. constructed a population of hundreds of thousands of mutant fungal strains, each with its own unique DNA ‘barcode’. The effects that mutations in over 6,000 genes had on growth and fat accumulation in these fungi were measured simultaneously in several experiments. This general approach is not new, but technical limitations had, until now, restricted its use in fungi to a few species. Coradetti, Pinel et al. identified hundreds of genes that affected the ability of R. toruloides to metabolise fat. Many of these genes were related to genes with known roles in fat metabolism in other eukaryotes. Other genes are involved in different cell processes, such as the recycling of waste products in the cell. Their identification adds weight to the view that the links between these cellular processes and fat metabolism are deep and widespread amongst eukaryotes. Finally, some of the genes identified by Coradetti, Pinel et al. are not closely related to any well-studied genes. Further study of these genes could help us to understand why R. toruloides can accumulate much larger amounts of fat than most other fungi. The methods developed by Coradetti, Pinel et al. should be possible to implement in many species of fungi. As a result these techniques may eventually contribute to the development of new treatments for human fungal diseases, the protection of important food crops, and a deeper understanding of the roles various fungi play in the broader ecosystem.
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Affiliation(s)
| | - Dominic Pinel
- Energy Biosciences Institute, Berkeley, United States
| | | | - Masakazu Ito
- Energy Biosciences Institute, Berkeley, United States
| | - Stephen J Mondo
- United States Department of Energy Joint Genome Institute, Walnut Creek, United States
| | - Morgann C Reilly
- Joint BioEnergy Institute, Emeryville, United States.,Chemical and Biological Processes Development Group, Pacific Northwest National Laboratory, Richland, United States
| | - Ya-Fang Cheng
- Energy Biosciences Institute, Berkeley, United States
| | - Stefan Bauer
- Energy Biosciences Institute, Berkeley, United States
| | - Igor V Grigoriev
- United States Department of Energy Joint Genome Institute, Walnut Creek, United States.,Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, United States.,Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | | | - Blake A Simmons
- Joint BioEnergy Institute, Emeryville, United States.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Rachel B Brem
- The Buck Institute for Research on Aging, Novato, United States.,Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, United States
| | - Adam P Arkin
- Energy Biosciences Institute, Berkeley, United States.,Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, United States.,Department of Bioengineering, University of California, Berkeley, Berkeley, United States
| | - Jeffrey M Skerker
- Energy Biosciences Institute, Berkeley, United States.,Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, United States.,Department of Bioengineering, University of California, Berkeley, Berkeley, United States
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13
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Wang Q, Du X, Ma K, Shi P, Liu W, Sun J, Peng M, Huang Z. A critical role for very long-chain fatty acid elongases in oleic acid-mediated Saccharomyces cerevisiae cytotoxicity. Microbiol Res 2018; 207:1-7. [DOI: 10.1016/j.micres.2017.11.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 11/03/2017] [Accepted: 11/04/2017] [Indexed: 11/28/2022]
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14
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Graef M. Lipid droplet-mediated lipid and protein homeostasis in budding yeast. FEBS Lett 2018; 592:1291-1303. [PMID: 29397034 PMCID: PMC5947121 DOI: 10.1002/1873-3468.12996] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Revised: 01/24/2018] [Accepted: 01/25/2018] [Indexed: 12/25/2022]
Abstract
Lipid droplets are conserved specialized organelles that store neutral lipids. Our view on this unique organelle has evolved from a simple fat deposit to a highly dynamic and functionally diverse hub—one that mediates the buffering of fatty acid stress and the adaptive reshaping of lipid metabolism to promote membrane and organelle homeostasis and the integrity of central proteostasis pathways, including autophagy, which ensure stress resistance and cell survival. This Review will summarize the recent developments in the budding yeast Saccharomyces cerevisiae, as this model organism has been instrumental in deciphering the fundamental mechanisms and principles of lipid droplet biology and interconnecting lipid droplets with many unanticipated cellular functions applicable to many other cell systems.
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Affiliation(s)
- Martin Graef
- Max Planck Institute for Biology of Ageing, Cologne, Germany.,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
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15
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Yeast Cells Exposed to Exogenous Palmitoleic Acid Either Adapt to Stress and Survive or Commit to Regulated Liponecrosis and Die. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2018; 2018:3074769. [PMID: 29636840 PMCID: PMC5831759 DOI: 10.1155/2018/3074769] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2017] [Revised: 11/27/2017] [Accepted: 12/20/2017] [Indexed: 12/11/2022]
Abstract
A disturbed homeostasis of cellular lipids and the resulting lipotoxicity are considered to be key contributors to many human pathologies, including obesity, metabolic syndrome, type 2 diabetes, cardiovascular diseases, and cancer. The yeast Saccharomyces cerevisiae has been successfully used for uncovering molecular mechanisms through which impaired lipid metabolism causes lipotoxicity and elicits different forms of regulated cell death. Here, we discuss mechanisms of the “liponecrotic” mode of regulated cell death in S. cerevisiae. This mode of regulated cell death can be initiated in response to a brief treatment of yeast with exogenous palmitoleic acid. Such treatment prompts the incorporation of exogenously added palmitoleic acid into phospholipids and neutral lipids. This orchestrates a global remodeling of lipid metabolism and transfer in the endoplasmic reticulum, mitochondria, lipid droplets, and the plasma membrane. Certain features of such remodeling play essential roles either in committing yeast to liponecrosis or in executing this mode of regulated cell death. We also outline four processes through which yeast cells actively resist liponecrosis by adapting to the cellular stress imposed by palmitoleic acid and maintaining viability. These prosurvival cellular processes are confined in the endoplasmic reticulum, lipid droplets, peroxisomes, autophagosomes, vacuoles, and the cytosol.
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16
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An ARV1 homologue from a filarial nematode is functional in yeast. J Helminthol 2017; 93:12-20. [PMID: 29183411 DOI: 10.1017/s0022149x17001109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The transmembrane protein, ARV1, plays a key role in intracellular sterol homeostasis by controlling sterol distribution and cellular uptake. To date, only the ARV1s from yeast and humans have been characterized to some extent. In this study, the ARV1 of an animal filarial parasite, Setaria digitata (SdARV1), was characterized; its cDNA was 761 bp and encoded a protein of 217 amino acids, with a predicted molecular weight of 25 kDa, containing a highly conserved ARV1 homology domain and three transmembrane domains in the bioinformatic analyses. Information required to cluster members belonging to a particular taxon has been revealed in phylogenetic analyses of ARV1 sequences derived from different organisms. Reverse transcription-polymerase chain reaction (RT-PCR) analyses indicated that SdARV1 was expressed in different developmental stages - microfilariae and adult male and female worms. Experiments carried out with a single copy of the SdARV1 under the control of the PMA-1 promoter in a temperature-sensitive Saccharomyces cerevisiae mutant strain indicated full complementation of the mutant phenotype, with growth at a non-permissive temperature (37°C). Microscopic observations of cellular morphology with Gram staining revealed alteration of the shape from shrunken to oval, in mutant and complemented strains, respectively. Assessment of free sterol levels extracted from mutant yeast and complemented strains indicated that the level of sterol was significantly higher in the former compared to the latter, which had sterol levels similar to those of the wild type. Thus, the results of the current study suggest that SdARV1 is ubiquitously expressed in different developmental stages of S. digitata, and that it is a true functional homologue of mammalian and yeast ARV1s, which have crucial phylogenetic information that follows classical evolutionary trends. Finally, this is the first study to report the biological function of nematode ARV1.
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17
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Rajakumar T, Munkacsi AB, Sturley SL. Exacerbating and reversing lysosomal storage diseases: from yeast to humans. MICROBIAL CELL 2017; 4:278-293. [PMID: 28913343 PMCID: PMC5597791 DOI: 10.15698/mic2017.09.588] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Lysosomal storage diseases (LSDs) arise from monogenic deficiencies in lysosomal proteins and pathways and are characterized by a tissue-wide accumulation of a vast variety of macromolecules, normally specific to each genetic lesion. Strategies for treatment of LSDs commonly depend on reduction of the offending metabolite(s) by substrate depletion or enzyme replacement. However, at least 44 of the ~50 LSDs are currently recalcitrant to intervention. Murine models have provided significant insights into our understanding of many LSD mechanisms; however, these systems do not readily permit phenotypic screening of compound libraries, or the establishment of genetic or gene-environment interaction networks. Many of the genes causing LSDs are evolutionarily conserved, thus facilitating the application of models system to provide additional insight into LSDs. Here, we review the utility of yeast models of 3 LSDs: Batten disease, cystinosis, and Niemann-Pick type C disease. We will focus on the translation of research from yeast models into human patients suffering from these LSDs. We will also discuss the use of yeast models to investigate the penetrance of LSDs, such as Niemann-Pick type C disease, into more prevalent syndromes including viral infection and obesity.
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Affiliation(s)
- Tamayanthi Rajakumar
- School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand 6012
| | - Andrew B Munkacsi
- School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand 6012.,Centre for Biodiscovery, Victoria University of Wellington, Wellington, New Zealand 6012
| | - Stephen L Sturley
- Department of Genetics and Development, Columbia University Medical Center, New York, NY 10032
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18
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Recent Advances in Ergosterol Biosynthesis and Regulation Mechanisms in Saccharomyces cerevisiae. Indian J Microbiol 2017; 57:270-277. [PMID: 28904410 DOI: 10.1007/s12088-017-0657-1] [Citation(s) in RCA: 104] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 06/27/2017] [Indexed: 01/04/2023] Open
Abstract
Ergosterol, an important component of the fungal cell membrane, is not only essential for fungal growth and development but also very important for adaptation to stress in fungi. Ergosterol is also a direct precursor for steroid drugs. The biosynthesis of ergosterol can be divided into three modules: mevalonate, farnesyl pyrophosphate (farnesyl-PP) and ergosterol biosynthesis. The regulation of ergosterol content is mainly achieved by feedback regulation of ergosterol synthase activity through transcription, translation and posttranslational modification. The synthesis of HMG-CoA, catalyzed by HMGR, is a major metabolic check point in ergosterol biosynthesis. Excessive sterols can be subsequently stored in lipid droplets or secreted into the extracellular milieu by esterification or acetylation to avoid toxic effects. As sterols are insoluble, the intracellular transport of ergosterol in cells requires transporters. In recent years, great progress has been made in understanding ergosterol biosynthesis and its regulation in Saccharomyces cerevisiae. However, few reviews have focused on these studies, especially the regulation of biosynthesis and intracellular transport. Therefore, this review summarizes recent research progress on the physiological functions, biosynthesis, regulation of biosynthesis and intracellular transportation of ergosterol in S. cerevisiae.
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19
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Ballweg S, Ernst R. Control of membrane fluidity: the OLE pathway in focus. Biol Chem 2017; 398:215-228. [DOI: 10.1515/hsz-2016-0277] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 10/18/2016] [Indexed: 11/15/2022]
Abstract
Abstract
The maintenance of a fluid lipid bilayer is key for membrane integrity and cell viability. We are only beginning to understand how eukaryotic cells sense and maintain the characteristic lipid compositions and bulk membrane properties of their organelles. One of the key factors determining membrane fluidity and phase behavior is the proportion of saturated and unsaturated acyl chains in membrane lipids. Saccharomyces cerevisiae is an ideal model organism to study the regulation of the lipid acyl chain composition via the OLE pathway. The OLE pathway comprises all steps involved in the regulated mobilization of the transcription factors Mga2 and Spt23 from the endoplasmic reticulum (ER), which then drive the expression of OLE1 in the nucleus. OLE1 encodes for the essential Δ9-fatty acid desaturase Ole1 and is crucial for de novo biosynthesis of unsaturated fatty acids (UFAs) that are used as lipid building blocks. This review summarizes our current knowledge of the OLE pathway, the best-characterized, eukaryotic sense-and-control system regulating membrane lipid saturation, and identifies open questions to indicate future directions.
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20
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Proper Sterol Distribution Is Required for Candida albicans Hyphal Formation and Virulence. G3-GENES GENOMES GENETICS 2016; 6:3455-3465. [PMID: 27587298 PMCID: PMC5100844 DOI: 10.1534/g3.116.033969] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Candida albicans is an opportunistic fungus responsible for the majority of systemic fungal infections. Multiple factors contribute to C. albicans pathogenicity. C. albicans strains lacking CaArv1 are avirulent. Arv1 has a conserved Arv1 homology domain (AHD) that has a zinc-binding domain containing two cysteine clusters. Here, we explored the role of the CaAHD and zinc-binding motif in CaArv1-dependent virulence. Overall, we found that the CaAHD was necessary but not sufficient for cells to be virulent, whereas the zinc-binding domain was essential, as Caarv1/Caarv1 cells expressing the full-length zinc-binding domain mutants, Caarv1C3S and Caarv1C28S, were avirulent. Phenotypically, we found a direct correlation between the avirulence of Caarv1/Caarv1, Caarrv1AHD, Caarv1C3S, and Caarv1C28S cells and defects in bud site selection, septa formation and localization, and hyphal formation and elongation. Importantly, all avirulent mutant strains lacked the ability to maintain proper sterol distribution. Overall, our results have established the importance of the AHD and zinc-binding domain in fungal invasion, and have correlated an avirulent phenotype with the inability to maintain proper sterol distribution.
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21
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Identification of Yeast Mutants Exhibiting Altered Sensitivity to Valinomycin and Nigericin Demonstrate Pleiotropic Effects of Ionophores on Cellular Processes. PLoS One 2016; 11:e0164175. [PMID: 27711131 PMCID: PMC5053447 DOI: 10.1371/journal.pone.0164175] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 09/21/2016] [Indexed: 01/04/2023] Open
Abstract
Ionophores such as valinomycin and nigericin are potent tools for studying the impact of ion perturbance on cellular functions. To obtain a broader picture about molecular components involved in mediating the effects of these drugs on yeast cells under respiratory growth conditions, we performed a screening of the haploid deletion mutant library covering the Saccharomyces cerevisiae nonessential genes. We identified nearly 130 genes whose absence leads either to resistance or to hypersensitivity to valinomycin and/or nigericin. The processes affected by their protein products range from mitochondrial functions through ribosome biogenesis and telomere maintenance to vacuolar biogenesis and stress response. Comparison of the results with independent screenings performed by our and other laboratories demonstrates that although mitochondria might represent the main target for both ionophores, cellular response to the drugs is very complex and involves an intricate network of proteins connecting mitochondria, vacuoles, and other membrane compartments.
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22
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Palmer EE, Jarrett KE, Sachdev RK, Al Zahrani F, Hashem MO, Ibrahim N, Sampaio H, Kandula T, Macintosh R, Gupta R, Conlon DM, Billheimer JT, Rader DJ, Funato K, Walkey CJ, Lee CS, Loo C, Brammah S, Elakis G, Zhu Y, Buckley M, Kirk EP, Bye A, Alkuraya FS, Roscioli T, Lagor WR. Neuronal deficiency of ARV1 causes an autosomal recessive epileptic encephalopathy. Hum Mol Genet 2016; 25:3042-3054. [PMID: 27270415 DOI: 10.1093/hmg/ddw157] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 04/29/2016] [Accepted: 05/18/2016] [Indexed: 12/21/2022] Open
Abstract
We report an individual who presented with severe neurodevelopmental delay and an intractable infantile-onset seizure disorder. Exome sequencing identified a homozygous single nucleotide change that abolishes a splice donor site in the ARV1 gene (c.294 + 1G > A homozygous). This variant completely prevented splicing in minigene assays, and resulted in exon skipping and an in-frame deletion of 40 amino acids in primary human fibroblasts (NP_073623.1: p.(Lys59_Asn98del). The p.(Lys59_Asn98del) and previously reported p.(Gly189Arg) ARV1 variants were evaluated for protein expression and function. The p.(Gly189Arg) variant partially rescued the temperature-dependent growth defect in arv1Δ yeast, while p.(Lys59-Asn98del) completely failed to rescue at restrictive temperature. In contrast to wild type human ARV1, neither variant expressed detectable levels of protein in mammalian cells. Mice with a neuronal deletion of Arv1 recapitulated the human phenotype, exhibiting seizures and a severe survival defect in adulthood. Our data support ARV1 deficiency as a cause of autosomal recessive epileptic encephalopathy.
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Affiliation(s)
- Elizabeth E Palmer
- Department of Women and Children's Health, Randwick Campus, University of New South Wales, NSW 2031, Australia.,Genetics of Learning Disability Service, Waratah, NSW 2298, Australia
| | - Kelsey E Jarrett
- Department of Molecular Physiology and Biophysics.,Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, TX 77030, USA
| | - Rani K Sachdev
- Department of Women and Children's Health, Randwick Campus, University of New South Wales, NSW 2031, Australia.,Sydney Children's Hospital, Randwick, NSW 2031, Australia
| | - Fatema Al Zahrani
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh 11211, Saudi Arabia
| | - Mais Omar Hashem
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh 11211, Saudi Arabia
| | - Niema Ibrahim
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh 11211, Saudi Arabia
| | - Hugo Sampaio
- Department of Women and Children's Health, Randwick Campus, University of New South Wales, NSW 2031, Australia.,Sydney Children's Hospital, Randwick, NSW 2031, Australia
| | - Tejaswi Kandula
- Department of Women and Children's Health, Randwick Campus, University of New South Wales, NSW 2031, Australia.,Sydney Children's Hospital, Randwick, NSW 2031, Australia
| | | | - Rajat Gupta
- Department of Molecular Physiology and Biophysics
| | - Donna M Conlon
- Division of Translational Medicine and Human Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jeffrey T Billheimer
- Division of Translational Medicine and Human Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Daniel J Rader
- Division of Translational Medicine and Human Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Kouichi Funato
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyam, Higashi-Hiroshima 739-8528, Japan
| | - Christopher J Walkey
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | | | - Christine Loo
- Department of Women and Children's Health, Randwick Campus, University of New South Wales, NSW 2031, Australia.,SEALS pathology, Randwick, NSW 2031, Australia
| | - Susan Brammah
- Electron Microscope Unit, Concord Repatriation General Hospital, Concord, NSW 2139, Australia
| | | | - Ying Zhu
- Genetics of Learning Disability Service, Waratah, NSW 2298, Australia.,SEALS pathology, Randwick, NSW 2031, Australia
| | | | - Edwin P Kirk
- Department of Women and Children's Health, Randwick Campus, University of New South Wales, NSW 2031, Australia.,Sydney Children's Hospital, Randwick, NSW 2031, Australia.,SEALS pathology, Randwick, NSW 2031, Australia
| | - Ann Bye
- Department of Women and Children's Health, Randwick Campus, University of New South Wales, NSW 2031, Australia.,Sydney Children's Hospital, Randwick, NSW 2031, Australia
| | - Fowzan S Alkuraya
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh 11211, Saudi Arabia
| | - Tony Roscioli
- Sydney Children's Hospital, Randwick, NSW 2031, Australia.,Kinghorn Centre for Clinical Genomics, Garvan Institute, 370 Victoria St Darlinghurst, Sydney, Australia.,St Vincent's Clinical School, University of New South Wales, Sydney, Australia
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23
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Knockdown of triglyceride synthesis does not enhance palmitate lipotoxicity or prevent oleate-mediated rescue in rat hepatocytes. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:1005-1014. [PMID: 27249207 DOI: 10.1016/j.bbalip.2016.05.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 05/14/2016] [Accepted: 05/26/2016] [Indexed: 12/14/2022]
Abstract
Experiments in a variety of cell types, including hepatocytes, consistently demonstrate the acutely lipotoxic effects of saturated fatty acids, such as palmitate (PA), but not unsaturated fatty acids, such as oleate (OA). PA+OA co-treatment fully prevents PA lipotoxicity through mechanisms that are not well defined but which have been previously attributed to more efficient esterification and sequestration of PA into triglycerides (TGs) when OA is abundant. However, this hypothesis has never been directly tested by experimentally modulating the relative partitioning of PA/OA between TGs and other lipid fates in hepatocytes. In this study, we found that addition of OA to PA-treated hepatocytes enhanced TG synthesis, reduced total PA uptake and PA lipid incorporation, decreased phospholipid saturation and rescued PA-induced ER stress and lipoapoptosis. Knockdown of diacylglycerol acyltransferase (DGAT), the rate-limiting step in TG synthesis, significantly reduced TG accumulation without impairing OA-mediated rescue of PA lipotoxicity. In both wild-type and DGAT-knockdown hepatocytes, OA co-treatment significantly reduced PA lipid incorporation and overall phospholipid saturation compared to PA-treated hepatocytes. These data indicate that OA's protective effects do not require increased conversion of PA into inert TGs, but instead may be due to OA's ability to compete against PA for cellular uptake and/or esterification and, thereby, normalize the composition of cellular lipids in the presence of a toxic PA load.
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24
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Curtin C, Cordente T. What's old is new again: yeast mutant screens in the era of pooled segregant analysis by genome sequencing. MICROBIAL CELL 2016; 3:132-134. [PMID: 28357345 PMCID: PMC5349087 DOI: 10.15698/mic2016.04.488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
While once de-rigueur for identification of genes involved in
biological processes, screening of chemically induced mutant populations is an
approach that has largely been superseded for model organisms such as
Saccharomyces cerevisiae. Availability of single gene
deletion/overexpression libraries and combinatorial synthetic genetic arrays
provide yeast researchers more structured ways to probe genetic networks.
Furthermore, in the age of inexpensive DNA sequencing, methodologies such as
mapping of quantitative trait loci (QTL) by pooled segregant analysis and
genome-wide association enable the identification of multiple naturally
occurring allelic variants that contribute to polygenic phenotypes of interest.
This is, however, contingent on the capacity to screen large numbers of
individuals and existence of sufficient natural phenotypic variation within the
available population. The latter cannot be guaranteed and non-selectable,
industrially relevant phenotypes, such as production of volatile aroma
compounds, pose severe limitations on the use of modern genetic techniques due
to expensive and time-consuming downstream analyses. An interesting approach to
overcome these issues can be found in Den Abt et al. 1 (this issue of Microbial
Cell), where a combination of repeated rounds of chemical
mutagenesis and pooled segregant analysis by whole genome sequencing was applied
to identify genes involved in ethyl acetate formation, demonstrating a new path
for industrial yeast strain development and bringing classical mutant screens
into the 21st century
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Affiliation(s)
- Chris Curtin
- The Australian Wine Research Institute, Urrbrae, SA 5064, Australia
| | - Toni Cordente
- The Australian Wine Research Institute, Urrbrae, SA 5064, Australia
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25
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Warchol I, Gora M, Wysocka-Kapcinska M, Komaszylo J, Swiezewska E, Sojka M, Danikiewicz W, Plochocka D, Maciejak A, Tulacz D, Leszczynska A, Kapur S, Burzynska B. Genetic engineering and molecular characterization of yeast strain expressing hybrid human-yeast squalene synthase as a tool for anti-cholesterol drug assessment. J Appl Microbiol 2016; 120:877-88. [PMID: 26757023 DOI: 10.1111/jam.13053] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Revised: 10/27/2015] [Accepted: 01/05/2016] [Indexed: 11/29/2022]
Abstract
AIMS The main objective of the study is molecular and biological characterization of the human-yeast hybrid squalene synthase (SQS), as a promising target for treatment of hypercholesterolaemia. METHODS AND RESULTS The human-yeast hybrid SQS, with 67% amino acids, including the catalytic site derived from human enzyme, was expressed in Saccharomyces cerevisiae strain deleted of its own SQS gene. The constructed strain has a decreased level of sterols compared to the control strain. The mevalonate pathway and sterol biosynthesis genes are induced and the level of triacylglycerols is increased. Treatment of the strain with rosuvastatin or zaragozic acid, two mevalonate pathway inhibitors, decreased the amounts of squalene, lanosterol and ergosterol, and up-regulated expression of several genes encoding enzymes responsible for biosynthesis of ergosterol precursors. Conversely, expression of the majority genes implicated in the biosynthesis of other mevalonate pathway end products, ubiquinone and dolichol, was down-regulated. CONCLUSIONS The S. cerevisiae strain constructed in this study enables to investigate the physiological and molecular effects of inhibitors on cell functioning. SIGNIFICANCE AND IMPACT OF THE STUDY The yeast strain expressing hybrid SQS with the catalytic core of human enzyme is a convenient tool for efficient screening for novel inhibitors of cholesterol-lowering properties.
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Affiliation(s)
- I Warchol
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - M Gora
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - M Wysocka-Kapcinska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - J Komaszylo
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - E Swiezewska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - M Sojka
- Institute of Organic Chemistry, Polish Academy of Sciences, Warsaw, Poland
| | - W Danikiewicz
- Institute of Organic Chemistry, Polish Academy of Sciences, Warsaw, Poland
| | - D Plochocka
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - A Maciejak
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - D Tulacz
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - A Leszczynska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - S Kapur
- Department of Biological Science, Birla Institute of Technology & Science (BITS), Hyderabad, India
| | - B Burzynska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
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Ikeda A, Kajiwara K, Iwamoto K, Makino A, Kobayashi T, Mizuta K, Funato K. Complementation analysis reveals a potential role of human ARV1 in GPI anchor biosynthesis. Yeast 2015; 33:37-42. [PMID: 26460143 DOI: 10.1002/yea.3138] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Revised: 10/01/2015] [Accepted: 10/02/2015] [Indexed: 01/20/2023] Open
Abstract
ARV1 is involved in regulating lipid homeostasis but also in the biosynthesis of glycosylphosphatidylinositol (GPI) in Saccharomyces cerevisiae. Here, we examined whether human ARV1 can complement the role of yeast ARV1 in GPI biosynthesis. Overexpression of human ARV1 could rescue the phenotypes associated with GPI anchor synthesis defect in the yeast arv1Δ mutant. The results suggest that Arv1 function in GPI biosynthesis may be conserved in all eukaryotes, from yeast to humans.
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Affiliation(s)
- Atsuko Ikeda
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Japan
| | - Kentaro Kajiwara
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Japan
| | | | - Asami Makino
- Lipid Biology Laboratory and RIKEN, Saitama, Japan
| | | | - Keiko Mizuta
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Japan
| | - Kouichi Funato
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Japan
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Deletion of murine Arv1 results in a lean phenotype with increased energy expenditure. Nutr Diabetes 2015; 5:e181. [PMID: 26479315 PMCID: PMC4631934 DOI: 10.1038/nutd.2015.32] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2015] [Accepted: 06/28/2015] [Indexed: 12/17/2022] Open
Abstract
Background: ACAT-related enzyme 2 required for viability 1 (ARV1) is a putative lipid transporter of the endoplasmic reticulum that is conserved across eukaryotic species. The ARV1 protein contains a conserved N-terminal cytosolic zinc ribbon motif known as the ARV1 homology domain, followed by multiple transmembrane regions anchoring it in the ER. Deletion of ARV1 in yeast results in defective sterol trafficking, aberrant lipid synthesis, ER stress, membrane disorganization and hypersensitivity to fatty acids (FAs). We sought to investigate the role of Arv1 in mammalian lipid metabolism. Methods: Homologous recombination was used to disrupt the Arv1 gene in mice. Animals were examined for alterations in lipid and lipoprotein levels, body weight, body composition, glucose tolerance and energy expenditure. Results: Global loss of Arv1 significantly decreased total cholesterol and high-density lipoprotein cholesterol levels in the plasma. Arv1 knockout mice exhibited a dramatic lean phenotype, with major reductions in white adipose tissue (WAT) mass and body weight on a chow diet. This loss of WAT is accompanied by improved glucose tolerance, higher adiponectin levels, increased energy expenditure and greater rates of whole-body FA oxidation. Conclusions: This work identifies Arv1 as an important player in mammalian lipid metabolism and whole-body energy homeostasis.
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28
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Klug L, Daum G. Yeast lipid metabolism at a glance. FEMS Yeast Res 2014; 14:369-88. [DOI: 10.1111/1567-1364.12141] [Citation(s) in RCA: 199] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 01/23/2014] [Accepted: 02/02/2014] [Indexed: 01/07/2023] Open
Affiliation(s)
- Lisa Klug
- Institute of Biochemistry; Graz University of Technology; Graz Austria
| | - Günther Daum
- Institute of Biochemistry; Graz University of Technology; Graz Austria
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