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Xie J, Rybak JM, Martin-Vicente A, Guruceaga X, Thorn HI, Nywening AV, Ge W, Parker JE, Kelly SL, Rogers PD, Fortwendel JR. The sterol C-24 methyltransferase encoding gene, erg6, is essential for viability of Aspergillus species. Nat Commun 2024; 15:4261. [PMID: 38769341 PMCID: PMC11106247 DOI: 10.1038/s41467-024-48767-3] [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: 08/28/2023] [Accepted: 05/09/2024] [Indexed: 05/22/2024] Open
Abstract
Triazoles, the most widely used class of antifungal drugs, inhibit the biosynthesis of ergosterol, a crucial component of the fungal plasma membrane. Inhibition of a separate ergosterol biosynthetic step, catalyzed by the sterol C-24 methyltransferase Erg6, reduces the virulence of pathogenic yeasts, but its effects on filamentous fungal pathogens like Aspergillus fumigatus remain unexplored. Here, we show that the lipid droplet-associated enzyme Erg6 is essential for the viability of A. fumigatus and other Aspergillus species, including A. lentulus, A. terreus, and A. nidulans. Downregulation of erg6 causes loss of sterol-rich membrane domains required for apical extension of hyphae, as well as altered sterol profiles consistent with the Erg6 enzyme functioning upstream of the triazole drug target, Cyp51A/Cyp51B. Unexpectedly, erg6-repressed strains display wild-type susceptibility against the ergosterol-active triazole and polyene antifungals. Finally, we show that erg6 repression results in significant reduction in mortality in a murine model of invasive aspergillosis. Taken together with recent studies, our work supports Erg6 as a potentially pan-fungal drug target.
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Affiliation(s)
- Jinhong Xie
- Graduate Program in Pharmaceutical Sciences, College of Graduate Health Sciences, University of Tennessee Health Science Center, Memphis, TN, USA
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Jeffrey M Rybak
- Department of Pharmacy and Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Adela Martin-Vicente
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Xabier Guruceaga
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Harrison I Thorn
- Graduate Program in Pharmaceutical Sciences, College of Graduate Health Sciences, University of Tennessee Health Science Center, Memphis, TN, USA
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Ashley V Nywening
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA
- Integrated Program in Biomedical Sciences, College of Graduate Health Sciences, University of Tennessee Health Science Center, Memphis, TN, USA
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Wenbo Ge
- Department of Pharmacy and Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Josie E Parker
- Molecular Biosciences Division, School of Biosciences, Cardiff University, Cardiff, Wales, UK
| | - Steven L Kelly
- Institute of Life Science, Swansea University Medical School, Swansea, Wales, UK
| | - P David Rogers
- Department of Pharmacy and Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Jarrod R Fortwendel
- Department of Clinical Pharmacy and Translational Science, College of Pharmacy, University of Tennessee Health Science Center, Memphis, TN, USA.
- Department of Microbiology, Immunology, and Biochemistry, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, USA.
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Darnet S, Blary A, Chevalier Q, Schaller H. Phytosterol Profiles, Genomes and Enzymes - An Overview. FRONTIERS IN PLANT SCIENCE 2021; 12:665206. [PMID: 34093623 PMCID: PMC8172173 DOI: 10.3389/fpls.2021.665206] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Accepted: 04/20/2021] [Indexed: 05/12/2023]
Abstract
The remarkable diversity of sterol biosynthetic capacities described in living organisms is enriched at a fast pace by a growing number of sequenced genomes. Whereas analytical chemistry has produced a wealth of sterol profiles of species in diverse taxonomic groups including seed and non-seed plants, algae, phytoplanktonic species and other unicellular eukaryotes, functional assays and validation of candidate genes unveils new enzymes and new pathways besides canonical biosynthetic schemes. An overview of the current landscape of sterol pathways in the tree of life is tentatively assembled in a series of sterolotypes that encompass major groups and provides also peculiar features of sterol profiles in bacteria, fungi, plants, and algae.
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Affiliation(s)
| | | | | | - Hubert Schaller
- Plant Isoprenoid Biology Team, Institut de Biologie Moléculaire des Plantes du CNRS, Université de Strasbourg, Strasbourg, France
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Nes WD, Zhou W, Ganapathy K, Liu J, Vatsyayan R, Chamala S, Hernandez K, Miranda M. Sterol 24-C-methyltransferase: An enzymatic target for the disruption of ergosterol biosynthesis and homeostasis in Cryptococcus neoformans. Arch Biochem Biophys 2009; 481:210-8. [DOI: 10.1016/j.abb.2008.11.003] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Revised: 10/30/2008] [Accepted: 11/01/2008] [Indexed: 10/21/2022]
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Abstract
Pneumocystis can transiently colonize healthy individuals without causing adverse symptoms, and most people test positive for exposure to this organism early in life. However, it can cause Pneumocystis pneumonia (PcP) in people with impaired immune systems and is a major cause of death in HIV/AIDS. Although it has close affinities to the Ascomycetes, Pneumocystis has features unlike those of any single group of fungi. For example, Pneumocystis does not synthesize ergosterol, which is consistent with the inefficacy of amphotericin B and some triazoles in clearing PcP. Pneumocystis sterols include distinct delta7 24-alkylsterols. Metabolic radiolabeling experiments demonstrated that P. carinii synthesizes sterols de novo. Cholesterol is the most abundant sterol in Pneumocystis; most, if not all, is scavenged from the mammalian host lung by the pathogen. The P. carinii erg7, erg6, and erg11 genes have been cloned, sequenced, and expressed in heterologous systems. The recombinant P. carinii S-adenosyl-L-methionine:C-24 sterol methyl transferase (SAM:SMT) has a preference for lanosterol over zymosterol as substrate, and the enzyme can catalyze the transfer of either one or two methyl groups to the C-24 position of the sterol side chain. Two different sterol compositions were detected among human-derived P. jirovecii; one was dominated by C28 and C29 sterols, and the other had high proportions of higher molecular mass components, notably the C32 sterol pneumocysterol. The latter phenotype apparently represents organisms blocked at 14alpha-demethylation of the sterol nucleus. These studies suggest that SAM:SMT is an attractive drug target for developing new chemotherapy for PcP.
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Affiliation(s)
- Edna S Kaneshiro
- Department of Biological Sciences, University of Cincinnati, Cincinnati, Ohio 45221, USA.
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Kanagasabai R, Zhou W, Liu J, Nguyen TTM, Veeramachaneni P, Nes WD. Disruption of ergosterol biosynthesis, growth, and the morphological transition inCandida albicansby sterol methyltransferase inhibitors containing sulfur at C-25 in the sterol side chain. Lipids 2004; 39:737-46. [PMID: 15638241 DOI: 10.1007/s11745-004-1290-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The sterol substrate analog 25-thialanosterol and its corresponding sulfonium salt were evaluated for their ability to serve as antifungal agents and to inhibit sterol methyltransferase (SMT) activity in Candida albicans. Both compounds inhibited cell proliferation, were fungistatic, interrupted the yeast-like-form to germ-tube-form transition, and resulted in the accumulation of zymosterol and related delta24-sterols concurrent with a decrease in ergosterol, as was expected for the specific inhibition of SMT activity. Feedback on sterol synthesis was evidenced by elevated levels of cellular sterols in treated vs. control cultures. However, neither farnesol nor squalene accumulated in significant amounts in treated cultures, suggesting that carbon flux is channeled from the isoprenoid pathway to the sterol pathway with minor interruption or redirection until blockage at the C-methylation step. Activity assays using solubilized C. albicans SMT confirmed the inhibitors impair SMT action. Kinetic analysis indicated that 25-thialanosterol inhibited SMT with the properties of a time-dependent mechanism-based inactivator Ki of 5 microM and apparent kinact of 0.013 min(-1), whereas the corresponding sulfonium salt was a reversible-type transition state analog exhibiting a Ki of 20 nM. The results are interpreted to imply changes in ergosterol homeostasis as influenced by SMT activity can control growth and the morphological transition in C. albicans, possibly affecting disease development.
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Affiliation(s)
- Ragu Kanagasabai
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, USA
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9
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Mechanism-based enzyme inactivators of phytosterol biosynthesis. Molecules 2004; 9:185-203. [PMID: 18007423 DOI: 10.3390/90400185] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2004] [Accepted: 03/08/2004] [Indexed: 11/16/2022] Open
Abstract
Current progress on the mechanism and substrate recognition by sterol methyl transferase (SMT), the role of mechanism-based inactivators, other inhibitors of SMT action to probe catalysis and phytosterol synthesis is reported. SMT is a membrane-bound enzyme which catalyzes the coupled C-methylation-deprotonation reaction of sterol acceptor molecules generating the 24-alkyl sterol side chains of fungal ergosterol and plant sitosterol. This C-methylation step can be rate-limiting in the post-lanosterol (fungal) or post-cycloartenol (plant) pathways. A series of sterol analogs designed to impair SMT activity irreversibly have provided deep insight into the C-methylation reaction and topography of the SMT active site and as reviewed provide leads for the development of antifungal agents.
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Mangla AT, Nes WD. Sterol C-methyl transferase from Prototheca wickerhamii mechanism, sterol specificity and inhibition. Bioorg Med Chem 2000; 8:925-36. [PMID: 10882005 DOI: 10.1016/s0968-0896(00)00040-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The membrane-bound sterol methyl transferase (SMT) enzyme from Prototheca wickerhamii, a non-photosynthetic, yeast-like alga, was found to C-methylate appropriate delta24(25)-sterol acceptor molecules to delta25(27)-24beta-methyl products stereoselectively. Incubation with pairs of substrates--[2H3-methyl]AdoMet and cycloartenol, and AdoMet and [27-(13)C]lanosterol--followed by 1H and 13C NMR analysis of the isotopically labeled products demonstrated the si-face (beta-face attack) mechanism of C-methylation and the regiospecificity of delta25(27)-double bond formation from the pro-Z methyl group (C27) on lanosterol. The enzyme has a substrate preference for a sterol with a 3beta-hydroxyl group, a planar nucleus and a side chain oriented into a 'right-handed' structure (20R-chirality) characteristic of the native substrate, cycloartenol. The apparent native molecular weight of the SMT was determined to be approximately 154,000, as measured by Superose 6 FPLC. A series of sterol analogues which contain heteroatoms substituted for C24 and C25 or related structural modifications, including steroidal alkaloids, havs been used to probe further the active site and mechanism of action of the SMT enzyme. Sterol side chains containing isoelectronic modifications of a positively charged moiety in the form of an ammonium group substituted for carbon at C25, C24, C23 or C22 are particularly potent non-competitive inhibitors (Ki for the most potent inhibitor tested, 25-azacycloartanol, was ca. 2 nM, four orders of magnitude less than the Km for cycloartenol of 28 microM), supporting the intermediacy of the 24-methyl C24(25)-carbenium ion intermediate. Ergosterol, but neither cholesterol nor sitosterol, was found to inhibit SMT activity (Ki = 80 microM). The combination of results suggests that the interrelationships of substrate functional groups within the active center of a delta24(25) to delta25(27) 24beta-methyl-SMT could be approximated thereby allowing the rational design of C-methylation inhibitors to be formulated and tested.
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Affiliation(s)
- A T Mangla
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock 79409, USA
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Nes WD, He L, Mangla AT. 4,4,14 alpha-trimethyl 9 beta,19-cyclo-5 alpha-26-homocholesta-24,26-dien-3 beta-ol: a potent mechanism-based inactivator of delta 24(25)- to delta 25(27)-sterol methyl transferase. Bioorg Med Chem Lett 1998; 8:3449-52. [PMID: 9934450 DOI: 10.1016/s0960-894x(98)00651-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The title compound (4A) was synthesized and tested as a mechanism-based inactivator of the sterol methyl transferase (SMT) enzyme from Prototheca wickerhamii. Using cycloartenol as substrate, 4A was found to exhibit time-dependent inactivation kinetics, generating a Ki value of 30 microM and Kinact value of 0.30 min-1.
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Affiliation(s)
- W D Nes
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock 79409, USA
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