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Mackinder JR, Hinkel LA, Schutz K, Eckstrom K, Fisher K, Wargo MJ. Sphingosine induction of the Pseudomonas aeruginosa hemolytic phospholipase C/sphingomyelinase (PlcH). J Bacteriol 2024; 206:e0038223. [PMID: 38411048 PMCID: PMC10955842 DOI: 10.1128/jb.00382-23] [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: 11/07/2023] [Accepted: 02/01/2024] [Indexed: 02/28/2024] Open
Abstract
Hemolytic phospholipase C, PlcH, is an important virulence factor for Pseudomonas aeruginosa. PlcH preferentially hydrolyzes sphingomyelin and phosphatidylcholine, and this hydrolysis activity drives tissue damage and inflammation and interferes with the oxidative burst of immune cells. Among other contributors, transcription of plcH was previously shown to be induced by phosphate starvation via PhoB and the choline metabolite, glycine betaine, via GbdR. Here, we show that sphingosine can induce plcH transcription and result in secreted PlcH enzyme activity. This induction is dependent on the sphingosine-sensing transcriptional regulator SphR. The SphR induction of plcH occurs from the promoter for the gene upstream of plcH that encodes the neutral ceramidase, CerN, and transcriptional readthrough of the cerN transcription terminator. Evidence for these conclusions came from mutation of the SphR binding site in the cerN promoter, mutation of the cerN terminator, enhancement of cerN termination by adding the rrnB terminator, and reverse transcriptase PCR (RT-PCR) showing that the intergenic region between cerN and plcH is made as RNA during sphingosine, but not choline, induction. We also observed that, like glycine betaine induction, sphingosine induction of plcH is under catabolite repression control, which likely explains why such induction was not seen in other studies using sphingosine in rich media. The addition of sphingosine as a novel inducer for PlcH points to the regulation of plcH transcription as a site for the integration of multiple host-derived signals. IMPORTANCE PlcH is a secreted phospholipase C/sphingomyelinase that is important for the virulence of Pseudomonas aeruginosa. Here, we show that sphingosine, which presents itself or as a product of P. aeruginosa sphingomyelinase and ceramidase activity, leads to the induction of plcH transcription. This transcriptional induction occurs from the promoter of the upstream ceramidase gene generating a conditional operon. The transcript on which plcH resides, therefore, is different depending on which host molecule or condition leads to induction, and this may have implications for PlcH post-transcriptional regulation. This work also adds to our understanding of P. aeruginosa with host-derived sphingolipids.
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Affiliation(s)
- Jacob R. Mackinder
- Department of Microbiology and Molecular Genetics, Larner College of Medicine, University of Vermont, Burlington, Vermont, USA
- Cellular, Molecular, and Biomedical Sciences Graduate Program, University of Vermont, Burlington, Vermont, USA
| | - Lauren A. Hinkel
- Department of Microbiology and Molecular Genetics, Larner College of Medicine, University of Vermont, Burlington, Vermont, USA
- Cellular, Molecular, and Biomedical Sciences Graduate Program, University of Vermont, Burlington, Vermont, USA
| | - Kristin Schutz
- Department of Microbiology and Molecular Genetics, Larner College of Medicine, University of Vermont, Burlington, Vermont, USA
| | - Korin Eckstrom
- Department of Microbiology and Molecular Genetics, Larner College of Medicine, University of Vermont, Burlington, Vermont, USA
| | - Kira Fisher
- Department of Microbiology and Molecular Genetics, Larner College of Medicine, University of Vermont, Burlington, Vermont, USA
| | - Matthew J. Wargo
- Department of Microbiology and Molecular Genetics, Larner College of Medicine, University of Vermont, Burlington, Vermont, USA
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2
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Singh V, Rai R, Mathew BJ, Chourasia R, Singh AK, Kumar A, Chaurasiya SK. Phospholipase C: underrated players in microbial infections. Front Cell Infect Microbiol 2023; 13:1089374. [PMID: 37139494 PMCID: PMC10149971 DOI: 10.3389/fcimb.2023.1089374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Accepted: 03/21/2023] [Indexed: 05/05/2023] Open
Abstract
During bacterial infections, one or more virulence factors are required to support the survival, growth, and colonization of the pathogen within the host, leading to the symptomatic characteristic of the disease. The outcome of bacterial infections is determined by several factors from both host as well as pathogen origin. Proteins and enzymes involved in cellular signaling are important players in determining the outcome of host-pathogen interactions. phospholipase C (PLCs) participate in cellular signaling and regulation by virtue of their ability to hydrolyze membrane phospholipids into di-acyl-glycerol (DAG) and inositol triphosphate (IP3), which further causes the activation of other signaling pathways involved in various processes, including immune response. A total of 13 PLC isoforms are known so far, differing in their structure, regulation, and tissue-specific distribution. Different PLC isoforms have been implicated in various diseases, including cancer and infectious diseases; however, their roles in infectious diseases are not clearly understood. Many studies have suggested the prominent roles of both host and pathogen-derived PLCs during infections. PLCs have also been shown to contribute towards disease pathogenesis and the onset of disease symptoms. In this review, we have discussed the contribution of PLCs as a determinant of the outcome of host-pathogen interaction and pathogenesis during bacterial infections of human importance.
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Affiliation(s)
- Vinayak Singh
- Molecular Signalling Lab, Department of Biological Science and Engineering, Maulana Azad National Institute of Technology, Bhopal, Madhya Pradesh, India
| | - Rupal Rai
- Molecular Signalling Lab, Department of Biological Science and Engineering, Maulana Azad National Institute of Technology, Bhopal, Madhya Pradesh, India
| | - Bijina J. Mathew
- Molecular Signalling Lab, Department of Biological Science and Engineering, Maulana Azad National Institute of Technology, Bhopal, Madhya Pradesh, India
| | - Rashmi Chourasia
- Department of Chemistry, IES University, Bhopal, Madhya Pradesh, India
| | - Anirudh K. Singh
- School of Sciences, SAM Global University, Raisen, Madhya Pradesh, India
| | - Awanish Kumar
- Department of Biotechnology, National Institute of Technology, Raipur, Chhattisgarh, India
| | - Shivendra K. Chaurasiya
- Molecular Signalling Lab, Department of Biological Science and Engineering, Maulana Azad National Institute of Technology, Bhopal, Madhya Pradesh, India
- *Correspondence: Shivendra K. Chaurasiya,
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3
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Wolfmeier H, Wardell SJT, Liu LT, Falsafi R, Draeger A, Babiychuk EB, Pletzer D, Hancock REW. Targeting the Pseudomonas aeruginosa Virulence Factor Phospholipase C With Engineered Liposomes. Front Microbiol 2022; 13:867449. [PMID: 35369481 PMCID: PMC8971843 DOI: 10.3389/fmicb.2022.867449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Accepted: 02/28/2022] [Indexed: 11/13/2022] Open
Abstract
Engineered liposomes composed of the naturally occurring lipids sphingomyelin (Sm) and cholesterol (Ch) have been demonstrated to efficiently neutralize toxins secreted by Gram-positive bacteria such as Streptococcus pneumoniae and Staphylococcus aureus. Here, we hypothesized that liposomes are capable of neutralizing cytolytic virulence factors secreted by the Gram-negative pathogen Pseudomonas aeruginosa. We used the highly virulent cystic fibrosis P. aeruginosa Liverpool Epidemic Strain LESB58 and showed that sphingomyelin (Sm) and a combination of sphingomyelin with cholesterol (Ch:Sm; 66 mol/% Ch and 34 mol/% Sm) liposomes reduced lysis of human bronchial and red blood cells upon challenge with the Pseudomonas secretome. Mass spectrometry of liposome-sequestered Pseudomonas proteins identified the virulence-promoting hemolytic phospholipase C (PlcH) as having been neutralized. Pseudomonas aeruginosa supernatants incubated with liposomes demonstrated reduced PlcH activity as assessed by the p-nitrophenylphosphorylcholine (NPPC) assay. Testing the in vivo efficacy of the liposomes in a murine cutaneous abscess model revealed that Sm and Ch:Sm, as single dose treatments, attenuated abscesses by >30%, demonstrating a similar effect to that of a mutant lacking plcH in this infection model. Thus, sphingomyelin-containing liposome therapy offers an interesting approach to treat and reduce virulence of complex infections caused by P. aeruginosa and potentially other Gram-negative pathogens expressing PlcH.
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Affiliation(s)
- Heidi Wolfmeier
- Department of Microbiology and Immunology, Centre for Microbial Diseases and Immunity Research, University of British Columbia, Vancouver, BC, Canada
- Institute of Anatomy and Cell Biology, Paracelsus Medical University, Salzburg, Austria
| | - Samuel J. T. Wardell
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Leo T. Liu
- Department of Microbiology and Immunology, Centre for Microbial Diseases and Immunity Research, University of British Columbia, Vancouver, BC, Canada
| | - Reza Falsafi
- Department of Microbiology and Immunology, Centre for Microbial Diseases and Immunity Research, University of British Columbia, Vancouver, BC, Canada
| | | | | | - Daniel Pletzer
- Department of Microbiology and Immunology, Centre for Microbial Diseases and Immunity Research, University of British Columbia, Vancouver, BC, Canada
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
- *Correspondence: Daniel Pletzer,
| | - Robert E. W. Hancock
- Department of Microbiology and Immunology, Centre for Microbial Diseases and Immunity Research, University of British Columbia, Vancouver, BC, Canada
- Robert E. W. Hancock,
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Bose AL, Bhattacharjee D, Goswami D. Mixed micelles and bicontinuous microemulsions: Promising media for enzymatic reactions. Colloids Surf B Biointerfaces 2021; 209:112193. [PMID: 34768101 DOI: 10.1016/j.colsurfb.2021.112193] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 10/19/2021] [Accepted: 10/28/2021] [Indexed: 02/08/2023]
Abstract
Enzymes, the natural catalysts, replace catalysts of chemical origin in a wide spectrum of reactions and generally work under environment friendly conditions. Various strategies are adopted to modify catalytic activities of enzymes further, of which one is application of novel reaction medium. This work reviews applicability of novel media like mixed micelles and bicontinuous microemulsions in enzymatic reactions and points out their capability to play bigger roles in enzyme catalysis. Ionic reverse micelles reduced catalytic activities of enzymes through denaturation. Addition of nonionic surfactant to these reverse micelles led to corresponding mixed micelles and thus restored or sometimes enhanced catalytic abilities of enzymes. Mixed micelles comprising of two nonionic surfactants, bicontinuous microemulsion containing two anionic surfactants also acted as efficient reaction media for enzymes. Even a cationic/anionic/nonionic mixed micelle was found to increase activity of enzyme. Mixed micelles and bicontinuous microemulsions comprising of anionic and zwitterionic surfactants augmented enzyme catalysis. Mixed micelles and bicontinuous microemulsions containing ionic liquid and surfactant also had critical impact on enzyme catalysis. Catalytic abilities of enzymes altered significantly in substrate/surfactant and bile salt/surfactant mixed micelles. Concentrations of individual surfactant, molar ratio of surfactants, and molar ratio of water to total surfactants had notable impacts on enzyme catalysis in those media.
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Affiliation(s)
- Abir Lal Bose
- Department of Chemical Engineering, University College of Science and Technology, University of Calcutta, 92, A. P. C. Road, Kolkata 700009, India.
| | - Debapriya Bhattacharjee
- Department of Chemical Engineering, University College of Science and Technology, University of Calcutta, 92, A. P. C. Road, Kolkata 700009, India.
| | - Debajyoti Goswami
- Department of Chemical Engineering, University College of Science and Technology, University of Calcutta, 92, A. P. C. Road, Kolkata 700009, India.
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Monturiol-Gross L, Villalta-Romero F, Flores-Díaz M, Alape-Girón A. Bacterial phospholipases C with dual activity: phosphatidylcholinesterase and sphingomyelinase. FEBS Open Bio 2021; 11:3262-3275. [PMID: 34709730 PMCID: PMC8634861 DOI: 10.1002/2211-5463.13320] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 10/25/2021] [Accepted: 10/27/2021] [Indexed: 02/06/2023] Open
Abstract
Bacterial phospholipases and sphingomyelinases are lipolytic esterases that are structurally and evolutionarily heterogeneous. These enzymes play crucial roles as virulence factors in several human and animal infectious diseases. Some bacterial phospholipases C (PLCs) have both phosphatidylcholinesterase and sphingomyelinase C activities. Among them, Listeria
monocytogenes PlcB, Clostridium perfringens PLC, and Pseudomonas aeruginosa PlcH are the most deeply understood. In silico predictions of substrates docking with these three bacterial enzymes provide evidence that they interact with different substrates at the same active site. This review discusses structural aspects, substrate specificity, and the mechanism of action of those bacterial enzymes on target cells and animal infection models to shed light on their roles in pathogenesis.
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Affiliation(s)
- Laura Monturiol-Gross
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Fabian Villalta-Romero
- Centro de Investigación en Biotecnología, Escuela de Biología, Instituto Tecnológico de Costa Rica, Cartago, Costa Rica
| | - Marietta Flores-Díaz
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica
| | - Alberto Alape-Girón
- Instituto Clodomiro Picado, Facultad de Microbiología, Universidad de Costa Rica, San José, Costa Rica.,Departamento de Bioquímica, Escuela de Medicina, Universidad de Costa Rica, San José, Costa Rica
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Bernhard W. Choline in cystic fibrosis: relations to pancreas insufficiency, enterohepatic cycle, PEMT and intestinal microbiota. Eur J Nutr 2020; 60:1737-1759. [PMID: 32797252 DOI: 10.1007/s00394-020-02358-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 08/03/2020] [Indexed: 12/11/2022]
Abstract
BACKGROUND Cystic Fibrosis (CF) is an autosomal recessive disorder with life-threatening organ manifestations. 87% of CF patients develop exocrine pancreas insufficiency, frequently starting in utero and requiring lifelong pancreatic enzyme substitution. 99% develop progressive lung disease, and 20-60% CF-related liver disease, from mild steatosis to cirrhosis. Characteristically, pancreas, liver and lung are linked by choline metabolism, a critical nutrient in CF. Choline is a tightly regulated tissue component in the form of phosphatidylcholine (Ptd'Cho) and sphingomyelin (SPH) in all membranes and many secretions, particularly of liver (bile, lipoproteins) and lung (surfactant, lipoproteins). Via its downstream metabolites, betaine, dimethylglycine and sarcosine, choline is the major one-carbon donor for methionine regeneration from homocysteine. Methionine is primarily used for essential methylation processes via S-adenosyl-methionine. CLINICAL IMPACT CF patients with exocrine pancreas insufficiency frequently develop choline deficiency, due to loss of bile Ptd'Cho via feces. ~ 50% (11-12 g) of hepatic Ptd'Cho is daily secreted into the duodenum. Its re-uptake requires cleavage to lyso-Ptd'Cho by pancreatic and small intestinal phospholipases requiring alkaline environment. Impaired CFTR-dependent bicarbonate secretion, however, results in low duodenal pH, impaired phospholipase activity, fecal Ptd'Cho loss and choline deficiency. Low plasma choline causes decreased availability for parenchymal Ptd'Cho metabolism, impacting on organ functions. Choline deficiency results in hepatic choline/Ptd'Cho accretion from lung tissue via high density lipoproteins, explaining the link between choline deficiency and lung function. Hepatic Ptd'Cho synthesis from phosphatidylethanolamine by phosphatidylethanolamine-N-methyltransferase (PEMT) partly compensates for choline deficiency, but frequent single nucleotide polymorphisms enhance choline requirement. Additionally, small intestinal bacterial overgrowth (SIBO) frequently causes intraluminal choline degradation in CF patients prior to its absorption. As adequate choline supplementation was clinically effective and adult as well as pediatric CF patients suffer from choline deficiency, choline supplementation in CF patients of all ages should be evaluated.
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Affiliation(s)
- Wolfgang Bernhard
- Department of Neonatology, University Children's Hospital, Faculty of Medicine, Eberhard-Karls-University, Calwer Straße 7, 72076, Tübingen, Germany.
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7
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Mechanism of catalysis and inhibition of Mycobacterium tuberculosis SapM, implications for the development of novel antivirulence drugs. Sci Rep 2019; 9:10315. [PMID: 31312014 PMCID: PMC6635428 DOI: 10.1038/s41598-019-46731-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 06/10/2019] [Indexed: 01/02/2023] Open
Abstract
Mycobacterium tuberculosis (Mtb) SapM is a secreted virulence factor critical for intracellular survival of the pathogen. The role of SapM in phagosome maturation arrest in host macrophages suggests its potential as a drug target to assist in the clearance of tuberculosis infection. However, the mechanism of action of SapM at the molecular level remains unknown. In this study, we provide new insights into the mechanism of catalysis, substrate specificity and inhibition of SapM, and we identify the critical residues for catalysis and substrate binding. Our findings demonstrate that SapM is an atypical monoester alkaline phosphatase, with a serine-based mechanism of catalysis probably metal-dependent. Particularly relevant to SapM function and pathogenesis, is its activity towards PI(4,5)P2 and PI3P, two phosphoinositides that function at the early stages of microbial phagocytosis and phagosome formation. This suggests that SapM may have a pleiotropic role with a wider importance on Mtb infection than initially thought. Finally, we have identified two inhibitors of SapM, L-ascorbic acid and 2-phospho-L-ascorbic, which define two different mechanisms by which the catalytic activity of this phosphatase could be regulated. Critically, we demonstrate that 2-phospho-L-ascorbic reduces mycobacterial survival in macrophage infections, hence confirming the potential of SapM as a therapeutic drug target.
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8
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Massai F, Saleeb M, Doruk T, Elofsson M, Forsberg Å. Development, Optimization, and Validation of a High Throughput Screening Assay for Identification of Tat and Type II Secretion Inhibitors of Pseudomonas aeruginosa. Front Cell Infect Microbiol 2019; 9:250. [PMID: 31355152 PMCID: PMC6635566 DOI: 10.3389/fcimb.2019.00250] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 06/26/2019] [Indexed: 11/13/2022] Open
Abstract
Antibiotics are becoming less effective in treatment of infections caused by multidrug-resistant Pseudomonas aeruginosa. Antimicrobial therapies based on the inhibition of specific virulence-related traits, as opposed to growth inhibitors, constitute an innovative and appealing approach to tackle the threat of P. aeruginosa infections. The twin-arginine translocation (Tat) pathway plays an important role in the pathogenesis of P. aeruginosa, and constitutes a promising target for the development of anti-pseudomonal drugs. In this study we developed and optimized a whole-cell, one-well assay, based on native phospholipase C activity, to identify compounds active against the Tat system. Statistical robustness, sensitivity and consequently suitability for high-throughput screening (HTS) were confirmed by a dry run/pre-screening test scoring a Z′ of 0.82 and a signal-to-noise ratio of 49. Using this assay, we evaluated ca. 40,000 molecules and identified 59 initial hits as possible Tat inhibitors. Since phospholipase C is exported into the periplasm by Tat, and subsequently translocated across the outer membrane by the type II secretion system (T2SS), our assay could also identify T2SS inhibitors. To validate our hits and discriminate between compounds that inhibited either Tat or T2SS, two separate counter assays were developed and optimized. Finally, three Tat inhibitors and one T2SS inhibitor were confirmed by means of dose-response analysis and additional counter and confirming assays. Although none of the identified inhibitors was suitable as a lead compound for drug development, this study validates our assay as a simple, efficient, and HTS compatible method for the identification of Tat and T2SS inhibitors.
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Affiliation(s)
- Francesco Massai
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå University, Umeå, Sweden.,Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
| | - Michael Saleeb
- Department of Chemistry, Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
| | - Tugrul Doruk
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå University, Umeå, Sweden.,Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
| | - Mikael Elofsson
- Department of Chemistry, Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
| | - Åke Forsberg
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå University, Umeå, Sweden.,Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
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9
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Sinha AK, Dutta A, Chandravanshi M, Kanaujia SP. An insight into bacterial phospholipase C classification and their translocation through Tat and Sec pathways: A data mining study. Meta Gene 2019. [DOI: 10.1016/j.mgene.2019.100547] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
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10
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Kareem SM, Al-Kadmy IMS, Al-Kaabi MH, Aziz SN, Ahmad M. Acinetobacter baumannii virulence is enhanced by the combined presence of virulence factors genes phospholipase C (plcN) and elastase (lasB). Microb Pathog 2017; 110:568-572. [PMID: 28780324 DOI: 10.1016/j.micpath.2017.08.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 07/22/2017] [Accepted: 08/01/2017] [Indexed: 01/18/2023]
Abstract
The ability of multidrug resistance Acinetobacter baumannii to persist in any circumstances regard to the acquisition of many virulence factors genes and antibiotic resistance genes is major concern in the hospitals environments. In this study, thirty A. baumannii isolates were collected from blood infections from hospitalized patients were subjected to screening for virulence factors genes plcN and lasB by conventional PCR. The pathogenicity of representative isolates bearing these gene were tested using galleria mellonella infection assay and adhesion-invasion assay on A549 cell line, and compared with other strain without this gene. Phylogenetic tree revealed that isolates were sorted in two major groups one of them contained two clusters (Group II and III), and another had the other group (Group I). All the 30 A. baumannii isolates were investigated for the presence of virulence factors genes (plc-N and lasB genes) and results showed that, 16 (53.33%) were harboring lasB genes while 7 (23.3%) isolates were harboring plcN gene The presence of any of these gene enhance the killing ability of A. baumannii strain and increased invasiveness in A549 cell line. Increase nosocomial infection with A. baumannii isolates is serious problem especially because of its potency to gain virulence factors genes and its ability to persist in hospital environments. So the shed light in finding which virulence factors these isolates which have is necessary to discover new antimicrobials that targeting the virulence factor of these powerful pathogens.
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Affiliation(s)
- Sawsan Mohammed Kareem
- Biotechnology Branch, Department of Biology, College of Science, Al-Mustansiriyah University, Baghdad, Iraq
| | - Israa M S Al-Kadmy
- Biotechnology Branch, Department of Biology, College of Science, Al-Mustansiriyah University, Baghdad, Iraq.
| | | | - Sarah Naji Aziz
- Biotechnology Branch, Department of Biology, College of Science, Al-Mustansiriyah University, Baghdad, Iraq
| | - Mohammad Ahmad
- Medical Surgical Nursing Department, College of Nursing, King Saud University, Saudi Arabia
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11
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Okino N, Ito M. Molecular mechanism for sphingosine-induced Pseudomonas ceramidase expression through the transcriptional regulator SphR. Sci Rep 2016; 6:38797. [PMID: 27941831 PMCID: PMC5150637 DOI: 10.1038/srep38797] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Accepted: 11/11/2016] [Indexed: 01/08/2023] Open
Abstract
Pseudomonas aeruginosa, an opportunistic, but serious multidrug-resistant pathogen, secretes a ceramidase capable of cleaving the N-acyl linkage of ceramide to generate fatty acids and sphingosine. We previously reported that the secretion of P. aeruginosa ceramidase was induced by host-derived sphingolipids, through which phospholipase C-induced hemolysis was significantly enhanced. We herein investigated the gene(s) regulating sphingolipid-induced ceramidase expression and identified SphR, which encodes a putative AraC family transcriptional regulator. Disruption of the sphR gene in P. aeruginosa markedly decreased the sphingomyelin-induced secretion of ceramidase, reduced hemolytic activity, and resulted in the loss of sphingomyelin-induced ceramidase expression. A microarray analysis confirmed that sphingomyelin significantly induced ceramidase expression in P. aeruginosa. Furthermore, an electrophoretic mobility shift assay revealed that SphR specifically bound free sphingoid bases such as sphingosine, dihydrosphingosine, and phytosphingosine, but not sphingomyelin or ceramide. A β-galactosidase-assisted promoter assay showed that sphingosine activated ceramidase expression through SphR at a concentration of 100 nM. Collectively, these results demonstrated that sphingosine induces the secretion of ceramidase by promoting the mRNA expression of ceramidase through SphR, thereby enhancing hemolytic phospholipase C-induced cytotoxicity. These results facilitate understanding of the physiological role of bacterial ceramidase in host cells.
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Affiliation(s)
- Nozomu Okino
- The Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
| | - Makoto Ito
- The Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
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Aureli M, Schiumarini D, Loberto N, Bassi R, Tamanini A, Mancini G, Tironi M, Munari S, Cabrini G, Dechecchi MC, Sonnino S. Unravelling the role of sphingolipids in cystic fibrosis lung disease. Chem Phys Lipids 2016; 200:94-103. [DOI: 10.1016/j.chemphyslip.2016.08.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 08/22/2016] [Accepted: 08/25/2016] [Indexed: 12/13/2022]
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13
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Abstract
Bacterial sphingomyelinases and phospholipases are a heterogeneous group of esterases which are usually surface associated or secreted by a wide variety of Gram-positive and Gram-negative bacteria. These enzymes hydrolyze sphingomyelin and glycerophospholipids, respectively, generating products identical to the ones produced by eukaryotic enzymes which play crucial roles in distinct physiological processes, including membrane dynamics, cellular signaling, migration, growth, and death. Several bacterial sphingomyelinases and phospholipases are essential for virulence of extracellular, facultative, or obligate intracellular pathogens, as these enzymes contribute to phagosomal escape or phagosomal maturation avoidance, favoring tissue colonization, infection establishment and progression, or immune response evasion. This work presents a classification proposal for bacterial sphingomyelinases and phospholipases that considers not only their enzymatic activities but also their structural aspects. An overview of the main physiopathological activities is provided for each enzyme type, as are examples in which inactivation of a sphingomyelinase- or a phospholipase-encoding gene impairs the virulence of a pathogen. The identification of sphingomyelinases and phospholipases important for bacterial pathogenesis and the development of inhibitors for these enzymes could generate candidate vaccines and therapeutic agents, which will diminish the impacts of the associated human and animal diseases.
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14
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Revisiting the role of phospholipases C in virulence and the lifecycle of Mycobacterium tuberculosis. Sci Rep 2015; 5:16918. [PMID: 26603639 PMCID: PMC4658479 DOI: 10.1038/srep16918] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 10/22/2015] [Indexed: 12/02/2022] Open
Abstract
Mycobacterium tuberculosis, the agent of human tuberculosis has developed
different virulence mechanisms and virulence-associated tools during its evolution
to survive and multiply inside the host. Based on previous reports and by analogy
with other bacteria, phospholipases C (PLC) of M. tuberculosis were thought
to be among these tools. To get deeper insights into the function of PLCs, we
investigated their putative involvement in the intracellular lifestyle of M.
tuberculosis, with emphasis on phagosomal rupture and virulence, thereby
re-visiting a research theme of longstanding interest. Through the construction and
use of an M. tuberculosis H37Rv PLC-null mutant (ΔPLC) and
control strains, we found that PLCs of M. tuberculosis were not required for
induction of phagosomal rupture and only showed marginal, if any, impact on
virulence of M. tuberculosis in the cellular and mouse infection models used
in this study. In contrast, we found that PLC-encoding genes were strongly
upregulated under phosphate starvation and that PLC-proficient M.
tuberculosis strains survived better than ΔPLC mutants under
conditions where phosphatidylcholine served as sole phosphate source, opening new
perspectives for studies on the role of PLCs in the lifecycle of M.
tuberculosis.
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Extracellular Lipase and Protease Production from a Model Drinking Water Bacterial Community Is Functionally Robust to Absence of Individual Members. PLoS One 2015; 10:e0143617. [PMID: 26599415 PMCID: PMC4657875 DOI: 10.1371/journal.pone.0143617] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 11/06/2015] [Indexed: 12/13/2022] Open
Abstract
Bacteria secrete enzymes into the extracellular space to hydrolyze macromolecules into constituents that can be imported for microbial nutrition. In bacterial communities, these enzymes and their resultant products can be modeled as community property. Our goal was to investigate the impact of individual community member absence on the resulting community production of exoenzymes (extracellular enzymes) involved in lipid and protein hydrolysis. Our model community contained nine bacteria isolated from the potable water system of the International Space Station. Bacteria were grown in static conditions individually, all together, or in all combinations of eight species and exoproduct production was measured by colorimetric or fluorometric reagents to assess short chain and long chain lipases, choline-specific phospholipases C, and proteases. The exoenzyme production of each species grown alone varied widely, however, the enzyme activity levels of the mixed communities were functionally robust to absence of any single species, with the exception of phospholipase C production in one community. For phospholipase C, absence of Chryseobacterium gleum led to increased choline-specific phospholipase C production, correlated with increased growth of Burkholderia cepacia and Sphingomonas sanguinis. Because each individual species produced different enzyme activity levels in isolation, we calculated an expected activity value for each bacterial mixture using input levels or known final composition. This analysis suggested that robustness of each exoenzyme activity is not solely mediated by community composition, but possibly influenced by bacterial communication, which is known to regulate such pathways in many bacteria. We conclude that in this simplified model of a drinking water bacterial community, community structure imposes constraints on production and/or secretion of exoenzymes to generate a level appropriate to exploit a given nutrient environment.
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Clostridium perfringens Alpha-Toxin Induces Gm1a Clustering and Trka Phosphorylation in the Host Cell Membrane. PLoS One 2015; 10:e0120497. [PMID: 25910247 PMCID: PMC4409118 DOI: 10.1371/journal.pone.0120497] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2014] [Accepted: 01/23/2015] [Indexed: 01/13/2023] Open
Abstract
Clostridium perfringens alpha-toxin elicits various immune responses such as the release of cytokines, chemokines, and superoxide via the GM1a/TrkA complex. Alpha-toxin possesses phospholipase C (PLC) hydrolytic activity that contributes to signal transduction in the pathogenesis of gas gangrene. Little is known about the relationship between lipid metabolism and TrkA activation by alpha-toxin. Using live-cell fluorescence microscopy, we monitored transbilayer movement of diacylglycerol (DAG) with the yellow fluorescent protein-tagged C1AB domain of protein kinase C-γ (EYFP-C1AB). DAG accumulated at the marginal region of the plasma membrane in alpha toxin-treated A549 cells, which also exhibited GM1a clustering and TrkA phosphorylation. Annexin V binding assays showed that alpha-toxin induced the exposure of phosphatidylserine on the outer leaflet of the plasma membrane. However, H148G, a variant toxin which binds cell membrane and has no enzymatic activity, did not induce DAG translocation, GM1a clustering, or TrkA phosphorylation. Alpha-toxin also specifically activated endogenous phospholipase Cγ-1 (PLCγ-1), a TrkA adaptor protein, via phosphorylation. U73122, an endogenous PLC inhibitor, and siRNA for PLCγ-1 inhibited the formation of DAG and release of IL-8. GM1a accumulation and TrkA phosphorylation in A549 cells treated with alpha-toxin were also inhibited by U73122. These results suggest that the flip-flop motion of hydrophobic lipids such as DAG leads to the accumulation of GM1a and TrkA. We conclude that the formation of DAG by alpha-toxin itself (first step) and activation of endogenous PLCγ-1 (second step) leads to alterations in membrane dynamics, followed by strong phosphorylation of TrkA.
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Mineta S, Murayama K, Sugimori D. Characterization of glycerophosphoethanolamine ethanolaminephosphodiesterase from Streptomyces sanglieri. J Biosci Bioeng 2015; 119:123-30. [DOI: 10.1016/j.jbiosc.2014.07.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 07/05/2014] [Accepted: 07/09/2014] [Indexed: 02/08/2023]
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Elleboudy NS, Aboulwafa MM, Hassouna NAH. Phospholipase C from Pseudomonas aeruginosa and Bacillus cereus; characterization of catalytic activity. ASIAN PAC J TROP MED 2014; 7:860-6. [DOI: 10.1016/s1995-7645(14)60150-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 06/15/2014] [Accepted: 07/25/2014] [Indexed: 10/24/2022] Open
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Sugimori D, Ogasawara J, Okuda K, Murayama K. Purification, characterization, molecular cloning, and extracellular production of a novel bacterial glycerophosphocholine cholinephosphodiesterase from Streptomyces sanglieri. J Biosci Bioeng 2013; 117:422-30. [PMID: 24211038 DOI: 10.1016/j.jbiosc.2013.10.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Revised: 10/04/2013] [Accepted: 10/04/2013] [Indexed: 10/26/2022]
Abstract
A novel metal ion-independent glycerophosphocholine cholinephosphodiesterase (GPC-CP) of Streptomyces sanglieri was purified 53-fold from culture supernatant with 1.1% recovery (583 U/mg-protein). The enzyme functions as a monomer with a molecular mass of 66 kDa. The gene encoding the enzyme consists of a 1941-bp ORF that produces a signal peptide of 38 amino acids for secretion and a 646 amino acid mature protein with a calculated molecular mass of 70,447 Da. The maximum activity was found at pH 7.2 and 40°C. The enzyme hydrolyzed glycerol-3-phosphocholine (GPC) over a broad temperature range (37-60°C) and within a narrow pH range near pH 7. The enzyme was stable at 50°C for 30 min and between pH 5-10.5. The enzyme exhibited specificity toward GPC and glycerol-3-phosphoethanolamine and hydrolyzed glycerol-3-phosphate and lysophosphatidylcholine. However, the enzyme showed no activity toward any diacylglycerophospholipids and little activity toward other glycerol-3-phosphodiesters and lysophospholipids. The enzyme was not inhibited in the presence of 2 mM SDS and Mg(2+); however, Cu(2+), Zn(2+), and Co(2+) remarkably inhibited activity. Enzyme activity was also slightly enhanced by Ca(2+), Na(+), EDTA, DTT, and 2-mercaptoethanol. During the hydrolysis of GPC at 37°C and pH 7.2, apparent Vmax and turnover number (kcat) were determined to be 24.7 μmol min(-1) mg-protein(-1) and 29.0 s(-1), respectively. The apparent Km and kcat/Km values were 1.41 mM and 20.6 mM(-1) s(-1), respectively. GPC hydrolysis by GPC-CP might represent a new metabolic pathway for acquisition of a phosphorus source in actinomycetes.
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Affiliation(s)
- Daisuke Sugimori
- Department of Symbiotic Systems Science and Technology, Graduate School of Symbiotic Systems Science and Technology, Fukushima University, 1 Kanayagawa, Fukushima 960-1296, Japan.
| | - Junki Ogasawara
- Department of Symbiotic Systems Science and Technology, Graduate School of Symbiotic Systems Science and Technology, Fukushima University, 1 Kanayagawa, Fukushima 960-1296, Japan
| | - Koki Okuda
- Department of Symbiotic Systems Science and Technology, Graduate School of Symbiotic Systems Science and Technology, Fukushima University, 1 Kanayagawa, Fukushima 960-1296, Japan
| | - Kazutaka Murayama
- Division of Biomedical Measurements and Diagnostics, Graduate School of Biomedical Engineering, Tohoku University, 2-1 Seiryo, Aoba, Sendai 980-8575, Japan
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Adaptation-based resistance to siderophore-conjugated antibacterial agents by Pseudomonas aeruginosa. Antimicrob Agents Chemother 2013; 57:4197-207. [PMID: 23774440 DOI: 10.1128/aac.00629-13] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Multidrug resistance in Gram-negative bacteria has become so threatening to human health that new antibacterial platforms are desperately needed to combat these deadly infections. The concept of siderophore conjugation, which facilitates compound uptake across the outer membrane by hijacking bacterial iron acquisition systems, has received significant attention in recent years. While standard in vitro MIC and resistance frequency methods demonstrate that these compounds are potent, broad-spectrum antibacterial agents whose activity should not be threatened by unacceptably high spontaneous resistance rates, recapitulation of these results in animal models can prove unreliable, partially because of the differences in iron availability in these different methods. Here, we describe the characterization of MB-1, a novel siderophore-conjugated monobactam that demonstrates excellent in vitro activity against Pseudomonas aeruginosa when tested using standard assay conditions. Unfortunately, the in vitro findings did not correlate with the in vivo results we obtained, as multiple strains were not effectively treated by MB-1 despite having low MICs. To address this, we also describe the development of new in vitro assays that were predictive of efficacy in mouse models, and we provide evidence that competition with native siderophores could contribute to the recalcitrance of some P. aeruginosa isolates in vivo.
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Aurass P, Schlegel M, Metwally O, Harding CR, Schroeder GN, Frankel G, Flieger A. The Legionella pneumophila Dot/Icm-secreted effector PlcC/CegC1 together with PlcA and PlcB promotes virulence and belongs to a novel zinc metallophospholipase C family present in bacteria and fungi. J Biol Chem 2013; 288:11080-92. [PMID: 23457299 PMCID: PMC3630882 DOI: 10.1074/jbc.m112.426049] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Revised: 02/19/2013] [Indexed: 11/06/2022] Open
Abstract
Legionella pneumophila is a water-borne bacterium that causes pneumonia in humans. PlcA and PlcB are two previously defined L. pneumophila proteins with homology to the phosphatidylcholine-specific phospholipase C (PC-PLC) of Pseudomonas fluorescens. Additionally, we found that Lpg0012 shows similarity to PLCs and has been shown to be a Dot/Icm-injected effector, CegC1, which is designated here as PlcC. It remained unclear, however, whether these L. pneumophila proteins exhibit PLC activity. PlcC expressed in Escherichia coli hydrolyzed a broad phospholipid spectrum, including PC, phosphatidylglycerol (PG), and phosphatidylinositol. The addition of Zn(2+) ions activated, whereas EDTA inhibited, PlcC-derived PLC activity. Protein homology search revealed that the three Legionella enzymes and P. fluorescens PC-PLC share conserved domains also present in uncharacterized fungal proteins. Fifteen conserved amino acids were essential for enzyme activity as identified via PlcC mutagenesis. Analysis of defined L. pneumophila knock-out mutants indicated Lsp-dependent export of PG-hydrolyzing PLC activity. PlcA and PlcB exhibited PG-specific activity and contain a predicted Sec signal sequence. In line with the reported requirement of host cell contact for Dot/Icm-dependent effector translocation, PlcC showed cell-associated PC-specific PLC activity after bacterial growth in broth. A PLC triple mutant, but not single or double mutants, exhibited reduced host killing in a Galleria mellonella infection model, highlighting the importance of the three PLCs in pathogenesis. In summary, we describe here a novel Zn(2+)-dependent PLC family present in Legionella, Pseudomonas, and fungi with broad substrate preference and function in virulence.
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Affiliation(s)
- Philipp Aurass
- From the Division of Bacterial Infections, Robert Koch-Institut, Burgstrasse 37, 38855 Wernigerode, Germany and
| | - Maren Schlegel
- From the Division of Bacterial Infections, Robert Koch-Institut, Burgstrasse 37, 38855 Wernigerode, Germany and
| | - Omar Metwally
- From the Division of Bacterial Infections, Robert Koch-Institut, Burgstrasse 37, 38855 Wernigerode, Germany and
| | - Clare R. Harding
- the MRC Centre for Molecular Bacteriology and Infection, Division of Cell and Molecular Biology, Imperial College London, London SW7 2AZ, United Kingdom
| | - Gunnar N. Schroeder
- the MRC Centre for Molecular Bacteriology and Infection, Division of Cell and Molecular Biology, Imperial College London, London SW7 2AZ, United Kingdom
| | - Gad Frankel
- the MRC Centre for Molecular Bacteriology and Infection, Division of Cell and Molecular Biology, Imperial College London, London SW7 2AZ, United Kingdom
| | - Antje Flieger
- From the Division of Bacterial Infections, Robert Koch-Institut, Burgstrasse 37, 38855 Wernigerode, Germany and
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22
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Kuhle K, Flieger A. Legionella phospholipases implicated in virulence. Curr Top Microbiol Immunol 2013; 376:175-209. [PMID: 23925490 DOI: 10.1007/82_2013_348] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Phospholipases are diverse enzymes produced in eukaryotic hosts and their bacterial pathogens. Several pathogen phospholipases have been identified as major virulence factors acting mainly in two different modes: on the one hand, they have the capability to destroy host membranes and on the other hand they are able to manipulate host signaling pathways. Reaction products of bacterial phospholipases may act as secondary messengers within the host and therefore influence inflammatory cascades and cellular processes, such as proliferation, migration, cytoskeletal changes as well as membrane traffic. The lung pathogen and intracellularly replicating bacterium Legionella pneumophila expresses a variety of phospholipases potentially involved in disease-promoting processes. So far, genes encoding 15 phospholipases A, three phospholipases C, and one phospholipase D have been identified. These cell-associated or secreted phospholipases may contribute to intracellular establishment, to egress of the pathogen from the host cell, and to the observed lung pathology. Due to the importance of phospholipase activities for host cell processes, it is conceivable that the pathogen enzymes may mimic or substitute host cell phospholipases to drive processes for the pathogen's benefit. The following chapter summarizes the current knowledge on the L. pneumophila phospholipases, especially their substrate specificity, localization, mode of secretion, and impact on host cells.
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Affiliation(s)
- Katja Kuhle
- FG 11 - Division of Enteropathogenic Bacteria and Legionella, Robert Koch-Institut, Burgstr. 37, 38855, Wernigerode, Germany
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23
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Ibarguren M, Sot J, Montes LR, Vasil AI, Vasil ML, Goñi FM, Alonso A. Recruitment of a phospholipase C/sphingomyelinase into non-lamellar lipid droplets during hydrolysis of lipid bilayers. Chem Phys Lipids 2012; 166:12-7. [PMID: 23253877 DOI: 10.1016/j.chemphyslip.2012.12.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 11/30/2012] [Accepted: 12/01/2012] [Indexed: 01/05/2023]
Abstract
When giant unilamellar vesicles (GUVs) composed of sphingomyelin, phosphatidylcholine, phosphatidylethanolamine, and cholesterol are treated with PlcHR(2), a phospholipase C/sphingomyelinase from Pseudomonas aeruginosa, the initial stages of lipid hydrolysis do not cause large changes in vesicle morphology (Ibarguren et al., 2011). However, when hydrolysis progresses confocal fluorescence microscopy reveals the formation of lipid aggregates, whose morphology is not compatible with that of bilayers. Smaller vesicles or droplets can also be seen inside the GUV. Our studies indicate that these aggregates or droplets are enriched in the non-lamellar lipid ceramide, an end-product of PlcHR(2) reaction. Moreover, the aggregates/droplets appear enriched in the hydrolytic enzyme PlcHR(2). At a final stage GUVs containing the enzyme-enriched droplets disintegrate and vanish from the microscope field. The observed non-lamellar enzyme-rich structures may be related to intermediates in the process of aggregation and fusion although the experimental design prevents vesicle free diffusion in the aqueous medium, thus actual aggregation or fusion cannot be observed.
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Affiliation(s)
- Maitane Ibarguren
- Unidad de Biofísica (Centro Mixto CSIS-UPV/EHU), Departamento de Bioquímica, Universidad del País Vasco, Barrio Sarriena s/n, 48940 Bilbao, Spain
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24
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High-level over-expression, purification, and crystallization of a novel phospholipase C/sphingomyelinase from Pseudomonas aeruginosa. Protein Expr Purif 2012. [PMID: 23201280 PMCID: PMC3601568 DOI: 10.1016/j.pep.2012.11.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The hemolytic phospholipase C/sphingomyelinase PlcH from the
opportunistic pathogen Pseudomonas aeruginosa represents the
founding member of a growing family of virulence factors identified in a wide range of
bacterial and fungal pathogens. In P. aeruginosa PlcH is
co-expressed with a 17 kDa chaperone (PlcR2) and secreted as a fully
folded heterodimer (PlcHR2) of approximately 95 kDa, by the twin
arginine translocase (TAT) via the cytoplasmic membrane and through the outer membrane, by
the Xcp (TypeII) secretory system. PlcHR2 has been shown to be an important virulence
factor in model P. aeruginosa infections and is selectively
cytotoxic, at picomolar concentrations to mammalian endothelial cells. Here we report how
the various challenges starting from protein overexpression in the native organism
P. aeruginosa, the use of detergents in the crystallization and
data collection using the most advanced μ-focus synchrotron beam lines were overcome.
Native diffraction data of this heterodimeric protein complex were collected up to a
resolution of 4 Å, whereas needle-shaped crystals of
l-selenomethionine substituted PlcHR2 with a maximum
diameter of 10 micron were used to collect data sets with a maximum resolution of
2.75 Å.
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25
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Identification and evaluation of twin-arginine translocase inhibitors. Antimicrob Agents Chemother 2012; 56:6223-34. [PMID: 23006747 DOI: 10.1128/aac.01575-12] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The twin-arginine translocase (TAT) in some bacterial pathogens, including Pseudomonas aeruginosa, Burkholderia pseudomallei, and Mycobacterium tuberculosis, contributes to pathogenesis by translocating extracellular virulence determinants across the inner membrane into the periplasm, thereby allowing access to the Xcp (type II) secretory system for further export in Gram-negative organisms, or directly to the outside surface of the cell, as in M. tuberculosis. TAT-mediated secretion appreciably contributes to virulence in both animal and plant models of bacterial infection. Consequently, TAT function is an attractive target for small-molecular-weight compounds that alone or in conjunction with extant antimicrobial agents could become novel therapeutics. The TAT-transported hemolytic phospholipase C (PlcH) of P. aeruginosa and its multiple orthologs produced by the above pathogens can be detected by an accurate and reproducible colorimetric assay using a synthetic substrate that detects phospholipase C activity. Such an assay could be an effective indicator of TAT function. Using carefully constructed recombinant strains to precisely control the expression of PlcH, we developed a high-throughput screening (HTS) assay to evaluate, in duplicate, >80,000 small-molecular-weight compounds as possible TAT inhibitors. Based on additional TAT-related functional assays, purified PlcH protein inhibition experiments, and repeat experiments of the initial screening assay, 39 compounds were selected from the 122 initial hits. Finally, to evaluate candidate inhibitors for TAT specificity, we developed a TAT titration assay that determines whether inhibition of TAT-mediated secretion can be overcome by increasing the levels of TAT expression. The compounds N-phenyl maleimide and Bay 11-7082 appear to directly affect TAT function based on this approach.
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Oda M, Kabura M, Takagishi T, Suzue A, Tominaga K, Urano S, Nagahama M, Kobayashi K, Furukawa K, Furukawa K, Sakurai J. Clostridium perfringens alpha-toxin recognizes the GM1a-TrkA complex. J Biol Chem 2012; 287:33070-9. [PMID: 22847002 DOI: 10.1074/jbc.m112.393801] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Clostridium perfringens alpha-toxin is the major virulence factor in the pathogenesis of gas gangrene. Alpha-toxin is a 43-kDa protein with two structural domains; the N-domain contains the catalytic site and coordinates the divalent metal ions, and the C-domain is a membrane-binding site. The role of the exposed loop region (72-93 residues) in the N-domain, however, has been unclear. Here we show that this loop contains a ganglioside binding motif (H … SXWY … G) that is the same motif seen in botulinum neurotoxin and directly binds to a specific conformation of the ganglioside Neu5Acα2-3(Galβ1-3GalNAcβ1-4)Galβ1-4Glcβ1Cer (GM1a) through a carbohydrate moiety. Confocal microscopy analysis using fluorescently labeled BODIPY-GM1a revealed that the toxin colocalized with GM1a and induced clustering of GM1a on the cell membranes. Alpha-toxin was only slightly toxic in β1,4-N-acetylgalactosaminyltransferase knock-out mice, which lack the a-series gangliosides that contain GM1a, but was highly toxic in α2,8-sialyltransferase knock-out mice, which lack both b-series and c-series gangliosides, similar to the control mice. Moreover, experiments with site-directed mutants indicated that Trp-84 and Tyr-85 in the exposed alpha-toxin loop play an important role in the interaction with GM1a and subsequent activation of TrkA. These results suggest that binding of alpha-toxin to GM1a facilitates the activation of the TrkA receptor and induces a signal transduction cascade that promotes the release of chemokines. Therefore, we conclude that GM1a is the primary cellular receptor for alpha-toxin, which can be a potential target for drug developed against this pathogen.
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Affiliation(s)
- Masataka Oda
- Department of Microbiology, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima 770-8514, Japan.
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Goñi FM, Montes LR, Alonso A. Phospholipases C and sphingomyelinases: Lipids as substrates and modulators of enzyme activity. Prog Lipid Res 2012; 51:238-66. [DOI: 10.1016/j.plipres.2012.03.002] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Revised: 03/23/2012] [Accepted: 03/26/2012] [Indexed: 11/30/2022]
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Urbina P, Collado MI, Alonso A, Goñi FM, Flores-Díaz M, Alape-Girón A, Ruysschaert JM, Lensink MF. Unexpected wide substrate specificity of C. perfringens α-toxin phospholipase C. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2618-27. [DOI: 10.1016/j.bbamem.2011.06.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 06/09/2011] [Accepted: 06/13/2011] [Indexed: 02/05/2023]
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Wargo MJ, Gross MJ, Rajamani S, Allard JL, Lundblad LKA, Allen GB, Vasil ML, Leclair LW, Hogan DA. Hemolytic phospholipase C inhibition protects lung function during Pseudomonas aeruginosa infection. Am J Respir Crit Care Med 2011; 184:345-54. [PMID: 21562128 DOI: 10.1164/rccm.201103-0374oc] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
RATIONALE The opportunistic pathogen Pseudomonas aeruginosa causes both acute and chronic lung infections and is particularly problematic in patients with cystic fibrosis and those undergoing mechanical ventilation. Decreased lung function contributes significantly to morbidity and mortality during P. aeruginosa infection, and damage inflicted by P. aeruginosa virulence factors contributes to lung function decline. OBJECTIVES We sought to describe direct contribution of a bacterial phospholipase C/sphingomyelinase, PlcHR, to alteration of host lung physiology and characterize a potential therapeutic for protection of lung function. METHODS We infected C57Bl/6 mice with P. aeruginosa wild-type or isogenic plcHR deletion strains and measured lung function using computer-controlled ventilators. For in vivo testing, miltefosine was delivered intraperitoneally 1 hour after infection. Infection and respiratory endpoints were at 24 hours after infection. MEASUREMENTS AND MAIN RESULTS P. aeruginosa wild-type infection caused significant lung function impairment, whereas the effects of a ΔplcHR strain infection were much less severe. Surfactometry analysis of bronchoalveolar lavage fluid indicated that PlcHR decreased pulmonary surfactant function. Miltefosine has structural similarity to the PC and sphingomyelin substrates of PlcHR, and we found that it inhibits the cleavage of these choline-containing lipids in vitro. Miltefosine administration after P. aeruginosa infection limited the negative effects of PlcHR activity on lung function. CONCLUSIONS We have directly linked production of a single virulence factor in P. aeruginosa with effects on lung function, and demonstrated that the inhibitor miltefosine protects lung function from PlcHR-dependent surfactant dysfunction.
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Affiliation(s)
- Matthew J Wargo
- Department of Microbiology and Molecular Genetics, University of Vermont College of Medicine, Burlington, VT 05405, USA.
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Schrempf H, Koebsch I, Walter S, Engelhardt H, Meschke H. Extracellular Streptomyces vesicles: amphorae for survival and defence. Microb Biotechnol 2011; 4:286-99. [PMID: 21342473 PMCID: PMC3818868 DOI: 10.1111/j.1751-7915.2011.00251.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Accepted: 01/12/2011] [Indexed: 11/27/2022] Open
Abstract
Blue-pigmented exudates arise as droplets on sporulated lawns of Streptomyces coelicolor M110 grown on agar plates. Our electron microscopical and biochemical studies suggest that droplets contain densely packed vesicles with large assemblies of different protein types and/or the polyketide antibiotic actinorhodin. Frozen-hydrated vesicles were unilamellar with a typical bilayer membrane, and ranged from 80 to 400 nm in diameter with a preferred width of 150-300 nm. By means of cryo-electron tomography, three types were reconstructed three-dimensionally: vesicles that were filled with particulate material, likely protein assemblies, those that contained membrane-bound particles, and a vesicle that showed a higher contrast inside, but lacked particles. Our LC/MS analyses of generated tryptic peptides led to the identification of distinct proteins that carry often a predicted N-terminal signal peptide with a twin-arginine motif or lack a canonical signal sequence. The proteins are required for a range of processes: the acquisition of inorganic as well as organic phosphate, iron ions, and of distinct carbon sources, energy metabolism and redox balance, defence against oxidants and tellurites, the tailoring of actinorhodin, folding and assembly of proteins, establishment of turgor, and different signalling cascades. Our novel findings have immense implications for understanding new avenues of environmental biology of streptomycetes and for biotechnological applications.
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Affiliation(s)
- Hildgund Schrempf
- FB Biology/Chemistry, Applied Genetics of Microorganisms, University Osnabrück, Barbarastr. 13, D-49069 Osnabrück, Germany.
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Ibarguren M, López DJ, Montes LR, Sot J, Vasil AI, Vasil ML, Goñi FM, Alonso A. Imaging the early stages of phospholipase C/sphingomyelinase activity on vesicles containing coexisting ordered-disordered and gel-fluid domains. J Lipid Res 2011; 52:635-45. [PMID: 21252263 DOI: 10.1194/jlr.m012591] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The binding and early stages of activity of a phospholipase C/sphingomyelinase from Pseudomonas aeruginosa on giant unilamellar vesicles (GUV) have been monitored using fluorescence confocal microscopy. Both the lipids and the enzyme were labeled with specific fluorescent markers. GUV consisted of a mixture of phosphatidylcholine, sphingomyelin, phosphatidylethanolamine, and cholesterol in equimolar ratios, to which 5-10 mol% of the enzyme end-product ceramide and/or diacylglycerol were occasionally added. Morphological examination of the GUV in the presence of enzyme reveals that, although the enzyme diffuses rapidly throughout the observation chamber, detectable enzyme binding appears to be a slow, random process, with new bound-enzyme-containing vesicles appearing for several minutes. Enzyme binding to the vesicles appears to be a cooperative process. After the initial cluster of bound enzyme is detected, further binding and catalytic activity follow rapidly. After the activity has started, the enzyme is not released by repeated washing, suggesting a "scooting" mechanism for the hydrolytic activity. The enzyme preferentially binds the more disordered domains, and, in most cases, the catalytic activity causes the disordering of the other domains. Simultaneously, peanut- or figure-eight-shaped vesicles containing two separate lipid domains become spherical. At a further stage of lipid hydrolysis, lipid aggregates are formed and vesicles disintegrate.
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Affiliation(s)
- Maitane Ibarguren
- Unidad de Biofísica (Centro Mixto CSIC-UPV/EHU), Departamento de Bioquímica, Universidad del País Vasco, Bilbao, Spain
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López DJ, Collado MI, Ibarguren M, Vasil AI, Vasil ML, Goñi FM, Alonso A. Multiple phospholipid substrates of phospholipase C/sphingomyelinase HR2 from Pseudomonas aeruginosa. Chem Phys Lipids 2011; 164:78-82. [DOI: 10.1016/j.chemphyslip.2010.11.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2010] [Revised: 11/02/2010] [Accepted: 11/02/2010] [Indexed: 01/08/2023]
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Costas MJ, Pinto RM, Cordero PM, Cabezas A, Alves-Pereira I, Cameselle JC, Ribeiro JM. CGDEase, a Pseudomonas fluorescens protein of the PLC/APase superfamily with CDP-ethanolamine and (dihexanoyl)glycerophosphoethanolamine hydrolase activity induced by osmoprotectants under phosphate-deficient conditions. Mol Microbiol 2010; 78:1556-76. [PMID: 21143324 DOI: 10.1111/j.1365-2958.2010.07425.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A novel enzyme, induced by choline, ethanolamine, glycine betaine or dimethylglycine, was released at low temperature and phosphate from Pseudomonas fluorescens (CECT 7229) suspensions at low cell densities. It is a CDP-ethanolamine pyrophosphatase/(dihexanoyl)glycerophosphoethanolamine phosphodiesterase (CGDEase) less active on choline derivatives, and inactive on long-chain phospholipids, CDP-glycerol and other NDP-X compounds. The reaction pattern was typical of phospholipase C (PLC), as either phosphoethanolamine or phosphocholine was produced. Peptide-mass analyses, gene cloning and expression provided a molecular identity for CGDEase. Bioinformatic studies assigned it to the PLC branch of the phospholipase C/acid phosphatase (PLC/APase) superfamily, revealed an irregular phylogenetic distribution of close CGDEase relatives, and suggested their genes are not in operons or conserved contexts. A theoretical CGDEase structure was supported by mutagenesis of two predicted active-site residues, which yielded essentially inactive mutants. Biological relevance is supported by comparisons with CGDEase relatives, induction by osmoprotectants (not by osmotic stress itself) and repression by micromolar phosphate. The low bacterial density requirement was related to phosphate liberation from lysed bacteria in denser populations, rather than to a classical quorum-sensing effect. The results fit better a CGDEase role in phosphate scavenging than in osmoprotection.
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Affiliation(s)
- María Jesús Costas
- Departamento de Bioquímica y Biología Molecular y Genética, Universidad de Extremadura, Badajoz E-06006, Spain
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Vachieri SG, Clark GC, Alape-Girón A, Flores-Díaz M, Justin N, Naylor CE, Titball RW, Basak AK. Comparison of a nontoxic variant ofClostridium perfringensα-toxin with the toxic wild-type strain. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2010; 66:1067-74. [DOI: 10.1107/s090744491003369x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Accepted: 08/20/2010] [Indexed: 11/10/2022]
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Urbina P, Flores-Díaz M, Alape-Girón A, Alonso A, Goñi FM. Effects of bilayer composition and physical properties on the phospholipase C and sphingomyelinase activities of Clostridium perfringens α-toxin. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:279-86. [PMID: 20727345 DOI: 10.1016/j.bbamem.2010.08.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Revised: 07/30/2010] [Accepted: 08/11/2010] [Indexed: 01/15/2023]
Abstract
α-Toxin, a major determinant of Clostridium perfringens toxicity, exhibits both phospholipase C and sphingomyelinase activities. Our studies with large unilamellar vesicles containing a variety of lipid mixtures reveal that both lipase activities are enhanced by cholesterol and by lipids with an intrinsic negative curvature, e.g. phosphatidylethanolamine. Conversely lysophospholipids, that possess a positive intrinsic curvature, inhibit the α-toxin lipase activities. Phospholipids with a net negative charge do not exert any major effect on the lipase activities, and the same lack of effect is seen with the lysosomal lipid bis (monoacylglycero) phosphate. Ganglioside GT1b has a clear inhibitory effect, while the monosialic ganglioside GM3 is virtually ineffectual even when incorporated at 6mol % in the vesicles. The length of the lag periods appears to be inversely related to the maximum (post-lag) enzyme activities. Moreover, and particularly in the presence of cholesterol, lag times increase with pH. Both lipase activities are sensitive to vesicle size, but in opposite ways: while phospholipase C is higher with larger vesicles, sphingomyelinase activity is lower. The combination of our results with previous structural studies suggests that α-toxin lipase activities have distinct, but partially overlapping and interacting active sites.
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Affiliation(s)
- Patricia Urbina
- Unidad de Biofísica (Centro Mixto CSIC-UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, Aptdo. 644, 48080 Bilbao, Spain
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Sinorhizobium meliloti phospholipase C required for lipid remodeling during phosphorus limitation. Proc Natl Acad Sci U S A 2009; 107:302-7. [PMID: 20018679 DOI: 10.1073/pnas.0912930107] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Rhizobia are Gram-negative soil bacteria able to establish nitrogen-fixing root nodules with their respective legume host plants. Besides phosphatidylglycerol, cardiolipin, and phosphatidylethanolamine, rhizobial membranes contain phosphatidylcholine (PC) as a major membrane lipid. Under phosphate-limiting conditions of growth, some bacteria replace their membrane phospholipids with lipids lacking phosphorus. In Sinorhizobium meliloti, these phosphorus-free lipids are sulfoquinovosyl diacylglycerol, ornithine-containing lipid, and diacylglyceryl trimethylhomoserine (DGTS). Pulse-chase experiments suggest that the zwitterionic phospholipids phosphatidylethanolamine and PC act as biosynthetic precursors of DGTS under phosphorus-limiting conditions. A S. meliloti mutant, deficient in the predicted phosphatase SMc00171 was unable to degrade PC or to form DGTS in a similar way as the wild type. Cell-free extracts of Escherichia coli, in which SMc00171 had been expressed, convert PC to phosphocholine and diacylglycerol, showing that SMc00171 functions as a phospholipase C. Diacylglycerol , in turn, is the lipid anchor from which biosynthesis is initiated during the formation of the phosphorus-free membrane lipid DGTS. Inorganic phosphate can be liberated from phosphocholine. These data suggest that, in S. meliloti under phosphate-limiting conditions, membrane phospholipids provide a pool for metabolizable inorganic phosphate, which can be used for the synthesis of other essential phosphorus-containing biomolecules. This is an example of an intracellular phospholipase C in a bacterial system; however, the ability to degrade endogenous preexisting membrane phospholipids as a source of phosphorus may be a general property of Gram-negative soil bacteria.
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End-products diacylglycerol and ceramide modulate membrane fusion induced by a phospholipase C/sphingomyelinase from Pseudomonas aeruginosa. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1798:59-64. [PMID: 19891956 DOI: 10.1016/j.bbamem.2009.10.017] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Revised: 10/27/2009] [Accepted: 10/28/2009] [Indexed: 01/17/2023]
Abstract
A phospholipase C/sphingomyelinase from Pseudomonas aeruginosa has been assayed on vesicles containing phosphatidylcholine, sphingomyelin, phosphatidylethanolamine and cholesterol at equimolar ratios. The enzyme activity modifies the bilayer chemical composition giving rise to diacylglycerol (DAG) and ceramide (Cer). Assays of enzyme activity, enzyme-induced aggregation and fusion have been performed. Ultrastructural evidence of vesicle fusion at various stages of the process is presented, based on cryo-EM observations. The two enzyme lipidic end-products, DAG and Cer, have opposite effects on the bilayer physical properties; the former abolishes lateral phase separation, while the latter generates a new gel phase [Sot et al., FEBS Lett. 582, 3230-3236 (2008)]. Addition of either DAG, or Cer, or both to the liposome mixture causes an increase in enzyme binding to the bilayers and a decrease in lag time of hydrolysis. These two lipids also have different effects on the enzyme activity, DAG enhancing enzyme-induced vesicle aggregation and fusion, Cer inhibiting the hydrolytic activity. These effects are explained in terms of the different physical properties of the two lipids. DAG increases bilayers fluidity and decreases lateral separation of lipids, thus increasing enzyme activity and substrate accessibility to the enzyme. Cer has the opposite effect mainly because of its tendency to sequester sphingomyelin, an enzyme substrate, into rigid domains, presumably less accessible to the enzyme.
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Vasil ML, Stonehouse MJ, Vasil AI, Wadsworth SJ, Goldfine H, Bolcome RE, Chan J. A complex extracellular sphingomyelinase of Pseudomonas aeruginosa inhibits angiogenesis by selective cytotoxicity to endothelial cells. PLoS Pathog 2009; 5:e1000420. [PMID: 19424430 PMCID: PMC2673038 DOI: 10.1371/journal.ppat.1000420] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Accepted: 04/08/2009] [Indexed: 11/19/2022] Open
Abstract
The hemolytic phospholipase C (PlcHR) expressed by Pseudomonas aeruginosa is the original member of a Phosphoesterase Superfamily, which includes phosphorylcholine-specific phospholipases C (PC-PLC) produced by frank and opportunistic pathogens. PlcHR, but not all its family members, is also a potent sphingomyelinase (SMase). Data presented herein indicate that picomolar (pM) concentrations of PlcHR are selectively lethal to endothelial cells (EC). An RGD motif of PlcHR contributes to this selectivity. Peptides containing an RGD motif (i.e., GRGDS), but not control peptides (i.e., GDGRS), block the effects of PlcHR on calcium signaling and cytotoxicity to EC. Moreover, RGD variants of PlcHR (e.g., RGE, KGD) are significantly reduced in their binding and toxicity, but retain the enzymatic activity of the wild type PlcHR. PlcHR also inhibits several EC-dependent in vitro assays (i.e., EC migration, EC invasion, and EC tubule formation), which represent key processes involved in angiogenesis (i.e., formation of new blood vessels from existing vasculature). Finally, the impact of PlcHR in an in vivo model of angiogenesis in transgenic zebrafish, and ones treated with an antisense morpholino to knock down a key blood cell regulator, were evaluated because in vitro assays cannot fully represent the complex processes of angiogenesis. As little as 2 ng/embryo of PlcHR was lethal to approximately 50% of EGFP-labeled EC at 6 h after injection of embryos at 48 hpf (hours post-fertilization). An active site mutant of PlcHR (Thr178Ala) exhibited 120-fold reduced inhibitory activity in the EC invasion assay, and 20 ng/embryo elicited no detectable inhibitory activity in the zebrafish model. Taken together, these observations are pertinent to the distinctive vasculitis and poor wound healing associated with P. aeruginosa sepsis and suggest that the potent antiangiogenic properties of PlcHR are worthy of further investigation for the treatment of diseases where angiogenesis contributes pathological conditions (e.g., vascularization of tumors, diabetic retinopathy).
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Affiliation(s)
- Michael L Vasil
- Department of Microbiology, University of Colorado Denver, Anschutz Medical Center, Aurora, Colorado, United States of America.
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Long-distance delivery of bacterial virulence factors by Pseudomonas aeruginosa outer membrane vesicles. PLoS Pathog 2009; 5:e1000382. [PMID: 19360133 PMCID: PMC2661024 DOI: 10.1371/journal.ppat.1000382] [Citation(s) in RCA: 426] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Accepted: 03/16/2009] [Indexed: 01/08/2023] Open
Abstract
Bacteria use a variety of secreted virulence factors to manipulate host cells, thereby causing significant morbidity and mortality. We report a mechanism for the long-distance delivery of multiple bacterial virulence factors, simultaneously and directly into the host cell cytoplasm, thus obviating the need for direct interaction of the pathogen with the host cell to cause cytotoxicity. We show that outer membrane-derived vesicles (OMV) secreted by the opportunistic human pathogen Pseudomonas aeruginosa deliver multiple virulence factors, including beta-lactamase, alkaline phosphatase, hemolytic phospholipase C, and Cif, directly into the host cytoplasm via fusion of OMV with lipid rafts in the host plasma membrane. These virulence factors enter the cytoplasm of the host cell via N-WASP-mediated actin trafficking, where they rapidly distribute to specific subcellular locations to affect host cell biology. We propose that secreted virulence factors are not released individually as naked proteins into the surrounding milieu where they may randomly contact the surface of the host cell, but instead bacterial derived OMV deliver multiple virulence factors simultaneously and directly into the host cell cytoplasm in a coordinated manner.
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Rossignol G, Merieau A, Guerillon J, Veron W, Lesouhaitier O, Feuilloley MGJ, Orange N. Involvement of a phospholipase C in the hemolytic activity of a clinical strain of Pseudomonas fluorescens. BMC Microbiol 2008; 8:189. [PMID: 18973676 PMCID: PMC2613904 DOI: 10.1186/1471-2180-8-189] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2008] [Accepted: 10/30/2008] [Indexed: 11/21/2022] Open
Abstract
Background Pseudomonas fluorescens is a ubiquitous Gram-negative bacterium frequently encountered in hospitals as a contaminant of injectable material and surfaces. This psychrotrophic bacterium, commonly described as unable to grow at temperatures above 32°C, is now considered non pathogenic. We studied a recently identified clinical strain of P. fluorescens biovar I, MFN1032, which is considered to cause human lung infection and can grow at 37°C in laboratory conditions. Results We found that MFN1032 secreted extracellular factors with a lytic potential at least as high as that of MF37, a psychrotrophic strain of P. fluorescens or the mesophilic opportunistic pathogen, Pseudomonas aeruginosa PAO1. We demonstrated the direct, and indirect – through increases in biosurfactant release – involvement of a phospholipase C in the hemolytic activity of this bacterium. Sequence analysis assigned this phospholipase C to a new group of phospholipases C different from those produced by P. aeruginosa. We show that changes in PlcC production have pleiotropic effects and that plcC overexpression and plcC extinction increase MFN1032 toxicity and colonization, respectively. Conclusion This study provides the first demonstration that a PLC is involved in the secreted hemolytic activity of a clinical strain of Pseudomonas fluorescens. Moreover, this phospholipase C seems to belong to a complex biological network associated with the biosurfactant production.
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Affiliation(s)
- Gaelle Rossignol
- Laboratory of Cold Microbiology, UPRES EA 4312, University of Rouen, 55 rue Saint Germain, 27000 Evreux, France
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Montes LR, López DJ, Sot J, Bagatolli LA, Stonehouse MJ, Vasil ML, Wu BX, Hannun YA, Goñi FM, Alonso A. Ceramide-enriched membrane domains in red blood cells and the mechanism of sphingomyelinase-induced hot-cold hemolysis. Biochemistry 2008; 47:11222-30. [PMID: 18826261 DOI: 10.1021/bi801139z] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Hot-cold hemolysis is the phenomenon whereby red blood cells, preincubated at 37 degrees C in the presence of certain agents, undergo rapid hemolysis when transferred to 4 degrees C. The mechanism of this phenomenon is not understood. PlcHR 2, a phospholipase C/sphingomyelinase from Pseudomonas aeruginosa, that is the prototype of a new phosphatase superfamily, induces hot-cold hemolysis. We found that the sphingomyelinase, but not the phospholipase C activity, is essential for hot-cold hemolysis because the phenomenon occurs not only in human erythrocytes that contain both phosphatidylcholine (PC) and sphingomyelin (SM) but also in goat erythrocytes, which lack PC. However, in horse erythrocytes, with a large proportion of PC and almost no SM, hot-cold hemolysis induced by PlcHR 2 is not observed. Fluorescence microscopy observations confirm the formation of ceramide-enriched domains as a result of PlcHR 2 activity. After cooling down to 4 degrees C, the erythrocyte ghost membranes arising from hemolysis contain large, ceramide-rich domains. We suggest that formation of these rigid domains in the originally flexible cell makes it fragile, thus highly susceptible to hemolysis. We also interpret the slow hemolysis observed at 37 degrees C as a phenomenon of gradual release of aqueous contents, induced by the sphingomyelinase activity, as described by Ruiz-Arguello et al. [(1996) J. Biol. Chem. 271, 26616]. These hypotheses are supported by the fact that ceramidase, which is known to facilitate slow hemolysis at 37 degrees C, actually hinders hot-cold hemolysis. Differential scanning calorimetry of erytrocyte membranes treated with PlcHR 2 demonstrates the presence of ceramide-rich domains that are rigid at 4 degrees C but fluid at 37 degrees C. Ceramidase treatment causes the disapperance of the calorimetric signal assigned to ceramide-rich domains. Finally, in liposomes composed of SM, PC, and cholesterol, which exhibit slow release of aqueous contents at 37 degrees C, addition of 10 mol % ceramide and transfer to 4 degrees C cause a large increase in the rate of solute efflux.
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Affiliation(s)
- L-Ruth Montes
- Unidad de Biofisica (Centro Mixto CSIC-UPV/EHU) and Departamento de Bioquimica, Universidad del Pais Vasco, Aptdo. 644, 48080 Bilbao, Spain
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Abstract
We previously reported that the novel Pseudomonas aeruginosa toxin Cif is capable of decreasing apical membrane expression of the cystic fibrosis transmembrane conductance regulator (CFTR). We further demonstrated that Cif is capable of degrading the synthetic epoxide hydrolase (EH) substrate S-NEPC [(2S,3S)-trans-3-phenyl-2-oxiranylmethyl 4-nitrophenol carbonate], suggesting that Cif may be reducing apical membrane expression of CFTR via its EH activity. Here we report that Cif is capable of degrading the xenobiotic epoxide epibromohydrin (EBH) to its vicinal diol 3-bromo-1,2-propanediol. We also demonstrate that this epoxide is a potent inducer of cif gene expression. We show that the predicted TetR family transcriptional repressor encoded by the PA2931 gene, which is immediately adjacent to and divergently transcribed from the cif-containing, three-gene operon, negatively regulates cif gene expression by binding to the promoter region immediately upstream of the cif-containing operon. Furthermore, this protein-DNA interaction is disrupted by the epoxide EBH in vitro, suggesting that the binding of EBH by the PA2931 protein product drives the disassociation from its DNA-binding site. Given its role as a repressor of cif gene expression, we have renamed PA2931 as CifR. Finally, we demonstrate that P. aeruginosa strains isolated from cystic fibrosis patient sputum with increased cif gene expression are impaired for the expression of the cifR gene.
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Pseudomonas aeruginosa twitching motility-mediated chemotaxis towards phospholipids and fatty acids: specificity and metabolic requirements. J Bacteriol 2008; 190:4038-49. [PMID: 18390654 DOI: 10.1128/jb.00129-08] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa demonstrates type IV pilus-mediated directional twitching motility up a gradient of phosphatidylethanolamine (PE). Only one of four extracellular phospholipases C of P. aeruginosa (i.e., PlcB), while not required for twitching motility per se, is required for twitching-mediated migration up a gradient of PE or phosphatidylcholine. Whether other lipid metabolism genes are associated with this behavior was assessed by analysis of transcription during twitching up a PE gradient in comparison to transcription during twitching in the absence of any externally applied phospholipid. Data support the hypothesis that PE is further degraded and that the long-chain fatty acid (LCFA) moieties of PE are completely metabolized via beta-oxidation and the glyoxylate shunt. It was discovered that P. aeruginosa exhibits twitching-mediated chemotaxis toward unsaturated LCFAs (e.g., oleic acid), but not saturated LCFAs (e.g., stearic acid) of corresponding lengths. Analysis of mutants that are deficient in glyoxylate shunt enzymes, specifically isocitrate lyase (DeltaaceA) and malate synthase (DeltaaceB), suggested that the complete metabolism of LCFAs through this pathway was required for the migration of P. aeruginosa up a gradient of PE or unsaturated LCFAs. At this point, our data suggested that this process should be classified as energy taxis. However, further evaluation of the ability of the DeltaaceA and DeltaaceB mutants to migrate up a gradient of PE or unsaturated LCFAs in the presence of an alternative energy source clearly indicated that metabolism of LCFAs for energy is not required for chemotaxis toward these compounds.
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Lipolytic enzymes in Mycobacterium tuberculosis. Appl Microbiol Biotechnol 2008; 78:741-9. [PMID: 18309478 DOI: 10.1007/s00253-008-1397-2] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2007] [Revised: 02/04/2008] [Accepted: 02/05/2008] [Indexed: 10/22/2022]
Abstract
Mycobacterium tuberculosis is a bacterial pathogen that can persist for decades in an infected patient without causing a disease. In vivo, the tubercle bacillus present in the lungs store triacylglycerols in inclusion bodies. The same process can be observed in vitro when the bacteria infect adipose tissues. Indeed, before entering in the dormant state, bacteria accumulate lipids originating from the host cell membrane degradation and from de novo synthesis. During the reactivation phase, these lipids are hydrolysed and the infection process occurs. The degradation of both extra and intracellular lipids can be directly related to the presence of lipolytic enzymes in mycobacteria, which have been ignored during a long period particularly due to the difficulties to obtain a high expression level of these enzymes in M. tuberculosis. The completion of the M. tuberculosis genome offered new opportunity to this kind of study. The aim of this review is to focus on the recent results obtained in the field of mycobacterium lipolytic enzymes and although no experimental proof has been shown in vivo, it is tempting to speculate that these enzymes could be involved in the virulence and pathogenicity processes.
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Côtes K, Dhouib R, Douchet I, Chahinian H, deCaro A, Carrière F, Canaan S. Characterization of an exported monoglyceride lipase from Mycobacterium tuberculosis possibly involved in the metabolism of host cell membrane lipids. Biochem J 2008; 408:417-27. [PMID: 17784850 PMCID: PMC2267359 DOI: 10.1042/bj20070745] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The Rv0183 gene of the Mycobacterium tuberculosis H37Rv strain, which has been implicated as a lysophospholipase, was cloned and expressed in Escherichia coli. The purified Rv0183 protein did not show any activity when lysophospholipid substrates were used, but preferentially hydrolysed monoacylglycerol substrates with a specific activity of 290 units x mg(-1) at 37 degrees C. Rv0183 hydrolyses both long chain di- and triacylglycerols, as determined using the monomolecular film technique, although the turnover was lower than with MAG (monoacyl-glycerol). The enzyme shows an optimum activity at pH values ranging from 7.5 to 9.0 using mono-olein as substrate and is inactivated by serine esterase inhibitors such as E600, PMSF and tetrahydrolipstatin. The catalytic triad is composed of Ser110, Asp226 and His256 residues, as confirmed by the results of site-directed mutagenesis. Rv0183 shows 35% sequence identity with the human and mouse monoglyceride lipases and well below 15% with the other bacterial lipases characterized so far. Homologues of Rv0183 can be identified in other mycobacterial genomes such as Mycobacterium bovis, Mycobacterium smegmatis, and even Mycobacterium leprae, which is known to contain a low number of genes involved in the replication process within the host cells. The results of immunolocalization studies performed with polyclonal antibodies raised against the purified recombinant Rv0183 suggested that the enzyme was present only in the cell wall and culture medium of M. tuberculosis. Our results identify Rv0183 as the first exported lipolytic enzyme to be characterized in M. tuberculosis and suggest that Rv0183 may be involved in the degradation of the host cell lipids.
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Affiliation(s)
- Karen Côtes
- Laboratoire d'Enzymologie Interfaciale et de Physiologie de la Lipolyse, UPR 9025 - CNRS, 31 Chemin Joseph Aiguier, F-13402 Marseille Cedex 20, France
| | - Rabeb Dhouib
- Laboratoire d'Enzymologie Interfaciale et de Physiologie de la Lipolyse, UPR 9025 - CNRS, 31 Chemin Joseph Aiguier, F-13402 Marseille Cedex 20, France
| | - Isabelle Douchet
- Laboratoire d'Enzymologie Interfaciale et de Physiologie de la Lipolyse, UPR 9025 - CNRS, 31 Chemin Joseph Aiguier, F-13402 Marseille Cedex 20, France
| | - Henri Chahinian
- Laboratoire d'Enzymologie Interfaciale et de Physiologie de la Lipolyse, UPR 9025 - CNRS, 31 Chemin Joseph Aiguier, F-13402 Marseille Cedex 20, France
| | - Alain deCaro
- Laboratoire d'Enzymologie Interfaciale et de Physiologie de la Lipolyse, UPR 9025 - CNRS, 31 Chemin Joseph Aiguier, F-13402 Marseille Cedex 20, France
| | - Frédéric Carrière
- Laboratoire d'Enzymologie Interfaciale et de Physiologie de la Lipolyse, UPR 9025 - CNRS, 31 Chemin Joseph Aiguier, F-13402 Marseille Cedex 20, France
| | - Stéphane Canaan
- Laboratoire d'Enzymologie Interfaciale et de Physiologie de la Lipolyse, UPR 9025 - CNRS, 31 Chemin Joseph Aiguier, F-13402 Marseille Cedex 20, France
- To whom correspondence should be sent (email )
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Saslowsky DE, Lencer WI. Conversion of apical plasma membrane sphingomyelin to ceramide attenuates the intoxication of host cells by cholera toxin. Cell Microbiol 2008; 10:67-80. [PMID: 18052945 DOI: 10.1111/j.1462-5822.2007.01015.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cholera toxin (CT) enters host cells by binding to ganglioside GM1 in the apical plasma membrane (PM). GM1 carries CT retrograde from the PM to the endoplasmic reticulum (ER), where a portion of the toxin, the A1-chain, retro-translocates to the cytosol, causing disease. Trafficking in this pathway appears to depend on the association of CT-GM1 complexes with sphingomyelin (SM)- and cholesterol-rich membrane microdomains termed lipid rafts. Here, we find that in polarized intestinal epithelia, the conversion of apical membrane SM to ceramide by bacterial sphingomyelinase attenuates CT toxicity, consistent with the lipid raft hypothesis. The effect is reversible, specific to toxin entry via the apical membrane, and recapitulated by the addition of exogenous long-chain ceramides. Conversion of apical membrane SM to ceramide inhibits the efficiency of toxin endocytosis, but retrograde trafficking from the apical PM to the Golgi and ER is not affected. This result suggests that the cause for toxin resistance occurs at steps required for retro-translocation of the CT A1-chain to the cytosol.
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Affiliation(s)
- David E Saslowsky
- Children's Hospital, Harvard Digestive Diseases Center, Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA.
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Korbsrisate S, Tomaras AP, Damnin S, Ckumdee J, Srinon V, Lengwehasatit I, Vasil ML, Suparak S. Characterization of two distinct phospholipase C enzymes from Burkholderia pseudomallei. MICROBIOLOGY-SGM 2007; 153:1907-1915. [PMID: 17526847 DOI: 10.1099/mic.0.2006/003004-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Burkholderia pseudomallei is a serious bacterial pathogen that can cause a lethal infection in humans known as melioidosis. In this study two of its phospholipase C (PLC) enzymes (Plc-1 and Plc-2) were characterized. Starting with a virulent strain, two single mutants were constructed, each with one plc gene inactivated, and one double mutant with both plc genes inactivated. The single plc mutants exhibited decreased extracellular PLC activity in comparison to the wild-type strain, thereby demonstrating that the two genes encoded functional extracellular PLCs. Growth comparisons between the wild-type and PLC mutants in egg-yolk-supplemented medium indicated that both PLCs contributed to egg-yolk phospholipid utilization. Both PLCs hydrolysed phosphatidylcholine and sphingomyelin but neither was haemolytic for human erythrocytes. Experimental infections of eukaryotic cells demonstrated that Plc-1 itself had no effect on plaque-forming efficiency but it had an additive effect on increasing the efficiency of Plc-2 to form plaques. Only Plc-2 had a significant role in host cell cytotoxicity. In contrast, neither Plc-1 nor Plc-2 appeared to play any role in multinucleated giant cell (MNGC) formation or induction of apoptotic death in the cells studied. These data suggested that PLCs contribute, at least in part, to B. pseudomallei virulence and support the view that Plc-1 and Plc-2 are not redundant virulence factors.
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Affiliation(s)
- Sunee Korbsrisate
- Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
| | - Andrew P Tomaras
- Department of Microbiology, University of Colorado at Denver and Health Sciences Center Aurora, CO 80045, USA
| | - Suwat Damnin
- Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
| | - Jutturong Ckumdee
- Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
| | - Varintip Srinon
- Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
| | | | - Michael L Vasil
- Department of Microbiology, University of Colorado at Denver and Health Sciences Center Aurora, CO 80045, USA
| | - Supaporn Suparak
- Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
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Liffourrena AS, Massimelli MJ, Forrellad MA, Lisa AT, Domenech CE, Lucchesi GI. Tetradecyltrimethylammonium Inhibits Pseudomonas aeruginosa Hemolytic Phospholipase C Induced by Choline. Curr Microbiol 2007; 55:530-6. [PMID: 17899264 DOI: 10.1007/s00284-007-9027-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2007] [Accepted: 07/05/2007] [Indexed: 11/29/2022]
Abstract
Pseudomonas aeruginosa expresses hemolytic phospholipase C (PlcH) with choline or under phosphate-limiting conditions. PlcH from these conditions were differently eluted from the Celite-545 column after application of an ammonium sulfate linear reverse gradient. The PlcH from supernatants of bacteria grown in the presence of choline was eluted with 30% ammonium sulfate and was more than 85% inhibited by tetradecyltrimethylammonium. PlcH from supernatants of bacteria grown with succinate and ammonium ions in a low-phosphate medium was eluted as a peak with 10% of salt and was less than 10% inhibited by tetradecyltrimethylammonium. PlcH from low phosphate was purified associated with a protein of 17 kDa. This complex was dissociated and separated on a Sephacryl S-200 column with 1% (w/v) sodium dodecyl sulfate. After this dissociation, the resulting protein of 70 kDa, corresponding to PlcH, was inhibited by tetradecyltrimethylammonium, showing a protection effect of the accompanying protein. RT-PCR analyses showed that in choline media, the plcH gene was expressed independently of plcR. In low-phosphate medium, the plcH gene was expressed as a plcHR operon. Because plcR encodes for chaperone proteins, this result correlates with the observation that PlcH from supernatants of bacteria grown in the presence of choline was purified without an accompanying protein. The consequence of the absence of this chaperone was that tetradecyltrimethylammonium inhibited the PlcH activity.
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Affiliation(s)
- Andrés S Liffourrena
- Departamento de Biología Molecular, Facultad de Ciencias Exactas, Fisicoquímicas y Naturales, Universidad Nacional de Río Cuarto, CP5800, Río Cuarto, Córdoba, Argentina
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49
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Montes LR, Ibarguren M, Goñi FM, Stonehouse M, Vasil ML, Alonso A. Leakage-free membrane fusion induced by the hydrolytic activity of PlcHR(2), a novel phospholipase C/sphingomyelinase from Pseudomonas aeruginosa. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:2365-72. [PMID: 17560896 DOI: 10.1016/j.bbamem.2007.04.024] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2007] [Revised: 04/24/2007] [Accepted: 04/26/2007] [Indexed: 11/29/2022]
Abstract
PlcHR(2) is the paradigm member of a novel phospholipase C/phosphatase superfamily, with members in a variety of bacterial species. This paper describes the phospholipase C and sphingomyelinase activities of PlcHR(2) when the substrate is in the form of large unilamellar vesicles, and the subsequent effects of lipid hydrolysis on vesicle and bilayer stability, including vesicle fusion. PlcHR(2) cleaves phosphatidylcholine and sphingomyelin at equal rates, but is inactive on phospholipids that lack choline head groups. Calcium in the millimolar range does not modify in any significant way the hydrolytic activity of PlcHR(2) on choline-containing phospholipids. The catalytic activity of the enzyme induces vesicle fusion, as demonstrated by the concomitant observation of intervesicular total lipid mixing, inner monolayer-lipid mixing, and aqueous contents mixing. No release of vesicular contents is detected under these conditions. The presence of phosphatidylserine in the vesicle composition does not modify significantly PlcHR(2)-induced liposome aggregation, as long as Ca(2+) is present, but completely abolishes fusion, even in the presence of the cation. Each of the various enzyme-induced phenomena have their characteristic latency periods, that increase in the order lipid hydrolysis<vesicle aggregation<total lipid mixing<inner lipid mixing<contents mixing. Concomitant measurements of the threshold diacylglyceride+ceramide concentrations in the bilayer show that late events, e.g. lipid mixing, require a higher concentration of PlcHR(2) products than early ones, e.g. aggregation. When the above results are examined in the context of the membrane effects of other phospholipid phosphocholine hydrolases it can be concluded that aggregation is necessary, but not sufficient for membrane fusion to occur, that diacylglycerol is far more fusogenic than ceramide, and that vesicle membrane permeabilization occurs independently from vesicle fusion.
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Affiliation(s)
- L-Ruth Montes
- Unidad de Biofísica (Centro Mixto CSIC-UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, Aptdo. 644, 48080 Bilbao, Spain
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50
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Ramu Y, Xu Y, Lu Z. Inhibition of CFTR Cl- channel function caused by enzymatic hydrolysis of sphingomyelin. Proc Natl Acad Sci U S A 2007; 104:6448-53. [PMID: 17400751 PMCID: PMC1851081 DOI: 10.1073/pnas.0701354104] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Numerous mutations in the cystic fibrosis (CF) transmembrane conductance regulator (CFTR, a Cl(-) channel) disrupt salt and fluid transport and lead to the formation of thick mucus in patients' airways. Obstruction by mucus predisposes CF patients to chronic infections and inflammation, which become gradually harder to control and eventually fatal. Aggressive antibiotic therapy and supportive measures have dramatically lengthened CF patients' lives. Here, we report that sphingomyelinases (SMase) from human respiratory pathogens strongly inhibit CFTR function. The hydrolysis of sphingomyelin by SMase makes it more difficult to activate CFTR by phosphorylation of its regulatory domain. By inhibiting CFTR currents, SMase-producing respiratory tract bacteria may not only aggravate pulmonary infection in some CF patients but may also elicit a condition, analogous to CFTR deficiency, in non-CF patients suffering from bacterial lung infection.
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Affiliation(s)
- Yajamana Ramu
- Department of Physiology, University of Pennsylvania, 3700 Hamilton Walk, Philadelphia, PA 19104
| | - Yanping Xu
- Department of Physiology, University of Pennsylvania, 3700 Hamilton Walk, Philadelphia, PA 19104
| | - Zhe Lu
- Department of Physiology, University of Pennsylvania, 3700 Hamilton Walk, Philadelphia, PA 19104
- *To whom correspondence should be addressed. E-mail:
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