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Johnstone BA, Joseph R, Christie MP, Morton CJ, McGuiness C, Walsh JC, Böcking T, Tweten RK, Parker MW. Cholesterol-dependent cytolysins: The outstanding questions. IUBMB Life 2022; 74:1169-1179. [PMID: 35836358 PMCID: PMC9712165 DOI: 10.1002/iub.2661] [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: 06/01/2022] [Accepted: 06/23/2022] [Indexed: 11/06/2022]
Abstract
The cholesterol-dependent cytolysins (CDCs) are a major family of bacterial pore-forming proteins secreted as virulence factors by Gram-positive bacterial species. CDCs are produced as soluble, monomeric proteins that bind specifically to cholesterol-rich membranes, where they oligomerize into ring-shaped pores of more than 30 monomers. Understanding the details of the steps the toxin undergoes in converting from monomer to a membrane-spanning pore is a continuing challenge. In this review we summarize what we know about CDCs and highlight the remaining outstanding questions that require answers to obtain a complete picture of how these toxins kill cells.
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Affiliation(s)
- Bronte A Johnstone
- Department of Biochemistry and Pharmacology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
- ARC Centre for Cryo-electron Microscopy of Membrane Proteins, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Riya Joseph
- Department of Biochemistry and Pharmacology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
- ARC Centre for Cryo-electron Microscopy of Membrane Proteins, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Michelle P Christie
- Department of Biochemistry and Pharmacology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
- ARC Centre for Cryo-electron Microscopy of Membrane Proteins, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Craig J Morton
- Department of Biochemistry and Pharmacology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Conall McGuiness
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - James C Walsh
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Till Böcking
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Rodney K Tweten
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Michael W Parker
- Department of Biochemistry and Pharmacology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
- ARC Centre for Cryo-electron Microscopy of Membrane Proteins, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
- Australian Cancer Research Foundation Rational Drug Discovery Centre, St Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia
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McGuinness C, Walsh JC, Bayly-Jones C, Dunstone MA, Christie MP, Morton CJ, Parker MW, Böcking T. Single-molecule analysis of the entire perfringolysin O pore formation pathway. eLife 2022; 11:74901. [PMID: 36000711 PMCID: PMC9457685 DOI: 10.7554/elife.74901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 08/16/2022] [Indexed: 11/20/2022] Open
Abstract
The cholesterol-dependent cytolysin perfringolysin O (PFO) is secreted by Clostridium perfringens as a bacterial virulence factor able to form giant ring-shaped pores that perforate and ultimately lyse mammalian cell membranes. To resolve the kinetics of all steps in the assembly pathway, we have used single-molecule fluorescence imaging to follow the dynamics of PFO on dye-loaded liposomes that lead to opening of a pore and release of the encapsulated dye. Formation of a long-lived membrane-bound PFO dimer nucleates the growth of an irreversible oligomer. The growing oligomer can insert into the membrane and open a pore at stoichiometries ranging from tetramers to full rings (~35 mers), whereby the rate of insertion increases linearly with the number of subunits. Oligomers that insert before the ring is complete continue to grow by monomer addition post insertion. Overall, our observations suggest that PFO membrane insertion is kinetically controlled.
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Affiliation(s)
- Conall McGuinness
- EMBL Australia Node in Single Molecule Science, University of New South Wales, Sydney, Australia
| | - James C Walsh
- EMBL Australia Node in Single Molecule Science, University of New South Wales, Sydney, Australia
| | - Charles Bayly-Jones
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Australia
| | - Michelle A Dunstone
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Australia
| | - Michelle P Christie
- Department of Biochemistry and Pharmacology, University of Melbourne, Melbourne, Australia
| | - Craig J Morton
- Department of Biochemistry and Pharmacology, University of Melbourne, Melbourne, Australia
| | - Michael W Parker
- Australian Cancer Research Foundation Rational Drug Discovery Centre, St Vincents Institute of Medical Research, Fitzroy, Australia
| | - Till Böcking
- EMBL Australia Node in Single Molecule Science, University of New South Wales, Sydney, Australia
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The molecular mechanisms of listeriolysin O-induced lipid membrane damage. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183604. [PMID: 33722646 DOI: 10.1016/j.bbamem.2021.183604] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 03/05/2021] [Accepted: 03/05/2021] [Indexed: 12/22/2022]
Abstract
Listeria monocytogenes is an intracellular food-borne pathogen that causes listeriosis, a severe and potentially life-threatening disease. Listeria uses a number of virulence factors to proliferate and spread to various cells and tissues. In this process, three bacterial virulence factors, the pore-forming protein listeriolysin O and phospholipases PlcA and PlcB, play a crucial role. Listeriolysin O belongs to a family of cholesterol-dependent cytolysins that are mostly expressed by gram-positive bacteria. Its unique structural features in an otherwise conserved three-dimensional fold, such as the acidic triad and proline-glutamate-serine-threonine-like sequence, enable the regulation of its intracellular activity as well as distinct extracellular functions. The stability of listeriolysin O is pH- and temperature-dependent, and this provides another layer of control of its activity in cells. Moreover, many recent studies have demonstrated a unique mechanism of pore formation by listeriolysin O, i.e., the formation of arc-shaped oligomers that can subsequently fuse to form membrane defects of various shapes and sizes. During listerial invasion of host cells, these membrane defects can disrupt phagosome membranes, allowing bacteria to escape into the cytosol and rapidly multiply. The activity of listeriolysin O is profoundly dependent on the amount and accessibility of cholesterol in the lipid membrane, which can be modulated by the phospholipase PlcB. All these prominent features of listeriolysin O play a role during different stages of the L. monocytogenes life cycle by promoting the proliferation of the pathogen while mitigating excessive damage to its replicative niche in the cytosol of the host cell.
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Evans JC, Tweten RK. How protein engineering has revealed the molecular mechanisms of pore-forming toxins. Methods Enzymol 2021; 649:47-70. [PMID: 33712197 DOI: 10.1016/bs.mie.2021.01.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Pore-forming proteins are found in prokaryotes, vertebrates, and invertebrates, and when involved in pathogenic processes they are classified as pore-forming toxins (PFTs). The use of gene engineering methods in combination with the information provided by the high-resolution crystal structures of the PFTs have allowed investigators to gain a deep understanding of their pore-forming mechanisms. In this chapter, we discuss how protein engineering has helped us and others to reveal the molecular mechanisms of pore formation by prokaryotic PFTs with an emphasis on our experiences with the cholesterol-dependent cytolysins (CDCs).
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Affiliation(s)
- Jordan C Evans
- Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Rodney K Tweten
- Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States.
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Johnstone BA, Christie MP, Morton CJ, Parker MW. X-ray crystallography shines a light on pore-forming toxins. Methods Enzymol 2021; 649:1-46. [PMID: 33712183 DOI: 10.1016/bs.mie.2021.01.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A common form of cellular attack by pathogenic bacteria is to secrete pore-forming toxins (PFTs). Capable of forming transmembrane pores in various biological membranes, PFTs have also been identified in a diverse range of other organisms such as sea anemones, earthworms and even mushrooms and trees. The mechanism of pore formation by PFTs is associated with substantial conformational changes in going from the water-soluble to transmembrane states of the protein. The determination of the crystal structures for numerous PFTs has shed much light on our understanding of these proteins. Other than elucidating the atomic structural details of PFTs and the conformational changes that must occur for pore formation, crystal structures have revealed structural homology that has led to the discovery of new PFTs and new PFT families. Here we review some key crystallographic results together with complimentary approaches for studying PFTs. We discuss how these studies have impacted our understanding of PFT function and guided research into biotechnical applications.
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Affiliation(s)
- Bronte A Johnstone
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC, Australia
| | - Michelle P Christie
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC, Australia
| | - Craig J Morton
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC, Australia
| | - Michael W Parker
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC, Australia; St. Vincent's Institute of Medical Research, Fitzroy, VIC, Australia.
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Li Y, Li Y, Mengist HM, Shi C, Zhang C, Wang B, Li T, Huang Y, Xu Y, Jin T. Structural Basis of the Pore-Forming Toxin/Membrane Interaction. Toxins (Basel) 2021; 13:toxins13020128. [PMID: 33572271 PMCID: PMC7914777 DOI: 10.3390/toxins13020128] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 01/13/2021] [Accepted: 02/02/2021] [Indexed: 12/14/2022] Open
Abstract
With the rapid growth of antibiotic-resistant bacteria, it is urgent to develop alternative therapeutic strategies. Pore-forming toxins (PFTs) belong to the largest family of virulence factors of many pathogenic bacteria and constitute the most characterized classes of pore-forming proteins (PFPs). Recent studies revealed the structural basis of several PFTs, both as soluble monomers, and transmembrane oligomers. Upon interacting with host cells, the soluble monomer of bacterial PFTs assembles into transmembrane oligomeric complexes that insert into membranes and affect target cell-membrane permeability, leading to diverse cellular responses and outcomes. Herein we have reviewed the structural basis of pore formation and interaction of PFTs with the host cell membrane, which could add valuable contributions in comprehensive understanding of PFTs and searching for novel therapeutic strategies targeting PFTs and interaction with host receptors in the fight of bacterial antibiotic-resistance.
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Affiliation(s)
- Yajuan Li
- Department of Clinical Laboratory, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, China; (Y.L.); (C.S.); (B.W.); (T.L.); (Y.H.)
| | - Yuelong Li
- Hefei National Laboratory for Physical Sciences at Microscale, Laboratory of Structural Immunology, CAS Key Laboratory of Innate Immunity and Chronic Disease, Division of Life Sciences and Medicine, School of Basic Medical Sciences, University of Science and Technology of China, Hefei 230027, China; (Y.L.); (H.M.M.); (C.Z.)
| | - Hylemariam Mihiretie Mengist
- Hefei National Laboratory for Physical Sciences at Microscale, Laboratory of Structural Immunology, CAS Key Laboratory of Innate Immunity and Chronic Disease, Division of Life Sciences and Medicine, School of Basic Medical Sciences, University of Science and Technology of China, Hefei 230027, China; (Y.L.); (H.M.M.); (C.Z.)
| | - Cuixiao Shi
- Department of Clinical Laboratory, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, China; (Y.L.); (C.S.); (B.W.); (T.L.); (Y.H.)
| | - Caiying Zhang
- Hefei National Laboratory for Physical Sciences at Microscale, Laboratory of Structural Immunology, CAS Key Laboratory of Innate Immunity and Chronic Disease, Division of Life Sciences and Medicine, School of Basic Medical Sciences, University of Science and Technology of China, Hefei 230027, China; (Y.L.); (H.M.M.); (C.Z.)
| | - Bo Wang
- Department of Clinical Laboratory, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, China; (Y.L.); (C.S.); (B.W.); (T.L.); (Y.H.)
| | - Tingting Li
- Department of Clinical Laboratory, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, China; (Y.L.); (C.S.); (B.W.); (T.L.); (Y.H.)
| | - Ying Huang
- Department of Clinical Laboratory, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, China; (Y.L.); (C.S.); (B.W.); (T.L.); (Y.H.)
| | - Yuanhong Xu
- Department of Clinical Laboratory, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, China; (Y.L.); (C.S.); (B.W.); (T.L.); (Y.H.)
- Correspondence: (Y.X.); (T.J.); Tel.: +86-13505694447 (Y.X.); +86-17605607323 (T.J.)
| | - Tengchuan Jin
- Hefei National Laboratory for Physical Sciences at Microscale, Laboratory of Structural Immunology, CAS Key Laboratory of Innate Immunity and Chronic Disease, Division of Life Sciences and Medicine, School of Basic Medical Sciences, University of Science and Technology of China, Hefei 230027, China; (Y.L.); (H.M.M.); (C.Z.)
- Correspondence: (Y.X.); (T.J.); Tel.: +86-13505694447 (Y.X.); +86-17605607323 (T.J.)
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Abstract
The cholesterol-dependent cytolysins’ pore-forming mechanism relies on the ability to sense the completion of the oligomeric prepore structure and initiate the insertion of the β-barrel pore from the assembled prepore structure. These studies show that a conserved motif is an important component of the sensor that triggers the prepore-to-pore transition and that it is conserved in a large family of previously unidentified CDC-like proteins, the genes for which are present in a vast array of microbial species that span most terrestrial environments, as well as most animal and human microbiomes. These studies establish the foundation for future investigations that will probe the contribution of this large family of CDC-like proteins to microbial survival and human disease. The cholesterol-dependent cytolysins (CDCs) are bacterial, β-barrel, pore-forming toxins. A central enigma of the pore-forming mechanism is how completion of the prepore is sensed to initiate its conversion to the pore. We identified a motif that is conserved between the CDCs and a diverse family of nearly 300 uncharacterized proteins present in over 220 species that span at least 10 bacterial and 2 eukaryotic phyla. Except for this motif, these proteins exhibit little similarity to the CDCs at the primary structure level. Studies herein show this motif is a critical component of the sensor that initiates the prepore-to-pore transition in the CDCs. We further show by crystallography, single particle analysis, and biochemical studies of one of these CDC-like (CDCL) proteins from Elizabethkingia anophelis, a commensal of the malarial mosquito midgut, that a high degree of structural similarity exists between the CDC and CDCL monomer structures and both form large oligomeric pore complexes. Furthermore, the conserved motif in the E. anophelis CDCL crystal structure occupies a nearly identical position and makes similar contacts to those observed in the structure of the archetype CDC, perfringolysin O (PFO). This suggests a common function in the CDCs and CDCLs and may explain why only this motif is conserved in the CDCLs. Hence, these studies identify a critical component of the sensor involved in initiating the prepore-to-pore transition in the CDCs, which is conserved in a large and diverse group of distant relatives of the CDCs.
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An Intermolecular π-Stacking Interaction Drives Conformational Changes Necessary to β-Barrel Formation in a Pore-Forming Toxin. mBio 2019; 10:mBio.01017-19. [PMID: 31266869 PMCID: PMC6606804 DOI: 10.1128/mbio.01017-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
A unique feature of the CDC/MACPF/SNTX (cholesterol-dependent cytolysin/membrane attack complex perforin/stonefish toxin) superfamily of pore-forming toxins is that the β-strands that comprise the β-barrel pore are derived from a pair of α-helical bundles. These studies reveal the molecular basis by which the formation of intermolecular interactions within the prepore complex drive the disruption of intramolecular interactions within each monomer of the prepore to trigger the α-helical–to–β-strand transition and formation of the β-barrel pore. The crystal structures of the soluble monomers of the pore-forming cholesterol-dependent cytolysins (CDCs) contain two α-helical bundles that flank a twisted core β-sheet. This protein fold is the hallmark of the CDCs, as well as of the membrane attack complex/perforin immune defense proteins and the stonefish toxins. To form the β-barrel pore, a core β-sheet is flattened to align the membrane-spanning β-hairpins. Concomitantly with this conformational change, the two α-helical bundles that flank the core β-sheet break their restraining contacts and refold into two membrane-spanning β-hairpins of the β-barrel pore. The studies herein show that in the monomer structure of the archetype CDC perfringolysin O (PFO), a conserved Met-Met-Phe triad simultaneously contributes to maintaining the twist in this core β-sheet, as well as restricting the α-helical–to–β-strand transition necessary to form one of two membrane-spanning β-hairpins. A previously identified intermolecular π-stacking interaction is now shown to disrupt the interactions mediated by this conserved triad. This is required to establish the subsequent intermolecular electrostatic interaction, which has previously been shown to drive the final conformational changes necessary to form the β-barrel pore. Hence, these studies show that the intermolecular π-stacking and electrostatic interactions work in tandem to flatten the core β-sheet and initiate the α-helical–to–β-strand transitions to form the β-barrel pore.
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Morton CJ, Sani MA, Parker MW, Separovic F. Cholesterol-Dependent Cytolysins: Membrane and Protein Structural Requirements for Pore Formation. Chem Rev 2019; 119:7721-7736. [DOI: 10.1021/acs.chemrev.9b00090] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Craig J. Morton
- Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Marc-Antoine Sani
- School of Chemistry, Bio21 Institute, University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Michael W. Parker
- Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Parkville, Victoria 3010, Australia
- St. Vincent’s Institute of Medical Research, Fitzroy, Victoria 3065, Australia
| | - Frances Separovic
- School of Chemistry, Bio21 Institute, University of Melbourne, Melbourne, Victoria 3010, Australia
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