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Sayson SG, Ashbaugh A, Cushion MT. Extracellular vesicles from Pneumocystis carinii-infected rats impair fungal viability but are dispensable for macrophage functions. Microbiol Spectr 2024; 12:e0365323. [PMID: 38236033 PMCID: PMC10845964 DOI: 10.1128/spectrum.03653-23] [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: 11/03/2023] [Accepted: 11/28/2023] [Indexed: 01/19/2024] Open
Abstract
Pneumocystis spp. are host obligate fungal pathogens that can cause severe pneumonia in mammals and rely heavily on their host for essential nutrients. The lack of a sustainable in vitro culture system poses challenges in understanding their metabolism, and the acquisition of essential nutrients from host lungs remains unexplored. Transmission electron micrographs show that extracellular vesicles (EVs) are found near Pneumocystis spp. within the lung. We hypothesized that EVs transport essential nutrients to the fungi during infection. To investigate this, EVs from P. carinii- and P. murina-infected rodents were biochemically and functionally characterized. These EVs contained host proteins involved in cellular, metabolic, and immune processes as well as proteins with homologs found in other fungal EV proteomes, indicating that Pneumocystis may release EVs. Notably, EV uptake by P. carinii indicated their potential involvement in nutrient acquisition and a possibility for using engineered EVs for efficient therapeutic delivery. However, EVs added to P. carinii in vitro did not show increased growth or viability, implying that additional nutrients or factors are necessary to support their metabolic requirements. Exposure of macrophages to EVs increased proinflammatory cytokine levels but did not affect macrophages' ability to kill or phagocytose P. carinii. These findings provide vital insights into P. carinii and host EV interactions, yet the mechanisms underlying P. carinii's survival in the lung remain uncertain. These studies are the first to isolate, characterize, and functionally assess EVs from Pneumocystis-infected rodents, promising to enhance our understanding of host-pathogen dynamics and therapeutic potential.IMPORTANCEPneumocystis spp. are fungal pathogens that can cause severe pneumonia in mammals, relying heavily on the host for essential nutrients. The absence of an in vitro culture system poses challenges in understanding their metabolism, and the acquisition of vital nutrients from host lungs remains unexplored. Extracellular vesicles (EVs) are found near Pneumocystis spp., and it is hypothesized that these vesicles transport nutrients to the pathogenic fungi. Pneumocystis proteins within the EVs showed homology to other fungal EV proteomes, suggesting that Pneumocystis spp. release EVs. While EVs did not significantly enhance P. carinii growth in vitro, P. carinii displayed active uptake of these vesicles. Moreover, EVs induced proinflammatory cytokine production in macrophages without compromising their ability to combat P. carinii. These findings provide valuable insights into EV dynamics during host-pathogen interactions in Pneumocystis pneumonia. However, the precise underlying mechanisms remain uncertain. This research also raises the potential for engineered EVs in therapeutic applications.
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Affiliation(s)
- Steven G. Sayson
- Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
- The Veterans Affairs Medical Center, Cincinnati, Ohio, USA
| | - Alan Ashbaugh
- Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
- The Veterans Affairs Medical Center, Cincinnati, Ohio, USA
| | - Melanie T. Cushion
- Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
- The Veterans Affairs Medical Center, Cincinnati, Ohio, USA
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Sayson SG, Ashbaugh A, Cushion MT. Extracellular Vesicles from Pneumocystis carinii -Infected Rats Impair Fungal Viability but are Dispensable for Macrophage Functions. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.19.558454. [PMID: 37786700 PMCID: PMC10541577 DOI: 10.1101/2023.09.19.558454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/04/2023]
Abstract
Pneumocystis spp. are host obligate fungal pathogens that can cause severe pneumonia in mammals and rely heavily on their host for essential nutrients. The lack of a sustainable in vitro culture system poses challenges in understanding their metabolism and the acquisition of essential nutrients from host lungs remains unexplored. Transmission electron micrographs show Extracellular Vesicles (EVs) are found near Pneumocystis spp. within the lung. We hypothesized that EVs transport essential nutrients to the fungi during infection. To investigate this, EVs from P. carinii and P. murina infected rodents were biochemically and functionally characterized. These EVs contained host proteins involved in cellular, metabolic, and immune processes as well as proteins with homologs found in other fungal EV proteomes, indicating Pneumocystis may release EVs. Notably, EV uptake by P. carinii indicated their potential involvement in nutrient acquisition and indicate a possibility for using engineered EVs for efficient therapeutic delivery. However, EVs added to P. carinii in vitro , did not show increased growth or viability, implying that additional nutrients or factors are necessary to support their metabolic requirements. Exposure of macrophages to EVs increased proinflammatory cytokine levels, but did not affect macrophages' ability to kill or phagocytose P. carinii . These findings provide vital insights into P. carinii and host EV interactions, yet the mechanisms underlying P. carinii 's survival in the lung remain uncertain. These studies are the first to isolate, characterize, and functionally assess EVs from Pneumocystis -infected rodents, promising to enhance our understanding of host-pathogen dynamics and therapeutic potential.
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Retallack GJ. Damaged Dickinsonia specimens provide clues to Ediacaran vendobiont biology. PLoS One 2022; 17:e0269638. [PMID: 35709144 PMCID: PMC9202952 DOI: 10.1371/journal.pone.0269638] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 05/19/2022] [Indexed: 12/14/2022] Open
Abstract
Recently reported specimens of the enigmatic Ediacaran fossil Dickinsonia from Russia show damage and repair that provides evidence of how they grew, and of their biological affinities. Marginal and terminal areas of wilting deformation are necrotic zones separating regenerated growth, sometimes on two divergent axes, rather than a single axis. Necrotic zones of damage to Dickinsonia are not a thick scar or callus, like a wound or amputation. Nor are they smooth transitions to a regenerated tail or arm. The wilted necrotic zone is most like damage by freezing, salt, or sunburn of leaves and lichens, compatible with evidence of terrestrial habitat from associated frigid and gypsic paleosols. Dickinsonia did not regrow by postembryonic addition of modules from a subterminal or patterned growth zone as in earthworms, myriapods, trilobites, crustaceans, and lizards. Rather Dickinsonia postembryonic regrowth from sublethal damage was from microscopic apical and lateral meristems, as in plants and lichens. Considered as fungal, Dickinsonia, and perhaps others of Class Vendobionta, were more likely Glomeromycota or Mucoromycotina, rather than Ascomycota or Basidiomycota.
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Affiliation(s)
- Gregory J. Retallack
- Department of Earth Sciences, University of Oregon, Eugene, Oregon, United States of America
- * E-mail:
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Ma L, Cissé OH, Kovacs JA. A Molecular Window into the Biology and Epidemiology of Pneumocystis spp. Clin Microbiol Rev 2018; 31:e00009-18. [PMID: 29899010 PMCID: PMC6056843 DOI: 10.1128/cmr.00009-18] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Pneumocystis, a unique atypical fungus with an elusive lifestyle, has had an important medical history. It came to prominence as an opportunistic pathogen that not only can cause life-threatening pneumonia in patients with HIV infection and other immunodeficiencies but also can colonize the lungs of healthy individuals from a very early age. The genus Pneumocystis includes a group of closely related but heterogeneous organisms that have a worldwide distribution, have been detected in multiple mammalian species, are highly host species specific, inhabit the lungs almost exclusively, and have never convincingly been cultured in vitro, making Pneumocystis a fascinating but difficult-to-study organism. Improved molecular biologic methodologies have opened a new window into the biology and epidemiology of Pneumocystis. Advances include an improved taxonomic classification, identification of an extremely reduced genome and concomitant inability to metabolize and grow independent of the host lungs, insights into its transmission mode, recognition of its widespread colonization in both immunocompetent and immunodeficient hosts, and utilization of strain variation to study drug resistance, epidemiology, and outbreaks of infection among transplant patients. This review summarizes these advances and also identifies some major questions and challenges that need to be addressed to better understand Pneumocystis biology and its relevance to clinical care.
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Affiliation(s)
- Liang Ma
- Critical Care Medicine Department, NIH Clinical Center, Bethesda, Maryland, USA
| | - Ousmane H Cissé
- Critical Care Medicine Department, NIH Clinical Center, Bethesda, Maryland, USA
| | - Joseph A Kovacs
- Critical Care Medicine Department, NIH Clinical Center, Bethesda, Maryland, USA
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5
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Joffrion TM, Cushion MT. Sterol biosynthesis and sterol uptake in the fungal pathogen Pneumocystis carinii. FEMS Microbiol Lett 2010; 311:1-9. [PMID: 20528942 DOI: 10.1111/j.1574-6968.2010.02007.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Members of the fungal genus Pneumocystis colonize healthy mammalian hosts without causing apparent disease, but colonization in immunocompromised hosts may result in a potentially fatal pneumonia known as Pneumocystis pneumonia. Although Pneumocystis are fungi, this genus has characteristics that make it atypical among other fungi. Pneumocystis do not appear to synthesize the major fungal sterol, ergosterol, and biochemical analyses have shown that they utilize cholesterol rather than ergosterol as the bulk sterol. Pneumocystis carinii appears to scavenge exogenous sterols, including cholesterol, from its mammalian host. As a result, it has long been held that their ability to scavenge cholesterol from their hosts, and their inability to undergo sterol biosynthesis, makes them resistant to antifungal drugs that target ergosterol or ergosterol biosynthesis. However, genome scans and in vitro assays indicate the presence of sterol biosynthetic genes within the P. carinii genome, and targeted inhibition of these enzymes resulted in reduced viability of P. carinii, suggesting that these enzymes are functional within the organism. Heterologous expression of P. carinii sterol genes, along with biochemical analyses of the lipid content of P. carinii cellular membranes, have provided an insight into sterol biosynthesis and the sterol-scavenging mechanisms used by these fungi.
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Affiliation(s)
- Tiffany M Joffrion
- Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
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Abstract
Pneumocystis is a genus containing many species of non-culturable fungi, each of which infects a different mammalian host. Pneumonia caused by Pneumocystis is a problem in immunodeficient humans, but not in normal humans. Nevertheless, it appears that Pneumocystis organisms cannot survive and proliferate outside of their mammalian hosts, suggesting that Pneumocystis parasitizes immunocompetent mammals. Residence in immunocompetent hosts may rely on camouflage perpetrated by antigenic variation. In P. carinii, which is found in rats, there exist three families of genes that appear to be designed to create antigenic variation. One gene family, which encodes the major surface glycoprotein (MSG), contains nearly 100 members. Expression of the MSG family is controlled by restricting transcription to the one gene that is linked to a unique expression site. Changes in the sequence of the MSG gene linked to the expression site occur and appear to be caused by recombination with MSG genes not at the expression site. Preliminary evidence suggests that gene conversion is the predominant recombination mechanism.
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Affiliation(s)
- James R Stringer
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Cincinnati, Ohio 45267-0524, USA.
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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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Giner JL, Zhao H, Amit Z, Kaneshiro ES. Sterol composition of Pneumocystis jirovecii with blocked 14alpha-demethylase activity. J Eukaryot Microbiol 2005; 51:634-43. [PMID: 15666720 DOI: 10.1111/j.1550-7408.2004.tb00597.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Several drugs that interact with membrane sterols or inhibit their syntheses are effective in clearing a number of fungal infections. The AIDS-associated lung infection caused by Pneumocystis jirovecii is not cleared by many of these therapies. Pneumocystis normally synthesizes distinct C28 and C29 24-alkylsterols, but ergosterol, the major fungal sterol, is not among them. Two distinct sterol compositional phenotypes were previously observed in P. jirovecii. One was characterized by delta7 C28 and C29 24-alkylsterols with only low proportions of higher molecular mass components. In contrast, the other type was dominated by high C31 and C32 24-alkylsterols, especially pneumocysterol. In the present study, 28 molecular species were elucidated by nuclear magnetic resonance analysis of a human lung specimen containing P. jirovecii representing the latter sterol profile phenotype. Fifteen of the 28 had the methyl group at C-14 of the sterol nucleus and these represented 96% of the total sterol mass in the specimen (excluding cholesterol). These results strongly suggest that sterol 14alpha-demethylase was blocked in these organisms. Twenty-four of the 28 were 24-alkylsterols, indicating that methylation of the C-24 position of the sterol side chain by S-adenosyl-L-methionine:sterol C-24 methyl transferase was fully functional.
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Affiliation(s)
- José-Luis Giner
- Department of Chemistry, State University of New York-ESF, Syracuse, NY 13210, USA.
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Morales IJ, Vohra PK, Puri V, Kottom TJ, Limper AH, Thomas CF. Characterization of a lanosterol 14 alpha-demethylase from Pneumocystis carinii. Am J Respir Cell Mol Biol 2003; 29:232-8. [PMID: 12606318 DOI: 10.1165/rcmb.2003-0012oc] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Pneumocystis carinii (PC) causes severe pneumonia in immunocompromised patients. PC is intrinsically resistant to treatment with azole antifungal medications. The enzyme lanosterol 14 alpha-demethylase (Erg11) is the target for azole antifungals. We cloned PCERG11 and compared its sequence to Erg11 proteins present in azole-resistant organisms, and performed chromosomal and Northern blot analysis for PCERG11. Of 13 potential sites which could confer resistance to azoles, two were identical to azole-resistant Candida. By site-directed mutagenesis we changed these two sites in PCERG11 to those present in azole-sensitive Candida to generate PCERG11-SDM (E113D, T125K). We tested the susceptibility of ERG11 deletion strains of Saccharomyces cerevisiae (SC) expressing PCERG11, PCERG11-SDM, and wild-type SCERG11 to three azole antifungals: fluconazole, itraconazole, and voriconazole. PCERG11 required a 2.2-fold higher dose of voriconazole and 3.5-fold higher dose of fluconazole than SCERG11 for a 50% reduction in growth. No difference was observed in the sensitivity to itraconazole. PCERG11-SDM has increased sensitivity to fluconazole and voriconazole, but not itraconazole. We believe that the molecular structure of the lanosterol 14 alpha-demethylase encoded by PCERG11 confers inherent resistance to azole antifungals and plays an integral part in the overall resistance of this PC to azole therapy.
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Affiliation(s)
- Ian J Morales
- Thoracic Diseases Research Unit, Division of Pulmonary, Critical Care and Internal Medicine, Department of Medicine, Mayo Clinic and Foundation, Rochester, MN 55905, USA
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Worsham DN, Basselin M, Smulian AG, Beach DH, Kaneshiro ES. Evidence for Cholesterol Scavenging by Pneumocystis and Potential Modifications of Host-Synthesized Sterols by the P. carinii SAM:SMT. J Eukaryot Microbiol 2003; 50 Suppl:678-9. [PMID: 14736216 DOI: 10.1111/j.1550-7408.2003.tb00683.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- D Nicole Worsham
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, USA
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11
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Abstract
Pneumocystis lacks ergosterol, and several antimycotics that bind ergosterol in fungal membranes or inhibit its synthesis are ineffective against Pneumocystis pneumonia. The organism synthesizes C(28) and C(29) Delta(7) 24-alkylsterols, 24-alkyllanosterol derivatives, and Delta(5) 24-alkylsterols, which may be produced by modifying scavenged Delta(5) sterols. Mammals cannot desaturate C-22 and alkylate C-24 of sterols, thus, these processes are particularly attractive targets for antifungal drug development. Recent data indicate that C-22 desaturation is not, but C-24 alkylation is an attractive target in P. carinii. The P. carinii S-adenosyl-L-methionine:sterol C-24 methyl transferase (SAM:SMT) has unique properties; it prefers lanosterol as its sterol substrate.
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Affiliation(s)
- Edna S Kaneshiro
- Department of Biological Sciences, University of Cincinnati, OH 45221, USA.
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Giner JL, Beach DH, Parish EJ, Jayasimhulu K, Kaneshiro ES. Definitive structural identities of 42 sterol components in Pneumocystis carinii. J Eukaryot Microbiol 2002; Suppl:142S-143S. [PMID: 11906032 DOI: 10.1111/j.1550-7408.2001.tb00490.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- J L Giner
- Department of Chemistry, SUNY, ESF, Syracuse, NY 13210, USA
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13
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Kaneshiro ES, Rosenfeld JA, Basselin M, Bradshaw S, Stringer JR, Smulian AG, Giner JL. Pneumocystis carinii erg6 gene: sequencing and expression of recombinant SAM:sterol methyltransferase in heterologous systems. J Eukaryot Microbiol 2002; Suppl:144S-146S. [PMID: 11906033 DOI: 10.1111/j.1550-7408.2001.tb00491.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- E S Kaneshiro
- Department of Biological Sciences, University of Cincinnati, OH, USA.
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Giner JL, Zhao H, Beach DH, Parish EJ, Jayasimhulu K, Kaneshiro ES. Comprehensive and definitive structural identities of Pneumocystis carinii sterols. J Lipid Res 2002; 43:1114-24. [PMID: 12091496 DOI: 10.1194/jlr.m200113-jlr200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pneumocystis causes a type of pneumonia in immunodeficient mammals, such as AIDS patients. Mammals cannot alkylate the C-24 position of the sterol side chain, nor can they desaturate C-22. Thus, the reactions leading to these sterol modifications are particularly attractive targets for the development of drugs against fungal and protozoan pathogens that make them. In the present study, the definitive structures of 43 sterol molecular species in rat-derived Pneumocystis carinii were elucidated by nuclear magnetic resonance spectroscopy. Ergosterol, Delta(5,7) sterols, trienes, and tetraenes were not among them. Most (32 of the 43) were 24-alkylsterols, products of S-adenosyl-L-methionine:C-24 sterol methyl transferase (SAM:SMT) enzyme activity. Their abundance is consistent with the suggestion that SAM:SMT is highly active in this organism and that the enzyme is an excellent anti-Pneumocystis drug target. In contrast, the comprehensive analysis strongly suggest that P. carinii does not form Delta(22) sterols, thus C-22 desaturation does not appear to be a drug target in this pathogen. The lanosterol derivatives, 24-methylenelanost-8-en-3 beta-ol and (Z)-24-ethylidenelanost-8-en-3 beta-ol (pneumocysterol), previously identified in human-derived Pneumocystis jiroveci, were also detected among the sterols of the rat-derived P. carinii organisms.
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Affiliation(s)
- José-Luis Giner
- Department of Chemistry, State University of New York, ESF, Syracuse, NY 13210, USA
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Kaneshiro ES, Rosenfeld JA, Basselin-Eiweida M, Stringer JR, Keely SP, Smulian AG, Giner JL. The Pneumocystis carinii drug target S-adenosyl-L-methionine:sterol C-24 methyl transferase has a unique substrate preference. Mol Microbiol 2002; 44:989-99. [PMID: 12010494 DOI: 10.1046/j.1365-2958.2002.02932.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Pneumocystis is an opportunistic pathogen that can cause pneumonitis in immunodeficient people such as AIDS patients. Pneumocystis remains difficult to study in the absence of culture methods for luxuriant growth. Recombinant protein technology now makes it possible to avoid some major obstacles. The P. carinii expressed sequence tag (EST) database contains 11 entries of a sequence encoding a protein homologous to S-adenosyl-L-methionine (SAM):C-24 sterol methyl transferase (SMT), suggesting high activity of this enzyme in the organism. We sequenced the erg6 cDNA, identified the putative peptide motifs for the sterol and SAM binding sites in the deduced amino acid sequence and expressed the protein in Escherichia coli. Unlike SAM:SMT from other organisms, the P. carinii enzyme had higher affinities for lanosterol and 24-methylenelanosterol than for zymosterol, the preferred substrate in other fungi. Cycloartenol was not a productive substrate. With lanosterol and 24-methylenelanosterol as substrates, the major reaction products were 24-methylenelanosterol and pneumocysterol respectively. Thus, the P. carinii SAM:SMT catalysed the transfer of both the first and the second methyl groups to the sterol C-24 position, and the substrate preference was found to be a unique property of the P. carinii SAM:SMT. These observations, together with the absence of SAM:SMT among mammals, further support the identification of sterol C-24 alkylation reactions as excellent targets for the development of drugs specifically directed against this pathogen.
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Affiliation(s)
- Edna S Kaneshiro
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221-0006, USA.
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Fontaine J, Grandmougin-Ferjani A, Hartmann MA, Sancholle M. Sterol biosynthesis by the arbuscular mycorrhizal fungus Glomus intraradices. Lipids 2001; 36:1357-63. [PMID: 11834088 DOI: 10.1007/s11745-001-0852-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Ri-T-DNA-transformed carrot roots were used for investigating sterol metabolism by the arbuscular mycorrhizal (AM) fungus Glomus intraradices under three distinct experimental conditions: (i) a symbiotic stage (fungus still attached to the host roots); (ii) a detached stage (fungus physically separated from the roots); and (iii) a germinating stage (germinating spores). In all three stages, G. intraradices was found to contain a mixture of 24-alkylated sterols, with 24-methyl and 24-ethyl cholesterol as the main compounds, but no ergosterol, the predominant sterol in most fungi. Feeding experiments with [1-14C]sodium acetate were performed to check the ability of the fungus to synthesize sterols. Whatever the experimental conditions, G. intraradices was able to actively take up exogenous acetate and to incorporate it into sterols and their precursors. Our data provide first evidence for de novo sterol synthesis by an AM fungus.
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Affiliation(s)
- J Fontaine
- Laboratoire de Mycologie/Phytopathologie/Environnement, Université du Littoral Côte d'Opale, Calais, France
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Abstract
This article describes the most commonly used procedures and recent laboratory methodologies using gas and liquid chromatography developed for separation and quantitation of non-saponifiable steroidal lipids from clinical (human) studies, edible fats and oils or fatty foods.
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Affiliation(s)
- P Volin
- Caloniuksenk. 10 C 47, Helsinki, Finland
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