1
|
Rivero-Hernández AL, Hervis YP, Valdés-Tresanco ME, Escalona-Rodríguez FA, Cancelliere R, Relova-Hernández E, Romero-Hernández G, Pérez-Rivera E, Torres-Palacios Y, Cartaya-Quintero P, Ros U, Porchetta A, Micheli L, Fernández LE, Laborde R, Álvarez C, Sagan S, Lanio ME, Pazos Santos IF. Decoupling immunomodulatory properties from lipid binding in the α-pore-forming toxin Sticholysin II. Int J Biol Macromol 2024; 280:136244. [PMID: 39368578 DOI: 10.1016/j.ijbiomac.2024.136244] [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: 07/04/2024] [Revised: 09/28/2024] [Accepted: 09/30/2024] [Indexed: 10/07/2024]
Abstract
Sticholysin II (StII), a pore-forming toxin from the marine anemone Stichodactyla helianthus, enhances an antigen-specific cytotoxic T lymphocyte (CTL) response when co-encapsulated in liposomes with a model antigen. This capacity does not depend exclusively on its pore-forming activity and is partially supported by its ability to activate Toll-like receptor 4 (TLR4) in dendritic cells, presumably by interacting with this receptor or by triggering signaling cascades upon binding to lipid membrane. In order to investigate whether the lipid binding capacity of StII is required for immunomodulation, we designed a mutant in which the aromatic amino acids from the interfacial binding site Trp110, Tyr111 and Trp114 were substituted by Ala. In the present work, we demonstrated that StII3A keeps the secondary structure composition and global folding of StII, while it loses its lipid binding and permeabilization abilities. Despite this, StII3A upregulates dendritic cells maturation markers, enhances an antigen-specific effector CD8+ T cells response and confers antitumor protection in a preventive scenario in C57BL/6 mice. Our results indicate that a mechanism independent of its lipid binding ability is involved in the immunomodulatory capacity of StII, pointing to StII3A as a promising candidate to improve the reliability of the Sts-based vaccine platform.
Collapse
Affiliation(s)
- Ada L Rivero-Hernández
- Center for Protein Studies/Department of Biochemistry, Faculty of Biology, University of Havana, Havana 10400, Cuba; NanoCancer, Center of Molecular Immunology (CIM), Havana 11600, Cuba.
| | - Yadira P Hervis
- Center for Protein Studies/Department of Biochemistry, Faculty of Biology, University of Havana, Havana 10400, Cuba; Sorbonne Université, École normale supérieure, PSL University, CNRS, Laboratoire des Biomolécules, LBM, 75005 Paris, France
| | - Mario E Valdés-Tresanco
- Center for Protein Studies/Department of Biochemistry, Faculty of Biology, University of Havana, Havana 10400, Cuba; Center for Molecular Simulations and Department of Biological Sciences, University of Calgary, Alberta T2N 1N4, Canada.
| | - Felipe A Escalona-Rodríguez
- Center for Protein Studies/Department of Biochemistry, Faculty of Biology, University of Havana, Havana 10400, Cuba; NanoCancer, Center of Molecular Immunology (CIM), Havana 11600, Cuba.
| | - Rocco Cancelliere
- Department of Chemical Sciences and Technologies, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, Rome 00133, Italy.
| | | | - Glenda Romero-Hernández
- Center for Protein Studies/Department of Biochemistry, Faculty of Biology, University of Havana, Havana 10400, Cuba; NanoCancer, Center of Molecular Immunology (CIM), Havana 11600, Cuba.
| | - Eric Pérez-Rivera
- Center for Protein Studies/Department of Biochemistry, Faculty of Biology, University of Havana, Havana 10400, Cuba; NanoCancer, Center of Molecular Immunology (CIM), Havana 11600, Cuba
| | - Yusniel Torres-Palacios
- Center for Protein Studies/Department of Biochemistry, Faculty of Biology, University of Havana, Havana 10400, Cuba; NanoCancer, Center of Molecular Immunology (CIM), Havana 11600, Cuba.
| | - Patricia Cartaya-Quintero
- Center for Protein Studies/Department of Biochemistry, Faculty of Biology, University of Havana, Havana 10400, Cuba; NanoCancer, Center of Molecular Immunology (CIM), Havana 11600, Cuba
| | - Uris Ros
- Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), Cologne 50931, Germany.
| | - Alessandro Porchetta
- Department of Chemical Sciences and Technologies, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, Rome 00133, Italy.
| | - Laura Micheli
- Department of Chemical Sciences and Technologies, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, Rome 00133, Italy.
| | | | - Rady Laborde
- Center for Protein Studies/Department of Biochemistry, Faculty of Biology, University of Havana, Havana 10400, Cuba; NanoCancer, Center of Molecular Immunology (CIM), Havana 11600, Cuba.
| | - Carlos Álvarez
- Center for Protein Studies/Department of Biochemistry, Faculty of Biology, University of Havana, Havana 10400, Cuba; NanoCancer, Center of Molecular Immunology (CIM), Havana 11600, Cuba.
| | - Sandrine Sagan
- Sorbonne Université, École normale supérieure, PSL University, CNRS, Laboratoire des Biomolécules, LBM, 75005 Paris, France.
| | - Maria Eliana Lanio
- Center for Protein Studies/Department of Biochemistry, Faculty of Biology, University of Havana, Havana 10400, Cuba; NanoCancer, Center of Molecular Immunology (CIM), Havana 11600, Cuba.
| | - Isabel F Pazos Santos
- Center for Protein Studies/Department of Biochemistry, Faculty of Biology, University of Havana, Havana 10400, Cuba; NanoCancer, Center of Molecular Immunology (CIM), Havana 11600, Cuba.
| |
Collapse
|
2
|
Donato M, Soto C, Lanio ME, Itri R, Álvarez C. The pore-forming activity of sticholysin I is enhanced by the presence of a phospholipid hydroperoxide in membrane. Toxicon 2021; 204:44-55. [PMID: 34736955 DOI: 10.1016/j.toxicon.2021.10.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 10/23/2021] [Accepted: 10/29/2021] [Indexed: 11/19/2022]
Abstract
Sticholysin I (StI) is a pore-forming toxin (PFT) belonging to the actinoporin protein family characterized by high permeabilizing activity in membranes. StI readily associates with sphingomyelin (SM)-containing membranes originating pores that can lead to cell death. Binding and pore-formation are critically dependent on the physicochemical properties of membrane. 1-palmitoyl-2-oleoylphosphatidylcholine hydroperoxide (POPC-OOH) is an oxidized phospholipid (OxPL) containing an -OOH moiety in the unsaturated hydrocarbon chain which orientates towards the bilayer interface. This orientation causes an increase in the lipid molecular area, lateral expansion and decrease in bilayer thickness, elastic and bending modulus, as well as modification of lipid packing. Taking advantage of membrane structural changes promoted by POPC-OOH, we investigated its influence on the permeabilizing ability of StI. Here we report the action of StI on Giant Unilamellar Vesicles (GUVs) made of 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) and SM containing increasing amount of POPC-OOH to assess vesicle permeability changes when compared to OxPL-lacking membranes. Inclusion of POPC-OOH in membranes did not promote spontaneous vesicle leaking but resulted in increased membrane permeability due to StI action. StI activity did not modify the fluid-gel phase coexistence boundaries neither in POPC:SM or POPC-OOH:SM membranes. However, the StI insertion mechanism in membrane seems to differ between POPC:SM and POPC-OOH:SM mixtures as suggested by changes in the time course of monolayer surface tension measurements, even though a preferable binding of the toxin to OxPL-containing systems could not be here demonstrated. In summary, modifications in the membrane imposed by lipid hydroperoxidation favor StI permeabilizing activity.
Collapse
Affiliation(s)
- Maressa Donato
- Instituto de Física, Universidade de São Paulo (USP), São Paulo, SP, Brazil; Center for Laser and Applications, Nuclear and Energy Research Institute, São Paulo, Brazil
| | - Carmen Soto
- Centro de Estudio de Proteínas, Facultad de Biología, Universidad de La Habana, CP, 10400, La Habana, Cuba
| | - María Eliana Lanio
- Centro de Estudio de Proteínas, Facultad de Biología, Universidad de La Habana, CP, 10400, La Habana, Cuba
| | - Rosangela Itri
- Instituto de Física, Universidade de São Paulo (USP), São Paulo, SP, Brazil.
| | - Carlos Álvarez
- Centro de Estudio de Proteínas, Facultad de Biología, Universidad de La Habana, CP, 10400, La Habana, Cuba.
| |
Collapse
|
3
|
Palacios-Ortega J, García-Linares S, Rivera-de-Torre E, Heras-Márquez D, Gavilanes JG, Slotte JP, Martínez-Del-Pozo Á. Structural foundations of sticholysin functionality. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2021; 1869:140696. [PMID: 34246789 DOI: 10.1016/j.bbapap.2021.140696] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 07/05/2021] [Accepted: 07/06/2021] [Indexed: 01/22/2023]
Abstract
Actinoporins constitute a family of α pore-forming toxins produced by sea anemones. The soluble fold of these proteins consists of a β-sandwich flanked by two α-helices. Actinoporins exert their activity by specifically recognizing sphingomyelin at their target membranes. Once there, they penetrate the membrane with their N-terminal α-helices, a process that leads to the formation of cation-selective pores. These pores kill the target cells by provoking an osmotic shock on them. In this review, we examine the role and relevance of the structural features of actinoporins, down to the residue level. We look at the specific amino acids that play significant roles in the function of actinoporins and their fold. Particular emphasis is given to those residues that display a high degree of conservation across the actinoporin sequences known to date. In light of the latest findings in the field, the membrane requirements for pore formation, the effect of lipid composition, and the process of pore formation are also discussed.
Collapse
Affiliation(s)
- Juan Palacios-Ortega
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, Madrid, Spain; Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.
| | - Sara García-Linares
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, Madrid, Spain
| | - Esperanza Rivera-de-Torre
- Department of Biochemistry and Biotechnology, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Diego Heras-Márquez
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, Madrid, Spain
| | - José G Gavilanes
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, Madrid, Spain
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Álvaro Martínez-Del-Pozo
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, Madrid, Spain
| |
Collapse
|
4
|
Functional and Structural Variation among Sticholysins, Pore-Forming Proteins from the Sea Anemone Stichodactyla helianthus. Int J Mol Sci 2020; 21:ijms21238915. [PMID: 33255441 PMCID: PMC7727798 DOI: 10.3390/ijms21238915] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 11/19/2020] [Accepted: 11/20/2020] [Indexed: 12/15/2022] Open
Abstract
Venoms constitute complex mixtures of many different molecules arising from evolution in processes driven by continuous prey-predator interactions. One of the most common compounds in these venomous cocktails are pore-forming proteins, a family of toxins whose activity relies on the disruption of the plasmatic membranes by forming pores. The venom of sea anemones, belonging to the oldest lineage of venomous animals, contains a large amount of a characteristic group of pore-forming proteins known as actinoporins. They bind specifically to sphingomyelin-containing membranes and suffer a conformational metamorphosis that drives them to make pores. This event usually leads cells to death by osmotic shock. Sticholysins are the actinoporins produced by Stichodactyla helianthus. Three different isotoxins are known: Sticholysins I, II, and III. They share very similar amino acid sequence and three-dimensional structure but display different behavior in terms of lytic activity and ability to interact with cholesterol, an important lipid component of vertebrate membranes. In addition, sticholysins can act in synergy when exerting their toxin action. The subtle, but important, molecular nuances that explain their different behavior are described and discussed throughout the text. Improving our knowledge about sticholysins behavior is important for eventually developing them into biotechnological tools.
Collapse
|
5
|
Rivera-de-Torre E, Palacios-Ortega J, Garb JE, Slotte JP, Gavilanes JG, Martínez-Del-Pozo Á. Structural and functional characterization of sticholysin III: A newly discovered actinoporin within the venom of the sea anemone Stichodactyla helianthus. Arch Biochem Biophys 2020; 689:108435. [PMID: 32485153 DOI: 10.1016/j.abb.2020.108435] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 05/23/2020] [Accepted: 05/25/2020] [Indexed: 01/19/2023]
Abstract
Actinoporins are a family of pore-forming toxins produced by sea anemones as part of their venomous cocktail. These proteins remain soluble and stably folded in aqueous solution, but when interacting with sphingomyelin-containing lipid membranes, they become integral oligomeric membrane structures that form a pore permeable to cations, which leads to cell death by osmotic shock. Actinoporins appear as multigenic families within the genome of sea anemones: several genes encoding very similar actinoporins are detected within the same species. The Caribbean Sea anemone Stichodactyla helianthus produces three actinoporins (sticholysins I, II and III; StnI, StnII and StnIII) that differ in their toxic potency. For example, StnII is about four-fold more effective than StnI against sheep erythrocytes in causing hemolysis, and both show synergy. However, StnIII, recently discovered in the S. helianthus transcriptome, has not been characterized so far. Here we describe StnIII's spectroscopic and functional properties and show its potential to interact with the other Stns. StnIII seems to maintain the well-preserved fold of all actinoporins, characterized by a high content of β-sheet, but it is significantly less thermostable. Its functional characterization shows that the critical concentration needed to form active pores is higher than for either StnI or StnII, suggesting differences in behavior when oligomerizing on membrane surfaces. Our results show that StnIII is an interesting and unexpected piece in the puzzle of how this Caribbean Sea anemone species modulates its venomous activity.
Collapse
Affiliation(s)
- Esperanza Rivera-de-Torre
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Madrid, Spain; Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland; Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA, USA
| | - Juan Palacios-Ortega
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Madrid, Spain; Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Jessica E Garb
- Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA, USA
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - José G Gavilanes
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Madrid, Spain
| | - Álvaro Martínez-Del-Pozo
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Madrid, Spain.
| |
Collapse
|
6
|
Partida-Hanon A, Maestro-López M, Vitale S, Turrà D, Di Pietro A, Martínez-Del-Pozo Á, Bruix M. Structure of Fungal α Mating Pheromone in Membrane Mimetics Suggests a Possible Role for Regulation at the Water-Membrane Interface. Front Microbiol 2020; 11:1090. [PMID: 32582073 PMCID: PMC7289986 DOI: 10.3389/fmicb.2020.01090] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 04/30/2020] [Indexed: 12/14/2022] Open
Abstract
Fusarium oxysporum is a highly destructive plant pathogen and an emerging pathogen of humans. Like other ascomycete fungi, F. oxysporum secretes α-pheromone, a small peptide that functions both as a chemoattractant and as a quorum-sensing signal. Three of the ten amino acid residues of α-pheromone are tryptophan, an amino acid whose sidechain has high affinity for lipid bilayers, suggesting a possible interaction with biological membranes. Here we tested the effect of different lipid environments on α-pheromone structure and function. Using spectroscopic and calorimetric approaches, we show that this peptide interacts with negatively charged model phospholipid vesicles. Fluorescence emission spectroscopy and nuclear magnetic resonance (NMR) measurements revealed a key role of the positively charged groups and Trp residues. Furthermore, NMR-based calculation of the 3D structure in the presence of micelles, formed by lipid surfactants, suggests that α-pheromone can establish an intramolecular disulfide bond between the two cysteine residues during interaction with membranes, but not in the absence of lipid mimetics. Remarkably, this oxidized version of α-pheromone lacks biological activity as a chemoattractant and quorum-sensing molecule. These results suggest the presence of a previously unidentified redox regulated control of α-pheromone activity at the surface of the plasma membrane that could influence the interaction with its cognate G-protein coupled receptor.
Collapse
Affiliation(s)
- Angélica Partida-Hanon
- Department of Biological Physical Chemistry, Institute of Physical Chemistry Rocasolano, CSIC, Madrid, Spain
| | - Moisés Maestro-López
- Department of Biochemistry and Molecular Biology, Faculty of Chemistry, Complutense University, Madrid, Spain
| | - Stefania Vitale
- Departmento de Genética, Universidad de Córdoba and Campus de Excelencia Agroalimentario (ceiA3), Córdoba, Spain
| | - David Turrà
- Departmento de Genética, Universidad de Córdoba and Campus de Excelencia Agroalimentario (ceiA3), Córdoba, Spain
| | - Antonio Di Pietro
- Departmento de Genética, Universidad de Córdoba and Campus de Excelencia Agroalimentario (ceiA3), Córdoba, Spain
| | - Álvaro Martínez-Del-Pozo
- Department of Biochemistry and Molecular Biology, Faculty of Chemistry, Complutense University, Madrid, Spain
| | - Marta Bruix
- Department of Biological Physical Chemistry, Institute of Physical Chemistry Rocasolano, CSIC, Madrid, Spain
| |
Collapse
|
7
|
Pore-forming toxins from sea anemones: from protein-membrane interaction to its implications for developing biomedical applications. ADVANCES IN BIOMEMBRANES AND LIPID SELF-ASSEMBLY 2020. [DOI: 10.1016/bs.abl.2020.02.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
|
8
|
Hervis YP, Valle A, Dunkel S, Klare JP, Canet L, Lanio ME, Alvarez C, Pazos IF, Steinhoff HJ. Architecture of the pore forming toxin sticholysin I in membranes. J Struct Biol 2019; 208:30-42. [PMID: 31330179 DOI: 10.1016/j.jsb.2019.07.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 07/02/2019] [Accepted: 07/17/2019] [Indexed: 12/28/2022]
Abstract
Sticholysin I (StI) is a toxin produced by the sea anemone Stichodactyla helianthus and belonging to the actinoporins family. Upon binding to sphingomyelin-containing membranes StI forms oligomeric pores, thereby leading to cell death. According to recent controversial experimental evidences, the pore architecture of actinoporins is a debated topic. Here, we investigated the StI topology in membranes by site-directed spin labeling and electron paramagnetic resonance spectroscopy. The results reveal that StI in membrane exhibits an oligomeric architecture with heterogeneous stoichiometry of predominantly eight or nine protomers, according to the available structural models. The StI topology resembles the conic pore structure reported for the actinoporin fragaceatoxin C. Our data show that StI coexists in two membrane-associated conformations, with the N-terminal segment either attached to the protein core or inserted in the membrane forming the pore. This finding suggests a 'pre-pore' to 'pore' transition determined by a conformational change that detaches the N-terminal segment.
Collapse
Affiliation(s)
- Yadira P Hervis
- Center for Protein Studies/Department of Biochemistry, University of Havana, Calle 25 #455 e/I y J, Vedado, Plaza de la Revolución, ZIP 10400, Havana, Cuba.
| | - Aisel Valle
- Center for Protein Studies/Department of Biochemistry, University of Havana, Calle 25 #455 e/I y J, Vedado, Plaza de la Revolución, ZIP 10400, Havana, Cuba.
| | - Sabrina Dunkel
- Department of Physics, University of Osnabrueck, Barbarastr. 7, 49076 Osnabrueck, Germany.
| | - Johann P Klare
- Department of Physics, University of Osnabrueck, Barbarastr. 7, 49076 Osnabrueck, Germany.
| | - Liem Canet
- Center for Protein Studies/Department of Biochemistry, University of Havana, Calle 25 #455 e/I y J, Vedado, Plaza de la Revolución, ZIP 10400, Havana, Cuba.
| | - Maria E Lanio
- Center for Protein Studies/Department of Biochemistry, University of Havana, Calle 25 #455 e/I y J, Vedado, Plaza de la Revolución, ZIP 10400, Havana, Cuba.
| | - Carlos Alvarez
- Center for Protein Studies/Department of Biochemistry, University of Havana, Calle 25 #455 e/I y J, Vedado, Plaza de la Revolución, ZIP 10400, Havana, Cuba.
| | - Isabel F Pazos
- Center for Protein Studies/Department of Biochemistry, University of Havana, Calle 25 #455 e/I y J, Vedado, Plaza de la Revolución, ZIP 10400, Havana, Cuba.
| | - Heinz-J Steinhoff
- Department of Physics, University of Osnabrueck, Barbarastr. 7, 49076 Osnabrueck, Germany.
| |
Collapse
|
9
|
Palacios-Ortega J, García-Linares S, Rivera-de-Torre E, Gavilanes JG, Martínez-Del-Pozo Á, Slotte JP. Sticholysin, Sphingomyelin, and Cholesterol: A Closer Look at a Tripartite Interaction. Biophys J 2019; 116:2253-2265. [PMID: 31146924 DOI: 10.1016/j.bpj.2019.05.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 05/05/2019] [Accepted: 05/10/2019] [Indexed: 02/06/2023] Open
Abstract
Actinoporins are a group of soluble toxic proteins that bind to membranes containing sphingomyelin (SM) and oligomerize to form pores. Sticholysin II (StnII) is a member of the actinoporin family produced by Stichodactyla helianthus. Cholesterol (Chol) is known to enhance the activity of StnII. However, the molecular mechanisms behind this activation have remained obscure, although the activation is not Chol specific but rather sterol specific. To further explore how bilayer lipids affect or are affected by StnII, we have used a multiprobe approach (fluorescent analogs of both Chol and SM) in combination with a series of StnII tryptophan (Trp) mutants to study StnII/bilayer interactions. First, we compared StnII bilayer permeabilization in the presence of Chol or oleoyl-ceramide (OCer). The comparison was done because both Chol and OCer have a 1-hydroxyl, which helps to orient the molecule in the bilayer (although OCer has additional polar functional groups). Both Chol and OCer also have increased affinity for SM, which StnII may recognize. However, our results show that only Chol was able to activate StnII-induced bilayer permeabilization; OCer failed to activate it. To further examine possible Chol/StnII interactions, we measured Förster resonance energy transfer between Trp in StnII and cholestatrienol, a fluorescent analog of Chol. We could show higher Förster resonance energy transfer efficiency between cholestatrienol and Trps in position 100 and 114 of StnII when compared to three other Trp positions further away from the bilayer binding region of StnII. Taken together, our results suggest that StnII was able to attract Chol to its vicinity, maybe by showing affinity for Chol. SM interactions are known to be important for StnII binding to bilayers, and Chol is known to facilitate subsequent permeabilization of the bilayers by StnII. Our results help to better understand the role of these important membrane lipids for the bilayer properties of StnII.
Collapse
Affiliation(s)
- Juan Palacios-Ortega
- Departamento de Bioquímica y Biología Molecular, Universidad Complutense, Madrid, Spain; Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
| | - Sara García-Linares
- Departamento de Bioquímica y Biología Molecular, Universidad Complutense, Madrid, Spain
| | | | - José G Gavilanes
- Departamento de Bioquímica y Biología Molecular, Universidad Complutense, Madrid, Spain
| | | | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.
| |
Collapse
|
10
|
Ros U, Carretero GPB, Paulino J, Crusca E, Pazos F, Cilli EM, Lanio ME, Schreier S, Alvarez C. Self-association and folding in membrane determine the mode of action of peptides from the lytic segment of sticholysins. Biochimie 2018; 156:109-117. [PMID: 30326255 DOI: 10.1016/j.biochi.2018.10.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 10/11/2018] [Indexed: 01/09/2023]
Abstract
Sticholysin I and II (Sts: St I and St II) are proteins of biomedical interest that form pores upon the insertion of their N-terminus in the plasma membrane. Peptides spanning the N-terminal residues of StI (StI1-31) or StII (StII1-30) can mimic the permeabilizing ability of these toxins, emerging as candidates to rationalize their potential biomedical applications. These peptides have different activities that correlate with their hydrophobicity. However, it is not clear how this property contributes to peptide folding in solution or upon binding to membranes. Here we compared the conformational properties of these peptides and shorter versions lacking the hydrophobic segment 1-11 of StI (StI12-31) or 1-10 of StII (StII11-30). Folding of peptides was assessed in solution and in membrane mimetic systems and related with their ability to bind to membranes and to permeabilize lipid vesicles. Our results suggest that the differences in activity among peptides could be ascribed to their different folding propensity and different membrane binding properties. In solution, StII1-30 tends to acquire α-helical conformation coexisting with self-associated structures, while StI1-31 remains structureless. Both peptides fold as α-helix in membrane; but StII1-30 also self-associates in the lipid environment, a process that is favored by its higher affinity for membrane. We stress the contribution of the non-polar/polar balance of the 1-10 amino acid sequence of the peptides as a determining factor for different self-association capabilities. Such difference in hydrophobicity seems to determine the molecular path of peptides folding upon binding to membranes, with an impact in their permeabilizing activity. This study contributes to a better understanding of the molecular mechanisms underlying the permeabilizing activity of Sts N-terminal derived peptides, with connotation for the exploitation of these small molecules as alternative of the full-length toxins in clinical settings.
Collapse
Affiliation(s)
- Uris Ros
- Center for Protein Studies, Biology Faculty, University of Havana, Havana, Cuba
| | - Gustavo P B Carretero
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Joana Paulino
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Edson Crusca
- Department of Biochemistry, Institute of Chemistry, São Paulo State University, Araraquara, São Paulo, Brazil
| | - Fabiola Pazos
- Center for Protein Studies, Biology Faculty, University of Havana, Havana, Cuba
| | - Eduardo M Cilli
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Maria E Lanio
- Center for Protein Studies, Biology Faculty, University of Havana, Havana, Cuba
| | - Shirley Schreier
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Carlos Alvarez
- Center for Protein Studies, Biology Faculty, University of Havana, Havana, Cuba.
| |
Collapse
|
11
|
Carretero GPB, Vicente EF, Cilli EM, Alvarez CM, Jenssen H, Schreier S. Dissecting the mechanism of action of actinoporins. Role of the N-terminal amphipathic α-helix in membrane binding and pore activity of sticholysins I and II. PLoS One 2018; 13:e0202981. [PMID: 30161192 PMCID: PMC6117003 DOI: 10.1371/journal.pone.0202981] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Accepted: 08/13/2018] [Indexed: 11/19/2022] Open
Abstract
Actinoporins sticholysin I and sticholysin II (St I, St II) are proposed to lyse model and biomembranes via toroidal pore formation by their N-terminal domain. Based on the hypothesis that peptide fragments can reproduce the structure and function of this domain, the behavior of peptides containing St I residues 12–31 (StI12-31), St II residues 11–30 (StII11-30), and its TOAC-labeled analogue (N-TOAC-StII11-30) was examined. Molecular modeling showed a good match with experimental structures, indicating amphipathic α-helices in the same regions as in the toxins. CD spectra revealed that the peptides were essentially unstructured in aqueous solution, acquiring α-helical conformation upon interaction with micelles and large unilamellar vesicles (LUV) of variable lipid composition. Fluorescence quenching studies with NBD-containing lipids indicated that N-TOAC-StII11-30’s nitroxide moiety is located in the membranes polar head group region. Pyrene-labeled phospholipid inter-leaflet redistribution suggested that the peptides form toroidal pores, according to the mechanism of action proposed for the toxins. Binding occurred only to negatively charged LUV, indicating the importance of electrostatic interactions; in contrast the peptides bound to both negatively charged and zwitterionic micelles, pointing to a lesser influence of these interactions. In addition, differences between bilayers and micelles in head group packing and in curvature led to differences in peptide-membrane interaction. We propose that the peptides topography in micelles resembles that of the toxins in the toroidal pore. The peptides mimicked the toxins permeabilizing activity, St II peptides being more effective than StI12-31. To our knowledge, this is the first demonstration that differences in the toxins N-terminal amphipathic α-helix play a role in the difference between St I and St II activities.
Collapse
Affiliation(s)
- Gustavo P. B. Carretero
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
- Department of Science and Environment, Roskilde University, Roskilde, Denmark
| | - Eduardo F. Vicente
- Faculty of Science and Engineering, State University of São Paulo, Tupã, Brazil
| | - Eduardo M. Cilli
- Institute of Chemistry, State University of São Paulo, Araraquara, Brazil
| | | | - Håvard Jenssen
- Department of Science and Environment, Roskilde University, Roskilde, Denmark
| | - Shirley Schreier
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
- * E-mail:
| |
Collapse
|
12
|
Cloning, purification and characterization of nigrelysin, a novel actinoporin from the sea anemone Anthopleura nigrescens. Biochimie 2018; 156:206-223. [PMID: 30036605 DOI: 10.1016/j.biochi.2018.07.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 07/19/2018] [Indexed: 12/15/2022]
Abstract
Actinoporins constitute a unique class of pore-forming toxins found in sea anemones that being secreted as soluble monomers are able to bind and permeabilize membranes leading to cell death. The interest in these proteins has risen due to their high cytotoxicity that can be properly used to design immunotoxins against tumor cells and antigen-releasing systems to cell cytosol. In this work we describe a novel actinoporin produced by Anthopleura nigrescens, an anemone found in the Central American Pacific Ocean. Here we report the amino acid sequence of an actinoporin as deduced from cDNA obtained from total body RNA. The synthetic DNA sequence encoding for one cytolysin variant was expressed in BL21 Star (DE3) Escherichia coli and the protein purified by chromatography on CM Sephadex C-25 with more than 97% homogeneity as verified by MS-MS and HPLC analyses. This actinoporin comprises 179 amino acid residues, consistent with its observed isotope-averaged molecular mass of 19 661 Da. The toxin lacks Cys and readily permeabilizes erythrocytes, as well as L1210 cells. CD spectroscopy revealed that its secondary structure is dominated by beta structure (58.5%) with 5.5% of α-helix, and 35% of random structure. Moreover, binding experiments to lipidic monolayers and to liposomes, as well as permeabilization studies in vesicles, revealed that the affinity of this toxin for sphingomyelin-containing membranes is quite similar to sticholysin II (StII). Comparison by spectroscopic techniques and modeling the three-dimensional structure of nigrelysin (Ng) showed a high homology with StII but several differences were also detectable. Taken together, these results reinforce the notion that Ng is a novel member of the actinoporin pore-forming toxin (PFT) family with a HA as high as that of StII, the most potent actinoporin so far described, but with peculiar structural characteristics contributing to expand the understanding of the structure-function relationship in this protein family.
Collapse
|
13
|
Rivera-de-Torre E, Palacios-Ortega J, García-Linares S, Gavilanes JG, Martínez-Del-Pozo Á. One single salt bridge explains the different cytolytic activities shown by actinoporins sticholysin I and II from the venom of Stichodactyla helianthus. Arch Biochem Biophys 2017; 636:79-89. [PMID: 29138096 DOI: 10.1016/j.abb.2017.11.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 11/06/2017] [Accepted: 11/10/2017] [Indexed: 10/18/2022]
Abstract
Sticholysins I and II (StnI and StnII), α-pore forming toxins from the sea anemone Stichodactyla helianthus, are water-soluble toxic proteins which upon interaction with lipid membranes of specific composition bind to the bilayer, extend and insert their N-terminal α-helix, and become oligomeric integral membrane structures. The result is a pore that leads to cell death by osmotic shock. StnI and StnII show 93% of sequence identity, but also different membrane pore-forming activities. The hydrophobicity profile along the first 18 residues revealed differences which were canceled by substituting StnI amino acids 2 and 9. Accordingly, the StnID9A mutant, and the corresponding StnIE2AD9A variant, showed enhanced hemolytic activity. They also revealed a key role for an exposed salt bridge between Asp9 and Lys68. This interaction is not possible in StnII but appears conserved in the other two well-characterized actinoporins, equinatoxin II and fragaceatoxin C. The StnII mutant A8D showed that this single replacement was enough to transform StnII into a version with impaired pore-forming activity. Overall, the results show the key importance of this salt bridge linking the N-terminal stretch to the β-sandwich core. A conclusion of general application for the understanding of salt bridges role in protein design, folding and stability.
Collapse
Affiliation(s)
- Esperanza Rivera-de-Torre
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain
| | - Juan Palacios-Ortega
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain
| | - Sara García-Linares
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain
| | - José G Gavilanes
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain.
| | - Álvaro Martínez-Del-Pozo
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain.
| |
Collapse
|
14
|
Palacios-Ortega J, García-Linares S, Rivera-de-Torre E, Gavilanes JG, Martínez-Del-Pozo Á, Slotte JP. Differential Effect of Bilayer Thickness on Sticholysin Activity. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:11018-11027. [PMID: 28933861 DOI: 10.1021/acs.langmuir.7b01765] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this study, we examined the influence of bilayer thickness on the activity of the actinoporin toxins sticholysin I and II (StnI and StnII) at 25 °C. Bilayer thickness was varied using dimonounsaturated phosphatidylcholine (PC) analogues (with 14:1, 16:1, 18:1, 20:1, and 22:1 acyl chains). In addition, N-14:0-sphingomyelin (SM) was always included because StnI and StnII are SM specific. Cholesterol was also incorporated as indicated. In cholesterol-free large unilamellar vesicles (LUVs) the PC:SM molar ratio was 4:1, and when cholesterol was included, the complete molar ratio was 4:1:0.5 (PC:SM:cholesterol, respectively). Stn toxins promote bilayer leakage through pores formed by oligomerized toxin monomers. Initial calcein leakage was moderately dependent on bilayer PC acyl chain length (and thus bilayer thickness), with higher rates observed with di-16:1 and di-18:1 PC bilayers. In the presence of cholesterol, the maximum rates of calcein leakage were observed in di-14:1 and di-16:1 PC bilayers. Using isothermal titration calorimetry to study the Stn-LUV interaction, we observed that the bilayer affinity constant (Ka) peaked with LUVs containing di-18:1 PC, and was lower in shorter and longer PC acyl chain bilayers. The presence of cholesterol increased the binding affinity approximately 30-fold at the optimal bilayer thickness (di-18:1-PC). We conclude that bilayer thickness affects both functional and conformational aspects of Stn membrane binding and pore formation. Moreover, the length of the actinoporins' N-terminal α-helix, which penetrates the membrane to form a functional pore, appears to be optimal for the membrane thickness represented by di-18:1 PC.
Collapse
Affiliation(s)
- Juan Palacios-Ortega
- Departamento de Bioquímica y Biología Molecular I, Universidad Complutense , Madrid 28040, Spain
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , 20500 Turku, Finland
| | - Sara García-Linares
- Departamento de Bioquímica y Biología Molecular I, Universidad Complutense , Madrid 28040, Spain
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , 20500 Turku, Finland
| | | | - José G Gavilanes
- Departamento de Bioquímica y Biología Molecular I, Universidad Complutense , Madrid 28040, Spain
| | - Álvaro Martínez-Del-Pozo
- Departamento de Bioquímica y Biología Molecular I, Universidad Complutense , Madrid 28040, Spain
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , 20500 Turku, Finland
| |
Collapse
|
15
|
García-Linares S, Rivera-de-Torre E, Palacios-Ortega J, Gavilanes JG, Martínez-del-Pozo Á. The Metamorphic Transformation of a Water-Soluble Monomeric Protein Into an Oligomeric Transmembrane Pore. ADVANCES IN BIOMEMBRANES AND LIPID SELF-ASSEMBLY 2017. [DOI: 10.1016/bs.abl.2017.06.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
|
16
|
García-Linares S, Rivera-de-Torre E, Morante K, Tsumoto K, Caaveiro JMM, Gavilanes JG, Slotte JP, Martínez-Del-Pozo Á. Differential Effect of Membrane Composition on the Pore-Forming Ability of Four Different Sea Anemone Actinoporins. Biochemistry 2016; 55:6630-6641. [PMID: 27933793 DOI: 10.1021/acs.biochem.6b01007] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Sea anemone actinoporins constitute a protein family of multigene pore-forming toxins (PFT). Equinatoxin II (EqtII), fragaceatoxin C (FraC), and sticholysins I and II (StnI and StnII, respectively), produced by three different sea anemone species, are the only actinoporins whose molecular structures have been studied in depth. These four proteins show high sequence identities and practically coincident three-dimensional structures. However, their pore-forming activity can be quite different depending on the model lipid system employed, a feature that has not been systematically studied before. Therefore, the aim of this work was to evaluate and compare the influence of several distinct membrane conditions on their particular pore-forming behavior. Using a complex model membrane system, such as sheep erythrocytes, StnII showed hemolytic activity much higher than those of the other three actinoporins studied. In lipid model systems, pore-forming ability when assayed against 4:1 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/sphingomyelin (SM) vesicles, with the membrane binding being the rate-limiting step, decreased in the following order: StnI > StnII > EqtII > FraC. When using 1:1:1 DOPC/SM/cholesterol LUVs, the presence of Chol not only enhanced membrane binding affinities by ∼2 orders of magnitude but also revealed how StnII was much faster than the other three actinoporins in producing calcein release. This ability agrees with the proposal that explains this behavior in terms of their high sequence variability along their first 30 N-terminal residues. The influence of interfacial hydrogen bonding in SM- or dihydro-SM-containing bilayers was also shown to be a generalized feature of the four actinoporins studied. It is finally hypothesized that this observed variable ability could be explained as a consequence of their distinct specificities and/or membrane binding affinities. Eventually, this behavior can be modulated by the nature of their natural target membranes or the interaction with not yet characterized isotoxin forms from the same sea anemone species.
Collapse
Affiliation(s)
- Sara García-Linares
- Departamento de Bioquímica y Biología Molecular I, Universidad Complutense , Madrid, Spain.,Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , Turku, Finland
| | | | - Koldo Morante
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Kouhei Tsumoto
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Jose M M Caaveiro
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - José G Gavilanes
- Departamento de Bioquímica y Biología Molecular I, Universidad Complutense , Madrid, Spain
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , Turku, Finland
| | | |
Collapse
|
17
|
García-Linares S, Maula T, Rivera-de-Torre E, Gavilanes JG, Slotte JP, Martínez-Del-Pozo Á. Role of the Tryptophan Residues in the Specific Interaction of the Sea Anemone Stichodactyla helianthus's Actinoporin Sticholysin II with Biological Membranes. Biochemistry 2016; 55:6406-6420. [PMID: 27933775 DOI: 10.1021/acs.biochem.6b00935] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Actinoporins are pore-forming toxins from sea anemones. Upon interaction with sphingomyelin-containing bilayers, they become integral oligomeric membrane structures that form a pore. Sticholysin II from Stichodactyla helianthus contains five tryptophans located at strategic positions; its role has now been studied using different mutants. Results show that W43 and W115 play a determinant role in maintaining the high thermostability of the protein, while W146 provides specific interactions for protomer-protomer assembly. W110 and W114 sustain the hydrophobic effect, which is one of the major driving forces for membrane binding in the presence of Chol. However, in its absence, additional interactions with sphingomyelin are required. These conclusions were confirmed with two sphingomyelin analogues, one of which had impaired hydrogen bonding properties. The results obtained support actinoporins' Trp residues playing a major role in membrane recognition and binding, but their residues have an only minor influence on the diffusion and oligomerization steps needed to assemble a functional pore.
Collapse
Affiliation(s)
- Sara García-Linares
- Departamento de Bioquímica y Biología Molecular I, Universidad Complutense , Madrid, Spain.,Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , Turku, Finland
| | - Terhi Maula
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , Turku, Finland
| | | | - José G Gavilanes
- Departamento de Bioquímica y Biología Molecular I, Universidad Complutense , Madrid, Spain
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , Turku, Finland
| | | |
Collapse
|
18
|
Rivera-de-Torre E, García-Linares S, Alegre-Cebollada J, Lacadena J, Gavilanes JG, Martínez-Del-Pozo Á. Synergistic Action of Actinoporin Isoforms from the Same Sea Anemone Species Assembled into Functionally Active Heteropores. J Biol Chem 2016; 291:14109-14119. [PMID: 27129251 DOI: 10.1074/jbc.m115.710491] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Indexed: 11/06/2022] Open
Abstract
Among the toxic polypeptides secreted in the venom of sea anemones, actinoporins are the pore-forming toxins whose toxic activity relies on the formation of oligomeric pores within biological membranes. Intriguingly, actinoporins appear as multigene families that give rise to many protein isoforms in the same individual displaying high sequence identities but large functional differences. However, the evolutionary advantage of producing such similar isotoxins is not fully understood. Here, using sticholysins I and II (StnI and StnII) from the sea anemone Stichodactyla helianthus, it is shown that actinoporin isoforms can potentiate each other's activity. Through hemolysis and calcein releasing assays, it is revealed that mixtures of StnI and StnII are more lytic than equivalent preparations of the corresponding isolated isoforms. It is then proposed that this synergy is due to the assembly of heteropores because (i) StnI and StnII can be chemically cross-linked at the membrane and (ii) the affinity of sticholysin mixtures for the membrane is increased with respect to any of them acting in isolation, as revealed by isothermal titration calorimetry experiments. These results help us understand the multigene nature of actinoporins and may be extended to other families of toxins that require oligomerization to exert toxicity.
Collapse
Affiliation(s)
- Esperanza Rivera-de-Torre
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid
| | - Sara García-Linares
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid
| | | | - Javier Lacadena
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid
| | - José G Gavilanes
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid.
| | - Álvaro Martínez-Del-Pozo
- Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid.
| |
Collapse
|
19
|
Weber DK, Yao S, Rojko N, Anderluh G, Lybrand TP, Downton MT, Wagner J, Separovic F. Characterization of the Lipid-Binding Site of Equinatoxin II by NMR and Molecular Dynamics Simulation. Biophys J 2016; 108:1987-96. [PMID: 25902438 DOI: 10.1016/j.bpj.2015.03.024] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 03/09/2015] [Accepted: 03/12/2015] [Indexed: 12/26/2022] Open
Abstract
Equinatoxin II (EqtII) is a soluble, 20 kDa pore-forming protein toxin isolated from the sea anemone Actinia equina. Although pore formation has long been known to occur in distinct stages, including monomeric attachment to phospholipid membranes followed by detachment of the N-terminal helical domain and oligomerization into the final pore assembly, atomistic-level detail of the protein-lipid interactions underlying these events remains elusive. Using high-resolution solution state NMR of uniformly-(15)N-labeled EqtII at the critical micelle concentration of dodecylphosphocholine, we have mapped the lipid-binding site through chemical shift perturbations. Subsequent docking of an EqtII monomer onto a dodecylphosphocholine micelle, followed by 400 ns of all-atom molecular dynamics simulation, saw several high-occupancy lipid-binding pockets stabilized by cation-π, hydrogen bonding, and hydrophobic interactions; and stabilization of the loop housing the conserved arginine-glycine-aspartate motif. Additional simulation of EqtII with an N-acetyl sphingomyelin micelle, for which high-resolution NMR data cannot be obtained due to aggregate formation, revealed that sphingomyelin specificity might occur via hydrogen bonding to the 3-OH and 2-NH groups unique to the ceramide backbone by side chains of D109 and Y113; and main chains of P81 and W112. Furthermore, a binding pocket formed by K30, K77, and P81, proximate to the hinge region of the N-terminal helix, was identified and may be implicated in triggering pore formation.
Collapse
Affiliation(s)
- Daniel K Weber
- School of Chemistry, University of Melbourne, Victoria, Australia; Bio21 Institute, University of Melbourne, Victoria, Australia
| | - Shenggen Yao
- Bio21 Institute, University of Melbourne, Victoria, Australia
| | - Nejc Rojko
- Laboratory for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Ljubljana, Slovenia
| | - Gregor Anderluh
- Laboratory for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Ljubljana, Slovenia
| | - Terry P Lybrand
- Center for Structural Biology, Department of Chemistry, Vanderbilt University, Nashville, Tennessee
| | - Matthew T Downton
- IBM Research Collaboratory for Life Sciences, Victorian Life Sciences Computation Initiative, University of Melbourne, Victoria, Australia
| | - John Wagner
- IBM Research Collaboratory for Life Sciences, Victorian Life Sciences Computation Initiative, University of Melbourne, Victoria, Australia
| | - Frances Separovic
- School of Chemistry, University of Melbourne, Victoria, Australia; Bio21 Institute, University of Melbourne, Victoria, Australia.
| |
Collapse
|
20
|
Rojko N, Dalla Serra M, Maček P, Anderluh G. Pore formation by actinoporins, cytolysins from sea anemones. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:446-56. [PMID: 26351738 DOI: 10.1016/j.bbamem.2015.09.007] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 08/31/2015] [Accepted: 09/02/2015] [Indexed: 11/30/2022]
Abstract
Actinoporins (APs) from sea anemones are ~20 kDa pore forming toxins with a β-sandwich structure flanked by two α-helices. The molecular mechanism of APs pore formation is composed of several well-defined steps. APs bind to membrane by interfacial binding site composed of several aromatic amino acid residues that allow binding to phosphatidylcholine and specific recognition of sphingomyelin. Subsequently, the N-terminal α-helix from the β-sandwich has to be inserted into the lipid/water interphase in order to form a functional pore. Functional studies and single molecule imaging revealed that only several monomers, 3-4, oligomerise to form a functional pore. In this model the α-helices and surrounding lipid molecules build toroidal pore. In agreement, AP pores are transient and electrically heterogeneous. On the contrary, crystallized oligomers of actinoporin fragaceatoxin C were found to be composed of eight monomers with no lipids present between the adjacent α-helices. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Maur Dalla Serra and Franco Gambale.
Collapse
Affiliation(s)
- Nejc Rojko
- Laboratory for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia
| | - Mauro Dalla Serra
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche & Fondazione Bruno Kessler, via alla Cascata 56/C, 38123 Trento, Italy
| | - Peter Maček
- Department of Biology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia
| | - Gregor Anderluh
- Laboratory for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia; Department of Biology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia.
| |
Collapse
|
21
|
Ros U, Rodríguez-Vera W, Pedrera L, Valiente PA, Cabezas S, Lanio ME, García-Sáez AJ, Alvarez C. Differences in activity of actinoporins are related with the hydrophobicity of their N-terminus. Biochimie 2015; 116:70-8. [DOI: 10.1016/j.biochi.2015.06.024] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Accepted: 06/25/2015] [Indexed: 10/23/2022]
|
22
|
The effect of cholesterol on the long-range network of interactions established among sea anemone Sticholysin II residues at the water-membrane interface. Mar Drugs 2015; 13:1647-65. [PMID: 25815890 PMCID: PMC4413179 DOI: 10.3390/md13041647] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 03/03/2015] [Accepted: 03/16/2015] [Indexed: 12/21/2022] Open
Abstract
Actinoporins are α-pore forming proteins with therapeutic potential, produced by sea anemones. Sticholysin II (StnII) from Stichodactyla helianthus is one of its most extensively characterized members. These proteins remain stably folded in water, but upon interaction with lipid bilayers, they oligomerize to form a pore. This event is triggered by the presence of sphingomyelin (SM), but cholesterol (Chol) facilitates pore formation. Membrane attachment and pore formation require changes involving long-distance rearrangements of residues located at the protein-membrane interface. The influence of Chol on membrane recognition, oligomerization, and/or pore formation is now studied using StnII variants, which are characterized in terms of their ability to interact with model membranes in the presence or absence of Chol. The results obtained frame Chol not only as an important partner for SM for functional membrane recognition but also as a molecule which significantly reduces the structural requirements for the mentioned conformational rearrangements to occur. However, given that the DOPC:SM:Chol vesicles employed display phase coexistence and have domain boundaries, the observed effects could be also due to the presence of these different phases on the membrane. In addition, it is also shown that the Arg51 guanidinium group is strictly required for membrane recognition, independently of the presence of Chol.
Collapse
|
23
|
Antonini V, Pérez-Barzaga V, Bampi S, Pentón D, Martínez D, Serra MD, Tejuca M. Functional characterization of sticholysin I and W111C mutant reveals the sequence of the actinoporin's pore assembly. PLoS One 2014; 9:e110824. [PMID: 25350457 PMCID: PMC4211696 DOI: 10.1371/journal.pone.0110824] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Accepted: 09/19/2014] [Indexed: 12/20/2022] Open
Abstract
The use of pore-forming toxins in the construction of immunotoxins against tumour cells is an alternative for cancer therapy. In this protein family one of the most potent toxins are the actinoporins, cytolysins from sea anemones. We work on the construction of tumour proteinase-activated immunotoxins using sticholysin I (StI), an actinoporin isolated from the sea anemone Stichodactyla helianthus. To accomplish this objective, recombinant StI (StIr) with a mutation in the membrane binding region has been employed. In this work, it was evaluated the impact of mutating tryptophan 111 to cysteine on the toxin pore forming capability. StI W111C is still able to permeabilize erythrocytes and liposomes, but at ten-fold higher concentration than StI. This is due to its lower affinity for the membrane, which corroborates the importance of residue 111 for the binding of actinoporins to the lipid bilayer. In agreement, other functional characteristics not directly associated to the binding, are essentially the same for both variants, that is, pores have oligomeric structures with similar radii, conductance, cation-selectivity, and instantaneous current-voltage behavior. In addition, this work provides experimental evidence sustaining the toroidal protein-lipid actinoporins lytic structures, since the toxins provoke the trans-bilayer movement (flip-flop) of a pyrene-labeled analogue of phosphatidylcholine in liposomes, indicating the existence of continuity between the outer and the inner membrane leaflet. Finally, our planar lipid membranes results have also contributed to a better understanding of the actinoporin's pore assembly mechanism. After the toxin binding and the N-terminal insertion in the lipid membrane, the pore assembly occurs by passing through different transient sub-conductance states. These states, usually 3 or 4, are due to the successive incorporation of N-terminal α-helices and lipid heads to the growing pores until a stable toroidal oligomeric structure is formed, which is mainly tetrameric.
Collapse
Affiliation(s)
- Valeria Antonini
- National Research Council of Italy - Institute of Biophysics and Bruno Kessler Foundation, Trento, Italy
| | - Victor Pérez-Barzaga
- Center for Protein Studies, Faculty of Biology, University of Havana, Vedado, Ciudad de La Habana, Cuba
| | - Silvia Bampi
- National Research Council of Italy - Institute of Biophysics and Bruno Kessler Foundation, Trento, Italy
| | - David Pentón
- Center for Protein Studies, Faculty of Biology, University of Havana, Vedado, Ciudad de La Habana, Cuba
| | - Diana Martínez
- Center for Protein Studies, Faculty of Biology, University of Havana, Vedado, Ciudad de La Habana, Cuba
| | - Mauro Dalla Serra
- National Research Council of Italy - Institute of Biophysics and Bruno Kessler Foundation, Trento, Italy
- * E-mail: (MDS); (MT)
| | - Mayra Tejuca
- Center for Protein Studies, Faculty of Biology, University of Havana, Vedado, Ciudad de La Habana, Cuba
- * E-mail: (MDS); (MT)
| |
Collapse
|
24
|
del Monte-Martínez A, González-Bacerio J, Romero L, Aragón C, Martínez D, Chávez MDLÁ, Álvarez C, Lanio ME, Guisán JM, Díaz J. Improved purification and enzymatic properties of a mixture of Sticholysin I and II: Isotoxins with hemolytic and phospholipase A2 activities from the sea anemone Stichodactyla helianthus. Protein Expr Purif 2014; 95:57-66. [DOI: 10.1016/j.pep.2013.11.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Revised: 11/27/2013] [Accepted: 11/29/2013] [Indexed: 11/28/2022]
|
25
|
García-Linares S, Richmond R, García-Mayoral MF, Bustamante N, Bruix M, Gavilanes JG, Martínez-del-Pozo Á. The sea anemone actinoporin (Arg-Gly-Asp) conserved motif is involved in maintaining the competent oligomerization state of these pore-forming toxins. FEBS J 2014; 281:1465-1478. [DOI: 10.1111/febs.12717] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 12/12/2013] [Accepted: 12/31/2013] [Indexed: 01/19/2023]
Affiliation(s)
- Sara García-Linares
- Departamento de Bioquímica y Biología Molecular I; Facultad de Ciencias Químicas; Universidad Complutense; Madrid Spain
| | - Ryan Richmond
- Departamento de Bioquímica y Biología Molecular I; Facultad de Ciencias Químicas; Universidad Complutense; Madrid Spain
| | | | | | - Marta Bruix
- Instituto de Química-Física Rocasolano; Madrid Spain
| | - José G. Gavilanes
- Departamento de Bioquímica y Biología Molecular I; Facultad de Ciencias Químicas; Universidad Complutense; Madrid Spain
| | - Álvaro Martínez-del-Pozo
- Departamento de Bioquímica y Biología Molecular I; Facultad de Ciencias Químicas; Universidad Complutense; Madrid Spain
| |
Collapse
|
26
|
López-Castilla A, Pazos F, Schreier S, Pires JR. Solution NMR analysis of the interaction between the actinoporin sticholysin I and DHPC micelles--correlation with backbone dynamics. Proteins 2013; 82:1022-34. [PMID: 24218049 DOI: 10.1002/prot.24475] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 10/26/2013] [Accepted: 11/04/2013] [Indexed: 11/08/2022]
Abstract
Sticholysin I (StI), an actinoporin expressed as a water-soluble protein by the sea anemone Stichodactyla helianthus, binds to natural and model membranes, forming oligomeric pores. It is proposed that the first event of a multistep pore formation mechanism consists of the monomeric protein attachment to the lipid bilayer. To date there is no high-resolution structure of the actinoporin pore or other membrane-bound form available. Here we evaluated StI:micelle complexes of variable lipid composition to look for a suitable model for NMR studies. Micelles of pure or mixed lysophospholipids and of dihexanoyl phosphatidylcholine (DHPC) were examined. The StI:DHPC micelle was found to be the best system, yielding a stable sample and good quality spectra. A comprehensive chemical shift perturbation analysis was performed to map the StI membrane recognition site in the presence of DHPC micelles. The region mapped (residues F(51), R(52), S(53) in loop 3; F(107), D(108), Y(109), W(111), Y(112), W(115) in loop 7; Q(129), Y(132), D(134), M(135), Y(136), Y(137), G(138) in helix-α2) is in agreement with previously reported data, but additional residues were found to interact, especially residues V(81), A(82), T(83), G(84) in loop 5, and A(85), A(87) in strand-β5. Backbone dynamics measurements of StI free in solution and bound to micelles highlighted the relevance of protein flexibility for membrane binding and suggested that a conformer selection process may take place during protein-membrane interaction. We conclude that the StI:DHPC micelles system is a suitable model for further characterization of an actinoporin membrane-bound form by solution NMR.
Collapse
Affiliation(s)
- Aracelys López-Castilla
- Centro de Estudio de Proteinas, Facultad de Biologia, Universidad de la Habana, Habana, Cuba; Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, RJ, Brazil
| | | | | | | |
Collapse
|
27
|
Ros U, Edwards MA, Epand RF, Lanio ME, Schreier S, Yip CM, Alvarez C, Epand RM. The sticholysin family of pore-forming toxins induces the mixing of lipids in membrane domains. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:2757-62. [DOI: 10.1016/j.bbamem.2013.08.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 07/30/2013] [Accepted: 08/02/2013] [Indexed: 11/17/2022]
|
28
|
Ros U, Souto ALCF, de Oliveira FJ, Crusca E, Pazos F, Cilli EM, Lanio ME, Schreier S, Alvarez C. Functional and topological studies with Trp-containing analogs of the peptide StII1-30derived from the N-terminus of the pore forming toxin sticholysin II: contribution to understand its orientation in membrane. Biopolymers 2013; 100:337-46. [DOI: 10.1002/bip.22211] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 12/14/2012] [Accepted: 01/14/2013] [Indexed: 11/10/2022]
Affiliation(s)
- Uris Ros
- Center for Protein Studies; Biology Faculty; University of Havana (UH); Havana; Cuba
| | - Ana Lucia C. F. Souto
- Department of Biochemistry; Institute of Chemistry; University of São Paulo (USP); São Paulo; Brazil
| | - Felipe J. de Oliveira
- Department of Biochemistry; Institute of Chemistry; University of São Paulo (USP); São Paulo; Brazil
| | - Edson Crusca
- Department of Biochemistry and Chemical Technology; Institute of Chemistry; São Paulo State University (UNESP); Araraquara; São Paulo; Brazil
| | - Fabiola Pazos
- Center for Protein Studies; Biology Faculty; University of Havana (UH); Havana; Cuba
| | - Eduardo M. Cilli
- Department of Biochemistry and Chemical Technology; Institute of Chemistry; São Paulo State University (UNESP); Araraquara; São Paulo; Brazil
| | - Maria E. Lanio
- Center for Protein Studies; Biology Faculty; University of Havana (UH); Havana; Cuba
| | - Shirley Schreier
- Department of Biochemistry; Institute of Chemistry; University of São Paulo (USP); São Paulo; Brazil
| | - Carlos Alvarez
- Center for Protein Studies; Biology Faculty; University of Havana (UH); Havana; Cuba
| |
Collapse
|
29
|
Rojko N, Kristan KČ, Viero G, Žerovnik E, Maček P, Dalla Serra M, Anderluh G. Membrane damage by an α-helical pore-forming protein, Equinatoxin II, proceeds through a succession of ordered steps. J Biol Chem 2013; 288:23704-15. [PMID: 23803608 DOI: 10.1074/jbc.m113.481572] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Actinoporin equinatoxin II (EqtII) is an archetypal example of α-helical pore-forming toxins that porate cellular membranes by the use of α-helices. Previous studies proposed several steps in the pore formation: binding of monomeric protein onto the membrane, followed by oligomerization and insertion of the N-terminal α-helix into the lipid bilayer. We studied these separate steps with an EqtII triple cysteine mutant. The mutant was engineered to monitor the insertion of the N terminus into the lipid bilayer by labeling Cys-18 with a fluorescence probe and at the same time to control the flexibility of the N-terminal region by the disulfide bond formed between cysteines introduced at positions 8 and 69. The insertion of the N terminus into the membrane proceeded shortly after the toxin binding and was followed by oligomerization. The oxidized, non-lytic, form of the mutant was still able to bind to membranes and oligomerize at the same level as the wild-type or the reduced form. However, the kinetics of the N-terminal helix insertion, the release of calcein from erythrocyte ghosts, and hemolysis of erythrocytes was much slower when membrane-bound oxidized mutant was reduced by the addition of the reductant. Results show that the N-terminal region needs to be inserted in the lipid membrane before the oligomerization into the final pore and imply that there is no need for a stable prepore formation. This is different from β-pore-forming toxins that often form β-barrel pores via a stable prepore complex.
Collapse
Affiliation(s)
- Nejc Rojko
- Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, 1000 Ljubljana, Slovenia
| | | | | | | | | | | | | |
Collapse
|
30
|
García-Linares S, Castrillo I, Bruix M, Menéndez M, Alegre-Cebollada J, Martínez-del-Pozo Á, Gavilanes JG. Three-dimensional structure of the actinoporin sticholysin I. Influence of long-distance effects on protein function. Arch Biochem Biophys 2013; 532:39-45. [PMID: 23376038 DOI: 10.1016/j.abb.2013.01.005] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Revised: 01/18/2013] [Accepted: 01/19/2013] [Indexed: 10/27/2022]
Abstract
Actinoporins are water-soluble proteins with the ability to form pores upon insertion into biological membranes. They constitute a family of proteins with high degree of sequence identities but different hemolytic activities, suggesting that minor conformational arrangements result in major functional changes. A good example of this situation is the sea anemone Stichodactyla helianthus which produces two very similar actinoporins, sticholysins I (StnI) and II (StnII), but of very different hemolytic efficiency. Within this idea, given that the high resolution three-dimensional structure of StnII is already known, we have now solved that one corresponding to StnI in order to analyze the influence of particular residues on the conformation and activity of these proteins. In addition, random mutagenesis has been also used to produce five less hemolytic variants of StnI. All these mutations map to functionally relevant regions because they are probably involved in conformational changes associated with pore formation, which take place after membrane binding, and involve long-distance rearrangements of the polypeptide chain of actinoporins.
Collapse
Affiliation(s)
- Sara García-Linares
- Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid, Spain
| | | | | | | | | | | | | |
Collapse
|
31
|
Garcia PS, Chieppa G, Desideri A, Cannata S, Romano E, Luly P, Rufini S. Sticholysin II: A pore-forming toxin as a probe to recognize sphingomyelin in artificial and cellular membranes. Toxicon 2012; 60:724-33. [DOI: 10.1016/j.toxicon.2012.05.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Revised: 02/11/2012] [Accepted: 05/24/2012] [Indexed: 12/31/2022]
|
32
|
García-Ortega L, Alegre-Cebollada J, García-Linares S, Bruix M, Martínez-Del-Pozo A, Gavilanes JG. The behavior of sea anemone actinoporins at the water-membrane interface. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2275-88. [PMID: 21621507 DOI: 10.1016/j.bbamem.2011.05.012] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 05/10/2011] [Accepted: 05/11/2011] [Indexed: 01/13/2023]
Abstract
Actinoporins constitute a group of small and basic α-pore forming toxins produced by sea anemones. They display high sequence identity and appear as multigene families. They show a singular behaviour at the water-membrane interface: In aqueous solution, actinoporins remain stably folded but, upon interaction with lipid bilayers, become integral membrane structures. These membranes contain sphingomyelin, display phase coexistence, or both. The water soluble structures of the actinoporins equinatoxin II (EqtII) and sticholysin II (StnII) are known in detail. The crystalline structure of a fragaceatoxin C (FraC) nonamer has been also determined. The three proteins fold as a β-sandwich motif flanked by two α-helices, one of them at the N-terminal end. Four regions seem to be especially important: A cluster of aromatic residues, a phosphocholine binding site, an array of basic amino acids, and the N-terminal α-helix. Initial binding of the soluble monomers to the membrane is accomplished by the cluster of aromatic amino acids, the array of basic residues, and the phosphocholine binding site. Then, the N-terminal α-helix detaches from the β-sandwich, extends, and lies parallel to the membrane. Simultaneously, oligomerization occurs. Finally, the extended N-terminal α-helix penetrates the membrane to build a toroidal pore. This model has been however recently challenged by the cryo-EM reconstruction of FraC bound to phospholipid vesicles. Actinoporins structural fold appears across all eukaryotic kingdoms in other functionally unrelated proteins. Many of these proteins neither bind to lipid membranes nor induce cell lysis. Finally, studies focusing on the therapeutic potential of actinoporins also abound.
Collapse
Affiliation(s)
- Lucía García-Ortega
- Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid, Spain
| | | | | | | | | | | |
Collapse
|
33
|
Pardo-Cea MA, Castrillo I, Alegre-Cebollada J, Martínez-del-Pozo Á, Gavilanes JG, Bruix M. Intrinsic local disorder and a network of charge-charge interactions are key to actinoporin membrane disruption and cytotoxicity. FEBS J 2011; 278:2080-9. [DOI: 10.1111/j.1742-4658.2011.08123.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|