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Najle SR, Hernández J, Ocaña-Pallarès E, García Siburu N, Nusblat AD, Nudel CB, Slamovits CH, Uttaro AD. Genome-wide Transcriptional Analysis of Tetrahymena thermophila Response to Exogenous Cholesterol. J Eukaryot Microbiol 2019; 67:209-222. [PMID: 31705733 DOI: 10.1111/jeu.12774] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 10/23/2019] [Accepted: 10/28/2019] [Indexed: 11/28/2022]
Abstract
The ciliate Tetrahymena thermophila does not require sterols for growth and synthesizes pentacyclic triterpenoid alcohols, mainly tetrahymanol, as sterol surrogates. However, when sterols are present in the environment, T. thermophila efficiently incorporates and modifies them. These modifications consist of desaturation reactions at positions C5(6), C7(8), and C22(23), and de-ethylation at C24 of 29-carbon sterols (i.e. phytosterols). Three out of four of the enzymes involved in the sterol modification pathway have been previously identified. However, identification of the sterol C22 desaturase remained elusive, as did other basic aspects of this metabolism. To get more insights into this peculiar metabolism, we here perform a whole transcriptome analysis of T. thermophila in response to exogenous cholesterol. We found 356 T. thermophila genes to be differentially expressed after supplementation with cholesterol for 2 h. Among those that were upregulated, we found two genes belonging to the long spacing family of desaturases that we tentatively identified by RNAi analysis as sterol C22 desaturases. Additionally, we determined that the inhibition of tetrahymanol synthesis after supplementation with cholesterol occurs by a transcriptional downregulation of genes involved in squalene synthesis and cyclization. Finally, we identified several uncharacterized genes that are likely involved in sterols transport and signaling.
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Affiliation(s)
- Sebastián R Najle
- Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Biología Molecular y Celular de Rosario, CONICET, Universidad Nacional de Rosario, Ocampo y Esmeralda s/n, S2000FHQ, Rosario, Argentina.,Institut de Biología Evolutiva (CSIC-Universitat Pompeu Fabra), Pg. Marítim de la Barceloneta 37-49, 08003, Barcelona, Catalonia, Spain
| | - Josefina Hernández
- Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Biología Molecular y Celular de Rosario, CONICET, Universidad Nacional de Rosario, Ocampo y Esmeralda s/n, S2000FHQ, Rosario, Argentina
| | - Eduard Ocaña-Pallarès
- Institut de Biología Evolutiva (CSIC-Universitat Pompeu Fabra), Pg. Marítim de la Barceloneta 37-49, 08003, Barcelona, Catalonia, Spain
| | - Nicolás García Siburu
- Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Biología Molecular y Celular de Rosario, CONICET, Universidad Nacional de Rosario, Ocampo y Esmeralda s/n, S2000FHQ, Rosario, Argentina
| | - Alejandro D Nusblat
- Facultad de Farmacia y Bioquímica, Instituto de Nanobiotecnología (NANOBIOTEC), CONICET, Universidad de Buenos Aires, Junín 956, C1113AAD, Buenos Aires, Argentina
| | - Clara B Nudel
- Facultad de Farmacia y Bioquímica, Instituto de Nanobiotecnología (NANOBIOTEC), CONICET, Universidad de Buenos Aires, Junín 956, C1113AAD, Buenos Aires, Argentina
| | - Claudio H Slamovits
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, B3H 4R2, Nova Scotia, Canada
| | - Antonio D Uttaro
- Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Biología Molecular y Celular de Rosario, CONICET, Universidad Nacional de Rosario, Ocampo y Esmeralda s/n, S2000FHQ, Rosario, Argentina
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Kennedy MA, Barbuch R, Bard M. Transcriptional regulation of the squalene synthase gene (ERG9) in the yeast Saccharomyces cerevisiae. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1445:110-22. [PMID: 10209263 DOI: 10.1016/s0167-4781(99)00035-4] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The ergosterol biosynthetic pathway is a specific branch of the mevalonate pathway. Since the cells requirement for sterols is greater than for isoprenoids, sterol biosynthesis must be regulated independently of isoprenoid biosynthesis. In this study we explored the transcriptional regulation of squalene synthase (ERG9) in Saccharomyces cerevisiae, the first enzyme dedicated to the synthesis of sterols. A mutant search was performed to identify genes that were involved in the regulation of the expression of an ERG9-lacZ promoter fusion. Mutants with phenotypes consistent with known sterol biosynthetic mutations (ERG3, ERG7, ERG24) increased expression of ERG9. In addition, treatment of wild-type cells with the sterol inhibitors zaragozic acid and ketoconazole, which target squalene synthase and the C-14 sterol demethylase respectively, also caused an increase in ERG9 expression. The data also demonstrate that heme mutants increased ERG9 expression while anaerobic conditions decreased expression. Additionally, the heme activator protein transcription factors HAP1 and HAP2/3/4, the yeast activator protein transcription factor yAP-1, and the phospholipid transcription factor complex INO2/4 regulate ERG9 expression. ERG9 expression is decreased in hap1, hap2/3/4, and yap-1 mutants while ino2/4 mutants showed an increase in ERG9 expression. This study demonstrates that ERG9 transcription is regulated by several diverse factors, consistent with the idea that as the first step dedicated to the synthesis of sterols, squalene synthase gene expression and ultimately sterol biosynthesis is highly regulated.
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Affiliation(s)
- M A Kennedy
- Department of Biology, Indiana University-Purdue University at Indianapolis, 723 W. Michigan Street, SL324, Indianapolis, IN 46202, USA
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Fegueur M, Richard L, Charles AD, Karst F. Isolation and primary structure of the ERG9 gene of Saccharomyces cerevisiae encoding squalene synthetase. Curr Genet 1991; 20:365-72. [PMID: 1807826 DOI: 10.1007/bf00317063] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The ERG9 gene of Saccharomyces cerevisiae has been cloned by complementation of the erg9-1 mutation which affects squalene synthetase. From the 5 kb insert isolated, the functional gene has been localized on a DNA fragment of 2.5 kb. The presence of squalene synthetase activity in E. coli bearing the yeast DNA fragment isolated, indicates that the structural gene encoding squalene synthetase has been cloned. The sequence of the 2.5 kb fragment contains an open reading frame which could encode a protein of 444 amino acids with a deduced relative molecular mass of 51,600. The amino acid sequence reveals one to four potential transmembrane domains with a hydrophobic segment in the C-terminal region. The N-terminus of the deduced protein strongly resembles the signal sequence of yeast invertase suggesting a specific mechanism of integration into the membranes of the endoplasmic reticulum.
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Affiliation(s)
- M Fegueur
- Laboratoire de Biochimie et Génétique des Microorganismes, Université de Poitiers, France
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4
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Mbaya B, Rigomier D, Edorh GG, Karst F, Schrevel J. Isoprenoid metabolism in Plasmodium falciparum during the intraerythrocytic phase of malaria. Biochem Biophys Res Commun 1990; 173:849-54. [PMID: 2268347 DOI: 10.1016/s0006-291x(05)80864-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Products of the isoprenoid metabolism were identified upon incubations of extracts from Plasmodium falciparum infected red blood cells with [14C] mevalonate. Uninfected erythrocytes and wild type yeast Saccharomyces cerevisiae extracts were used as controls. In parasitized red blood cells as well as in yeast extracts, mevalonate was converted into the biosynthetic isoprenoid precursors of sterol pathway until farnesyl pyrophosphate. In contrast, no mevalonate conversion was observed in uninfected erythrocyte extracts. The isoprenoid metabolism appeared stage-dependent as shown by the increase of radiolabelled farnesyl pyrophosphate amount at the beginning of the schizogonic phase (30-36 hours).
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Affiliation(s)
- B Mbaya
- Laboratoire de Biologie Cellulaire, URA CNRS n. 290, Poitiers, France
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M'Baya B, Fegueur M, Servouse M, Karst F. Regulation of squalene synthetase and squalene epoxidase activities in Saccharomyces cerevisiae. Lipids 1989; 24:1020-3. [PMID: 2693869 DOI: 10.1007/bf02544072] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Squalene synthetase (EC 2.5.1.21) and squalene epoxidase (EC 1.14 99.7) activities have been measured in cell-free extracts of wild type yeast grown in aerobic and semi-anaerobic conditions as well as in sterol-auxotrophic mutant strains grown aerobically. The results show that both enzymes are induced resulting in an almost two- to five-fold increase in enzymatic activities in mutant strains containing limited sterol amounts and are repressed in the wild type strain cultured in anaerobiosis in excess of sterol. The results show also that squalene epoxidase is repressed by lanosterol, and that the mevalonic acid pool may regulate squalene synthetase levels. The large change in the activities of the two enzymes, depending on the sterol needs of the cells, as well as their low specific activities in comparison with those of the enzymes involved in the early stages of sterol synthesis strongly suggests that squalene synthetase and squalene epoxidase are of importance in regulating the amount of sterol synthesized by yeast.
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Affiliation(s)
- B M'Baya
- Laboratoire de Biochimie et Genetique des Microorganismes, Universite de Poitiers, France
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Prasanna P, Holmlund CE. Identification in Tetrahymena pyriformis of 3-hydroxy-3-methyl glutaryl coenzyme a lyase: its purification and properties. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1987; 19:385-9. [PMID: 3109974 DOI: 10.1016/0020-711x(87)90013-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The major HMG-CoA utilizing enzyme activity in T. pyriformis has been determined to be HMG-CoA lyase. The enzyme was purified 32-fold to a specific activity of 431 units/mg from a mitochondrial fraction. Sephacryl S-200 chromatography gave an estimated molecular weight of 50,000 daltons for the HMG-CoA lyase. SDS gel electrophoresis revealed two bands stained by Coomassie Blue--a major band of 50,000 daltons and a minor band of 25,000 daltons. The latter is believed to be an impurity in the preparation. The enzyme has a pH optimum of 9.0, is stimulated slightly by sulfhydryl reagents, and requires a divalent cation for maximum activity. The KM for HMG-CoA is 15 microM.
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Wilton DC. The effect of excess mevalonic acid on ubiquinone and tetrahymanol biosynthesis in Tetrahymena pyriformis. Biochem J 1985; 229:551-3. [PMID: 3929773 PMCID: PMC1145090 DOI: 10.1042/bj2290551] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
When T. pyriformis is grown in the presence of 10(-2)M-mevalonic acid, the uptake exceeds the cell's requirement for this biosynthetic intermediate. The majority of the excess mevalonic acid is diverted into ubiquinone-8 biosynthesis whereas the biosynthesis of tetrahymanol, the major product of the mevalonic acid pathway, is unchanged. In the presence of excess external mevalonic acid, the biosynthesis of mevalonic acid by the cell is inhibited. It is proposed that ubiquinone biosynthesis is normally regulated by mevalonic acid availability, whereas tetrahymanol biosynthesis is regulated primarily at a later point in the pathway.
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Wilton DC. The effect of cholesterol on ubiquinone and tetrahymanol biosynthesis in Tetrahymena pyriformis. Biochem J 1983; 216:203-6. [PMID: 6418144 PMCID: PMC1152487 DOI: 10.1042/bj2160203] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The biosynthesis of ubiquinone-8 from radioactive mevalonate by cultures of Tetrahymena pyriformis is demonstrated. Under normal conditions the incorporation of this radioactive precursor into ubiquinone and the triterpenoid alcohol tetrahymanol reflects the amounts of these two compounds in the cell. Growth of T. pyriformis in the presence of cholesterol results in a complete inhibition of incorporation of radioactive mevalonate into tetrahymanol while there is a corresponding increase of radioactive incorporation into ubiquinone. This increased incorporation of mevalonic acid into ubiquinone must reflect a reduced level of mevalonic acid in the cell under these conditions and is not due to increased ubiquinone biosynthesis, indicating tight regulation of the pathway prior to mevalonate formation.
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