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Singh RB, Das S, Chodosh J, Sharma N, Zegans ME, Kowalski RP, Jhanji V. Paradox of complex diversity: Challenges in the diagnosis and management of bacterial keratitis. Prog Retin Eye Res 2021; 88:101028. [PMID: 34813978 DOI: 10.1016/j.preteyeres.2021.101028] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 11/09/2021] [Accepted: 11/12/2021] [Indexed: 12/12/2022]
Abstract
Bacterial keratitis continues to be one of the leading causes of corneal blindness in the developed as well as the developing world, despite swift progress since the dawn of the "anti-biotic era". Although, we are expeditiously developing our understanding about the different causative organisms and associated pathology leading to keratitis, extensive gaps in knowledge continue to dampen the efforts for early and accurate diagnosis, and management in these patients, resulting in poor clinical outcomes. The ability of the causative bacteria to subdue the therapeutic challenge stems from their large genome encoding complex regulatory networks, variety of unique virulence factors, and rapid secretion of tissue damaging proteases and toxins. In this review article, we have provided an overview of the established classical diagnostic techniques and therapeutics for keratitis caused by various bacteria. We have extensively reported our recent in-roads through novel tools for accurate diagnosis of mono- and poly-bacterial corneal infections. Furthermore, we outlined the recent progress by our group and others in understanding the sub-cellular genomic changes that lead to antibiotic resistance in these organisms. Finally, we discussed in detail, the novel therapies and drug delivery systems in development for the efficacious management of bacterial keratitis.
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Affiliation(s)
- Rohan Bir Singh
- Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, USA; Department of Ophthalmology, Leiden University Medical Center, 2333, ZA Leiden, the Netherlands
| | - Sujata Das
- Cornea and Anterior Segment Services, LV Prasad Eye Institute, Bhubaneshwar, India
| | - James Chodosh
- Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, USA
| | - Namrata Sharma
- Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
| | - Michael E Zegans
- Department of Ophthalmology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA
| | - Regis P Kowalski
- Department of Ophthalmology, University of Pittsburgh Medical Center, Pittsburgh, PA, USA; The Charles T Campbell Ophthalmic Microbiology Laboratory, University of Pittsburgh Medical Center, Pittsburgh, PA, USA
| | - Vishal Jhanji
- Department of Ophthalmology, University of Pittsburgh Medical Center, Pittsburgh, PA, USA; The Charles T Campbell Ophthalmic Microbiology Laboratory, University of Pittsburgh Medical Center, Pittsburgh, PA, USA.
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2
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α-Hemolysin suppresses osteogenesis by inducing lipid rafts accumulation in bone marrow stromal cells. Food Chem Toxicol 2020; 145:111689. [PMID: 32810588 DOI: 10.1016/j.fct.2020.111689] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Revised: 07/20/2020] [Accepted: 08/11/2020] [Indexed: 01/15/2023]
Abstract
α-hemolysin (Hla) is considered an essential virulent factor for Staphylococcus aureus (S. aureus) toxicity, the mechanism by which Hla affect bone metabolism is poorly understood. In this study, 2-month-old C57BL/6 mice were treated with Hla (40 μg/kg, i.p.) or S. aureus (1 × 106 CFU/ml, 100 μl, i.v.) with the presence or absence of methyl-β-cyclodextrin (MβCD) (300 mg/kg, i.p.). MicroCT analysis showed progressive bone loss from week 2 to week 4 after Hla treatment, accompanied by a decreased osteoblasts and increased osteoclasts in femoral metaphysis in mice. Further, Hla stimulated the expression of Caveolin-1 in vivo and in vitro, activated lipid rafts accumulation in cell membrane of bone marrow stromal cells (BMSCs), and suppressed osteogenesis of BMSCs. Destruction of lipid rafts with MβCD or inhibition of Caveolin-1 with Daidzein blocked the detrimental effect of Hla on osteogenesis of BMSCs. Importantly, treating mice with MβCD rescued the loss of osteoblasts and increased osteoclastogenesis induced by Hla as well as the bone loss induced by S. aureus infection. Together, we demonstrate that Hla induces bone destruction directly by suppressing osteogenesis and indirectly by stimulating osteoclastogenesis, and that lipid rafts may mediate the detrimental effect of Hla and S. aureus on osteogenesis and bone formation.
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3
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Möller N, Ziesemer S, Hildebrandt P, Assenheimer N, Völker U, Hildebrandt JP. S. aureus alpha-toxin monomer binding and heptamer formation in host cell membranes - Do they determine sensitivity of airway epithelial cells toward the toxin? PLoS One 2020; 15:e0233854. [PMID: 32470006 PMCID: PMC7259691 DOI: 10.1371/journal.pone.0233854] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 05/13/2020] [Indexed: 11/18/2022] Open
Abstract
Alpha-toxin (Hla) is a major virulence factor of Staphylococcus aureus (S. aureus) and plays an important role in S. aureus-induced pneumonia. It binds as a monomer to the cell surface of eukaryotic host cells and forms heptameric transmembrane pores. Sensitivities toward the toxin of various types of potential host cells have been shown to vary substantially, and the reasons for these differences are unclear. We used three human model airway epithelial cell lines (16HBE14o-, S9, A549) to correlate cell sensitivity (measured as rate of paracellular gap formation in the cell layers) with Hla monomer binding, presence of the potential Hla receptors ADAM10 or α5β1 integrin, presence of the toxin-stabilizing factor caveolin-1 as well as plasma membrane lipid composition (phosphatidylserine/choline, sphingomyelin). The abundance of ADAM10 correlated best with gap formation or cell sensitivities, respectively, when the three cell types were compared. Caveolin-1 or α5β1 integrin did not correlate with toxin sensitivity. The relative abundance of sphingomyelin in plasma membranes may also be used as a proxi for cellular sensitivity against alpha-toxin as sphingomyelin abundances correlated well with the intensities of alpha-toxin mediated gap formation in the cell layers.
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Affiliation(s)
- Nils Möller
- Animal Physiology and Biochemistry, University of Greifswald, Greifswald, Germany
| | - Sabine Ziesemer
- Animal Physiology and Biochemistry, University of Greifswald, Greifswald, Germany
| | - Petra Hildebrandt
- Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Nadine Assenheimer
- Animal Physiology and Biochemistry, University of Greifswald, Greifswald, Germany
| | - Uwe Völker
- Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Jan-Peter Hildebrandt
- Animal Physiology and Biochemistry, University of Greifswald, Greifswald, Germany
- * E-mail:
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4
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von Hoven G, Qin Q, Neukirch C, Husmann M, Hellmann N. Staphylococcus aureus α-toxin: small pore, large consequences. Biol Chem 2020; 400:1261-1276. [PMID: 30951494 DOI: 10.1515/hsz-2018-0472] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 03/26/2019] [Indexed: 12/14/2022]
Abstract
The small β-pore-forming α-toxin, also termed α-hemolysin or Hla is considered to be an important virulence factor of Staphylococcus aureus. Perforation of the plasma membrane (PM) by Hla leads to uncontrolled flux of ions and water. Already a small number of toxin pores seems to be sufficient to induce complex cellular responses, many of which depend on the efflux of potassium. In this article, we discuss the implications of secondary membrane lesions, for example, by endogenous channels, for Hla-mediated toxicity, for calcium-influx and membrane repair. Activation of purinergic receptors has been proposed to be a major contributor to the lytic effects of various pore forming proteins, but new findings raise doubts that this holds true for Hla. However, the recently discovered cellular pore forming proteins gasdermin D and Mixed lineage kinase domain-like pseudokinase (MLKL) which perforate the PM from the cytosolic side might contribute to both calcium-influx-dependent damage and membrane repair. Activation of endogenous pore forming proteins by Hla above a threshold concentration could explain the apparent dependence of pore characteristics on toxin concentrations. If secondary membrane damage in the aftermath of Hla-attack contributes significantly to overall PM permeability, it might be an interesting target for new therapeutic approaches.
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Affiliation(s)
- Gisela von Hoven
- Institute of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg-University Mainz, Obere Zahlbacher Straße 67, 55131 Mainz, Germany
| | - Qianqian Qin
- Institute of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg-University Mainz, Obere Zahlbacher Straße 67, 55131 Mainz, Germany
| | - Claudia Neukirch
- Institute of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg-University Mainz, Obere Zahlbacher Straße 67, 55131 Mainz, Germany
| | - Matthias Husmann
- Institute of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg-University Mainz, Obere Zahlbacher Straße 67, 55131 Mainz, Germany
| | - Nadja Hellmann
- Institute for Pharmacy and Biochemistry, Johannes Gutenberg-University Mainz, Johann-Joachim Becher-Weg 30, 55128 Mainz, Germany
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5
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Ziesemer S, Möller N, Nitsch A, Müller C, Beule AG, Hildebrandt JP. Sphingomyelin Depletion from Plasma Membranes of Human Airway Epithelial Cells Completely Abrogates the Deleterious Actions of S. aureus Alpha-Toxin. Toxins (Basel) 2019; 11:toxins11020126. [PMID: 30791542 PMCID: PMC6409578 DOI: 10.3390/toxins11020126] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 02/12/2019] [Accepted: 02/15/2019] [Indexed: 12/16/2022] Open
Abstract
Interaction of Staphylococcus aureus alpha-toxin (hemolysin A, Hla) with eukaryotic cell membranes is mediated by proteinaceous receptors and certain lipid domains in host cell plasma membranes. Hla is secreted as a 33 kDa monomer that forms heptameric transmembrane pores whose action compromises maintenance of cell shape and epithelial tightness. It is not exactly known whether certain membrane lipid domains of host cells facilitate adhesion of Ha monomers, oligomerization, or pore formation. We used sphingomyelinase (hemolysin B, Hlb) expressed by some strains of staphylococci to pre-treat airway epithelial model cells in order to specifically decrease the sphingomyelin (SM) abundance in their plasma membranes. Such a pre-incubation exclusively removed SM from the plasma membrane lipid fraction. It abrogated the formation of heptamers and prevented the formation of functional transmembrane pores. Hla exposure of rHlb pre-treated cells did not result in increases in [Ca2+]i, did not induce any microscopically visible changes in cell shape or formation of paracellular gaps, and did not induce hypo-phosphorylation of the actin depolymerizing factor cofilin as usual. Removal of sphingomyelin from the plasma membranes of human airway epithelial cells completely abrogates the deleterious actions of Staphylococcus aureus alpha-toxin.
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Affiliation(s)
- Sabine Ziesemer
- University of Greifswald, Animal Physiology and Biochemistry, Felix Hausdorff-Straße 1, D-17489 Greifswald, Germany.
| | - Nils Möller
- University of Greifswald, Animal Physiology and Biochemistry, Felix Hausdorff-Straße 1, D-17489 Greifswald, Germany.
| | - Andreas Nitsch
- University of Greifswald, Animal Physiology and Biochemistry, Felix Hausdorff-Straße 1, D-17489 Greifswald, Germany.
| | - Christian Müller
- University of Greifswald, Animal Physiology and Biochemistry, Felix Hausdorff-Straße 1, D-17489 Greifswald, Germany.
| | - Achim G Beule
- Department of Otorhinolaryngology, University Hospital, Münster, Germany and Department of Otorhinolaryngology, Head and Neck Surgery, Greifswald University Hospital, D-17489 Greifswald, Germany.
| | - Jan-Peter Hildebrandt
- University of Greifswald, Animal Physiology and Biochemistry, Felix Hausdorff-Straße 1, D-17489 Greifswald, Germany.
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6
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Lakhundi S, Siddiqui R, Khan NA. Pathogenesis of microbial keratitis. Microb Pathog 2017; 104:97-109. [DOI: 10.1016/j.micpath.2016.12.013] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 11/30/2016] [Accepted: 12/05/2016] [Indexed: 01/03/2023]
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7
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Richter E, Harms M, Ventz K, Gierok P, Chilukoti RK, Hildebrandt JP, Mostertz J, Hochgräfe F. A multi-omics approach identifies key hubs associated with cell type-specific responses of airway epithelial cells to staphylococcal alpha-toxin. PLoS One 2015; 10:e0122089. [PMID: 25816343 PMCID: PMC4376684 DOI: 10.1371/journal.pone.0122089] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 02/17/2015] [Indexed: 12/18/2022] Open
Abstract
Responsiveness of cells to alpha-toxin (Hla) from Staphylococcus aureus appears to occur in a cell-type dependent manner. Here, we compare two human bronchial epithelial cell lines, i.e. Hla-susceptible 16HBE14o- and Hla-resistant S9 cells, by a quantitative multi-omics strategy for a better understanding of Hla-induced cellular programs. Phosphoproteomics revealed a substantial impact on phosphorylation-dependent signaling in both cell models and highlights alterations in signaling pathways associated with cell-cell and cell-matrix contacts as well as the actin cytoskeleton as key features of early rHla-induced effects. Along comparable changes in down-stream activity of major protein kinases significant differences between both models were found upon rHla-treatment including activation of the epidermal growth factor receptor EGFR and mitogen-activated protein kinases MAPK1/3 signaling in S9 and repression in 16HBE14o- cells. System-wide transcript and protein expression profiling indicate induction of an immediate early response in either model. In addition, EGFR and MAPK1/3-mediated changes in gene expression suggest cellular recovery and survival in S9 cells but cell death in 16HBE14o- cells. Strikingly, inhibition of the EGFR sensitized S9 cells to Hla indicating that the cellular capacity of activation of the EGFR is a major protective determinant against Hla-mediated cytotoxic effects.
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Affiliation(s)
- Erik Richter
- Competence Center Functional Genomics, Junior Research Group Pathoproteomics, University of Greifswald, 17489, Greifswald, Germany
| | - Manuela Harms
- Competence Center Functional Genomics, Junior Research Group Pathoproteomics, University of Greifswald, 17489, Greifswald, Germany
| | - Katharina Ventz
- Competence Center Functional Genomics, Junior Research Group Pathoproteomics, University of Greifswald, 17489, Greifswald, Germany
| | - Philipp Gierok
- Department of Biochemistry, University of Greifswald, 17487, Greifswald, Germany
| | - Ravi Kumar Chilukoti
- Interfaculty Institute for Genetics and Functional Genomics, Department of Functional Genomics, University of Greifswald, 17489, Greifswald, Germany
| | - Jan-Peter Hildebrandt
- Animal Physiology and Biochemistry, Zoological Institute, University of Greifswald, 17487, Greifswald, Germany
| | - Jörg Mostertz
- Competence Center Functional Genomics, Junior Research Group Pathoproteomics, University of Greifswald, 17489, Greifswald, Germany
| | - Falko Hochgräfe
- Competence Center Functional Genomics, Junior Research Group Pathoproteomics, University of Greifswald, 17489, Greifswald, Germany
- * E-mail:
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8
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Hildebrandt JP. Pore-forming virulence factors of Staphylococcus aureus destabilize epithelial barriers-effects of alpha-toxin in the early phases of airway infection. AIMS Microbiol 2015. [DOI: 10.3934/microbiol.2015.1.11] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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9
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Schwiering M, Brack A, Stork R, Hellmann N. Lipid and phase specificity of α-toxin from S. aureus. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:1962-72. [PMID: 23590994 DOI: 10.1016/j.bbamem.2013.04.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Revised: 04/05/2013] [Accepted: 04/08/2013] [Indexed: 12/17/2022]
Abstract
The pore forming toxin Hla (α-toxin) from Staphylococcus aureus is an important pathogenic factor of the bacterium S. aureus and also a model system for the process of membrane-induced protein oligomerisation and pore formation. It has been shown that binding to lipid membranes at neutral or basic pH requires the presence of a phosphocholine-headgroup. Thus, sphingomyelin and phosphatidylcholine may serve as interaction partners in cellular membranes. Based on earlier studies it has been suggested that rafts of sphingomyelin are particularly efficient in toxin binding. In this study we compared the oligomerisation of Hla on liposomes of various lipid compositions in order to identify the preferred interaction partners and conditions. Hla seems to have an intrinsic preference for sphingomyelin compared to phosphatidylcholine due to a higher probability of oligomerisation of membrane bound monomer. We also can show that increasing the surface density of Hla-binding sites enhances the oligomerisation efficiency. Thus, preferential binding to lipid rafts can be expected in the cellular context. On the other hand, sphingomyelin in the liquid disordered phase is a more favourable binding partner for Hla than sphingomyelin in the liquid ordered phase, which makes the membrane outside of lipid rafts the more preferred region of interaction. Thus, the partitioning of Hla is expected to strongly depend on the exact composition of raft and non-raft domains in the membrane.
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Affiliation(s)
- M Schwiering
- Institute for Molecular Biophysics, University of Mainz, Mainz, Germany
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10
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Infectious keratitis: secreted bacterial proteins that mediate corneal damage. J Ophthalmol 2013; 2013:369094. [PMID: 23365719 PMCID: PMC3556867 DOI: 10.1155/2013/369094] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 12/12/2012] [Indexed: 12/17/2022] Open
Abstract
Ocular bacterial infections are universally treated with antibiotics, which can eliminate the organism but cannot reverse the damage caused by bacterial products already present. The three very common causes of bacterial keratitis—Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pneumoniae—all produce proteins that directly or indirectly cause damage to the cornea that can result in reduced vision despite antibiotic treatment. Most, but not all, of these proteins are secreted toxins and enzymes that mediate host cell death, degradation of stromal collagen, cleavage of host cell surface molecules, or induction of a damaging inflammatory response. Studies of these bacterial pathogens have determined the proteins of interest that could be targets for future therapeutic options for decreasing corneal damage.
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11
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Collins BM, Davis MJ, Hancock JF, Parton RG. Structure-based reassessment of the caveolin signaling model: do caveolae regulate signaling through caveolin-protein interactions? Dev Cell 2012; 23:11-20. [PMID: 22814599 DOI: 10.1016/j.devcel.2012.06.012] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Caveolin proteins drive formation of caveolae, specialized cell-surface microdomains that influence cell signaling. Signaling proteins are proposed to use conserved caveolin-binding motifs (CBMs) to associate with caveolae via the caveolin scaffolding domain (CSD). However, structural and bioinformatic analyses argue against such direct physical interactions: in the majority of signaling proteins, the CBM is buried and inaccessible. Putative CBMs do not form a common structure for caveolin recognition, are not enriched among caveolin-binding proteins, and are even more common in yeast, which lack caveolae. We propose that CBM/CSD-dependent interactions are unlikely to mediate caveolar signaling, and the basis for signaling effects should therefore be reassessed.
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Affiliation(s)
- Brett M Collins
- The Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia.
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12
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Oligomerization of Clostridium perfringens epsilon toxin is dependent upon caveolins 1 and 2. PLoS One 2012; 7:e46866. [PMID: 23056496 PMCID: PMC3462777 DOI: 10.1371/journal.pone.0046866] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 09/06/2012] [Indexed: 01/27/2023] Open
Abstract
Evidence from multiple studies suggests that Clostridium perfringens ε-toxin is a pore-forming toxin, assembling into oligomeric complexes in the plasma membrane of sensitive cells. In a previous study, we used gene-trap mutagenesis to identify mammalian factors contributing to toxin activity, including caveolin-2 (CAV2). In this study, we demonstrate the importance of caveolin-2 and its interaction partner, caveolin-1 (CAV1), in ε-toxin-induced cytotoxicity. Using CAV2-specific shRNA in a toxin-sensitive human kidney cell line, ACHN, we confirmed that cells deficient in CAV2 exhibit increased resistance to ε-toxin. Similarly, using CAV1-specific shRNA, we demonstrate that cells deficient in CAV1 also exhibit increased resistance to the toxin. Immunoprecipitation of CAV1 and CAV2 from ε-toxin-treated ACHN cells demonstrated interaction of both CAV1 and -2 with the toxin. Furthermore, blue-native PAGE indicated that the toxin and caveolins were components of a 670 kDa protein complex. Although ε-toxin binding was only slightly perturbed in caveolin-deficient cells, oligomerization of the toxin was dramatically reduced in both CAV1- and CAV2-deficient cells. These results indicate that CAV1 and -2 potentiate ε-toxin induced cytotoxicity by promoting toxin oligomerization – an event which is requisite for pore formation and, by extension, cell death.
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13
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Nishiyama A, Isobe H, Iwao Y, Takano T, Hung WC, Taneike I, Nakagawa S, Dohmae S, Iwakura N, Yamamoto T. Accumulation of staphylococcal Panton-Valentine leukocidin in the detergent-resistant membrane microdomains on the target cells is essential for its cytotoxicity. ACTA ACUST UNITED AC 2012; 66:343-52. [PMID: 22924956 DOI: 10.1111/j.1574-695x.2012.01027.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Revised: 07/24/2012] [Accepted: 07/27/2012] [Indexed: 12/23/2022]
Abstract
The mechanisms for the cytotoxicity of staphylococcal Panton-Valentine leukocidin (PVL), a pore-forming toxin consisting of LukS-PV and LukF-PV, in human immune cells are still unclear. Because LukS-PV binds to ganglioside GM1, a constituent of detergent-resistant membrane microdomains (DRMs) of the plasma membrane, the role of DRMs in PVL cytotoxicity was examined in human polymorphonuclear neutrophils (PMNs), monocytes, HL-60 cells, and THP-1 cells. PVL binding capacities in HL-60 and THP-1 cells were higher than those in PMNs and monocytes; however, the PVL concentration to obtain more than 80% cell lysis in HL-60 cells was 10 times higher than that in PMNs and PVL even at such concentration induced < 10% cell lysis in THP-1 cells. After incubation of PMNs with LukS-PV, more than 90% of LukS-PV bound to the detergent-soluble membranes. Subsequent incubation with LukF-PV at 4 °C induced the accumulation of more than 70% of PVL components and 170- to 220-kDa complex formation in DRMs in an actin-independent manner. However, only 30% of PVL was found, and complex formation was under detectable level in DRMs in HL-60 cells. PVL did not accumulate in DRMs in THP-1 cells. Our observations strongly indicate that PVL accumulation in DRMs is essential for PVL cytotoxicity.
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Affiliation(s)
- Akihito Nishiyama
- Division of Bacteriology, Department of Infectious Disease Control and International Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
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14
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Kloft N, Neukirch C, von Hoven G, Bobkiewicz W, Weis S, Boller K, Husmann M. A subunit of eukaryotic translation initiation factor 2α-phosphatase (CreP/PPP1R15B) regulates membrane traffic. J Biol Chem 2012; 287:35299-35317. [PMID: 22915583 DOI: 10.1074/jbc.m112.379883] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The constitutive reverter of eIF2α phosphorylation (CReP)/PPP1r15B targets the catalytic subunit of protein phosphatase 1 (PP1c) to phosphorylated eIF2α (p-eIF2α) to promote its dephosphorylation and translation initiation. Here, we report a novel role and mode of action of CReP. We found that CReP regulates uptake of the pore-forming Staphylococcus aureus α-toxin by epithelial cells. This function was independent of PP1c and translation, although p-eIF2α was involved. The latter accumulated at sites of toxin attack and appeared conjointly with α-toxin in early endosomes. CReP localized to membranes, interacted with phosphomimetic eIF2α, and, upon overexpression, induced and decorated a population of intracellular vesicles, characterized by accumulation of N-(lissamine rhodamine B sulfonyl)phosphatidylethanolamine (N-Rh-PE), a lipid marker of exosomes and intralumenal vesicles of multivesicular bodies. By truncation analysis, we delineated the CReP vesicle induction/association region, which comprises an amphipathic α-helix and is distinct from the PP1c interaction domain. CReP was also required for exocytosis from erythroleukemia cells and thus appears to play a broader role in membrane traffic. In summary, the mammalian traffic machinery co-opts p-eIF2α and CReP, regulators of translation initiation.
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Affiliation(s)
- Nicole Kloft
- Institute of Medical Microbiology and Hygiene, University Medical Center, Johannes Gutenberg-University Mainz, Hochhaus am Augustusplatz, 55131 Mainz, Germany
| | - Claudia Neukirch
- Institute of Medical Microbiology and Hygiene, University Medical Center, Johannes Gutenberg-University Mainz, Hochhaus am Augustusplatz, 55131 Mainz, Germany
| | - Gisela von Hoven
- Institute of Medical Microbiology and Hygiene, University Medical Center, Johannes Gutenberg-University Mainz, Hochhaus am Augustusplatz, 55131 Mainz, Germany
| | - Wiesia Bobkiewicz
- Institute of Medical Microbiology and Hygiene, University Medical Center, Johannes Gutenberg-University Mainz, Hochhaus am Augustusplatz, 55131 Mainz, Germany
| | - Silvia Weis
- Institute of Medical Microbiology and Hygiene, University Medical Center, Johannes Gutenberg-University Mainz, Hochhaus am Augustusplatz, 55131 Mainz, Germany
| | - Klaus Boller
- Department of Immunology, Morphology Section, Paul Ehrlich-Institute, 63225 Langen, Germany
| | - Matthias Husmann
- Institute of Medical Microbiology and Hygiene, University Medical Center, Johannes Gutenberg-University Mainz, Hochhaus am Augustusplatz, 55131 Mainz, Germany.
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15
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Vandenesch F, Lina G, Henry T. Staphylococcus aureus hemolysins, bi-component leukocidins, and cytolytic peptides: a redundant arsenal of membrane-damaging virulence factors? Front Cell Infect Microbiol 2012; 2:12. [PMID: 22919604 PMCID: PMC3417661 DOI: 10.3389/fcimb.2012.00012] [Citation(s) in RCA: 233] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2011] [Accepted: 01/31/2012] [Indexed: 12/17/2022] Open
Abstract
One key aspect of the virulence of Staphylococcus aureus lies in its ability to target the host cell membrane with a large number of membrane-damaging toxins and peptides. In this review, we describe the hemolysins, the bi-component leukocidins (which include the Panton Valentine leukocidin, LukAB/GH, and LukED), and the cytolytic peptides (phenol soluble modulins). While at first glance, all of these factors might appear redundant, it is now clear that some of these factors play specific roles in certain S. aureus life stages and diseases or target specific cell types or species. In this review, we present an update of the literature on toxin receptors and their cell type and species specificities. Furthermore, we review epidemiological studies and animal models illustrating the role of these membrane-damaging factors in various diseases. Finally, we emphasize the interplay of these factors with the host immune system and highlight all their non-lytic functions.
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Affiliation(s)
- François Vandenesch
- Bacterial Pathogenesis and Innate Immunity Laboratory, INSERM U851 "Immunity, Infection and Vaccination," Lyon, France
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Weeks AC, Balzli CL, Caballero A, Tang A, O'Callaghan R. Identification and potency of cyclodextrin-lipid inhibitors of Staphylococcus aureus α-toxin. Curr Eye Res 2011; 37:87-93. [PMID: 22050601 DOI: 10.3109/02713683.2011.624669] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
PURPOSE Staphylococcus aureus, a leading cause of bacterial keratitis, secretes α-toxin, a cytotoxin active on the corneal epithelium. This study describes the production and testing of chemical inhibitors of α-toxin action. METHODS Purified α-toxin was titered by its ability to lyse rabbit erythrocytes in buffered saline (PBS). To prepare potential toxin inhibitors, each of 18 lipids was incorporated into a complex with methyl-β-cyclodextrin (MβCD) or hydroxypropyl-β-cyclodextrin (HPβCD). Serial dilutions of each lipid-cyclodextrin (CD-lipid) complex were mixed with α-toxin prior to the addition of rabbit erythrocytes. Select CD-lipid complexes were mixed with 12 hemolytic units (HU) α-toxin and injected into the rabbit corneal stroma so the resulting corneal erosions could be measured at 4 and 8 hours post-injection (PI). Eyes injected with toxin alone, MβCD, or HPβCD alone served as controls. RESULTS Neither form of CD alone inhibited α-toxin. Of the 36 complexes prepared, 6 lipid-CD complexes were found to inhibit >100 HU of α-toxin. Four lipid complexes able to inhibit >200 HU of α-toxin were tested in toxin-injected corneas; at 4 and 8 hours PI, the complexes of cholesterol or lanosterol with MβCD and squalene or desmosterol with HPβCD caused a significant reduction in the corneal erosion size as compared to eyes injected with α-toxin alone (P ≤ 0.05). CONCLUSIONS Specific lipid inclusion complexes with either MβCD or HPβCD demonstrated a significant inhibition of α-toxin in both in vitro and in vivo assays. Changes in either the cyclodextrin or lipid of a complex affected the inhibitory activity.
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Affiliation(s)
- Anastasia C Weeks
- Department of Microbiology, University of Mississippi Medical Center, Jackson, MS 39216, USA
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Ivie SE, Fennessey CM, Sheng J, Rubin DH, McClain MS. Gene-trap mutagenesis identifies mammalian genes contributing to intoxication by Clostridium perfringens ε-toxin. PLoS One 2011; 6:e17787. [PMID: 21412435 PMCID: PMC3055893 DOI: 10.1371/journal.pone.0017787] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2010] [Accepted: 02/14/2011] [Indexed: 12/13/2022] Open
Abstract
The Clostridium perfringens ε-toxin is an extremely potent toxin associated with lethal toxemias in domesticated ruminants and may be toxic to humans. Intoxication results in fluid accumulation in various tissues, most notably in the brain and kidneys. Previous studies suggest that the toxin is a pore-forming toxin, leading to dysregulated ion homeostasis and ultimately cell death. However, mammalian host factors that likely contribute to ε-toxin-induced cytotoxicity are poorly understood. A library of insertional mutant Madin Darby canine kidney (MDCK) cells, which are highly susceptible to the lethal affects of ε-toxin, was used to select clones of cells resistant to ε-toxin-induced cytotoxicity. The genes mutated in 9 surviving resistant cell clones were identified. We focused additional experiments on one of the identified genes as a means of validating the experimental approach. Gene expression microarray analysis revealed that one of the identified genes, hepatitis A virus cellular receptor 1 (HAVCR1, KIM-1, TIM1), is more abundantly expressed in human kidney cell lines than it is expressed in human cells known to be resistant to ε-toxin. One human kidney cell line, ACHN, was found to be sensitive to the toxin and expresses a larger isoform of the HAVCR1 protein than the HAVCR1 protein expressed by other, toxin-resistant human kidney cell lines. RNA interference studies in MDCK and in ACHN cells confirmed that HAVCR1 contributes to ε-toxin-induced cytotoxicity. Additionally, ε-toxin was shown to bind to HAVCR1 in vitro. The results of this study indicate that HAVCR1 and the other genes identified through the use of gene-trap mutagenesis and RNA interference strategies represent important targets for investigation of the process by which ε-toxin induces cell death and new targets for potential therapeutic intervention.
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Affiliation(s)
- Susan E. Ivie
- Division of Infectious Disease, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Christine M. Fennessey
- Division of Infectious Disease, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Jinsong Sheng
- Division of Infectious Disease, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Donald H. Rubin
- Division of Infectious Disease, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Research Medicine, VA Tennessee Valley Healthcare System, Nashville, Tennessee, United States of America
| | - Mark S. McClain
- Division of Infectious Disease, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- * E-mail:
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Role of a disintegrin and metalloprotease 10 in Staphylococcus aureus alpha-hemolysin-mediated cellular injury. Proc Natl Acad Sci U S A 2010; 107:13473-8. [PMID: 20624979 DOI: 10.1073/pnas.1001815107] [Citation(s) in RCA: 336] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Staphylococcus aureus alpha-hemolysin (Hla), a potent cytotoxin, plays an important role in the pathogenesis of staphylococcal diseases, including those caused by methicillin-resistant epidemic strains. Hla is secreted as a water-soluble monomer that undergoes a series of conformational changes to generate a heptameric, beta-barrel structure in host membranes. Structural maturation of Hla depends on its interaction with a previously unknown proteinaceous receptor in the context of the cell membrane. It is reported here that a disintegrin and metalloprotease 10 (ADAM10) interacts with Hla and is required to initiate the sequence of events whereby the toxin is transformed into a cytolytic pore. Hla binding to the eukaryotic cell requires ADAM10 expression. Further, ADAM10 is required for Hla-mediated cytotoxicity, most notably when the toxin is present at low concentrations. These data thus implicate ADAM10 as the probable high-affinity toxin receptor. Upon Hla binding, ADAM10 relocalizes to caveolin 1-enriched lipid rafts that serve as a platform for the clustering of signaling molecules. It is demonstrated that the Hla-ADAM10 complex initiates intracellular signaling events that culminate in the disruption of focal adhesions.
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Biological relevance of natural alpha-toxin fragments from Staphylococcus aureus. J Membr Biol 2010; 233:93-103. [PMID: 20155474 DOI: 10.1007/s00232-010-9229-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Accepted: 01/08/2010] [Indexed: 10/19/2022]
Abstract
Serine proteases represent an essential part of cellular homeostasis by generating biologically active peptides. In bacteria, proteolysis serves two different roles: a major housekeeping function and the destruction of foreign or target cell proteins, thereby promoting bacterial invasion. In the process, other virulence factors such as exotoxins become affected. In Staphylococcus aureus culture supernatant, the pore-forming alpha-toxin is cleaved by the coexpressed V8 protease and aureolysin. The oligomerizing and pore-forming abilities of five such spontaneously occurring N- and C-terminal alpha-toxin fragments were studied. (3)H-marked alpha-toxin fragments bound to rabbit erythrocyte membranes but only fragments with intact C termini, missing 8, 12 and 71 amino acids from their N-terminal, formed stable oligomers. All isolated fragments induced intoxication of mouse adrenocortical Y1 cells in vitro, though the nature of membrane damage for a fragment, degraded at its C terminus, remained obscure. Only one fragment, missing the first eight N-terminal amino acids, induced irreversible intoxication of Y1 cells in the same manner as the intact toxin. Four of the isolated fragments caused swelling, indicating altered channel formation. Fragments missing 12 and 71 amino acids from the N terminus occupied the same binding sites on Y1 cell membranes, though they inhibited membrane damage caused by intact toxin. In conclusion, N-terminal deletions up to 71 amino acids are tolerated, though the kinetics of channel formation and the channel's properties are altered. In contrast, digestion at the C terminus results in nonfunctional species.
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Srivastava SS, Pany S, Sneh A, Ahmed N, Rahman A, Musti KV. Membrane bound monomer of Staphylococcal alpha-hemolysin induces caspase activation and apoptotic cell death despite initiation of membrane repair pathway. PLoS One 2009; 4:e6293. [PMID: 19621082 PMCID: PMC2708924 DOI: 10.1371/journal.pone.0006293] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Accepted: 06/09/2009] [Indexed: 02/07/2023] Open
Abstract
Background Wild type Staphylococcal α-hemolysin (α-HL) assembly on target mammalian cells usually results in necrotic form of cell death; however, caspase activation also occurs. The pathways of caspase activation due to binding/partial assembly by α-HL are unknown till date. Results Cells treated with H35N (a mutant of α-HL that remains as membrane bound monomer), have been shown to accumulate hypodiploid nuclei, activate caspases and induce intrinsic mitochondrial apoptotic pathway. We have earlier shown that the binding and assembly of α-HL requires functional form of Caveolin-1 which is an integral part of caveolae. In this report, we show that the caveolae of mammalian cells, which undergo a continuous cycle of ‘kiss and run’ dynamics with the plasma membrane, have become immobile upon the binding of the monomer. The cells treated with H35N were unable to recover despite activation of membrane repair mechanism involving caspase-1 dependent activation of sterol regulatory element binding protein-1. Conclusions This is for the first time we show the range of cellular changes and responses that take place immediately after the binding of the monomeric form of staphylococcal α-hemolysin.
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Affiliation(s)
| | - Satyabrata Pany
- National Centre for Cell Science, University of Pune Campus, Pune, India
| | - Amita Sneh
- National Centre for Cell Science, University of Pune Campus, Pune, India
| | - Neesar Ahmed
- National Centre for Cell Science, University of Pune Campus, Pune, India
| | - Aejazur Rahman
- National Centre for Cell Science, University of Pune Campus, Pune, India
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Staphylococcal alpha-toxin is not sufficient to mediate escape from phagolysosomes in upper-airway epithelial cells. Infect Immun 2009; 77:3611-25. [PMID: 19564384 DOI: 10.1128/iai.01478-08] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Intracellular Staphylococcus aureus has been implicated in the establishment of chronic infections. It is therefore imperative to understand by what means S. aureus is able to survive within cells. Here we use two expression systems with a fluorescent readout to assay alpha-toxin expression and function within phagolysosomes of infected upper-airway epithelial cells: avirulent Staphylococcus carnosus TM300 and phenotypically alpha-toxin-negative S. aureus laboratory strains. Data from CFU recovery assays suggest that the presence of alpha-toxin is not beneficial for the intracellular survival of recombinant Staphylococcus strains. This finding was corroborated by immunofluorescence studies: whereas S. carnosus and S. aureus are able to deliver S. aureus alpha-toxin to lumina of host cell phagolysosomes, the membrane integrity of these organelles was not affected. Alpha-toxin-expressing strains were detected exclusively within lysosome-associated membrane protein 1 (LAMP1)-yellow fluorescent protein (YFP)-positive vesicles. Measurements of intraphagosomal pH illustrated that all infected phagolysosomes acidified regardless of alpha-toxin expression. In contrast, S. aureus expressing Listeria monocytogenes listeriolysin O leads to the breakdown of the phagolysosomal membrane, as indicated by staphylococci that are not associated with LAMP1-YFP-decorated vesicles and that do not reside within an acidic cellular environment. Thus, our results suggest that staphylococcal alpha-toxin is not sufficient to mediate phagolysosomal escape in upper-airway epithelial cells.
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O’Hara F, Guex N, Word J, Miller L, Becker J, Walsh S, Scangarella N, West J, Shawar R, Amrine‐Madsen H. A Geographic Variant of theStaphylococcus aureusPanton‐Valentine Leukocidin Toxin and the Origin of Community‐Associated Methicillin‐ResistantS. aureusUSA300. J Infect Dis 2008; 197:187-94. [DOI: 10.1086/524684] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
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Alioua A, Lu R, Kumar Y, Eghbali M, Kundu P, Toro L, Stefani E. Slo1 caveolin-binding motif, a mechanism of caveolin-1-Slo1 interaction regulating Slo1 surface expression. J Biol Chem 2007; 283:4808-17. [PMID: 18079116 DOI: 10.1074/jbc.m709802200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The large conductance, voltage- and Ca2+-activated potassium (MaxiK, BK) channel and caveolin-1 play important roles in regulating vascular contractility. Here, we hypothesized that the MaxiK alpha-subunit (Slo1) and caveolin-1 may interact with each other. Slo1 and caveolin-1 physiological association in native vascular tissue is strongly supported by (i) detergent-free purification of caveolin-1-rich domains demonstrating a pool of aortic Slo1 co-migrating with caveolin-1 to light density sucrose fractions, (ii) reverse co-immunoprecipitation, and (iii) double immunolabeling of freshly isolated myocytes revealing caveolin-1 and Slo1 proximity at the plasmalemma. In HEK293T cells, Slo1-caveolin-1 association was unaffected by the smooth muscle MaxiK beta1-subunit. Sequence analysis revealed two potential caveolin-binding motifs along the Slo1 C terminus, one equivalent, 1007YNMLCFGIY1015, and another mirror image, 537YTEYLSSAF545, to the consensus sequence, varphiXXXXvarphiXXvarphi. Deletion of 1007YNMLCFGIY1015 caused approximately 80% loss of Slo1-caveolin-1 association while preserving channel normal folding and overall Slo1 and caveolin-1 intracellular distribution patterns. 537YTEYLSSAF545 deletion had an insignificant dissociative effect. Interestingly, caveolin-1 coexpression reduced Slo1 surface and functional expression near 70% without affecting channel voltage sensitivity, and deletion of 1007YNMLCFGIY1015 motif obliterated channel surface expression. The results suggest 1007YNMLCFGIY1015 possible participation in Slo1 plasmalemmal targeting and demonstrate its role as a main mechanism for caveolin-1 association with Slo1 potentially serving a dual role: (i) maintaining channels in intracellular compartments downsizing their surface expression and/or (ii) serving as anchor of plasma membrane resident channels to caveolin-1-rich membranes. Because the caveolin-1 scaffolding domain is juxtamembrane, it is tempting to suggest that Slo1-caveolin-1 interaction facilitates the tethering of the Slo1 C-terminal end to the membrane.
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Affiliation(s)
- Abderrahmane Alioua
- Department of Anesthesiology, Brain Research Institute, Cardiovascular Research Laboratories, UCLA, Los Angeles, CA 90095-1778, USA.
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Pany S, Krishnasastry MV. Aromatic residues of Caveolin-1 binding motif of alpha-hemolysin are essential for membrane penetration. Biochem Biophys Res Commun 2007; 363:197-202. [PMID: 17850762 DOI: 10.1016/j.bbrc.2007.08.132] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2007] [Accepted: 08/23/2007] [Indexed: 11/26/2022]
Abstract
We have created single cysteine Caveolin-1 binding motif mutants (SCCBMMs) of staphylococcal alpha-HL for understanding assembly and penetration. All SCCBMMs have normal folding like alpha-HL as examined by limited proteolysis, intrinsic fluorescence emission, no hemolytic activity and do not form hetero oligomers with alpha-HL indicating that the conformational changes occurred at the cell membrane are different to that of alpha-HL. While modification of SCCBMMs with a membrane impermeant reagent has resulted in reduced binding, badan modification has resulted in the enhancement of badan fluorescence with time of assembly (incubation time) indicating the change in environment of the badan and the need for the penetration of the aromatic amino acids. Our studies indicate that the conformational changes are probably initiated at the Caveolin-1 binding motif and provide a basis for differential mode of interaction of the Caveolin-1 binding motif depending upon the nature of the target cell membrane.
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Affiliation(s)
- Satyabrata Pany
- National Centre for Cell Science, Ganeshkhind Road, Pune 411007, Maharashtra, India
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25
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Liang X, Ji Y. Alpha-toxin interferes with integrin-mediated adhesion and internalization of Staphylococcus aureus by epithelial cells. Cell Microbiol 2006; 8:1656-68. [PMID: 16984420 DOI: 10.1111/j.1462-5822.2006.00740.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Staphylococcus aureus is an important human and animal pathogen. During infection, this bacterium is able to attach to and enter host cells by using its cell surface-associated factors to bind to the host's extracellular matrix (ECM) proteins. In this study, we determined that a protein exported by S. aureus, alpha-toxin, can interfere with the integrin-mediated adhesion and internalization of S. aureus by human lung epithelial cells (A549). The downregulation of alpha-toxin production significantly increased bacterial adhesion and invasion into the epithelial cells. In contrast, bacterial adhesion and invasion was inhibited by both overproduction of alpha-toxin and the addition of alpha-toxin to the culture medium. Moreover, our results showed that the quantitative effects on invasion closely parallel those of adherence. This suggests that the effect on invasion is probably secondary to, and a consequence of, the reduced adherence caused by alpha-toxin exposure. Specifically, we demonstrated that alpha-toxin interacts with the hosts' ECM protein's receptor, beta1-integrin, which indicates that beta1-integrin may be a potential receptor of alpha-toxin on epithelial cells. Taken together, our results indicate that exported alpha-toxin inhibits the adhesion and internalization of S. aureus by interfering with integrin-mediated pathogen-host cell interactions.
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Affiliation(s)
- Xudong Liang
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108, USA
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Tilley SJ, Saibil HR. The mechanism of pore formation by bacterial toxins. Curr Opin Struct Biol 2006; 16:230-6. [PMID: 16563740 DOI: 10.1016/j.sbi.2006.03.008] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Revised: 02/06/2006] [Accepted: 03/14/2006] [Indexed: 01/13/2023]
Abstract
A remarkable group of proteins challenge the notions that protein sequence determines a unique three-dimensional structure, and that membrane and soluble proteins are very distinct. The pore-forming toxins typically transform from soluble, monomeric proteins to oligomers that form transmembrane channels. Recent structural studies provide ideas about how these changes take place. The recently solved structures of the beta-pore-forming toxins LukS, epsilon-toxin and intermedilysin confirm that the pore-forming regions are initially folded up on the surfaces of the soluble precursors. To create the transmembrane pores, these regions must extend and refold into membrane-inserted beta-barrels.
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Affiliation(s)
- Sarah J Tilley
- School of Crystallography, Birkbeck College, Malet Street, London WC1E 7HX, UK
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Levin AM, Coroneus JG, Cocco MJ, Weiss GA. Exploring the interaction between the protein kinase A catalytic subunit and caveolin-1 scaffolding domain with shotgun scanning, oligomer complementation, NMR, and docking. Protein Sci 2006; 15:478-86. [PMID: 16452625 PMCID: PMC2249769 DOI: 10.1110/ps.051911706] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The techniques of phage-displayed homolog shotgun scanning, oligomer complementation, NMR secondary structure analysis, and computational docking provide a complementary suite of tools for dissecting protein-protein interactions. Focusing these tools on the interaction between the catalytic sub-unit of protein kinase A (PKAcat) and caveolin-1 scaffolding domain (CSD) reveals the first structural model for the interaction. Homolog shotgun scanning varied each CSD residue as either a wild-type or a homologous amino acid. Wild-type to homolog ratios from 116 different homologous CSD variants identified side-chain functional groups responsible for precise contacts with PKAcat. Structural analysis by NMR assigned an alpha-helical conformation to the central residues 84- 97 of CSD. The extensive mutagenesis data and NMR secondary structure information provided constraints for developing a model for the PKAcat-CSD interaction. Addition of synthetic CSD to phage-displayed CSD resulted in oligomer complementation, or enhanced binding to PKAcat. Together with previous experiments examining the interaction between CSD and endothelial nitric oxide synthase (eNOS), the results suggest a general oligomerization-dependent enhancement of binding between signal transducing enzymes and caveolin-1.
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Affiliation(s)
- Aron M Levin
- Department of Chemistry, University of California, Irvine, CA 92697, USA
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Jayasinghe L, Bayley H. The leukocidin pore: evidence for an octamer with four LukF subunits and four LukS subunits alternating around a central axis. Protein Sci 2005; 14:2550-61. [PMID: 16195546 PMCID: PMC2253299 DOI: 10.1110/ps.051648505] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The staphylococcal alpha-hemolysin (alphaHL) and leukocidin (Luk) polypeptides are members of a family of related beta-barrel pore-forming toxins. Upon binding to susceptible cells, alphaHL forms water-filled homoheptameric transmembrane pores. By contrast, Luk pores are formed by two classes of subunit, F and S, rendering a heptameric structure displeasing on symmetry grounds at least. Both the subunit stoichiometry and arrangement within the Luk pore have been contentious issues. Here we use chemical and genetic approaches to show that (1) the predominant, or perhaps the only, form of the Luk pore is an octamer; (2) the subunit stoichiometry is 1:1; and (3) the subunits are arranged in an alternating fashion about a central axis of symmetry, at least when a fused LukS-LukF construct is used. The experimental approaches we have used also open up new avenues for engineering the arrangement of the subunits of beta-barrel pore-forming toxins.
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Affiliation(s)
- Lakmal Jayasinghe
- Department of Chemistry, University of Oxford, Oxford OX1 3TA, England, United Kingdom
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Jayasinghe L, Miles G, Bayley H. Role of the amino latch of staphylococcal alpha-hemolysin in pore formation: a co-operative interaction between the N terminus and position 217. J Biol Chem 2005; 281:2195-204. [PMID: 16227199 DOI: 10.1074/jbc.m510841200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Staphylococcal alpha-hemolysin (alphaHL) is a beta barrel pore-forming toxin that is secreted by the bacterium as a water-soluble monomeric protein. Upon binding to susceptible cells, alphaHL assembles via an inactive prepore to form a water-filled homoheptameric transmembrane pore. The N terminus of alphaHL, which in the crystal structure of the fully assembled pore forms a latch between adjacent subunits, has been thought to play a vital role in the prepore to pore conversion. For example, the deletion of two N-terminal residues produced a completely inactive protein that was arrested in assembly at the prepore stage. In the present study, we have re-examined assembly with a comprehensive set of truncation mutants. Surprisingly, we found that after truncation of up to 17 amino acids, the ability of alphaHL to form functional pores was diminished, but still substantial. We then discovered that the mutation Ser(217) --> Asn, which was present in our original set of truncations but not in the new ones, promotes complete inactivation upon truncation of the N terminus. Therefore, the N terminus of alphaHL cannot be critical for the prepore to pore transformation as previously thought. Residue 217 is involved in the assembly process and must interact indirectly with the distant N terminus during the last step in pore formation. In addition, we provide evidence that an intact N terminus prevents the premature oligomerization of alphaHL monomers in solution.
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Affiliation(s)
- Lakmal Jayasinghe
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, United Kingdom
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Vijayvargia R, Kaur S, Krishnasastry MV. alpha-Hemolysin-induced dephosphorylation of EGF receptor of A431 cells is carried out by rPTPsigma. Biochem Biophys Res Commun 2005; 325:344-52. [PMID: 15522239 DOI: 10.1016/j.bbrc.2004.10.038] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2004] [Indexed: 10/26/2022]
Abstract
Earlier we have shown that the epidermal growth factor receptor was unable to retain its phospho Tyr signal after the assembly of staphylococcal alpha-hemolysin (alpha-HL). However, the nature of the protein tyrosine phosphatase (PTPase) or its identity is not known. In this report, we demonstrate that the alpha-HL elevates the activity of receptor like protein tyrosine phosphatase sigma (rPTPsigma). The alpha-HL induced dephosphorylation is prominent only in intact A431 cells. The PTPase activity is not inhibited if the alpha-HL treatment precedes PTPase inhibitor treatments. The anti-EGFr immunoprecipitates have exhibited higher PTPase activity after alpha-HL treatment of A431 cells. Interestingly, PTPase activity of anti-EGFr immunoprecipitates from the A431 cells expressing the antisense message of rPTPsigma has not increased despite alpha-HL treatment, confirming the role of rPTPsigma in the dephosphorylation of EGFr. The studies presented here will be useful in understanding the process of signal modulation by the assembly of alpha-HL.
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Affiliation(s)
- Ravi Vijayvargia
- National Centre for Cell Science, Ganeshkhind Road, Pune 411007, India
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Abstract
The year 2004 represents a milestone for the biosensor research community: in this year, over 1000 articles were published describing experiments performed using commercially available systems. The 1038 papers we found represent an approximately 10% increase over the past year and demonstrate that the implementation of biosensors continues to expand at a healthy pace. We evaluated the data presented in each paper and compiled a 'top 10' list. These 10 articles, which we recommend every biosensor user reads, describe well-performed kinetic, equilibrium and qualitative/screening studies, provide comparisons between binding parameters obtained from different biosensor users, as well as from biosensor- and solution-based interaction analyses, and summarize the cutting-edge applications of the technology. We also re-iterate some of the experimental pitfalls that lead to sub-optimal data and over-interpreted results. We are hopeful that the biosensor community, by applying the hints we outline, will obtain data on a par with that presented in the 10 spotlighted articles. This will ensure that the scientific community at large can be confident in the data we report from optical biosensors.
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Affiliation(s)
- Rebecca L Rich
- Center for Biomolecular Interaction Analysis, University of Utah, Salt Lake City, UT 84132, USA
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Vijayvargia R, Suresh CG, Krishnasastry MV. Functional form of Caveolin-1 is necessary for the assembly of alpha-hemolysin. Biochem Biophys Res Commun 2004; 324:1130-6. [PMID: 15485672 DOI: 10.1016/j.bbrc.2004.09.164] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2004] [Indexed: 10/26/2022]
Abstract
The assembly of alpha-HL was shown to rapidly progress upon its interaction with Caveolin-1. Treatment of A431 cells with alpha-HL has resulted in clustering of Caveolin-1 at cell-cell contacts. Consistent with this observation, alpha-HL mutants devoid of assembly property have not induced the clustering of Caveolin-1. While cholesterol depletion of A431 cells completely arrests the assembly of alpha-HL, chelation of membrane cholesterol results in its retarded assembly. Interestingly, HT29 cells, with low Caveolin-1 levels, are resistant to alpha-HL attack. Clustering of Caveolin-1, as seen in case of A431 cells, was readily observed in case of HT29 cells transfected with Caveolin-1 construct, thus overexpressing the full length Caveolin-1, upon alpha-HL treatment. A model was constructed to visualize the interactions between alpha-HL and Caveolin-1 which suggests that facile penetration of alpha-HL's beta-barrel might occur through protein-protein interactions with the surrounding 7 alpha-helices of Caveolin-1.
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Affiliation(s)
- Ravi Vijayvargia
- National Centre for Cell Science, Ganeshkhind Road, Pune 411007, India
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Vijayvargia R, Kaur S, Sangha N, Sahasrabuddhe AA, Surolia I, Shouche Y, Krishnasastry MV. Assembly of alpha-hemolysin on A431 cells leads to clustering of Caveolin-1. Biochem Biophys Res Commun 2004; 324:1124-9. [PMID: 15485671 DOI: 10.1016/j.bbrc.2004.09.165] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2004] [Indexed: 11/19/2022]
Abstract
Assembly and penetration of 14-strand beta-barrel of staphylococcal alpha-hemolysin (alpha-HL) is an intriguing phenomenon due to its water soluble property. alpha-HL interacts with the Caveolin-1 of A431 cells for its rapid assembly. A nine amino acid, non-hydrophobic peptide derived from alpha-HL has been shown to block the interaction of alpha-HL with the scaffolding domain of Caveolin-1. alpha-HL's presence was also detected in the Caveolin-1 enriched membrane fractions isolated by ultracentrifugation. Moreover, alpha-HL co-precipitates with Caveolin-1 specifically. In a time-dependent process, alpha-HL associates with the Caveolin-1 and co-localizes with Caveolin-1 that results in an extensive clustering of Caveolin-1 at cell-cell contacts. Mutants of alpha-HL devoid of Caveolin-1 binding motif failed to assemble into heptameric oligomers on the surface of A431 cells. Our data suggest that the conformational changes required to form the heptameric assembly might be triggered at the Caveolin-1 binding motif of alpha-HL.
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Affiliation(s)
- Ravi Vijayvargia
- National Centre for Cell Science, Ganeshkhind Road, Pune 411007, India
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