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Oliveira FFM, Paes HC, Peconick LDF, Fonseca FL, Marina CLF, Bocca AL, Homem-de-Mello M, Rodrigues ML, Albuquerque P, Nicola AM, Alspaugh JA, Felipe MSS, Fernandes L. Erg6 affects membrane composition and virulence of the human fungal pathogen Cryptococcus neoformans. Fungal Genet Biol 2020; 140:103368. [PMID: 32201128 DOI: 10.1016/j.fgb.2020.103368] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 02/12/2020] [Accepted: 02/17/2020] [Indexed: 12/12/2022]
Abstract
Ergosterol is the most important membrane sterol in fungal cells and a component not found in the membranes of human cells. We identified the ERG6 gene in the AIDS-associated fungal pathogen, Cryptococcus neoformans, encoding the sterol C-24 methyltransferase of fungal ergosterol biosynthesis. In this work, we have explored its relationship with high-temperature growth and virulence of C. neoformans by the construction of a loss-of-function mutant. In contrast to other genes involved in ergosterol biosynthesis, C. neoformans ERG6 is not essential for growth under permissive conditions in vitro. However, the erg6 mutant displayed impaired thermotolerance and increased susceptibility to osmotic and oxidative stress, as well as to different antifungal drugs. Total lipid analysis demonstrated a decrease in the erg6Δ strain membrane ergosterol content. In addition, this mutant strain was avirulent in an invertebrate model of C. neoformans infection. C. neoformans Erg6 was cyto-localized in the endoplasmic reticulum and Golgi complex. Our results demonstrate that Erg6 is crucial for growth at high temperature and virulence, likely due to its effects on C. neoformans membrane integrity and dynamics. These pathogen-focused investigations into ergosterol biosynthetic pathway components reinforce the multiple roles of ergosterol in the response of diverse fungal species to alterations in the environment, especially that of the infected host. These studies open perspectives to understand the participation of ergosterol in mechanism of resistance to azole and polyene drugs. Observed synergistic growth defects with co-inhibition of Erg6 and other components of the ergosterol biosynthesis pathway suggests novel approaches to treatment in human fungal infections.
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Affiliation(s)
- Fabiana Freire M Oliveira
- Faculty of Medicine, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Brasília, Federal District 70910-900, Brazil
| | - Hugo Costa Paes
- Faculty of Medicine, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Brasília, Federal District 70910-900, Brazil
| | - Luísa Defranco F Peconick
- Faculty of Ceilândia, Campus UnB Ceilândia, University of Brasília, Ceilândia Sul, Centro Metropolitano, Brasília, Federal District 72220-275, Brazil
| | - Fernanda L Fonseca
- Center for Technological Development in Health (CDTS), Fiocruz-RJ, Rio de Janeiro 21045-360, Brazil.
| | - Clara Luna Freitas Marina
- Laboratory of Applied Immunology, Institute of Biology, Room J1 28/8, Building J, 2nd Floor, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Brasilia, Federal District 70910-900, Brazil
| | - Anamélia Lorenzetti Bocca
- Laboratory of Applied Immunology, Institute of Biology, Room J1 28/8, Building J, 2nd Floor, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Brasilia, Federal District 70910-900, Brazil.
| | - Mauricio Homem-de-Mello
- Faculty of Health Science, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Brasília, Federal District 70910-900, Brazil.
| | - Márcio Lourenço Rodrigues
- Carlos Chagas Institute, Fiocruz-PR, Curitiba 81310-020, Brazil; Microbiology Institute, Federal University of Rio de Janeiro, Rio de Janeiro 21941-590, Brazil
| | - Patrícia Albuquerque
- Faculty of Ceilândia, Campus UnB Ceilândia, University of Brasília, Ceilândia Sul, Centro Metropolitano, Brasília, Federal District 72220-275, Brazil
| | - André Moraes Nicola
- Faculty of Medicine, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Brasília, Federal District 70910-900, Brazil
| | - J Andrew Alspaugh
- Duke University School of Medicine, Dept. of Medicine, Durham, DUMC Box 102359, 303 Sands Building, Research Drive, Durham, NC 27710, USA.
| | - Maria Sueli S Felipe
- Catolic University of Brasilia, Campus Asa Norte, SGAN 916 Módulo B Avenida W5, Asa Norte, Brasília, Federal District 70790-160, Brazil
| | - Larissa Fernandes
- Faculty of Ceilândia, Campus UnB Ceilândia, University of Brasília, Ceilândia Sul, Centro Metropolitano, Brasília, Federal District 72220-275, Brazil; Laboratory of Applied Immunology, Institute of Biology, Room J1 28/8, Building J, 2nd Floor, Campus Darcy Ribeiro, University of Brasília, Asa Norte, Brasilia, Federal District 70910-900, Brazil.
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Abe I. Biosynthetic studies on teleocidins in Streptomyces. J Antibiot (Tokyo) 2018; 71:763-768. [DOI: 10.1038/s41429-018-0069-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 04/20/2018] [Accepted: 05/07/2018] [Indexed: 11/09/2022]
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Miller MB, Patkar P, Singha UK, Chaudhuri M, David Nes W. 24-Methylenecyclopropane steroidal inhibitors: A Trojan horse in ergosterol biosynthesis that prevents growth of Trypanosoma brucei. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1862:305-313. [PMID: 27939999 DOI: 10.1016/j.bbalip.2016.12.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Revised: 11/23/2016] [Accepted: 12/05/2016] [Indexed: 01/09/2023]
Abstract
A new class of steroidal therapeutics based on phylogenetic-guided design of covalent inhibitors that target parasite-specific enzymes of ergosterol biosynthesis is shown to prevent growth of the protozoan-Trypanosoma brucei, responsible for sleeping sickness. In the presence of approximately 15±5μM 26,27-dehydrolanosterol, T. brucei procyclic or blood stream form growth is inhibited by 50%. This compound is actively converted by the parasite to an acceptable substrate of sterol C24-methyl transferase (SMT) that upon position-specific side chain methylation at C26 inactivates the enzyme. Treated cells show dose-dependent depletion of ergosterol and other 24β-methyl sterols with no accumulation of intermediates in contradistinction to profiles typical of tight binding inhibitor treatments to azoles showing loss of ergosterol accompanied by accumulation of toxic 14-methyl sterols. HEK cells accumulate 26,27-dehydrolanosterol without effect on cholesterol biosynthesis. During exposure of cloned TbSMT to 26,27-dehydrozymosterol, the enzyme is gradually inactivated (kcat/kinact=0.13min-1/0.08min-1; partition ratio of 1.6) while 26,27-dehydrolanosterol binds nonproductively. GC-MS analysis of the turnover product and bound intermediate released as a C26-methylated diol (C3-OH and C24-OH) confirmed substrate recognition and covalent binding to TbSMT. This study has potential implications for design of a novel class of chemotherapeutic leads functioning as mechanism-based inhibitors of ergosterol biosynthesis to treat neglected tropical diseases.
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Affiliation(s)
- Matthew B Miller
- Department of Chemistry and Biochemistry and Center for Chemical Biology, Texas Tech University, Lubbock, TX 79409, USA
| | - Presheet Patkar
- Department of Chemistry and Biochemistry and Center for Chemical Biology, Texas Tech University, Lubbock, TX 79409, USA
| | - Ujjal K Singha
- Department of Microbiology and Immunology, Meharry Medical College, Nashville, TN 37208, USA
| | - Minu Chaudhuri
- Department of Microbiology and Immunology, Meharry Medical College, Nashville, TN 37208, USA
| | - W David Nes
- Department of Chemistry and Biochemistry and Center for Chemical Biology, Texas Tech University, Lubbock, TX 79409, USA.
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Leaver DJ, Patkar P, Singha UK, Miller MB, Haubrich BA, Chaudhuri M, Nes WD. Fluorinated Sterols Are Suicide Inhibitors of Ergosterol Biosynthesis and Growth in Trypanosoma brucei. ACTA ACUST UNITED AC 2016; 22:1374-83. [PMID: 26496686 DOI: 10.1016/j.chembiol.2015.08.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 08/20/2015] [Accepted: 08/28/2015] [Indexed: 11/19/2022]
Abstract
Trypanosoma brucei, the causal agent for sleeping sickness, depends on ergosterol for growth. Here, we describe the effects of a mechanism-based inhibitor, 26-fluorolanosterol (26FL), which converts in vivo to a fluorinated substrate of the sterol C24-methyltransferase essential for sterol methylation and function of ergosterol, and missing from the human host. 26FL showed potent inhibition of ergosterol biosynthesis and growth of procyclic and bloodstream forms while having no effect on cholesterol biosynthesis or growth of human epithelial kidney cells. During exposure of cloned TbSMT to 26-fluorocholesta-5,7,24-trienol, the enzyme is gradually killed as a consequence of the covalent binding of the intermediate C25 cation to the active site (kcat/kinact = 0.26 min(-1)/0.24 min(-1); partition ratio of 1.08), whereas 26FL is non-productively bound. These results demonstrate that poisoning of ergosterol biosynthesis by a 26-fluorinated Δ(24)-sterol is a promising strategy for developing a new treatment for trypanosomiasis.
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Affiliation(s)
- David J Leaver
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, 2500 Broadway, Lubbock, TX 79409, USA; Institute of Chemistry and Biomedical Sciences, Nanjing University, 22 Hankou Road, Nanjing, Jiangsu, 210093, P.R. China
| | - Presheet Patkar
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, 2500 Broadway, Lubbock, TX 79409, USA
| | - Ujjal K Singha
- Department of Microbiology and Immunology, Meharry Medical College, 1005 Doctor D. B. Todd Jr. Boulevard, Nashville, TN 37208, USA
| | - Matthew B Miller
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, 2500 Broadway, Lubbock, TX 79409, USA
| | - Brad A Haubrich
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, 2500 Broadway, Lubbock, TX 79409, USA
| | - Minu Chaudhuri
- Department of Microbiology and Immunology, Meharry Medical College, 1005 Doctor D. B. Todd Jr. Boulevard, Nashville, TN 37208, USA
| | - W David Nes
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, 2500 Broadway, Lubbock, TX 79409, USA.
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Haubrich BA, Collins EK, Howard AL, Wang Q, Snell WJ, Miller MB, Thomas CD, Pleasant SK, Nes WD. Characterization, mutagenesis and mechanistic analysis of an ancient algal sterol C24-methyltransferase: Implications for understanding sterol evolution in the green lineage. PHYTOCHEMISTRY 2015; 113:64-72. [PMID: 25132279 PMCID: PMC5182512 DOI: 10.1016/j.phytochem.2014.07.019] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2014] [Revised: 07/11/2014] [Accepted: 06/09/2014] [Indexed: 05/15/2023]
Abstract
Sterol C24-methyltransferases (SMTs) constitute a group of sequence-related proteins that catalyze the pattern of sterol diversity across eukaryotic kingdoms. The only gene for sterol alkylation in green algae was identified and the corresponding catalyst from Chlamydomonas reinhardtii (Cr) was characterized kinetically and for product distributions. The properties of CrSMT were similar to those predicted for an ancient SMT expected to possess broad C3-anchoring requirements for substrate binding and formation of 24β-methyl/ethyl Δ(25(27))-olefin products typical of primitive organisms. Unnatural Δ(24(25))-sterol substrates, missing a C4β-angular methyl group involved with binding orientation, convert to product ratios in favor of Δ(24(28))-products. Remodeling the active site to alter the electronics of Try110 (to Leu) results in delayed timing of the hydride migration from methyl attack of the Δ(24)-bond, that thereby produces metabolic switching of product ratios in favor of Δ(25(27))-olefins or impairs the second C1-transfer activity. Incubation of [27-(13)C]lanosterol or [methyl-(2)H3]SAM as co-substrates established the CrSMT catalyzes a sterol methylation pathway by the "algal" Δ(25(27))-olefin route, where methylation proceeds by a conserved SN2 reaction and de-protonation proceeds from the pro-Z methyl group on lanosterol corresponding to C27. This previously unrecognized catalytic competence for an enzyme of sterol biosynthesis, together with phylogenomic analyses, suggest that mutational divergence of a promiscuous SMT produced substrate- and phyla-specific SMT1 (catalyzes first biomethylation) and SMT2 (catalyzes second biomethylation) isoforms in red and green algae, respectively, and in the case of SMT2 selection afforded modification in reaction channeling necessary for the switch in ergosterol (24β-methyl) biosynthesis to stigmasterol (24α-ethyl) biosynthesis during the course of land plant evolution.
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Affiliation(s)
- Brad A Haubrich
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, Lubbock, TX 79409, United States
| | - Emily K Collins
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, Lubbock, TX 79409, United States
| | - Alicia L Howard
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, Lubbock, TX 79409, United States
| | - Qian Wang
- Department of Cell Biology, University of Texas Southwestern Medical School, Dallas, TX 75390, United States
| | - William J Snell
- Department of Cell Biology, University of Texas Southwestern Medical School, Dallas, TX 75390, United States
| | - Matthew B Miller
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, Lubbock, TX 79409, United States
| | - Crista D Thomas
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, Lubbock, TX 79409, United States
| | - Stephanie K Pleasant
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, Lubbock, TX 79409, United States
| | - W David Nes
- Center for Chemical Biology and Department of Chemistry & Biochemistry, Texas Tech University, Lubbock, TX 79409, United States.
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Haubrich BA, Singha UK, Miller MB, Nes CR, Anyatonwu H, Lecordier L, Patkar P, Leaver DJ, Villalta F, Vanhollebeke B, Chaudhuri M, Nes WD. Discovery of an ergosterol-signaling factor that regulates Trypanosoma brucei growth. J Lipid Res 2014; 56:331-41. [PMID: 25424002 DOI: 10.1194/jlr.m054643] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ergosterol biosynthesis and homeostasis in the parasitic protozoan Trypanosoma brucei was analyzed by RNAi silencing and inhibition of sterol C24β-methyltransferase (TbSMT) and sterol 14α-demethylase [TbSDM (TbCYP51)] to explore the functions of sterols in T. brucei growth. Inhibition of the amount or activity of these enzymes depletes ergosterol from cells at <6 fg/cell for procyclic form (PCF) cells or <0.01 fg/cell for bloodstream form (BSF) cells and reduces infectivity in a mouse model of infection. Silencing of TbSMT expression by RNAi in PCF or BSF in combination with 25-azalanosterol (AZA) inhibited parasite growth and this inhibition was restored completely by adding synergistic cholesterol (7.8 μM from lipid-depleted media) with small amounts of ergosterol (1.2 μM) to the medium. These observations are consistent with the proposed requirement for ergosterol as a signaling factor to spark cell proliferation while imported cholesterol or the endogenously formed cholesta-5,7,24-trienol act as bulk membrane components. To test the potential chemotherapeutic importance of disrupting ergosterol biosynthesis using pairs of mechanism-based inhibitors that block two enzymes in the post-squalene segment, parasites were treated with AZA and itraconazole at 1 μM each (ED50 values) resulting in parasite death. Taken together, our results demonstrate that the ergosterol pathway is a prime drug target for intervention in T. brucei infection.
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Affiliation(s)
- Brad A Haubrich
- Center for Chemical Biology and Department of Chemistry and Biochemistry Texas Tech University, Lubbock, TX 79409
| | - Ujjal K Singha
- Department of Microbiology and Immunology, Meharry Medical College, Nashville, TN 37208
| | - Matthew B Miller
- Center for Chemical Biology and Department of Chemistry and Biochemistry Texas Tech University, Lubbock, TX 79409
| | - Craigen R Nes
- Center for Chemical Biology and Department of Chemistry and Biochemistry Texas Tech University, Lubbock, TX 79409
| | - Hosanna Anyatonwu
- Center for Chemical Biology and Department of Chemistry and Biochemistry Texas Tech University, Lubbock, TX 79409
| | - Laurence Lecordier
- Laboratoire de Parasitologie Moléculaire, IBMM, Université Libre de Bruxelles, B6041 Gosselies, Belgium
| | - Presheet Patkar
- Center for Chemical Biology and Department of Chemistry and Biochemistry Texas Tech University, Lubbock, TX 79409
| | - David J Leaver
- Center for Chemical Biology and Department of Chemistry and Biochemistry Texas Tech University, Lubbock, TX 79409 Institute of Chemistry and Biomedical Sciences, Nanjing University, Nanjing 210023, People's Republic of China
| | - Fernando Villalta
- Department of Microbiology and Immunology, Meharry Medical College, Nashville, TN 37208
| | - Benoit Vanhollebeke
- Laboratoire de Parasitologie Moléculaire, IBMM, Université Libre de Bruxelles, B6041 Gosselies, Belgium
| | - Minu Chaudhuri
- Department of Microbiology and Immunology, Meharry Medical College, Nashville, TN 37208
| | - W David Nes
- Center for Chemical Biology and Department of Chemistry and Biochemistry Texas Tech University, Lubbock, TX 79409
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Awakawa T, Zhang L, Wakimoto T, Hoshino S, Mori T, Ito T, Ishikawa J, Tanner ME, Abe I. A Methyltransferase Initiates Terpene Cyclization in Teleocidin B Biosynthesis. J Am Chem Soc 2014; 136:9910-3. [DOI: 10.1021/ja505224r] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Takayoshi Awakawa
- Graduate
School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Lihan Zhang
- Graduate
School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Toshiyuki Wakimoto
- Graduate
School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Shotaro Hoshino
- Graduate
School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Takahiro Mori
- Graduate
School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Takuya Ito
- Faculty
of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima 770-8514, Japan
| | - Jun Ishikawa
- National Institute of Infectious Diseases, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Martin E. Tanner
- Department
of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Ikuro Abe
- Graduate
School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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Wriessnegger T, Pichler H. Yeast metabolic engineering – Targeting sterol metabolism and terpenoid formation. Prog Lipid Res 2013; 52:277-93. [DOI: 10.1016/j.plipres.2013.03.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2012] [Revised: 03/26/2013] [Accepted: 03/27/2013] [Indexed: 12/28/2022]
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Effect of substrate features and mutagenesis of active site tyrosine residues on the reaction course catalysed by Trypanosoma brucei sterol C-24-methyltransferase. Biochem J 2011; 439:413-22. [DOI: 10.1042/bj20110865] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
TbSMT [Trypanosoma brucei 24-SMT (sterol C-24-methyltransferase)] synthesizes an unconventional 24-alkyl sterol product set consisting of Δ24(25)-, Δ24(28)- and Δ25(27)-olefins. The C-methylation reaction requires Si(β)-face C-24-methyl addition coupled to reversible migration of positive charge from C-24 to C-25. The hydride shifts responsible for charge migration in formation of multiple ergostane olefin isomers catalysed by TbSMT were examined by incubation of a series of sterol acceptors paired with AdoMet (S-adenosyl-L-methionine). Results obtained with zymosterol compared with the corresponding 24-2H and 27-13C derivatives revealed isotopic-sensitive branching in the hydride transfer reaction on the path to form a 24-methyl-Δ24(25)-olefin product (kinetic isotope effect, kH/kD=1.20), and stereospecific CH3→CH2 elimination at the C28 branch and C27 cis-terminal methyl to form Δ24(28) and Δ25(27) products respectively. Cholesta-5,7,22,24-tetraenol converted into ergosta-5,7,22,24(28)-tetraenol and 24β–hydroxy ergosta-5,7,23-trienol (new compound), whereas ergosta-5,24-dienol converted into 24-dimethyl ergosta-5,25(27)-dienol and cholesta-5,7,24-trienol converted into ergosta-5,7,25(27)trienol, ergosta-5,7,24(28)-trienol, ergosta-5,7,24-trienol and 24 dimethyl ergosta-5,7,25(27)-trienol. We made use of our prior research and molecular modelling of 24-SMT to identify contact amino acids that might affect catalysis. Conserved tyrosine residues at positions 66, 177 and 208 in TbSMT were replaced with phenylalanine residues. The substitutions generated variable loss of activity during the course of the first C-1-transfer reaction, which differs from the corresponding Erg6p mutants that afforded a gain in C-2-transfer activity. The results show that differences exist among 24-SMTs in control of C-1- and C-2-transfer activities by interactions of intermediate and aromatic residues in the activated complex and provide an opportunity for rational drug design of a parasite enzyme not synthesized by the human host.
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Affiliation(s)
- W David Nes
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, USA.
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11
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Ganapathy K, Kanagasabai R, Nguyen TTM, Nes WD. Purification, characterization and inhibition of sterol C24-methyltransferase from Candida albicans. Arch Biochem Biophys 2011; 505:194-201. [DOI: 10.1016/j.abb.2010.10.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Revised: 10/05/2010] [Accepted: 10/07/2010] [Indexed: 10/19/2022]
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Neelakandan AK, Song Z, Wang J, Richards MH, Wu X, Valliyodan B, Nguyen HT, Nes WD. Cloning, functional expression and phylogenetic analysis of plant sterol 24C-methyltransferases involved in sitosterol biosynthesis. PHYTOCHEMISTRY 2009; 70:1982-98. [PMID: 19818974 DOI: 10.1016/j.phytochem.2009.09.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Revised: 07/20/2009] [Accepted: 09/03/2009] [Indexed: 05/28/2023]
Abstract
Sterol 24C-methyltransferases (SMTs) constitute a group of sequence-related proteins that catalyze the distinct patterns of 24-alkyl sterols that occur throughout nature. Two SMT cDNAs (SMT2-1 and SMT2-2) were cloned by homology based PCR methods from young leaves of Glycine max (soybean) and the corresponding enzymes were expressed functionally in Escherichia coli. The full-length cDNA for SMT2-1 and SMT2-2 have open reading frames of 1086 bp and 1092 bp, respectively, and encode proteins of 361 and 363 residues with a calculated molecular mass of 40.3 and 40.4 kDa, respectively. The substrate preference of the two isoforms was similar yet they differed from SMT1; kinetically SMT2-1 and SMT2-2 generated k(cat) values for the optimal substrate 24(28)methylene lophenol of 0.8 min(-1) and 1.34 min(-1), respectively, compared to the activity of SMT1 that generated a k(cat) for the optimal substrate cycloartenol of 0.6 min(-1). SMT2-2 was purified to homogeneity and the subunit organization shown to be tetrameric in similar fashion to other cloned SMTs. Analysis of the accumulated products catalyzed by the recombinant enzymes demonstrated that soybean SMT2-1 and SMT2-2 operate transalkylation activities analogous to the soybean plant SMT1. Metabolite analyses correlated with transcript profiling of the three SMT isoforms during soybean maturation clearly demonstrated that SMT isoform expression determines specific C24-methyl to C24-ethyl ratios to flowering whereas with seed development there is a disconnection such that the SMT transcript levels decrease against an increase in sterol content; generally SMT2-2 is expressed more than SMT2-1 or SMT1. These observations suggest that the genes that encode SMT1 and SMT2 in sitosterol biosynthesis may have undergone divergent evolution. In support of this proposition, the genomic organization for SMT1 of fungi and protozoa align very closely with one another and to those of the plant SMT2; both sets of SMTs lack introns. Unexpectedly, the SMT1 from Glycine max and other embryophytes of diverse origin possess disparate intron-exon characteristics that can be shown relates back to the algae. Our results suggest that the order of SMT1 appearing before SMT2 in phytosterol synthesis arose recently in plant evolution in response to duplication of a more primitive SMT gene likely to have been bifunctional and catalytically promiscuous.
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Affiliation(s)
- Anjanasree K Neelakandan
- Division of Plant Sciences and National Center for Soybean Biotechnology, University of Missouri, Columbia, MO 65211, USA
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Liu J, Nes WD. Steroidal triterpenes: design of substrate-based inhibitors of ergosterol and sitosterol synthesis. Molecules 2009; 14:4690-706. [PMID: 19924096 PMCID: PMC6255433 DOI: 10.3390/molecules14114690] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2009] [Revised: 11/05/2009] [Accepted: 11/10/2009] [Indexed: 11/27/2022] Open
Abstract
This article reviews the design and study, in our own laboratory and others, of new steroidal triterpenes with a modified lanosterol or cycloartenol frame. These compounds, along with a number of known analogs with the cholestane skeleton, have been evaluated as reversible or irreversible inhibitors of sterol C24-methyltransferase (SMT) from plants, fungi and protozoa. The SMT catalyzes the C24-methylation reaction involved with the introduction of the C24-methyl group of ergosterol and the C24-ethyl group of sitosterol, cholesterol surrogates that function as essential membrane inserts in many photosynthetic and non-photosynthetic eukaryotic organisms. Sterol side chains constructed with a nitrogen, sulfur, bromine or fluorine atom, altered to possess a methylene cyclopropane group, or elongated to include terminal double or triple bonds are shown to exhibit different in vitro activities toward the SMT which are mirrored in the inhibition potencies detected in the growth response of treated cultured human and plant cells or microbes. Several of the substrate-based analogs surveyed here appear to be taxaspecific compounds acting as mechanism-based inactivators of the SMT, a crucial enzyme not synthesized by animals. Possible mechanisms for the inactivation process and generation of novel products catalyzed by the variant SMTs are discussed.
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Affiliation(s)
- Jialin Liu
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, USA.
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14
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Current awareness on yeast. Yeast 2009. [DOI: 10.1002/yea.1619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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