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Chiu YC, Yeh MC, Wang CH, Chen YA, Chang H, Lin HY, Ho MC, Lin SM. Structural basis for calcium-stimulating pore formation of Vibrio α-hemolysin. Nat Commun 2023; 14:5946. [PMID: 37741869 PMCID: PMC10517994 DOI: 10.1038/s41467-023-41579-x] [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: 05/30/2023] [Accepted: 09/10/2023] [Indexed: 09/25/2023] Open
Abstract
Vibrio α-hemolysins (αHLs) are β-pore-forming toxins secreted by Vibrio pathogens, crucial for the facilitation of bacterial infections through host cell lysis. These toxins are produced as inactive precursors, requiring proteolytic maturation and membrane association for activation within host tissues. Here, we investigate Vibrio campbellii αHL (VcαHL), and establish that its hemolytic activity is significantly stimulated by calcium ions, with an EC50 that aligns with physiological calcium concentrations. Furthermore, we illustrate the vital contribution of calcium ions to the oligomerization of VcαHL on membranes. Using X-ray crystallography and cryo-electron microscopy, we decipher both the immature and assembled structures of VcαHL and elucidate the conformational changes corresponding to toxin assembly. We also identify a calcium-binding module that is integral for VcαHL's calcium-dependent activation. These findings provide insights into the regulatory mechanisms of VcαHL and have the potential to inform the development of targeted therapeutic strategies against Vibrio infections.
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Affiliation(s)
- Yu-Chuan Chiu
- Department of Biotechnology and Bioindustry Sciences, National Cheng Kung University, Tainan, Taiwan
| | - Min-Chi Yeh
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Chun-Hsiung Wang
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Yu-An Chen
- Department of Biotechnology and Bioindustry Sciences, National Cheng Kung University, Tainan, Taiwan
| | - Hsiang Chang
- Department of Biotechnology and Bioindustry Sciences, National Cheng Kung University, Tainan, Taiwan
| | - Han-You Lin
- Department of Veterinary Medicine, School of Veterinary Medicine, National Taiwan University, Taipei, Taiwan
| | - Meng-Chiao Ho
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
- Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
- Graduate Institute of Biochemistry and Molecular Biology, National Taiwan University, Taipei, Taiwan
| | - Shih-Ming Lin
- Department of Biotechnology and Bioindustry Sciences, National Cheng Kung University, Tainan, Taiwan.
- Institute of Tropical Plant Sciences and Microbiology, National Cheng Kung University, Tainan, Taiwan.
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2
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Vidakovic L, Mikhaleva S, Jeckel H, Nisnevich V, Strenger K, Neuhaus K, Raveendran K, Ben-Moshe NB, Aznaourova M, Nosho K, Drescher A, Schmeck B, Schulte LN, Persat A, Avraham R, Drescher K. Biofilm formation on human immune cells is a multicellular predation strategy of Vibrio cholerae. Cell 2023; 186:2690-2704.e20. [PMID: 37295405 PMCID: PMC10256282 DOI: 10.1016/j.cell.2023.05.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 01/26/2023] [Accepted: 05/09/2023] [Indexed: 06/12/2023]
Abstract
Biofilm formation is generally recognized as a bacterial defense mechanism against environmental threats, including antibiotics, bacteriophages, and leukocytes of the human immune system. Here, we show that for the human pathogen Vibrio cholerae, biofilm formation is not only a protective trait but also an aggressive trait to collectively predate different immune cells. We find that V. cholerae forms biofilms on the eukaryotic cell surface using an extracellular matrix comprising primarily mannose-sensitive hemagglutinin pili, toxin-coregulated pili, and the secreted colonization factor TcpF, which differs from the matrix composition of biofilms on other surfaces. These biofilms encase immune cells and establish a high local concentration of a secreted hemolysin to kill the immune cells before the biofilms disperse in a c-di-GMP-dependent manner. Together, these results uncover how bacteria employ biofilm formation as a multicellular strategy to invert the typical relationship between human immune cells as the hunters and bacteria as the hunted.
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Affiliation(s)
| | - Sofya Mikhaleva
- Institute of Bioengineering and Global Health Institute, School of Life Sciences, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Hannah Jeckel
- Biozentrum, University of Basel, 4056 Basel, Switzerland; Department of Physics, Philipps-Universität Marburg, 35043 Marburg, Germany
| | - Valerya Nisnevich
- Department of Immunology and Regenerative Biology, Weizmann Institute of Science, 7610001 Rehovot, Israel
| | | | - Konstantin Neuhaus
- Biozentrum, University of Basel, 4056 Basel, Switzerland; Department of Physics, Philipps-Universität Marburg, 35043 Marburg, Germany
| | | | - Noa Bossel Ben-Moshe
- Department of Immunology and Regenerative Biology, Weizmann Institute of Science, 7610001 Rehovot, Israel
| | - Marina Aznaourova
- Institute for Lung Research, Center for Synthetic Microbiology (SYNMIKRO), Universities of Giessen and Marburg Lung Center, Philipps-Universität Marburg, 35043 Marburg, Germany
| | - Kazuki Nosho
- Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Antje Drescher
- Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Bernd Schmeck
- Institute for Lung Research, Center for Synthetic Microbiology (SYNMIKRO), Universities of Giessen and Marburg Lung Center, Philipps-Universität Marburg, 35043 Marburg, Germany; Department of Pulmonary and Critical Care Medicine, University Medical Center Marburg, 35043 Marburg, Germany; German Center for Infection Research (DZIF), 35043 Marburg, Germany; German Center for Lung Research (DZL), 35043 Marburg, Germany; Institute for Lung Health, 35392 Giessen, Germany
| | - Leon N Schulte
- Institute for Lung Research, Center for Synthetic Microbiology (SYNMIKRO), Universities of Giessen and Marburg Lung Center, Philipps-Universität Marburg, 35043 Marburg, Germany; German Center for Lung Research (DZL), 35043 Marburg, Germany
| | - Alexandre Persat
- Institute of Bioengineering and Global Health Institute, School of Life Sciences, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Roi Avraham
- Department of Immunology and Regenerative Biology, Weizmann Institute of Science, 7610001 Rehovot, Israel
| | - Knut Drescher
- Biozentrum, University of Basel, 4056 Basel, Switzerland.
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3
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Kaur D, Verma P, Singh M, Sharma A, Lata K, Mukhopadhaya A, Chattopadhyay K. Pore formation-independent cell death induced by a β-barrel pore-forming toxin. FASEB J 2022; 36:e22557. [PMID: 36125006 DOI: 10.1096/fj.202200788r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Revised: 08/16/2022] [Accepted: 09/06/2022] [Indexed: 11/11/2022]
Abstract
Vibrio cholerae cytolysin (VCC) is a β-barrel pore-forming toxin (β-PFT). It exhibits potent hemolytic activity against erythrocytes that appears to be a direct outcome of its pore-forming functionality. However, VCC-mediated cell-killing mechanism is more complicated in the case of nucleated mammalian cells. It induces apoptosis in the target nucleated cells, mechanistic details of which are still unclear. Furthermore, it has never been explored whether the ability of VCC to trigger programmed cell death is stringently dependent on its pore-forming activity. Here, we show that VCC can evoke hallmark features of the caspase-dependent apoptotic cell death even in the absence of the pore-forming ability. Our study demonstrates that VCC mutants with abortive pore-forming hemolytic activity can trigger apoptotic cell death responses and cytotoxicity, similar to those elicited by the wild-type toxin. VCC as well as its pore formation-deficient mutants display prominent propensity to translocate to the target cell mitochondria and cause mitochondrial membrane damage. Therefore, our results for the first time reveal that VCC, despite being an archetypical β-PFT, can kill target nucleated cells independent of its pore-forming functionality. These findings are intriguing for a β-PFT, whose destination is generally expected to remain limited on the target cell membranes, and whose mode of action is commonly attributed to the membrane-damaging pore-forming ability. Taken together, our study provides critical new insights regarding distinct implications of the two important virulence functionalities of VCC for the V. cholerae pathogenesis process: hemolytic activity for iron acquisition and cytotoxicity for tissue damage by the bacteria.
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Affiliation(s)
- Deepinder Kaur
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, India.,Immunology Program, Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Pratima Verma
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, India
| | - Mahendra Singh
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, India
| | - Arpita Sharma
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, India
| | - Kusum Lata
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, India
| | - Arunika Mukhopadhaya
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, India
| | - Kausik Chattopadhyay
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, India
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4
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Mondal AK, Sengupta N, Singh M, Biswas R, Lata K, Lahiri I, Dutta S, Chattopadhyay K. Glu289 residue in the pore-forming motif of Vibrio cholerae cytolysin is important for efficient β-barrel pore formation. J Biol Chem 2022; 298:102441. [PMID: 36055404 PMCID: PMC9520032 DOI: 10.1016/j.jbc.2022.102441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 08/17/2022] [Accepted: 08/21/2022] [Indexed: 11/19/2022] Open
Abstract
Vibrio cholerae cytolysin (VCC) is a potent membrane-damaging β-barrel pore-forming toxin (β-PFT). Upon binding to the target membranes, VCC monomers first assemble into oligomeric pre-pore intermediates, and subsequently transform into transmembrane β-barrel pores. VCC harbors a designated pore-forming motif, which, during oligomeric pore formation, inserts into the membrane and generates a transmembrane β-barrel scaffold. It remains an enigma how the molecular architecture of the pore-forming motif regulates the VCC pore-formation mechanism. Here, we show that a specific pore-forming motif residue, E289, plays crucial regulatory roles in the pore-formation mechanism of VCC. We find that the mutation of E289A drastically compromises pore-forming activity, without affecting the structural integrity and membrane-binding potential of the toxin monomers. Although our single-particle cryo-EM analysis reveals wild type-like oligomeric β-barrel pore formation by E289A-VCC in the membrane, we demonstrate that the mutant shows severely delayed kinetics in terms of pore-forming ability that can be rescued with elevated temperature conditions. We find that the pore-formation efficacy of E289A-VCC appears to be more profoundly dependent on temperature as compared to that of the wild type toxin. Our results suggest that the E289A mutation traps membrane-bound toxin molecules in the pre-pore-like intermediate state that is hindered from converting into the functional β-barrel pores by a large energy barrier, thus highlighting the importance of this residue for the pore-formation mechanism of VCC.
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Affiliation(s)
- Anish Kumar Mondal
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Manauli, Punjab, India
| | - Nayanika Sengupta
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Mahendra Singh
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Manauli, Punjab, India
| | - Rupam Biswas
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Kusum Lata
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Manauli, Punjab, India
| | - Indrajit Lahiri
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Manauli, Punjab, India
| | - Somnath Dutta
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Kausik Chattopadhyay
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Manauli, Punjab, India.
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5
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Gupta T, Mondal AK, Pani I, Chattopadhyay K, Pal SK. Elucidating liquid crystal-aqueous interface for the study of cholesterol-mediated action of a β-barrel pore forming toxin. SOFT MATTER 2022; 18:5293-5301. [PMID: 35790122 DOI: 10.1039/d2sm00447j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Pore-forming toxins (PFTs) produced by pathogenic bacteria serve as prominent virulence factors with potent cell-killing activity. Most of the β-barrel PFTs form transmembrane oligomeric pores in the membrane lipid bilayer in the presence of cholesterol. The pore-formation mechanisms of the PFTs highlight well-orchestrated regulated events in the membrane environment, which involve dramatic changes in the protein structure and organization. Also, concerted crosstalk between protein and membrane lipid components appears to play crucial roles in the process. Membrane-damaging lesions formed by the pore assembly of the PFTs would also be expected to impose drastic alterations in the membrane organization, details of which remain obscure in most of the cases. Prior reports have established that aqueous interfaces of liquid crystals (LCs) offer promise as responsive interfaces for biomolecular events (at physiologically relevant concentrations), which can be visualized as optical signals. Inspired by this, herein, we sought to understand the lipid membrane interactions of a β-barrel PFT i.e., Vibrio cholerae cytolysin (VCC), using LC-aqueous interfaces. Our results show the formation of dendritic patterns upon the addition of VCC to the lipid embedded with cholesterol over the LC film. In contrast, we did not observe any LC reorientation upon the addition of VCC to the lipid-laden LC-aqueous interface in the absence of cholesterol. An array of techniques such as polarizing optical microscopy (POM), atomic force microscopy (AFM), and fluorescence measurements were utilized to decipher the LC response to the lipid interactions of VCC occurring at these interfaces. Altogether, the results obtained from our study provide a novel platform to explore the mechanistic aspects of the protein-membrane interactions, in the process of membrane pore-formation by the membrane-damaging PFTs.
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Affiliation(s)
- Tarang Gupta
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, Knowledge City, Sector-81, SAS Nagar, Mohali 140306, India.
| | - Anish Kumar Mondal
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Knowledge City, Sector-81, SAS Nagar, Mohali 140306, India.
| | - Ipsita Pani
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, Knowledge City, Sector-81, SAS Nagar, Mohali 140306, India.
| | - Kausik Chattopadhyay
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Knowledge City, Sector-81, SAS Nagar, Mohali 140306, India.
| | - Santanu Kumar Pal
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, Knowledge City, Sector-81, SAS Nagar, Mohali 140306, India.
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6
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ISLAM AKMA, NAKATANI M, NAKAJIMA T, KOHDA T, MUKAMOTO M. The cytotoxicity and molecular mechanisms of the Clostridium perfringens NetB toxin. J Vet Med Sci 2021; 83:187-194. [PMID: 33342969 PMCID: PMC7972886 DOI: 10.1292/jvms.20-0623] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 12/02/2020] [Indexed: 11/22/2022] Open
Abstract
The necrotic enteritis toxin B-like (NetB) toxin secreted by Clostridium perfringens is a key virulence agent in the pathogenesis of avian necrotic enteritis, a disease that causes significant economic loss to the poultry industry worldwide. NetB was purified from Clostridium perfringens type G (CNEOP004) that was isolated from chickens with necrotic enteritis in Japan. EC50 of this purified NetB toward chicken liver-derived LMH cells was 0.63 µg/ml. In vivo pathogenicity of NetB to chicks produced characteristic lesions of necrotic enteritis. Analysis of the localization of the NetB monomer and oligomer molecules on LMH cells showed that both molecules of the toxin were localized in non-lipid raft regions. Moreover, removal of cholesterol with the cholesterol depletion assay carried out in LMH cells detected both oligomers and monomers of the NetB molecule. These data suggest that the NetB toxin may recognize membrane molecules different from cholesterol in non-raft region. Furthermore, NetB-binding molecules on LMH cell membranes using the toxin overlay assay with immunoblotting showed that protein molecules of different molecular sizes were bound to NetB on non-lipid raft fractions. Further studies are necessary to characterize these protein molecules to examine their specific association with NetB binding and oligomerization.
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Affiliation(s)
- AKM Azharul ISLAM
- Laboratory of Veterinary Epidemiology, Osaka Prefecture
University, 1-58 Rinku-Ourai-Kita, Izumisano, Osaka 598-8531, Japan
| | - Mitsuki NAKATANI
- Laboratory of Veterinary Epidemiology, Osaka Prefecture
University, 1-58 Rinku-Ourai-Kita, Izumisano, Osaka 598-8531, Japan
| | - Takayuki NAKAJIMA
- Laboratory of Veterinary Anatomy, Osaka Prefecture
University, 1-58 Rinku-Ourai-Kita, Izumisano, Osaka 598-8531, Japan
| | - Tomoko KOHDA
- Laboratory of Veterinary Epidemiology, Osaka Prefecture
University, 1-58 Rinku-Ourai-Kita, Izumisano, Osaka 598-8531, Japan
| | - Masafumi MUKAMOTO
- Laboratory of Veterinary Epidemiology, Osaka Prefecture
University, 1-58 Rinku-Ourai-Kita, Izumisano, Osaka 598-8531, Japan
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7
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Kashimoto T, Sugiyama H, Kawamidori K, Yamazaki K, Kado T, Matsuda K, Kodama T, Mukai T, Ueno S. Vibiro vulnificus hemolysin associates with gangliosides. BMC Microbiol 2020; 20:69. [PMID: 32228455 PMCID: PMC7106661 DOI: 10.1186/s12866-020-01755-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Accepted: 03/20/2020] [Indexed: 12/28/2022] Open
Abstract
Background Vibrio vulnificus hemolysin (VVH) is a pore-forming toxin secreted by Vibrio vulnificus. Cellular cholesterol was believed to be the receptor for VVH, because cholesterol could bind to VVH and preincubation with cholesterol inhibited cytotoxicity. It has been reported that specific glycans such as N-acetyl-D-galactosamine and N-acetyl-D-lactosamine bind to VVH, however, it has not been known whether these glycans could inhibit the cytotoxicity of VVH without oligomer formation. Thus, to date, binding mechanisms of VVH to cellular membrane, including specific receptors have not been elucidated. Results We show here that VVH associates with ganglioside GM1a, Fucosyl-GM1, GD1a, GT1c, and GD1b by glycan array. Among them, GM1a could pulldown VVH. Moreover, the GD1a inhibited the cytotoxicity of VVH without the formation of oligomers. Conclusion This is the first report of a molecule able to inhibit the binding of VVH to target cells without oligomerization of VVH.
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Affiliation(s)
- Takashige Kashimoto
- Laboratory of Veterinary Public Health, School of Veterinary Medicine and Animal Sciences, Kitasato University, Higashi 23-35-1, Towada, Aomori, 034-8628, Japan.
| | - Hiroyuki Sugiyama
- Laboratory of Veterinary Public Health, School of Veterinary Medicine and Animal Sciences, Kitasato University, Higashi 23-35-1, Towada, Aomori, 034-8628, Japan
| | - Keigo Kawamidori
- Laboratory of Veterinary Public Health, School of Veterinary Medicine and Animal Sciences, Kitasato University, Higashi 23-35-1, Towada, Aomori, 034-8628, Japan
| | - Kohei Yamazaki
- Laboratory of Veterinary Public Health, School of Veterinary Medicine and Animal Sciences, Kitasato University, Higashi 23-35-1, Towada, Aomori, 034-8628, Japan
| | - Takehiro Kado
- Laboratory of Veterinary Public Health, School of Veterinary Medicine and Animal Sciences, Kitasato University, Higashi 23-35-1, Towada, Aomori, 034-8628, Japan
| | - Kaho Matsuda
- Laboratory of Veterinary Public Health, School of Veterinary Medicine and Animal Sciences, Kitasato University, Higashi 23-35-1, Towada, Aomori, 034-8628, Japan
| | - Toshio Kodama
- Department of Bacterial Infections, International Research Center for Infectious Diseases, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan
| | - Takao Mukai
- Laboratory of Biomolecular Science, School of Veterinary Medicine and Animal Sciences, Kitasato University, Higashi 23-35-1, Towada, Aomori, Japan
| | - Shunji Ueno
- Laboratory of Veterinary Public Health, School of Veterinary Medicine and Animal Sciences, Kitasato University, Higashi 23-35-1, Towada, Aomori, 034-8628, Japan
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8
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Mondal AK, Chattopadhyay K. Taking Toll on Membranes: Curious Cases of Bacterial β-Barrel Pore-Forming Toxins. Biochemistry 2019; 59:163-170. [DOI: 10.1021/acs.biochem.9b00783] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Anish Kumar Mondal
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, SAS Nagar, Manauli, Mohali, Punjab 140306, India
| | - Kausik Chattopadhyay
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, SAS Nagar, Manauli, Mohali, Punjab 140306, India
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9
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Revisiting the role of cholesterol in regulating the pore-formation mechanism of Vibrio cholerae cytolysin, a membrane-damaging β-barrel pore-forming toxin. Biochem J 2018; 475:3039-3055. [DOI: 10.1042/bcj20180387] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 09/03/2018] [Accepted: 09/10/2018] [Indexed: 11/17/2022]
Abstract
Vibrio cholerae cytolysin (VCC) is a β-barrel pore-forming toxin with potent membrane-damaging cell-killing activity. Previous studies employing the model membranes of lipid vesicles (liposomes) have shown that pore formation by VCC requires the presence of cholesterol in the liposome membranes. However, the exact role of cholesterol in the mode of action of VCC still remains unclear. Most importantly, implication of cholesterol, if any, in regulating the pore-formation mechanism of VCC in the biomembranes of eukaryotic cells remains unexplored. Here, we show that the presence of cholesterol promotes the interaction of VCC with the membrane lipid bilayer, when non-lipid-dependent interactions are absent. However, in the case of biomembranes of human erythrocytes, where accessory interactions are available, cholesterol appears to play a less critical role in the binding step. Nevertheless, in the absence of an optimal level of membrane cholesterol in the human erythrocytes, membrane-bound fraction of the toxin remains trapped in the form of abortive oligomeric assembly, devoid of functional pore-forming activity. Our study also shows that VCC exhibits a prominent propensity to associate with the cholesterol-rich membrane micro-domains of human erythrocytes. Interestingly, mutation of the cholesterol-binding ability of VCC does not block association with the cholesterol-rich membrane micro-domains on human erythrocytes. Based on these results, we propose that the specific cholesterol-binding ability of VCC does not appear to dictate its association with the cholesterol-rich micro-domains on human erythrocytes. Rather, targeting of VCC toward the membrane micro-domains of human erythrocytes possibly acts to facilitate the cholesterol-dependent pore-formation mechanism of the toxin.
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10
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Kathuria R, Chattopadhyay K. Vibrio choleraecytolysin: Multiple facets of the membrane interaction mechanism of aβ-barrel pore-forming toxin. IUBMB Life 2018; 70:260-266. [DOI: 10.1002/iub.1725] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2018] [Accepted: 02/05/2018] [Indexed: 12/22/2022]
Affiliation(s)
- Reema Kathuria
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences; Indian Institute of Science Education and Research Mohali; Manauli, Mohali Punjab India
| | - Kausik Chattopadhyay
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences; Indian Institute of Science Education and Research Mohali; Manauli, Mohali Punjab India
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11
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Koufos E, Chang EH, Rasti ES, Krueger E, Brown AC. Use of a Cholesterol Recognition Amino Acid Consensus Peptide To Inhibit Binding of a Bacterial Toxin to Cholesterol. Biochemistry 2016; 55:4787-97. [PMID: 27504950 DOI: 10.1021/acs.biochem.6b00430] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Recognition of and binding to cholesterol on the host cell membrane is an initial step in the mechanism of numerous pathogens, including viruses, bacteria, and bacterial toxins; however, a viable method of inhibiting this interaction has not yet been uncovered. Here, we describe the mechanism by which a cholesterol recognition amino acid consensus peptide interacts with cholesterol and inhibits the activity of a cholesterol-binding bacterial leukotoxin (LtxA). Using a series of biophysical techniques, we have shown that the peptide recognizes the hydroxyl group of cholesterol with nanomolar affinity and does not disrupt membrane packing, suggesting that it sits primarily near the membrane surface. As a result, LtxA is unable to bind to cholesterol or subsequently become internalized in host cells. Additionally, because cholesterol is not being removed from the cell membrane, the peptide-treated target cells remain viable over extended periods of time. We have demonstrated the use of this peptide in the inhibition of toxin activity for an antivirulence approach to the treatment of bacterial disease, and we anticipate that this approach might have broad utility in the inhibition of viral and bacterial pathogenesis.
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Affiliation(s)
- Evan Koufos
- Department of Chemical and Biomolecular Engineering, Lehigh University , Bethlehem, Pennsylvania 18015, United States
| | - En Hyung Chang
- Department of Chemical and Biomolecular Engineering, Lehigh University , Bethlehem, Pennsylvania 18015, United States
| | - Elnaz S Rasti
- Department of Chemical and Biomolecular Engineering, Lehigh University , Bethlehem, Pennsylvania 18015, United States
| | - Eric Krueger
- Department of Chemical and Biomolecular Engineering, Lehigh University , Bethlehem, Pennsylvania 18015, United States
| | - Angela C Brown
- Department of Chemical and Biomolecular Engineering, Lehigh University , Bethlehem, Pennsylvania 18015, United States
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12
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Rai AK, Chattopadhyay K. Revisiting the oligomerization mechanism of Vibrio cholerae cytolysin, a beta-barrel pore-forming toxin. Biochem Biophys Res Commun 2016; 474:421-427. [DOI: 10.1016/j.bbrc.2016.05.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2016] [Accepted: 05/01/2016] [Indexed: 01/10/2023]
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13
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De S, Bubnys A, Alonzo F, Hyun J, Lary JW, Cole JL, Torres VJ, Olson R. The Relationship between Glycan Binding and Direct Membrane Interactions in Vibrio cholerae Cytolysin, a Channel-forming Toxin. J Biol Chem 2015; 290:28402-28415. [PMID: 26416894 DOI: 10.1074/jbc.m115.675967] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Indexed: 12/19/2022] Open
Abstract
Bacterial pore-forming toxins (PFTs) are structurally diverse pathogen-secreted proteins that form cell-damaging channels in the membranes of host cells. Most PFTs are released as water-soluble monomers that first oligomerize on the membrane before inserting a transmembrane channel. To modulate specificity and increase potency, many PFTs recognize specific cell surface receptors that increase the local toxin concentration on cell membranes, thereby facilitating channel formation. Vibrio cholerae cytolysin (VCC) is a toxin secreted by the human pathogen responsible for pandemic cholera disease and acts as a defensive agent against the host immune system. Although it has been shown that VCC utilizes specific glycan receptors on the cell surface, additional direct contacts with the membrane must also play a role in toxin binding. To better understand the nature of these interactions, we conducted a systematic investigation of the membrane-binding surface of VCC to identify additional membrane interactions important in cell targeting. Through cell-based assays on several human-derived cell lines, we show that VCC is unlikely to utilize high affinity protein receptors as do structurally similar toxins from Staphylococcus aureus. Next, we identified a number of specific amino acid residues that greatly diminish the VCC potency against cells and investigated the interplay between glycan binding and these direct lipid contacts. Finally, we used model membranes to parse the importance of these key residues in lipid and cholesterol binding. Our study provides a complete functional map of the VCC membrane-binding surface and insights into the integration of sugar, lipid, and cholesterol binding interactions.
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Affiliation(s)
- Swastik De
- Department of Molecular Biology and Biochemistry, Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut 06459
| | - Adele Bubnys
- Department of Molecular Biology and Biochemistry, Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut 06459
| | - Francis Alonzo
- Department of Microbiology, New York University School of Medicine, New York, New York 10016
| | - Jinsol Hyun
- Department of Molecular Biology and Biochemistry, Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut 06459
| | - Jeffrey W Lary
- Biotechnology-Bioservices Center, University of Connecticut, Storrs, Connecticut 06269
| | - James L Cole
- Biotechnology-Bioservices Center, University of Connecticut, Storrs, Connecticut 06269; Department of Molecular and Cell Biology and Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269
| | - Victor J Torres
- Department of Microbiology, New York University School of Medicine, New York, New York 10016
| | - Rich Olson
- Department of Molecular Biology and Biochemistry, Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut 06459.
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Rai AK, Chattopadhyay K. Revisiting the membrane interaction mechanism of a membrane-damaging β-barrel pore-forming toxinVibrio choleraecytolysin. Mol Microbiol 2015; 97:1051-62. [DOI: 10.1111/mmi.13084] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/05/2015] [Indexed: 01/14/2023]
Affiliation(s)
- Anand Kumar Rai
- Centre for Protein Science, Design and Engineering; Department of Biological Sciences; Indian Institute of Science Education and Research (IISER) Mohali; Sector 81, SAS Nagar, Manauli Mohali Punjab 140306 India
| | - Kausik Chattopadhyay
- Centre for Protein Science, Design and Engineering; Department of Biological Sciences; Indian Institute of Science Education and Research (IISER) Mohali; Sector 81, SAS Nagar, Manauli Mohali Punjab 140306 India
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15
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Morante K, Caaveiro JMM, Tanaka K, González-Mañas JM, Tsumoto K. A pore-forming toxin requires a specific residue for its activity in membranes with particular physicochemical properties. J Biol Chem 2015; 290:10850-61. [PMID: 25759390 DOI: 10.1074/jbc.m114.615211] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2014] [Indexed: 12/29/2022] Open
Abstract
The physicochemical landscape of the bilayer modulates membrane protein function. Actinoporins are a family of potent hemolytic proteins from sea anemones acting at the membrane level. This family of cytolysins preferentially binds to target membranes containing sphingomyelin, where they form lytic pores giving rise to cell death. Although the cytolytic activity of the actinoporin fragaceatoxin C (FraC) is sensitive to vesicles made of various lipid compositions, it is far from clear how this toxin adjusts its mechanism of action to a broad range of physiochemical landscapes. Herein, we show that the conserved residue Phe-16 of FraC is critical for pore formation in cholesterol-rich membranes such as those of red blood cells. The interaction of a panel of muteins of Phe-16 with model membranes composed of raft-like lipid domains is inactivated in cholesterol-rich membranes but not in cholesterol-depleted membranes. These results indicate that actinoporins recognize different membrane environments, resulting in a wider repertoire of susceptible target membranes (and preys) for sea anemones. In addition, this study has unveiled promising candidates for the development of protein-based biosensors highly sensitive to the concentration of cholesterol within the membrane.
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Affiliation(s)
- Koldo Morante
- From the Department of Bioengineering, Graduate School of Engineering and the Department of Biochemistry and Molecular Biology, University of the Basque Country, 48940 Leioa, Spain, and
| | - Jose M M Caaveiro
- From the Department of Bioengineering, Graduate School of Engineering and
| | - Koji Tanaka
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Juan Manuel González-Mañas
- the Department of Biochemistry and Molecular Biology, University of the Basque Country, 48940 Leioa, Spain, and
| | - Kouhei Tsumoto
- From the Department of Bioengineering, Graduate School of Engineering and Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan, the Medical Proteomics Laboratory, Institute of Medical Science, The University of Tokyo, Minato-ku, 108-8639 Tokyo, Japan
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Vibrio cholerae Cytolysin: Structure–Function Mechanism of an Atypical β-Barrel Pore-Forming Toxin. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 842:109-25. [DOI: 10.1007/978-3-319-11280-0_7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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17
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Fisher TW, Vyas M, He R, Nelson W, Cicero JM, Willer M, Kim R, Kramer R, May GA, Crow JA, Soderlund CA, Gang DR, Brown JK. Comparison of potato and asian citrus psyllid adult and nymph transcriptomes identified vector transcripts with potential involvement in circulative, propagative liberibacter transmission. Pathogens 2014; 3:875-907. [PMID: 25436509 PMCID: PMC4282890 DOI: 10.3390/pathogens3040875] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 10/18/2014] [Accepted: 10/20/2014] [Indexed: 01/01/2023] Open
Abstract
The potato psyllid (PoP) Bactericera cockerelli (Sulc) and Asian citrus psyllid (ACP) Diaphorina citri Kuwayama are the insect vectors of the fastidious plant pathogen, Candidatus Liberibacter solanacearum (CLso) and Ca. L. asiaticus (CLas), respectively. CLso causes Zebra chip disease of potato and vein-greening in solanaceous species, whereas, CLas causes citrus greening disease. The reliance on insecticides for vector management to reduce pathogen transmission has increased interest in alternative approaches, including RNA interference to abate expression of genes essential for psyllid-mediated Ca. Liberibacter transmission. To identify genes with significantly altered expression at different life stages and conditions of CLso/CLas infection, cDNA libraries were constructed for CLso-infected and -uninfected PoP adults and nymphal instars. Illumina sequencing produced 199,081,451 reads that were assembled into 82,224 unique transcripts. PoP and the analogous transcripts from ACP adult and nymphs reported elsewhere were annotated, organized into functional gene groups using the Gene Ontology classification system, and analyzed for differential in silico expression. Expression profiles revealed vector life stage differences and differential gene expression associated with Liberibacter infection of the psyllid host, including invasion, immune system modulation, nutrition, and development.
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Affiliation(s)
- Tonja W Fisher
- School of Plant Sciences, The University of Arizona, Tucson, AZ 85721, USA.
| | - Meenal Vyas
- School of Plant Sciences, The University of Arizona, Tucson, AZ 85721, USA.
| | - Ruifeng He
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA.
| | | | - Joseph M Cicero
- School of Plant Sciences, The University of Arizona, Tucson, AZ 85721, USA.
| | - Mark Willer
- BIO5, The University of Arizona, Tucson, AZ 85721, USA.
| | - Ryan Kim
- National Center for Genome Resources, 2935 Rodeo Park Drive East, Santa Fe, NM 87505, USA.
| | - Robin Kramer
- National Center for Genome Resources, 2935 Rodeo Park Drive East, Santa Fe, NM 87505, USA.
| | - Greg A May
- National Center for Genome Resources, 2935 Rodeo Park Drive East, Santa Fe, NM 87505, USA.
| | - John A Crow
- National Center for Genome Resources, 2935 Rodeo Park Drive East, Santa Fe, NM 87505, USA.
| | | | - David R Gang
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164, USA.
| | - Judith K Brown
- School of Plant Sciences, The University of Arizona, Tucson, AZ 85721, USA.
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Outer membrane vesicles mediate transport of biologically active Vibrio cholerae cytolysin (VCC) from V. cholerae strains. PLoS One 2014; 9:e106731. [PMID: 25187967 PMCID: PMC4154730 DOI: 10.1371/journal.pone.0106731] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Accepted: 07/28/2014] [Indexed: 12/03/2022] Open
Abstract
Background Outer membrane vesicles (OMVs) released from Gram-negative bacteria can serve as vehicles for the translocation of virulence factors. Vibrio cholerae produce OMVs but their putative role in translocation of effectors involved in pathogenesis has not been well elucidated. The V. cholerae cytolysin (VCC), is a pore-forming toxin that lyses target eukaryotic cells by forming transmembrane oligomeric β-barrel channels. It is considered a potent toxin that contributes to V. cholerae pathogenesis. The mechanisms involved in the secretion and delivery of the VCC have not been extensively studied. Methodology/Principal Findings OMVs from V. cholerae strains were isolated and purified using a differential centrifugation procedure and Optiprep centrifugation. The ultrastructure and the contents of OMVs were examined under the electron microscope and by immunoblot analyses respectively. We demonstrated that VCC from V. cholerae strain V:5/04 was secreted in association with OMVs and the release of VCC via OMVs is a common feature among V. cholerae strains. The biological activity of OMV-associated VCC was investigated using contact hemolytic assay and epithelial cell cytotoxicity test. It showed toxic activity on both red blood cells and epithelial cells. Our results indicate that the OMVs architecture might play a role in stability of VCC and thereby can enhance its biological activities in comparison with the free secreted VCC. Furthermore, we tested the role of OMV-associated VCC in host cell autophagy signalling using confocal microscopy and immunoblot analysis. We observed that OMV-associated VCC triggered an autophagy response in the target cell and our findings demonstrated for the first time that autophagy may operate as a cellular defence mechanism against an OMV-associated bacterial virulence factor. Conclusion/Significance Biological assays of OMVs from the V. cholerae strain V:5/04 demonstrated that OMV-associated VCC is indeed biologically active and induces toxicity on mammalian cells and furthermore can induce autophagy.
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Chow F, Gong Y, Lippa CF. The Potential Role of Insulin on the Shank-Postsynaptic Platform in Neurodegenerative Diseases Involving Cognition. Am J Alzheimers Dis Other Demen 2014; 29:303-10. [PMID: 24421411 PMCID: PMC10852640 DOI: 10.1177/1533317513518645] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Loss of synaptic function is critical in the pathogenesis of Alzheimer's disease (AD) and other central nervous system (CNS) degenerations. A promising candidate in the regulation of synaptic function is Shank, a protein that serves as a scaffold for excitatory synaptic receptors and proteins. Loss of Shank alters structure and function of the postsynaptic density (PSD). Shank proteins are associated with N-methyl-d-aspartate and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor loss at the PSD in AD; mutations in Shank also lead to autism spectrum disorders (ASDs) and schizophrenia, both of which affect cognition, suggesting that Shank may play a common pathologic role in AD, ASD, and schizophrenia. Shank protein directly associates with insulin receptor substrate protein p53 in PSD. Insulin and insulin sensitizers have been used in clinical trials for these diseases; this suggests that insulin signals may alter protein homeostasis at the shank-postsynaptic platform in PSDs; insulin could improve the function of synapses in these diseases.
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Affiliation(s)
- Frances Chow
- Department of Neurology, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Yuesong Gong
- Department of Neurology, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Carol F Lippa
- Department of Neurology, Drexel University College of Medicine, Philadelphia, PA, USA
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20
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Ganguly S, Mukherjee A, Mazumdar B, Ghosh AN, Banerjee KK. The β-prism lectin domain of Vibrio cholerae hemolysin promotes self-assembly of the β-pore-forming toxin by a carbohydrate-independent mechanism. J Biol Chem 2013; 289:4001-8. [PMID: 24356964 DOI: 10.1074/jbc.m113.522284] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vibrio cholerae cytolysin/hemolysin (VCC) is an amphipathic 65-kDa β-pore-forming toxin with a C-terminal β-prism lectin domain. Because deletion or point mutation of the lectin domain seriously compromises hemolytic activity, it is thought that carbohydrate-dependent interactions play a critical role in membrane targeting of VCC. To delineate the contributions of the cytolysin and lectin domains in pore formation, we used wild-type VCC, 50-kDa VCC (VCC(50)) without the lectin domain, and mutant VCC(D617A) with no carbohydrate-binding activity. VCC and its two variants with no carbohydrate-binding activity moved to the erythrocyte stroma with apparent association constants on the order of 10(7) M(-1). However, loss of the lectin domain severely reduced the efficiency of self-association of the VCC monomer with the β-barrel heptamer in the synthetic lipid bilayer from ∼83 to 27%. Notably, inactivation of the carbohydrate-binding activity by the D617A mutation marginally reduced oligomerization to ∼77%. Oligomerization of VCC(50) was temperature-insensitive; by contrast, VCC self-assembly increased with increasing temperature, suggesting that the process is driven by entropy and opposed by enthalpy. Asialofetuin, the β1-galactosyl-terminated glycoprotein inhibitor of VCC-induced hemolysis, promoted oligomerization of 65-kDa VCC to a species that resembled the membrane-inserted heptamer in stoichiometry and morphology but had reduced global amphipathicity. In conclusion, we propose (i) that the β-prism lectin domain facilitated toxin assembly by producing entropy during relocation in the heptamer and (ii) that glycoconjugates inhibited VCC by promoting its assembly to a water-soluble, less amphipathic oligomer variant with reduced ability to penetrate the bilayer.
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Ikigai H, Otsuru H, Yamamoto K, Shimamura T. Structural Requirements of Cholesterol for Binding toVibrio choleraeHemolysin. Microbiol Immunol 2013; 50:751-7. [PMID: 17053310 DOI: 10.1111/j.1348-0421.2006.tb03848.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cholesterol is necessary for the conversion of Vibrio cholerae hemolysin (VCH) monomers into oligomers in liposome membranes. Using different sterols, we determined the stereochemical structures of the VCH-binding active groups present in cholesterol. The VCH monomers are bound to cholesterol, diosgenin, campesterol, and ergosterol, which have a hydroxyl group at position C-3 (3betaOH) in the A ring and a C-C double bond between positions C-5 and C-6 (C-C Delta(5)) in the B ring. They are not bound to epicholesterol and dihydrocholesterol, which form a covalent link with a 3alphaOH group and a C-C single bond between positions C-5 and C-6, respectively. This result suggests that the 3betaOH group and the C-CDelta(5) bond in cholesterol are required for VCH monomer binding. We further examined VCH oligomer binding to cholesterol. However, this oligomer did not bind to cholesterol, suggesting that the disappearance of the cholesterol-binding potential of the VCH oligomer might be a result of the conformational change caused by the conversion of the monomer into the oligomer. VCH oligomer formation was observed in liposomes containing sterols with the 3betaOH group and the C-C Delta(5) bond, and it correlated with the binding affinity of the monomer to each sterol. Therefore, it seems likely that monomer binding to membrane sterol leads to the assembly of the monomer. However, since oligomer formation was induced by liposomes containing either epicholesterol or dihydrocholesterol, the 3betaOH group and the C-C Delta(5) bond were not essential for conversion into the oligomer.
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Affiliation(s)
- Hajime Ikigai
- Department of Chemistry and Biochemistry, Suzuka National College of Technology, Suzuka, Mie 510-0294, Japan.
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22
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Dutta S, Banerjee KK, Ghosh AN. Cryo-electron microscopy reveals the membrane insertion mechanism of V. cholerae hemolysin. J Biomol Struct Dyn 2013; 32:1434-42. [PMID: 24102290 DOI: 10.1080/07391102.2013.823564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Vibrio cholerae hemolysin (HlyA) is a 65 kDa pore-forming toxin which causes lysis of target eukaryotic cells by forming heptameric channels in the plasma membrane. Deletion of the 15 kDa C-terminus β-prism carbohydrate-binding domain generates a 50 kDa truncated variant (HlyA50) with 1000-fold-reduced pore-forming activity. Previously, we showed by cryo-electron microscopy that the two toxin oligomers have central channels, but the 65 kDa toxin oligomer is a seven-fold symmetric structure with bowl-, ring-, and arm-like domains, whereas the 50 kDa oligomer is an asymmetric jar-like heptamer. In the present study, we determined three-dimensional(3D) structures of HlyA and HlyA50 in presence of erythrocyte stroma and observed that interaction of the 65 kDa toxin with the stroma induced a significant decrease in the height of the β-barrel oligomer with a change in conformation of the ring- and arm-like domains of HlyA. These features were absent in interaction of HlyA50 with stroma. We propose that this conformational transition is critical for membrane-insertion of the toxin.
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Affiliation(s)
- Somnath Dutta
- a Division of Electron Microscopy , National Institute of Cholera and Enteric Diseases , P-33, C.I.T. Road, Scheme-XM, Beleghata, Kolkata , 700010 , India
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Synergistic and additive effects of chromosomal and plasmid-encoded hemolysins contribute to hemolysis and virulence in Photobacterium damselae subsp. damselae. Infect Immun 2013; 81:3287-99. [PMID: 23798530 DOI: 10.1128/iai.00155-13] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Photobacterium damselae subsp. damselae causes infections and fatal disease in marine animals and in humans. Highly hemolytic strains produce damselysin (Dly) and plasmid-encoded HlyA (HlyA(pl)). These hemolysins are encoded by plasmid pPHDD1 and contribute to hemolysis and virulence for fish and mice. In this study, we report that all the hemolytic strains produce a hitherto uncharacterized chromosome-encoded HlyA (HlyAch). Hemolysis was completely abolished in a single hlyAch mutant of a plasmidless strain and in a dly hlyApl hlyAch triple mutant. We found that Dly, HlyA(pl), and HlyAch are needed for full hemolytic values in strains harboring pPHDD1, and these values are the result of the additive effects between HlyApl and HlyAch, on the one hand, and of the synergistic effect of Dly with HlyApl and HlyAch, on the other hand. Interestingly, Dly-producing strains produced synergistic effects with strains lacking Dly production but secreting HlyA, constituting a case of the CAMP (Christie, Atkins, and Munch-Petersen) reaction. Environmental factors such as iron starvation and salt concentration were found to regulate the expression of the three hemolysins. We found that the contributions, in terms of the individual and combined effects, of the three hemolysins to hemolysis and virulence varied depending on the animal species tested. While Dly and HlyApl were found to be main contributors in the virulence for mice, we observed that the contribution of hemolysins to virulence for fish was mainly based on the synergistic effects between Dly and either of the two HlyA hemolysins rather than on their individual effects.
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Abstract
Hemolysins are a class of proteins defined by their ability to lyse red cells but have been described to exhibit pleiotropic functions. These proteins have been extensively studied in bacteria and more recently in fungi. Within the last decade, a number of studies have characterized fungal hemolysins and revealed a fascinating yet diverse group of proteins. The purpose of this review is to provide a synopsis of the known fungal hemolysins with an emphasis on those belonging to the aegerolysin protein family. New insight and perspective into fungal hemolysins in biotechnology and health are additionally presented.
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Affiliation(s)
- Ajay P Nayak
- Allergy and Clinical Immunology Branch, National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, WV 26505, USA.
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The Photobacterium damselae subsp. damselae hemolysins damselysin and HlyA are encoded within a new virulence plasmid. Infect Immun 2011; 79:4617-27. [PMID: 21875966 DOI: 10.1128/iai.05436-11] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Photobacterium damselae subsp. damselae (formerly Vibrio damsela) is a marine bacterium that causes infections and fatal disease in a wide range of marine animals and in humans. Highly hemolytic strains produce damselysin (Dly), a cytolysin encoded by the dly gene that is lethal for mice and has hemolytic activity. We found that Dly is encoded in the highly hemolytic strain RM-71 within a 153,429-bp conjugative plasmid that we dubbed pPHDD1. In addition to Dly, pPHDD1 also encodes a homologue of the pore-forming toxin HlyA. We found a direct correlation between presence of pPHDD1 and a strong hemolytic phenotype in a collection of P. damselae subsp. damselae isolates. Hemolysis was strongly reduced in a double dly hlyA mutant, demonstrating the role of the two pPHDD1-encoded genes in hemolysis. Interestingly, although single hlyA and dly mutants showed different levels of hemolysis reduction depending on the erythrocyte source, hemolysis was not abolished in any of the single mutants, suggesting that the hemolytic phenotype is the result of the additive effect of Dly and HlyA. We found that pPHDD1-encoded dly and hlyA genes are necessary for full virulence for mice and fish. Our results suggest that pPHDD1 can be considered as a driving force for the emergence of a highly hemolytic lineage of P. damselae subsp. damselae.
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Crystal structure of the Vibrio cholerae cytolysin heptamer reveals common features among disparate pore-forming toxins. Proc Natl Acad Sci U S A 2011; 108:7385-90. [PMID: 21502531 DOI: 10.1073/pnas.1017442108] [Citation(s) in RCA: 109] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Pore-forming toxins (PFTs) are potent cytolytic agents secreted by pathogenic bacteria that protect microbes against the cell-mediated immune system (by targeting phagocytic cells), disrupt epithelial barriers, and liberate materials necessary to sustain growth and colonization. Produced by gram-positive and gram-negative bacteria alike, PFTs are released as water-soluble monomeric or dimeric species, bind specifically to target membranes, and assemble transmembrane channels leading to cell damage and/or lysis. Structural and biophysical analyses of individual steps in the assembly pathway are essential to fully understanding the dynamic process of channel formation. To work toward this goal, we solved by X-ray diffraction the 2.9-Å structure of the 450-kDa heptameric Vibrio cholerae cytolysin (VCC) toxin purified and crystallized in the presence of detergent. This structure, together with our previously determined 2.3-Å structure of the VCC water-soluble monomer, reveals in detail the architectural changes that occur within the channel region and accessory lectin domains during pore formation including substantial rearrangements of hydrogen-bonding networks in the pore-forming amphipathic loops. Interestingly, a ring of tryptophan residues forms the narrowest constriction in the transmembrane channel reminiscent of the phenylalanine clamp identified in anthrax protective antigen [Krantz BA, et al. (2005) Science 309:777-781]. Our work provides an example of a β-barrel PFT (β-PFT) for which soluble and assembled structures are available at high-resolution, providing a template for investigating intermediate steps in assembly.
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Dutta S, Mazumdar B, Banerjee KK, Ghosh AN. Three-dimensional structure of different functional forms of the Vibrio cholerae hemolysin oligomer: a cryo-electron microscopic study. J Bacteriol 2010; 192:169-78. [PMID: 19854900 PMCID: PMC2798276 DOI: 10.1128/jb.00930-09] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2009] [Accepted: 10/12/2009] [Indexed: 11/20/2022] Open
Abstract
Vibrio cholerae hemolysin (HlyA) is a 65-kDa water-soluble pore-forming toxin that causes lysis of eukaryotic cells by destroying selective permeability of the plasma membrane bilayer. The HlyA monomer self-assembles on the target cell surface to the more stable beta-barrel amphipathic heptamer, which inserts into the membrane bilayer to form a diffusion channel. Deletion of the 15-kDa beta-prism lectin domain at the C terminus generates a 50-kDa hemolysin variant (HlyA50) with an approximately 1,000-fold decrease in hemolytic activity. Because functional differences are eventually dictated by structural differences, we determined three-dimensional structures of 65- and 50-kDa HlyA oligomers, using cryo-electron microscopy and single-particle methods. Our study clearly shows that the HlyA oligomer has sevenfold symmetry but that the HlyA50 oligomer is an asymmetric molecule. The HlyA oligomer has bowl-like, arm-like, and ring-like domains. The bowl-like domain is coupled with the ring-like domain, and seven side openings are present just beneath the ring-like domain. Although a central channel is present in both HlyA and HlyA50 oligomers, they differ in pore size as well as in shape of the molecules and channel. These structural differences may be relevant to the striking difference in efficiencies of functional channel formation by the two toxin forms.
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Affiliation(s)
- Somnath Dutta
- Division of Electron Microscopy, Division of Biochemistry, National Institute of Cholera and Enteric Diseases, P-33, C.I.T. Road, Scheme XM, Beleghata, Kolkata 700010, India
| | - Budhaditya Mazumdar
- Division of Electron Microscopy, Division of Biochemistry, National Institute of Cholera and Enteric Diseases, P-33, C.I.T. Road, Scheme XM, Beleghata, Kolkata 700010, India
| | - Kalyan K. Banerjee
- Division of Electron Microscopy, Division of Biochemistry, National Institute of Cholera and Enteric Diseases, P-33, C.I.T. Road, Scheme XM, Beleghata, Kolkata 700010, India
| | - Amar N. Ghosh
- Division of Electron Microscopy, Division of Biochemistry, National Institute of Cholera and Enteric Diseases, P-33, C.I.T. Road, Scheme XM, Beleghata, Kolkata 700010, India
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Berne S, Lah L, Sepčić K. Aegerolysins: structure, function, and putative biological role. Protein Sci 2009; 18:694-706. [PMID: 19309687 PMCID: PMC2762582 DOI: 10.1002/pro.85] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Revised: 01/19/2009] [Accepted: 01/26/2009] [Indexed: 12/13/2022]
Abstract
Aegerolysins, discovered in fungi, bacteria and plants, are highly similar proteins with interesting biological properties. Certain aegerolysins possess antitumoral, antiproliferative, and antibacterial activities. Further possible medicinal applications include their use in the prevention of atherosclerosis, or as vaccines. Additional biotechnological value of fungal aegerolysins lies in their involvement in development, which could improve cultivation of commercially important edible mushrooms. Besides, new insights on microheterogeneity of raft-like membrane domains could be gained by using aegerolysins as specific markers in cell and molecular biology. Although the exact function of aegerolysins in their producing organisms remains to be explained, they are biochemically well characterized all-beta structured proteins sharing the following common features: low isoelectric points, similar molecular weights (15-17 kDa), and stability in a wide pH range.
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Affiliation(s)
- Sabina Berne
- Medical Centre for Molecular Biology, Institute of Biochemistry, Faculty of Medicine, University of Ljubljana1000 Ljubljana, Slovenia
| | - Ljerka Lah
- Ljerka Lah, Laboratory for Biosynthesis and Biotransformation, National Institute of Chemistry1000 Ljubljana, Slovenia
| | - Kristina Sepčić
- Department of Biology, Biotechnical Faculty, University of Ljubljana1000 Ljubljana, Slovenia
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Debellis L, Diana A, Arcidiacono D, Fiorotto R, Portincasa P, Altomare DF, Spirlì C, de Bernard M. The Vibrio cholerae cytolysin promotes chloride secretion from intact human intestinal mucosa. PLoS One 2009; 4:e5074. [PMID: 19333391 PMCID: PMC2659442 DOI: 10.1371/journal.pone.0005074] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2008] [Accepted: 03/05/2009] [Indexed: 12/02/2022] Open
Abstract
Background The pathogenicity of the Vibrio cholerae strains belonging to serogroup O1 and O139 is due to the production of virulence factors such as cholera toxin (CT) and the toxin-coregulated pilus (TCP). The remaining serogroups, which mostly lack CT and TCP, are more frequently isolated from aquatic environmental sources than from clinical samples; nevertheless, these strains have been reported to cause human disease, such as sporadic outbreaks of watery diarrhoea and inflammatory enterocolitis. This evidence suggested the possibility that other virulence factor(s) than cholera toxin might be crucial in the pathogenesis of Vibrio cholerae-induced diarrhoea, but their nature remains unknown. VCC, the hemolysin produced by virtually all Vibrio cholerae strains, has been proposed as a possible candidate, though a clear-cut demonstration attesting VCC as crucial in the pathogenesis of Vibrio cholerae-induced diarrhoea is still lacking. Methodology/Principal Findings Electrophysiological parameters and paracellular permeability of stripped human healthy colon tissues, obtained at subtotal colectomy, mounted in Ussing chamber were studied in the presence or absence of VCC purified from culture supernatants of V. cholerae O1 El Tor strain. Short circuit current (ISC) and transepithelial resistance (RT) were measured by a computerized voltage clamp system. The exposure of sigmoid colon specimens to 1 nM VCC resulted in an increase of ISC by 20.7%, with respect to the basal values, while RT was reduced by 12.3%. Moreover, increase in ISC was abolished by bilateral Cl− reduction. Conclusion/Significance Our results demonstrate that VCC, by forming anion channels on the apical membrane of enterocytes, triggers an outward transcellular flux of chloride. Such an ion movement, associated with the outward movement of Na+ and water, might be responsible for the diarrhoea caused by the non-toxigenic strains of Vibrio cholerae.
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Affiliation(s)
- Lucantonio Debellis
- Department of General and Environmental Physiology, University of Bari, Bari, Italy
| | - Anna Diana
- Department of General and Environmental Physiology, University of Bari, Bari, Italy
| | | | - Romina Fiorotto
- Department of Internal Medicine, Section of Digestive Diseases, Yale University, New Haven, Connecticut, United States of America
| | - Piero Portincasa
- Clinica Medica “A. Murri”, Department of Internal and Public Medicine, University Medical School, Bari, Italy
| | - Donato Francesco Altomare
- Department of Emergency and Organ Transplantation, General Surgery and Liver Transplantation Units, University of Bari, Policlinico, Bari, Italy
| | - Carlo Spirlì
- Department of Internal Medicine, Section of Digestive Diseases, Yale University, New Haven, Connecticut, United States of America
| | - Marina de Bernard
- Venetian Institute of Molecular Medicine, Padua, Italy
- Department of Biology, University of Padua, Padua, Italy
- * E-mail:
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Löhner S, Walev I, Boukhallouk F, Palmer M, Bhakdi S, Angela V. Pore formation by
Vibrio cholerae
cytolysin follows the same archetypical mode as β‐barrel toxins from gram‐positive organisms. FASEB J 2009; 23:2521-8. [DOI: 10.1096/fj.08-127688] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Sabine Löhner
- Institute of Medical Microbiology and HygieneUniversity of MainzMainzGermany
| | - Iwan Walev
- Institute of Medical Microbiology and HygieneUniversity of MainzMainzGermany
| | - Fatima Boukhallouk
- Institute of Medical Microbiology and HygieneUniversity of MainzMainzGermany
| | - Michael Palmer
- Department of ChemistryUniversity of WaterlooWaterlooOntarioCanada
| | - Sucharit Bhakdi
- Institute of Medical Microbiology and HygieneUniversity of MainzMainzGermany
| | - Valeva Angela
- Institute of Medical Microbiology and HygieneUniversity of MainzMainzGermany
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31
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Mizuno T, Sultan SZ, Kaneko Y, Yoshimura T, Maehara Y, Nakao H, Tsuchiya T, Shinoda S, Miyoshi SI. Modulation of Vibrio mimicus hemolysin through limited proteolysis by an endogenous metalloprotease. FEBS J 2009; 276:825-34. [DOI: 10.1111/j.1742-4658.2008.06827.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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32
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Vibrio cholerae cytolysin is essential for high enterotoxicity and apoptosis induction produced by a cholera toxin gene-negative V. cholerae non-O1, non-O139 strain. Microb Pathog 2008; 44:118-28. [DOI: 10.1016/j.micpath.2007.08.013] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2007] [Accepted: 08/10/2007] [Indexed: 12/21/2022]
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33
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Arcidiacono D, Odom S, Frossi B, Rivera J, Paccani SR, Baldari CT, Pucillo C, Montecucco C, de Bernard M. The Vibrio cholerae cytolysin promotes activation of mast cell (T helper 2) cytokine production. Cell Microbiol 2007; 10:899-907. [PMID: 18005391 DOI: 10.1111/j.1462-5822.2007.01092.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Many strains of Vibrio cholerae produce a cytolysin (VCC) that forms oligomeric transmembrane pores responsible for vacuolization of several cell types in culture. Here we suggest that VCC could contribute to the T helper 2 (Th2) response seen in the natural infection; acting through TLR2, VCC enhances mast cells secretion of IL-4, IL-6 and TNF-alpha by 330-, 290- and 550-fold respectively. Moreover, VCC-induced cytokine production is dependent on increased cytosolic Ca(2+) and on the presence of the Src family kinases Lyn and Fyn, known to be required for FcepsilonRI-dependent activation of mast cells. These findings strongly suggest that VCC has a pro-inflammatory activity promoting a Th2-type immune profile.
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Affiliation(s)
- Diletta Arcidiacono
- Department of Biomedical Sciences, University of Padua, Via G. Colombo 3, 35121 Padua, Italy
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34
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Valeva A, Walev I, Weis S, Boukhallouk F, Wassenaar TM, Bhakdi S. Pro-inflammatory feedback activation cycle evoked by attack of Vibrio cholerae cytolysin on human neutrophil granulocytes. Med Microbiol Immunol 2007; 197:285-93. [PMID: 17882454 DOI: 10.1007/s00430-007-0061-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2007] [Indexed: 11/28/2022]
Abstract
Vibrio cholerae cytolysin (VCC) is a pore-forming toxin that is secreted in precursor form (pro-VCC) and requires proteolytic cleavage in order to attain membrane-permeabilizing properties. Pro-VCC can be activated both in solution and membrane-bound state. Processing of membrane-bound pro-VCC can in turn be achieved through the action of both cell-associated and soluble proteases. The current investigation describes the interaction of VCC with human neutrophil granulocytes. It is shown that pro-VCC binds to these cells and is cleaved by cell-bound serine proteases. Membrane permeabilization leads to granulocyte activation, as witnessed by the generation of reactive oxygen metabolites and liberation of granule constituents. A mutant toxin with unaltered binding properties but devoid of pore-forming activity did not elicit these effects. The secreted proteases cleave and activate further bound- and non-bound pro-VCC. A positive feedback loop is thus created that results in enhanced cytotoxicity towards both the targeted granulocytes and towards bystander cells that are not primarily killed by the protoxin. Thus, activation of neutrophil granulocytes by VCC fuels a positive feedback cycle that will cripple immune defence, augment inflammation, and enhance the cytotoxic action of the toxin on neighbouring tissue cells.
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Affiliation(s)
- Angela Valeva
- Institute of Medical Microbiology and Hygiene, University of Mainz, Augustusplatz, Mainz, Germany.
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35
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Kwiatkowska K, Hordejuk R, Szymczyk P, Kulma M, Abdel-Shakor AB, Płucienniczak A, Dołowy K, Szewczyk A, Sobota A. Lysenin-His, a sphingomyelin-recognizing toxin, requires tryptophan 20 for cation-selective channel assembly but not for membrane binding. Mol Membr Biol 2007; 24:121-34. [PMID: 17453419 DOI: 10.1080/09687860600995540] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Lysenin is 297 amino acid long toxin derived from the earthworm Eisenia foetida which specifically recognizes sphingomyelin and induces cell lysis. We synthesized lysenin gene supplemented with a polyhistidine tag, subcloned it into the pT7RS plasmid and the recombinant protein was produced in Escherichia coli. In order to obtain lysenin devoid of its lytic activity, the protein was mutated by substitution of tryptophan 20 by alanine. The recombinant mutant lysenin-His did not evoke cell lysis, although it retained the ability to specifically interact with sphingomyelin, as demonstrated by immunofluorescence microscopy and by dot blot lipid overlay and liposome binding assays. We found that the lytic activity of wild-type lysenin-His was correlated with the protein oligomerization during interaction with sphingomyelin-containing membranes and the amount of oligomers was increased with an elevation of sphingomyelin/lysenin ratio. Blue native gel electrophoresis indicated that trimers can be functional units of the protein, however, lysenin hexamers and nanomers were stabilized by chemical cross-linking of the protein and by sodium dodecyl sulfate. When incorporated into planar lipid bilayers, wild type lysenin-His formed cation-selective channels in a sphingomyelin-dependent manner. We characterized the channel activity by establishing its various open/closed states. In contrast, the mutant lysenin-His did not form channels and its correct oligomerization was strongly impaired. Based on these results we suggest that lysenin oligomerizes upon interaction with sphingomyelin in the plasma membrane, forming cation-selective channels. Their activity disturbs the ion balance of the cell, leading eventually to cell lysis.
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36
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Robertson SL, Smedley JG, Singh U, Chakrabarti G, Van Itallie CM, Anderson JM, McClane BA. Compositional and stoichiometric analysis of Clostridium perfringens enterotoxin complexes in Caco-2 cells and claudin 4 fibroblast transfectants. Cell Microbiol 2007; 9:2734-55. [PMID: 17587331 DOI: 10.1111/j.1462-5822.2007.00994.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Clostridium perfringens enterotoxin (CPE) binds to host cell receptors, forming a small complex precursor for two large complexes reportedly having molecular masses of approximately 155 or approximately 200 kDa. Formation of the approximately 155 kDa complex causes a Ca(2+) influx that leads to apoptosis or oncosis. CPE complex composition is currently poorly understood, although occludin was identified in the approximately 200 kDa complex. The current study used heteromer gel shift analysis to show both CPE large complexes contain six CPE molecules. Ferguson plots and size exclusion chromatography re-sized the approximately 155 and approximately 200 kDa complexes as approximately 425-500 kDa and approximately 550-660 kDa respectively. Co-immunoprecipitation and electroelution studies demonstrated both CPE-binding and non-CPE-binding claudins are associated with all three CPE complexes in Caco-2 cells and with small complex and approximately 425-500 kDa complex of claudin 4 transfectants. Fibroblast transfectants expressing claudin 4 or C-terminal truncated claudin 4 were CPE-sensitive and formed the approximately 425 kDa complex, indicating claudin-induced cell signalling is not required for CPE action and that expression of a single receptor claudin suffices for approximately 425-500 kDa CPE complex formation. These results identify CPE as a unique toxin that combines with tight junction proteins to form high-molecular-mass hexameric pores and alter membrane permeability.
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Affiliation(s)
- Susan L Robertson
- Department of Molecular Genetics and Biochemistry, University of Pittsburgh, Pittsburgh, PA, USA
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37
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Krasilnikov OV, Merzlyak PG, Lima VLM, Zitzer AO, Valeva A, Yuldasheva LN. Pore formation by Vibrio cholerae cytolysin requires cholesterol in both monolayers of the target membrane. Biochimie 2007; 89:271-7. [PMID: 17303303 DOI: 10.1016/j.biochi.2006.12.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2006] [Accepted: 12/18/2006] [Indexed: 11/19/2022]
Abstract
Vibrio cholerae cytolysin (VCC) forms oligomeric transmembrane pores in cholesterol-rich membranes. To better understand this process, we used planar bilayer membranes. In symmetric membranes, the rate of the channel formation by VCC has a superlinear dependency on the cholesterol membrane fraction. Thus, more than one cholesterol molecule can facilitate VCC-pore formation. In asymmetric membranes, the rate of pore formation is limited by the leaflet with the lower cholesterol content. Methyl-beta-cyclodextrin, which removes cholesterol from membranes, rapidly inhibits VCC pore formation, even when it is added to the side opposite that of VCC addition. The results suggest that cholesterol in both membrane leaflets aid VCC-pore formation and that either leaflet can function as a kinetic bottleneck with respect to the rate of pore-formation.
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Affiliation(s)
- Oleg V Krasilnikov
- Laboratory of Membrane Biophysics, Department of Biophysics and Radiobiology, Federal University of Pernambuco, Av. prof. Moraes Rego, S/N, 50670-901 Recife, PE, Brazil.
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38
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Rebolj K, Ulrih NP, Macek P, Sepcić K. Steroid structural requirements for interaction of ostreolysin, a lipid-raft binding cytolysin, with lipid monolayers and bilayers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:1662-70. [PMID: 16857161 DOI: 10.1016/j.bbamem.2006.06.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2006] [Revised: 05/22/2006] [Accepted: 06/01/2006] [Indexed: 11/20/2022]
Abstract
Ostreolysin, a cytolytic protein from the edible oyster mushroom (Pleurotus ostreatus), recognizes and binds specifically to membrane domains enriched in cholesterol and sphingomyelin (or saturated phosphatidylcholine). These events, leading to permeabilization of the membrane, suggest that a cholesterol-rich liquid-ordered membrane phase, which is characteristic of lipid rafts, could be its possible binding site. In this work, we present effects of ostreolysin on membranes containing various steroids. Binding and membrane permeabilizing activity of ostreolysin was studied using lipid mono- and bilayers composed of sphingomyelin combined, in a 1/1 molar ratio, with natural and synthetic steroids (cholesterol, ergosterol, beta-sitosterol, stigmasterol, lanosterol, 7-dehydrocholesterol, cholesteryl acetate, and 5-cholesten-3-one). Binding to membranes and lytic activity of the protein are both shown to be dependent on the intact sterol 3beta-OH group, and are decreased by introducing additional double bonds and methylation of the steroid skeleton or C17-isooctyl chain. The activity of ostreolysin mainly correlates with the ability of the steroids to promote formation of liquid-ordered membrane domains, and is the highest with cholesterol-containing membranes. Furthermore, increasing the cholesterol concentration enhanced ostreolysin binding in a highly cooperative manner, suggesting that the membrane lateral distribution and accessibility of the sterols are crucial for the activity of this new member of cholesterol-dependent cytolysins.
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Affiliation(s)
- Katja Rebolj
- Department of Biology, Biotechnical Faculty, University of Ljubljana, Vecna pot 111, 1000 Ljubljana, Slovenia
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39
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Pantano S, Montecucco C. A molecular model of the Vibrio cholerae cytolysin transmembrane pore. Toxicon 2005; 47:35-40. [PMID: 16330061 DOI: 10.1016/j.toxicon.2005.09.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2005] [Revised: 08/31/2005] [Accepted: 09/22/2005] [Indexed: 01/05/2023]
Abstract
The cytotoxic activity of some of the most pathogenic strains of Vibrio cholerae is associated with a cytolysin protein (VCC), which forms oligomeric transmembrane pores and changes the permeability of intestinal cells. We present here a model structure of the transmembrane pore of VCC based on sequence comparison with other pore-forming toxins. VCC is suggested to form a transmembrane beta-barrel pore with a relatively large trans vestibule region. Calculations of the electrostatic profile within the pore lumen provide a rationale for the low conductance and selectivity of the VCC ion channel.
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Affiliation(s)
- Sergio Pantano
- Venetian Institute of Molecular Medicine (VIMM),Via Orus 2, 35129, Padova, Italy.
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40
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Sugama J, Ohkubo S, Atsumi M, Nakahata N. Mastoparan changes the cellular localization of Galphaq/11 and Gbeta through its binding to ganglioside in lipid rafts. Mol Pharmacol 2005; 68:1466-74. [PMID: 16118364 DOI: 10.1124/mol.105.013524] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although it is known that mastoparan, a wasp venom toxin, directly activates Gi/o, mastoparan-induced biological responses are not always explained by this mechanism. For instance, we have demonstrated previously that mastoparan suppressed phosphoinositide hydrolysis induced by carbachol in human astrocytoma cells (FEBS Lett 206:91-94, 1990). In the present study, we examined whether mastoparan affected phosphoinositide hydrolysis by interacting with lipid rafts in PC-12 cells. Mastoparan inhibited UTP-induced increase in [Ca2+]i and phosphoinositide hydrolysis in a concentration-dependent manner. UTP-induced phosphoinositide hydrolysis occurred in lipid rafts, because methyl-beta-cyclodextrin, a disrupting regent of lipid rafts, inhibited the hydrolysis. Mastoparan changed the localization of Galphaq/11 and Gbeta together with cholesterol from lipid rafts to nonraft fractions or cytosol. These changes were inhibited by ganglioside mixtures, suggesting that mastoparan interacts with gangliosides in lipid rafts. In fact, ganglioside mixtures and neuraminidase, but not sialic acid, attenuated the inhibitory effect of mastoparan on phosphoinositide hydrolysis. Furthermore, fluorescence intensity of tyrosine residue of [Tyr3]mastoparan was potentiated by ganglioside mixtures, suggesting the direct binding of mastoparan to gangliosides. Mastoparan caused cytotoxicity of PC-12 cells in a concentration-dependent manner, determined by LDH release. The mastoparan-induced cytotoxicity was significantly inhibited by neuraminidase or gangliosides. The order of inhibitory potency of gangliosides was GT1b approximately GD1b > GD1a > GM1 >> GQ1b, but asialo-GM1 and sialic acid were inactive. These results suggest that mastoparan initially binds to gangliosides in lipid rafts and then it inhibits phosphoinositide hydrolysis by changing the localization of Galphaq/11 and Gbeta in lipid rafts.
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Affiliation(s)
- Jun Sugama
- Department of Cellular Signaling, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba 6-3, Aramaki, Aoba-ku, Sendai, Japan 980-8578
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41
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Olson R, Gouaux E. Crystal Structure of the Vibrio cholerae Cytolysin (VCC) Pro-toxin and its Assembly into a Heptameric Transmembrane Pore. J Mol Biol 2005; 350:997-1016. [PMID: 15978620 DOI: 10.1016/j.jmb.2005.05.045] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2005] [Revised: 05/10/2005] [Accepted: 05/12/2005] [Indexed: 11/25/2022]
Abstract
Pathogenic Vibrio cholerae secrete V. cholerae cytolysin (VCC), an 80 kDa pro-toxin that assembles into an oligomeric pore on target cell membranes following proteolytic cleavage and interaction with cell surface receptors. To gain insight into the activation and targeting activities of VCC, we solved the crystal structure of the pro-toxin at 2.3A by X-ray diffraction. The core cytolytic domain of VCC shares a fold similar to the staphylococcal pore-forming toxins, but in VCC an amino-terminal pro-domain and two carboxy-terminal lectin domains decorate the cytolytic domain. The pro-domain masks a protomer surface that likely participates in inter-protomer interactions in the cytolytic oligomer, thereby explaining why proteolytic cleavage and movement of the pro-domain is necessary for toxin activation. A single beta-octyl glucoside molecule outlines a possible receptor binding site on one lectin domain, and removal of this domain leads to a tenfold decrease in lytic activity toward rabbit erythrocytes. VCC activated by proteolytic cleavage assembles into an oligomeric species upon addition of soybean asolectin/cholesterol liposomes and this oligomer was purified in detergent micelles. Analytical ultracentrifugation and crystallographic analysis indicate that the resulting VCC oligomer is a heptamer. Taken together, these studies define the architecture of a pore forming toxin and associated lectin domains, confirm the stoichiometry of the assembled oligomer as heptameric, and suggest a common mechanism of assembly for staphylococcal and Vibrio cytolytic toxins.
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Affiliation(s)
- Rich Olson
- Department of Biochemistry and Molecular Biophysics, Columbia University, 650 W. 168th Street, New York, NY 10032, USA
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42
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Valeva A, Walev I, Boukhallouk F, Wassenaar TM, Heinz N, Hedderich J, Lautwein S, Möcking M, Weis S, Zitzer A, Bhakdi S. Identification of the membrane penetrating domain of Vibrio cholerae cytolysin as a β-barrel structure. Mol Microbiol 2005; 57:124-31. [PMID: 15948954 DOI: 10.1111/j.1365-2958.2005.04684.x] [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] [Indexed: 11/28/2022]
Abstract
Vibrio cholerae cytolysin (VCC) is an oligomerizing pore-forming toxin that is related to cytolysins of many other Gram-negative organisms. VCC contains six cysteine residues, of which two were found to be present in free sulphydryl form. The positions of two intramolecular disulphide bonds were mapped, and one was shown to be essential for correct folding of protoxin. Mutations were created in which the two free cysteines were deleted, so that single cysteine substitution mutants could be generated for site-specific labelling. Employment of polarity-sensitive fluorophores identified amino acid side-chains that formed part of the pore-forming domain of VCC. The sequence commenced at residue 311, and was deduced to form a beta-barrel in the assembled oligomer with the subsequent odd-numbered residues facing the lipid bilayer and even-numbered residues facing the lumen. Pro328/Lys329 were tentatively identified as the position at which the sequence turns back into the membrane and where the antiparallel beta-strand commences. This was deduced from fluorimetric analyses combined with experiments in which the pore was reversibly occluded by derivatization of sulphydryl groups with a bulky moiety. Our data support computer-based predictions that the membrane-permeabilizing amino acid sequence of VCC is homologous to the beta-barrel-forming sequence of staphylococcal cytolysins and identify the beta-barrel as a membrane-perforating structure that is highly conserved in evolution.
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Affiliation(s)
- Angela Valeva
- Institute of Medical Microbiology and Hygiene, University of Mainz, Augustusplatz, D55101 Mainz, Germany.
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43
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Guerra L, Teter K, Lilley BN, Stenerlöw B, Holmes RK, Ploegh HL, Sandvig K, Thelestam M, Frisan T. Cellular internalization of cytolethal distending toxin: a new end to a known pathway. Cell Microbiol 2005; 7:921-34. [PMID: 15953025 DOI: 10.1111/j.1462-5822.2005.00520.x] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The cytolethal distending toxins (CDTs) are unique in their ability to induce DNA damage, activate checkpoint responses and cause cell cycle arrest or apoptosis in intoxicated cells. However, little is known about their cellular internalization pathway. We demonstrate that binding of the Haemophilus ducreyi CDT (HdCDT) on the plasma membrane of sensitive cells was abolished by cholesterol extraction with methyl-beta-cyclodextrin. The toxin was internalized via the Golgi complex, and retrogradely transported to the endoplasmic reticulum (ER), as assessed by N-linked glycosylation. Further translocation from the ER did not require the ER-associated degradation (ERAD) pathway, and was Derlin-1 independent. The genotoxic activity of HdCDT was dependent on its internalization and its DNase activity, as induction of DNA double-stranded breaks was prevented in Brefeldin A-treated cells and in cells exposed to a catalytically inactive toxin. Our data contribute to a better understanding of the CDT mode of action and highlight two important aspects of the biology of this bacterial toxin family: (i) HdCDT translocation from the ER to the nucleus does not involve the classical pathways followed by other retrogradely transported toxins and (ii) toxin internalization is crucial for execution of its genotoxic activity.
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Affiliation(s)
- Lina Guerra
- Microbiology and Tumorbiology Center, Karolinska Institutet, Stockholm, Sweden
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44
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Nagamune H, Ohkura K, Sukeno A, Cowan G, Mitchell TJ, Ito W, Ohnishi O, Hattori K, Yamato M, Hirota K, Miyake Y, Maeda T, Kourai H. The human-specific action of intermedilysin, a homolog of streptolysin O, is dictated by domain 4 of the protein. Microbiol Immunol 2005; 48:677-92. [PMID: 15383705 DOI: 10.1111/j.1348-0421.2004.tb03479.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Intermedilysin is a pore-forming cytolysin belonging to the streptolysin O gene family known as the 'Cholesterol-binding/dependent cytolysins' and is unique within the family in that it is highly humanspecific. This specificity suggests interaction with a component of human cells other than cholesterol, the proposed receptor for the other toxins of the gene family. Indeed, intermedilysin showed no significant degree of affinity to free or liposome-embedded cholesterol. Characterization of intermedilysin undecapeptide mutants revealed that this lack of affinity to cholesterol was a result of the substitutions of intermedilysin in this region. Absorption assays with erythrocyte membranes from various animals, competitive inhibition with domain 4 of intermedilysin and liposome-binding assays of streptolysin O and intermedilysin indicated that cell membrane binding is the human-specific step of intermedilysin action, that the host cell membrane-binding site is located within domain 4 in common with other members of the family and that the receptor for this toxin is not cholesterol. The species specificity of undecapeptide mutants of intermedilysin and streptolysin O and chimeric mutants between intermedilysin and streptolysin O, and intermedilysin and pneumolysin indicated that domain 4 of intermedilysin determines the human-specific action step and the cell-binding site of domain 4 lies within the 56 amino acids of the C-terminal, excluding the undecapeptide region.
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Affiliation(s)
- Hideaki Nagamune
- Department of Biological Science and Technology, Faculty of Engineering, The University of Tokushima, #1, 2-chrome, Minamijosanjima-cho, Tokushima, Tokushima 770-8506, Japan.
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45
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Bittman R. The 2003 ASBMB-Avanti Award in Lipids Address: Applications of novel synthetic lipids to biological problems. Chem Phys Lipids 2004; 129:111-31. [PMID: 15081855 DOI: 10.1016/j.chemphyslip.2004.01.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2004] [Revised: 01/24/2004] [Accepted: 01/28/2004] [Indexed: 01/10/2023]
Abstract
This paper is an overview of the 2003 Avanti Award in Lipids address that was presented by Robert Bittman at the American Society for Biochemistry and Molecular Biology (ASBMB) Annual Meeting held in San Diego, CA in conjunction with meetings of five other FASEB Societies, April 15, 2003. The theme of the lecture is: "How can the chemical synthesis of unnatural lipids provide insights into problems ranging from cell biology to biophysics?" The following examples are presented: (1) novel ceramide analogs as experimental anticancer agents, (2) photoactivatable sphingosine 1-phosphate analogs as probes of protein targets of this bioactive lipid, (3) a 13C-enriched cerebroside as a quantitative probe of glycosphingolipid (GSL) transbilayer distribution in bilayers with and without sphingomyelin, (4) cis and trans unsaturated sphingomyelin analogs as modulators of the existence of cholesterol-enriched microdomains (rafts) that may facilitate fusion of alphaviruses with target membranes, (5) ceramide as an indirect enhancer of the permeabilization of membranes induced by cholesterol-specific cytolysins, (6) fluorescent GSL analogs of widely disparate structure as probes of the molecular features responsible for the selective internalization of GSLs in caveolae of living mammalian cells, (7) enantiomeric lysophosphatidic acid (LPA) analogs as probes of receptor subtypes that mediate LPA signaling, and (8) phosphonocholine analogs of the antitumor ether lipid ET-18-OCH3 as tools for discerning the primary targets that are critical for cytotoxic activity in tumor cells.
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Affiliation(s)
- Robert Bittman
- Department of Chemistry and Biochemistry, Queens College and The Graduate School of The City University of New York, Flushing, NY 11367, USA.
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Geisse N, Cover T, Henderson R, Edwardson J. Targeting of Helicobacter pylori vacuolating toxin to lipid raft membrane domains analysed by atomic force microscopy. Biochem J 2004; 381:911-7. [PMID: 15128269 PMCID: PMC1133903 DOI: 10.1042/bj20031719] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2003] [Revised: 04/30/2004] [Accepted: 05/06/2004] [Indexed: 11/17/2022]
Abstract
The Helicobacter pylori vacuolating toxin VacA causes several effects on mammalian cells in vitro, including intracellular vacuolation, formation of pores in the plasma membrane and apoptosis. When added to cells, VacA becomes associated with detergent-resistant membranes, indicating that it binds preferentially to lipid rafts. In the present study, we have used atomic force microscopy to examine directly the association of VacA with lipid domains in supported lipid bilayers. VacA did not bind to lipid bilayers at pH 7.6. In contrast, at pH 4.0, VacA associated with the bilayers in the form of 26-nm oligomeric complexes. VacA bound to bilayers produced from either brain lipids or SM (sphingomyelin) plus cholesterol, each of which lacked detectable lipid domains. Bilayers composed of DOPC (dioleoylphosphatidylcholine), SM and cholesterol contained clearly visible raft-like domains, and VacA preferentially associated with these rafts. VacA bound poorly to raft-like domains in DOPC/SM bilayers, indicating that cholesterol is required for efficient association of VacA with lipid domains. When PS (phosphatidylserine), an anionic phospholipid that does not partition significantly into rafts, was added to the mixture of DOPC, SM and cholesterol, VacA was excluded from the rafts, indicating that it binds more avidly to PS than to the raft components. A typical plasma membrane exhibits pronounced lipid asymmetry, with SM enriched in the outer leaflet and PS in the inner leaflet. Therefore it is probable that the association of VacA with rafts in DOPC/SM/cholesterol bilayers represents a useful model for understanding the interactions of VacA with membranes in vivo.
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Affiliation(s)
- Nicholas A. Geisse
- *Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K
| | - Timothy L. Cover
- †Departments of Medicine and Microbiology and Immunology, Vanderbilt University School of Medicine and Veterans Affairs Medical Center, Nashville, TN 37232, U.S.A
| | - Robert M. Henderson
- *Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K
| | - J. Michael Edwardson
- *Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K
- To whom correspondence should be addressed (e-mail )
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Tomita T, Noguchi K, Mimuro H, Ukaji F, Ito K, Sugawara-Tomita N, Hashimoto Y. Pleurotolysin, a Novel Sphingomyelin-specific Two-component Cytolysin from the Edible Mushroom Pleurotus ostreatus, Assembles into a Transmembrane Pore Complex. J Biol Chem 2004; 279:26975-82. [PMID: 15084605 DOI: 10.1074/jbc.m402676200] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Self-assembling, pore-forming cytolysins are illustrative molecules for the study of the assembly and membrane insertion of transmembrane pores. Here we purified pleurotolysin, a novel sphingomyelin-specific two-component cytolysin from the basidiocarps of Pleurotus ostreatus and studied the pore-forming properties of the cytolysin. Pleurotolysin consisted of non-associated A (17 kDa) and B (59 kDa) components, which cooperatively caused leakage of potassium ions from human erythrocytes and swelling of the cells at nanomolar concentrations, leading to colloid-osmotic hemolysis. Hemolytic assays in the presence of poly(ethylene glycol)s with different hydrodynamic diameters suggested that pleurotolysin formed membrane pores with a functional diameter of 3.8-5 nm. Pleurotolysin-induced lysis of human erythrocytes was specifically inhibited by the addition of sphingomyelin-cholesterol liposomes to the extracellular space. Pleurotolysin A specifically bound to sphingomyelin-cholesterol liposomes and caused leakage of the internal carboxyfluorescein in concert with pleurotolysin B. Experiments including solubilization of pleurotolysin-treated erythrocytes with 2% (w/v) SDS at 25 degrees C and SDS-polyacrylamide gel electrophoresis/Western immunoblotting showed that pleurotolysin A and B bound to human erythrocytes in this sequence and assembled into an SDS-stable, 700-kDa complex. Ring-shaped structures with outer and inner diameters of 14 and 7 nm, respectively, were isolated from the solubilized erythrocyte membranes by a sucrose gradient centrifugation. Pleurotolysin A and B formed an SDS-stable, ring-shaped complex of the same dimensions on sphingomyelin-cholesterol liposomes as well.
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Affiliation(s)
- Toshio Tomita
- Department of Microbial Biotechnology, Graduate School of Agricultural Science, Tohoku University, Aoba-ku, Sendai 981-8555, Japan.
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Valeva A, Walev I, Weis S, Boukhallouk F, Wassenaar TM, Endres K, Fahrenholz F, Bhakdi S, Zitzer A. A cellular metalloproteinase activates Vibrio cholerae pro-cytolysin. J Biol Chem 2004; 279:25143-8. [PMID: 15066987 DOI: 10.1074/jbc.m313913200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Many strains of Vibrio cholerae produce a cytolysin (VCC) that forms oligomeric transmembrane pores in animal cells. The molecule is secreted as a procytolysin (pro-VCC) of 79 kDa that must be cleaved at the N terminus to generate the active 65-kDa toxin. Processing can occur in solution, and previous studies have described the action of mature VCC thus generated. However, little is known about the properties of pro-VCC itself. In this study, it is shown that pro-VCC exist as a monomer in solution and binds as a monomer to eukaryotic cells. Bound pro-VCC can then be activated either by exogenous, extracellular, or by endogenous, cell-bound proteases. In both cases, cleavage generates the 65-kDa VCC that oligomerizes to form transmembrane pores. A wide variety of exogenous proteinases can mediate activation. In contrast, the activating cellular protease is selectively inhibited by the hydroxamate inhibitor TAPI, and thus probable candidates are members of the ADAM-metalloproteinase family. Furin, MMP-2, MMP-9, and serine proteinases were excluded. Cells over-expressing ADAM-17, also known as tumor necrosis factor alpha converting enzyme, displayed increased activation of VCC, and knockout cells lacking ADAM-17 had a markedly decreased capacity to cleave the protoxin. The possibility is raised that pro-VCC is targeted to membrane sites that selectively contain or are accessible to cellular ADAM-metalloproteinases. Although many microbial toxins are activated by furin, this is the first evidence for processing by a cellular metalloproteinase. We identified ADAM-17 as a potent activator of pro-VCC.
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Affiliation(s)
- Angela Valeva
- Institute of Medical Microbiology and Hygiene, University of Mainz, D55101 Mainz, Germany.
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Yadav SP, Kundu B, Ghosh JK. Identification and Characterization of an Amphipathic Leucine Zipper-like Motif in Escherichia coli Toxin Hemolysin E. J Biol Chem 2003; 278:51023-34. [PMID: 14525984 DOI: 10.1074/jbc.m310052200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hemolysin E (HlyE) is a 34 kDa protein toxin, recently isolated from a pathogenic strain of Escherichia coli, which is believed to exert its toxic activity via formation of pores in the target cell membrane. With the goal of understanding the involvement of different segments of hemolysin E in the membrane interaction and assembly of the toxin, a conserved, amphipathic leucine zipper-like motif has been identified. In order to evaluate the possible structural and functional roles of this segment in HlyE, a 30-residue peptide (H-205) corresponding to the leucine zipper motif (amino acid 205-234) and two mutant peptides of the same size were synthesized and labeled by fluorescent probes at their N termini. The results show that the wild-type H-205 binds to both zwitterionic (PC/Chol) and negatively charged (PC/PG/Chol) phospholipid vesicles and also self-assemble therein. Detailed membrane-binding experiments revealed that this synthetic motif (H-205) formed large aggregates and inserted into the bilayer of only negatively charged lipid vesicles but not of zwitterionic membrane. Although both the mutants bound to zwitterionic and negatively charged lipid vesicles, neither of them inserted into the lipid bilayers nor assembled in any of these lipid vesicles. Furthermore, H-205 adopted a significant helical structure in membrane mimetic environments and induced the permeation of monovalent ions and release of entrapped calcein across the phospholipid vesicles more efficiently than the mutant peptides. The results presented here indicate that this H-205 (amino acid 205-234) segment may be an important structural element in hemolysin E, which could play a significant role in the binding and assembly of the toxin in the target cell membrane and its destabilization.
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Affiliation(s)
- Sharada Prasad Yadav
- Molecular and Structural Biology Division, Central Drug Research Institute, Lucknow, India
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Laohachai KN, Bahadi R, Hardo MB, Hardo PG, Kourie JI. The role of bacterial and non-bacterial toxins in the induction of changes in membrane transport: implications for diarrhea. Toxicon 2003; 42:687-707. [PMID: 14757199 DOI: 10.1016/j.toxicon.2003.08.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Bacterial toxins induce changes in membrane transport which underlie the loss of electrolyte homeostasis associated with diarrhea. Bacterial- and their secreted toxin-types which have been linked with diarrhea include: (a) Vibrio cholerae (cholera toxin, E1 Tor hemolysin and accessory cholera enterotoxin); (b) Escherichia coli (heat stable enterotoxin, heat-labile enterotoxin and colicins); (c) Shigella dysenteriae (shiga-toxin); (d) Clostridium perfringens (C. perfringens enterotoxin, alpha-toxin, beta-toxin and theta-toxin); (e) Clostridium difficile (toxins A and B); (f) Staphylococcus aureus (alpha-haemolysin); (g) Bacillus cereus (cytotoxin K and haemolysin BL); and (h) Aeromonas hydrophila (aerolysin, heat labile cytotoxins and heat stable cytotoxins). The mechanisms of toxin-induced diarrhea include: (a) direct effects on ion transport in intestinal epithelial cells, i.e. direct toxin interaction with intrinsic ion channels in the membrane and (b) indirect interaction with ion transport in intestinal epithelial cells mediated by toxin binding to a membrane receptor. These effects consequently cause the release of second messengers, e.g. the release of adenosine 3',5'-cyclic monophosphate/guanosine 3',5'-monophosphate, IP(3), Ca2+ and/or changes in second messengers that are the result of toxin-formed Ca2+ and K+ permeable channels, which increase Ca2+ flux and augment changes in Ca2+ homeostasis and cause depolarisation of the membrane potential. Consequently, many voltage-dependent ion transport systems, e.g. voltage-dependent Ca2+ influx, are affected. The toxin-formed ion channels may act as a pathway for loss of fluid and electrolytes. Although most of the diarrhea-causing toxins have been reported to act via cation and anion channel formation, the properties of these channels have not been well studied, and the available biophysical properties that are needed for the characterization of these channels are inadequate.
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Affiliation(s)
- Karina N Laohachai
- Membrane Transport Group, Department of Chemistry, Building 33, The Faculty of Science, The Australian National University, Canberra, ACT 0200, Australia
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