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Gupta LK, Molla J, Prabhu AA. Story of Pore-Forming Proteins from Deadly Disease-Causing Agents to Modern Applications with Evolutionary Significance. Mol Biotechnol 2024; 66:1327-1356. [PMID: 37294530 DOI: 10.1007/s12033-023-00776-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Accepted: 05/21/2023] [Indexed: 06/10/2023]
Abstract
Animal venoms are a complex mixture of highly specialized toxic molecules. Among them, pore-forming proteins (PFPs) or toxins (PFTs) are one of the major disease-causing toxic elements. The ability of the PFPs in defense and toxicity through pore formation on the host cell surface makes them unique among the toxin proteins. These features made them attractive for academic and research purposes for years in the areas of microbiology as well as structural biology. All the PFPs share a common mechanism of action for the attack of host cells and pore formation in which the selected pore-forming motifs of the host cell membrane-bound protein molecules drive to the lipid bilayer of the cell membrane and eventually produces water-filled pores. But surprisingly their sequence similarity is very poor. Their existence can be seen both in a soluble state and also in transmembrane complexes in the cell membrane. PFPs are prevalent toxic factors that are predominately produced by all kingdoms of life such as virulence bacteria, nematodes, fungi, protozoan parasites, frogs, plants, and also from higher organisms. Nowadays, multiple approaches to applications of PFPs have been conducted by researchers both in basic as well as applied biological research. Although PFPs are very devastating for human health nowadays researchers have been successful in making these toxic proteins into therapeutics through the preparation of immunotoxins. We have discussed the structural, and functional mechanism of action, evolutionary significance through dendrogram, domain organization, and practical applications for various approaches. This review aims to emphasize the PFTs to summarize toxic proteins together for basic knowledge as well as to highlight the current challenges, and literature gap along with the perspective of promising biotechnological applications for their future research.
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Affiliation(s)
- Laxmi Kumari Gupta
- Bioprocess Development Laboratory, Department of Biotechnology, National Institute of Technology Warangal, Warangal, Telangana, 506004, India
| | - Johiruddin Molla
- Ghatal Rabindra Satabarsiki Mahavidyalaya Ghatal, Paschim Medinipur, Ghatal, West Bengal, 721212, India
| | - Ashish A Prabhu
- Bioprocess Development Laboratory, Department of Biotechnology, National Institute of Technology Warangal, Warangal, Telangana, 506004, India.
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Ahmed AF, Dai CF, Kuo YH, Sheu JH. The Invasive Anemone Condylactis sp. of the Coral Reef as a Source of Sulfur- and Nitrogen-Containing Metabolites and Cytotoxic 5,8-Epidioxy Steroids. Metabolites 2023; 13:metabo13030392. [PMID: 36984832 PMCID: PMC10056678 DOI: 10.3390/metabo13030392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 03/03/2023] [Accepted: 03/06/2023] [Indexed: 03/10/2023] Open
Abstract
The Condylactis-genus anemones were examined for their proteinaceous poisons over 50 years ago. On the other hand, the current research focuses on isolating and describing the non-proteinaceous secondary metabolites from the invasive Condylactis anemones, which help take advantage of their population outbreak as a new source of chemical candidates and potential drug leads. From an organic extract of Condylactis sp., a 1,2,4-thiadiazole-based alkaloid, identified as 3,5-bis(3-pyridinyl)-1,2,4-thiadiazole (1), was found to be a new natural alkaloid despite being previously synthesized. The full assignment of NMR data of compound 1, based on the analysis of 2D NMR correlations, is reported herein for the first time. The proposed biosynthetic precursor thionicotinamide (2) was also isolated for the first time from nature along with nicotinamide (3), uridine (5), hypoxanthine (6), and four 5,8-epidioxysteroids (7–10). A major secondary metabolite (−)-betonicine (4) was isolated from Condylactis sp. and found for the first time in marine invertebrates. The four 5,8-epidioxysteroids, among other metabolites, exhibited cytotoxicity (IC50 3.5–9.0 μg/mL) toward five cancer cell lines.
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Affiliation(s)
- Atallah F. Ahmed
- Department of Marine Resources, National Sun Yat-sen University, Kaohsiung 804, Taiwan
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia
- Department of Pharmacognosy, Faculty of Pharmacy, Mansoura University, Mansoura 35516, Egypt
| | - Chang-Feng Dai
- Institute of Oceanography, National Taiwan University, Taipei 106, Taiwan
| | - Yao-Haur Kuo
- Division of Herbal Drugs and Natural Products, National Research Institute of Chinese Medicine, Taipei 112, Taiwan
| | - Jyh-Horng Sheu
- Department of Marine Resources, National Sun Yat-sen University, Kaohsiung 804, Taiwan
- Institute of Natural Products, Kaohsiung Medical University, Kaohsiung 807, Taiwan
- Department of Medical Research, China Medical University Hospital, China Medical University, Taichung 404, Taiwan
- Frontier Center for Ocean Science and Technology, National Sun Yat-sen University, Kaohsiung 804, Taiwan
- Doctoral Degree Program in Marine Biotechnology, National Sun Yat-sen University, Kaohsiung 804, Taiwan
- Correspondence: ; Tel.: +88-(67)-5252000 (ext. 5030)
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Efremenko E, Aslanli A, Lyagin I. Advanced Situation with Recombinant Toxins: Diversity, Production and Application Purposes. Int J Mol Sci 2023; 24:ijms24054630. [PMID: 36902061 PMCID: PMC10003545 DOI: 10.3390/ijms24054630] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 02/14/2023] [Accepted: 02/20/2023] [Indexed: 03/04/2023] Open
Abstract
Today, the production and use of various samples of recombinant protein/polypeptide toxins is known and is actively developing. This review presents state-of-the-art in research and development of such toxins and their mechanisms of action and useful properties that have allowed them to be implemented into practice to treat various medical conditions (including oncology and chronic inflammation applications) and diseases, as well as to identify novel compounds and to detoxify them by diverse approaches (including enzyme antidotes). Special attention is given to the problems and possibilities of the toxicity control of the obtained recombinant proteins. The recombinant prions are discussed in the frame of their possible detoxification by enzymes. The review discusses the feasibility of obtaining recombinant variants of toxins in the form of protein molecules modified with fluorescent proteins, affine sequences and genetic mutations, allowing us to investigate the mechanisms of toxins' bindings to their natural receptors.
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Affiliation(s)
- Elena Efremenko
- Correspondence: ; Tel.: +7-(495)-939-3170; Fax: +7-(495)-939-5417
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Monastyrnaya MM, Kalina RS, Kozlovskaya EP. The Sea Anemone Neurotoxins Modulating Sodium Channels: An Insight at Structure and Functional Activity after Four Decades of Investigation. Toxins (Basel) 2022; 15:toxins15010008. [PMID: 36668828 PMCID: PMC9863223 DOI: 10.3390/toxins15010008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 12/13/2022] [Accepted: 12/15/2022] [Indexed: 12/24/2022] Open
Abstract
Many human cardiovascular and neurological disorders (such as ischemia, epileptic seizures, traumatic brain injury, neuropathic pain, etc.) are associated with the abnormal functional activity of voltage-gated sodium channels (VGSCs/NaVs). Many natural toxins, including the sea anemone toxins (called neurotoxins), are an indispensable and promising tool in pharmacological researches. They have widely been carried out over the past three decades, in particular, in establishing different NaV subtypes functional properties and a specific role in various pathologies. Therefore, a large number of publications are currently dedicated to the search and study of the structure-functional relationships of new sea anemone natural neurotoxins-potential pharmacologically active compounds that specifically interact with various subtypes of voltage gated sodium channels as drug discovery targets. This review presents and summarizes some updated data on the structure-functional relationships of known sea anemone neurotoxins belonging to four structural types. The review also emphasizes the study of type 2 neurotoxins, produced by the tropical sea anemone Heteractis crispa, five structurally homologous and one unique double-stranded peptide that, due to the absence of a functionally significant Arg14 residue, loses toxicity but retains the ability to modulate several VGSCs subtypes.
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Pinheiro-Junior EL, Kalina R, Gladkikh I, Leychenko E, Tytgat J, Peigneur S. A Tale of Toxin Promiscuity: The Versatile Pharmacological Effects of Hcr 1b-2 Sea Anemone Peptide on Voltage-Gated Ion Channels. Mar Drugs 2022; 20:md20020147. [PMID: 35200676 PMCID: PMC8878452 DOI: 10.3390/md20020147] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 02/10/2022] [Accepted: 02/14/2022] [Indexed: 12/29/2022] Open
Abstract
Sea anemones are a rich source of biologically active compounds. Among approximately 1100 species described so far, Heteractis crispa species, also known as sebae anemone, is native to the Indo-Pacific area. As part of its venom components, the Hcr 1b-2 peptide was first described as an ASIC1a and ASIC3 inhibitor. Using Xenopus laevis oocytes and the two-electrode voltage-clamp technique, in the present work we describe the remarkable lack of selectivity of this toxin. Besides the acid-sensing ion channels previously described, we identified 26 new targets of this peptide, comprising 14 voltage-gated potassium channels, 9 voltage-gated sodium channels, and 3 voltage-gated calcium channels. Among them, Hcr 1b-2 is the first sea anemone peptide described to interact with isoforms from the Kv7 family and T-type Cav channels. Taken together, the diversity of Hcr 1b-2 targets turns this toxin into an interesting tool to study different types of ion channels, as well as a prototype to develop new and more specific ion channel ligands.
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Affiliation(s)
- Ernesto Lopes Pinheiro-Junior
- Toxicology and Pharmacology, KU Leuven, O&N II Herestraat 49, P.O. Box 922, 3000 Leuven, Belgium
- Correspondence: (E.L.P.-J.); (J.T.); (S.P.); Tel.: +32-16-32-34-04 (E.L.P.-J. & J.T. & S.P.)
| | - Rimma Kalina
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 690022 Vladivostok, Russia; (R.K.); (I.G.); (E.L.)
| | - Irina Gladkikh
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 690022 Vladivostok, Russia; (R.K.); (I.G.); (E.L.)
| | - Elena Leychenko
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 690022 Vladivostok, Russia; (R.K.); (I.G.); (E.L.)
| | - Jan Tytgat
- Toxicology and Pharmacology, KU Leuven, O&N II Herestraat 49, P.O. Box 922, 3000 Leuven, Belgium
- Correspondence: (E.L.P.-J.); (J.T.); (S.P.); Tel.: +32-16-32-34-04 (E.L.P.-J. & J.T. & S.P.)
| | - Steve Peigneur
- Toxicology and Pharmacology, KU Leuven, O&N II Herestraat 49, P.O. Box 922, 3000 Leuven, Belgium
- Correspondence: (E.L.P.-J.); (J.T.); (S.P.); Tel.: +32-16-32-34-04 (E.L.P.-J. & J.T. & S.P.)
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Deep-Sea Anemones Are Prospective Source of New Antimicrobial and Cytotoxic Compounds. Mar Drugs 2021; 19:md19120654. [PMID: 34940653 PMCID: PMC8704684 DOI: 10.3390/md19120654] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Revised: 11/18/2021] [Accepted: 11/22/2021] [Indexed: 12/16/2022] Open
Abstract
The peculiarities of the survival and adaptation of deep-sea organisms raise interest in the study of their metabolites as promising drugs. In this work, the hemolytic, cytotoxic, antimicrobial, and enzyme-inhibitory activities of tentacle extracts from five species of sea anemones (Cnidaria, orders Actiniaria and Corallimorpharia) collected near the Kuril and Commander Islands of the Far East of Russia were evaluated for the first time. The extracts of Liponema brevicorne and Actinostola callosa demonstrated maximal hemolytic activity, while high cytotoxic activity against murine splenocytes and Ehrlich carcinoma cells was found in the extract of Actinostola faeculenta. The extracts of Corallimorphus cf. pilatus demonstrated the greatest activity against Ehrlich carcinoma cells but were not toxic to mouse spleen cells. Sea anemones C. cf. pilatus and Stomphia coccinea are promising sources of antimicrobial and antifungal compounds, being active against Gram-positive bacteria Bacillus subtilis, Staphylococcus aureus, and yeast Candida albicans. Moreover, all sea anemones contain α-galactosidase inhibitors. Peptide mass fingerprinting of L. brevicorne and C. cf. pilatus extracts provided a wide range of peptides, predominantly with molecular masses of 4000–5900 Da, which may belong to a known or new structural class of toxins. The obtained data allow concluding that deep-sea anemones are a promising source of compounds for drug discovery.
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Kvetkina A, Malyarenko O, Pavlenko A, Dyshlovoy S, von Amsberg G, Ermakova S, Leychenko E. Sea Anemone Heteractis crispa Actinoporin Demonstrates In Vitro Anticancer Activities and Prevents HT-29 Colorectal Cancer Cell Migration. Molecules 2020; 25:molecules25245979. [PMID: 33348592 PMCID: PMC7766076 DOI: 10.3390/molecules25245979] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 12/14/2020] [Accepted: 12/15/2020] [Indexed: 02/07/2023] Open
Abstract
Actinoporins are the most abundant group of sea anemone cytolytic toxins. Their membranolytic activity is of high interest for the development of novel anticancer drugs. However, to date the activity of actinoporins in malignant cells has been poorly studied. Here, we report on recombinant analog of Hct-S3 (rHct-S3), belonging to the combinatory library of Heteractis crispa actinoporins. rHct-S3 exhibited cytotoxic activity against breast MDA-MB-231 (IC50 = 7.3 µM), colorectal HT-29 (IC50 = 6.8 µM), and melanoma SK-MEL-28 (IC50 = 8.3 µM) cancer cells. The actinoporin effectively prevented epidermal growth factor -induced neoplastic transformation of JB6 Cl41 cells by 34% ± 0.2 and decreased colony formation of HT-29 cells by 47% ± 0.9, MDA-MB-231 cells by 37% ± 1.2, and SK-MEL-28 cells by 34% ± 3.6. Moreover, rHct-S3 decreased proliferation and suppressed migration of colorectal carcinoma cells by 31% ± 5.0 and 99% ± 6.4, respectively. The potent anti-migratory activity was proposed to mediate by decreased matrix metalloproteinases-2 and -9 expression. In addition, rHct-S3 induced programmed cell death by cleavage of caspase-3 and poly (ADP-ribose) polymerase, as well as regulation of Bax and Bcl-2. Our results indicate rHct-S3 to be a promising anticancer drug with a high anti-migratory potential.
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Affiliation(s)
- Aleksandra Kvetkina
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia; (O.M.); (A.P.); (S.E.); (E.L.)
- Correspondence: ; Tel.: +7-423-231-1168
| | - Olesya Malyarenko
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia; (O.M.); (A.P.); (S.E.); (E.L.)
| | - Aleksandra Pavlenko
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia; (O.M.); (A.P.); (S.E.); (E.L.)
| | - Sergey Dyshlovoy
- Department of Oncology, Hematology and Bone Marrow Transplantation with Section Pneumology, Hubertus Wald-Tumorzentrum, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany; (S.D.); (G.v.A.)
- Martini-Klinik, Prostate Cancer Center, University Hospital Hamburg-Eppendorf, 20251 Hamburg, Germany
- School of Natural Sciences, Far Eastern Federal University, Vladivostok 690922, Russia
| | - Gunhild von Amsberg
- Department of Oncology, Hematology and Bone Marrow Transplantation with Section Pneumology, Hubertus Wald-Tumorzentrum, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany; (S.D.); (G.v.A.)
- Martini-Klinik, Prostate Cancer Center, University Hospital Hamburg-Eppendorf, 20251 Hamburg, Germany
| | - Svetlana Ermakova
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia; (O.M.); (A.P.); (S.E.); (E.L.)
| | - Elena Leychenko
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia; (O.M.); (A.P.); (S.E.); (E.L.)
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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.
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Evaluation of different approaches used to study membrane permeabilization by actinoporins on model lipid vesicles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183311. [DOI: 10.1016/j.bbamem.2020.183311] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Revised: 03/12/2020] [Accepted: 04/13/2020] [Indexed: 02/01/2023]
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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.
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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.
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Ramírez-Carreto S, Miranda-Zaragoza B, Rodríguez-Almazán C. Actinoporins: From the Structure and Function to the Generation of Biotechnological and Therapeutic Tools. Biomolecules 2020; 10:E539. [PMID: 32252469 PMCID: PMC7226409 DOI: 10.3390/biom10040539] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 03/19/2020] [Accepted: 03/21/2020] [Indexed: 12/22/2022] Open
Abstract
Actinoporins (APs) are a family of pore-forming toxins (PFTs) from sea anemones. These biomolecules exhibit the ability to exist as soluble monomers within an aqueous medium or as constitutively open oligomers in biological membranes. Through their conformational plasticity, actinoporins are considered good candidate molecules to be included for the rational design of molecular tools, such as immunotoxins directed against tumor cells and stochastic biosensors based on nanopores to analyze unique DNA or protein molecules. Additionally, the ability of these proteins to bind to sphingomyelin (SM) facilitates their use for the design of molecular probes to identify SM in the cells. The immunomodulatory activity of actinoporins in liposomal formulations for vaccine development has also been evaluated. In this review, we describe the potential of actinoporins for use in the development of molecular tools that could be used for possible medical and biotechnological applications.
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Affiliation(s)
| | | | - Claudia Rodríguez-Almazán
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Avenida Universidad 2001, Cuernavaca, Morelos 62210, Mexico; (S.R.-C.); (B.M.-Z.)
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12
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Kvetkina A, Leychenko E, Chausova V, Zelepuga E, Chernysheva N, Guzev K, Pislyagin E, Yurchenko E, Menchinskaya E, Aminin D, Kaluzhskiy L, Ivanov A, Peigneur S, Tytgat J, Kozlovskaya E, Isaeva M. A new multigene HCIQ subfamily from the sea anemone Heteractis crispa encodes Kunitz-peptides exhibiting neuroprotective activity against 6-hydroxydopamine. Sci Rep 2020; 10:4205. [PMID: 32144281 PMCID: PMC7060258 DOI: 10.1038/s41598-020-61034-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 02/04/2020] [Indexed: 12/14/2022] Open
Abstract
The Kunitz/BPTI-type peptides are ubiquitous in numerous organisms including marine venomous animals. The peptides demonstrate various biological activities and therefore they are the subject of a number of investigations. We have discovered a new HCIQ subfamily belonging to recently described multigene HCGS family of Heteractis crispa Kunitz-peptides. The uniqueness of this subfamily is that the HCIQ precursors contain a propeptide terminating in Lys-Arg (endopeptidase cleavage site) the same as in the neuro- and cytotoxin ones. Moreover, the HCIQ genes contain two introns in contrast to HCGS genes with one intron. As a result of Sanger and amplicon deep sequencings, 24 HCIQ isoforms were revealed. The recombinant peptides for the most prevalent isoform (HCIQ2c1) and for the isoform with the rare substitution Gly17Glu (HCIQ4c7) were obtained. They can inhibit trypsin with Ki 5.2 × 10-8 M and Ki 1.9 × 10-7 M, respectively, and interact with some serine proteinases including inflammatory ones according to the SPR method. For the first time, Kunitz-peptides have shown to significantly increase neuroblastoma cell viability in an in vitro 6-OHDA-induced neurotoxicity model being a consequence of an effective decrease of ROS level in the cells.
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Affiliation(s)
- Aleksandra Kvetkina
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok, 690022, Russia
| | - Elena Leychenko
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok, 690022, Russia.
| | - Victoria Chausova
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok, 690022, Russia
| | - Elena Zelepuga
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok, 690022, Russia
| | - Nadezhda Chernysheva
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok, 690022, Russia
| | - Konstantin Guzev
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok, 690022, Russia
| | - Evgeny Pislyagin
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok, 690022, Russia
| | - Ekaterina Yurchenko
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok, 690022, Russia
| | - Ekaterina Menchinskaya
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok, 690022, Russia
| | - Dmitry Aminin
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok, 690022, Russia
- Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, 100, Shih-Chuan 1st Road, Kaohsiung, 80708, Taiwan
| | - Leonid Kaluzhskiy
- V.N. Orekhovich Institute of Biomedical Chemistry, 10, Pogodinskaya St., Moscow, 119121, Russia
| | - Alexis Ivanov
- V.N. Orekhovich Institute of Biomedical Chemistry, 10, Pogodinskaya St., Moscow, 119121, Russia
| | - Steve Peigneur
- Toxicology and Pharmacology, University of Leuven (KU Leuven), Campus Gasthuisberg, O&N2, Herestraat 49, P.O. Box 922, Leuven, B-3000, Belgium
| | - Jan Tytgat
- Toxicology and Pharmacology, University of Leuven (KU Leuven), Campus Gasthuisberg, O&N2, Herestraat 49, P.O. Box 922, Leuven, B-3000, Belgium
| | - Emma Kozlovskaya
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok, 690022, Russia
| | - Marina Isaeva
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch of the Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok, 690022, Russia
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13
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Sintsova O, Gladkikh I, Kalinovskii A, Zelepuga E, Monastyrnaya M, Kim N, Shevchenko L, Peigneur S, Tytgat J, Kozlovskaya E, Leychenko E. Magnificamide, a β-Defensin-Like Peptide from the Mucus of the Sea Anemone Heteractis magnifica, Is a Strong Inhibitor of Mammalian α-Amylases. Mar Drugs 2019; 17:md17100542. [PMID: 31546678 PMCID: PMC6835510 DOI: 10.3390/md17100542] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 09/16/2019] [Accepted: 09/17/2019] [Indexed: 01/07/2023] Open
Abstract
Sea anemones’ venom is rich in peptides acting on different biological targets, mainly on cytoplasmic membranes and ion channels. These animals are also a source of pancreatic α-amylase inhibitors, which have the ability to control the glucose level in the blood and can be used for the treatment of prediabetes and type 2 diabetes mellitus. Recently we have isolated and characterized magnificamide (44 aa, 4770 Da), the major α-amylase inhibitor of the sea anemone Heteractis magnifica mucus, which shares 84% sequence identity with helianthamide from Stichodactyla helianthus. Herein, we report some features in the action of a recombinant analog of magnificamide. The recombinant peptide inhibits porcine pancreatic and human saliva α-amylases with Ki’s equal to 0.17 ± 0.06 nM and 7.7 ± 1.5 nM, respectively, and does not show antimicrobial or channel modulating activities. We have concluded that the main function of magnificamide is the inhibition of α-amylases; therefore, its functionally active recombinant analog is a promising agent for further studies as a potential drug candidate for the treatment of the type 2 diabetes mellitus.
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Affiliation(s)
- Oksana Sintsova
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
| | - Irina Gladkikh
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
| | - Aleksandr Kalinovskii
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
- School of Natural Sciences, Far Eastern Federal University, 8, Sukhanova St, Vladivostok 690090, Russia.
| | - Elena Zelepuga
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
| | - Margarita Monastyrnaya
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
| | - Natalia Kim
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
| | - Lyudmila Shevchenko
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
| | - Steve Peigneur
- Toxicology and Pharmacology, University of Leuven (KU Leuven), Campus Gasthuisberg, O&N2, Herestraat 49, P.O. Box 922, Leuven B-3000, Belgium.
| | - Jan Tytgat
- Toxicology and Pharmacology, University of Leuven (KU Leuven), Campus Gasthuisberg, O&N2, Herestraat 49, P.O. Box 922, Leuven B-3000, Belgium.
| | - Emma Kozlovskaya
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
| | - Elena Leychenko
- G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, 159, Pr. 100 let Vladivostoku, Vladivostok 690022, Russia.
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14
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Yap WY, Tan KJSX, Hwang JS. Expansion of Hydra actinoporin-like toxin (HALT) gene family: Expression divergence and functional convergence evolved through gene duplication. Toxicon 2019; 170:10-20. [PMID: 31513812 DOI: 10.1016/j.toxicon.2019.09.007] [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: 05/30/2019] [Revised: 08/27/2019] [Accepted: 09/03/2019] [Indexed: 11/15/2022]
Abstract
Hydra actinoporin-like toxin 1 (HALT-1) was previously shown to cause cytolysis and haemolysis in a number of human cells and has similar functional properties to the actinoporins equinatoxin and sticholysin. In addition to HALT-1, five other HALTs (HALTs 2, 3, 4, 6 and 7) were also isolated from Hydra magnipapillata and expressed as recombinant proteins in this study. We demonstrated that recombinant HALTs have cytolytic activity on HeLa cells but each exhibited a different range of toxicity. All six recombinant HALTs bound to sulfatide, while rHALT-1 and rHALT-3 bound to two additional sphingolipids, lysophosphatidic acid and sphingosine-1-phosphate as indicated by the protein-lipid overlay assay. When either tryptophan133 or tyrosine129 of HALT-1 was mutated, the mutant protein lost binding to sulfatide, lysophosphatidic acid and sphingosine-1-phosphate. As further verification of HALTs' binding to sulfatide, we performed ELISA for each HALT. To determine the cell-type specific gene expression of seven HALTs in Hydra, we searched for individual HALT expression in the single-cell RNA-seq data set of Single Cell Portal. The results showed that HALT-1, 4 and 7 were expressed in differentiating stenoteles. HALT-1 and HALT-6 were expressed in the female germline during oogenesis. HALT-2 was strongly expressed in the gland and mucous cells in the endoderm. Information on HALT-3 and HALT-5 could not be found in the single-cell data set. Our findings show that subfunctionalisation of gene expression following duplication enabled HALTs to become specialized in various cell types of the interstitial cell lineage.
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Affiliation(s)
- Wei Yuen Yap
- Faculty of Applied Sciences, UCSI University, No. 1, Jalan Menara Gading, UCSI Heights Cheras, 56000, Kuala Lumpur, Malaysia
| | - Katrina Joan Shu Xian Tan
- Faculty of Applied Sciences, UCSI University, No. 1, Jalan Menara Gading, UCSI Heights Cheras, 56000, Kuala Lumpur, Malaysia
| | - Jung Shan Hwang
- Department of Medical Sciences, School of Healthcare and Medical Sciences, Sunway University, No. 5 Jalan Universiti, Bandar Sunway, 47500, Selangor Darul Ehsan, Malaysia.
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15
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Morante K, Bellomio A, Viguera AR, González-Mañas JM, Tsumoto K, Caaveiro JMM. The Isolation of New Pore-Forming Toxins from the Sea Anemone Actinia fragacea Provides Insights into the Mechanisms of Actinoporin Evolution. Toxins (Basel) 2019; 11:toxins11070401. [PMID: 31295915 PMCID: PMC6669745 DOI: 10.3390/toxins11070401] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 06/29/2019] [Accepted: 07/05/2019] [Indexed: 01/23/2023] Open
Abstract
Random mutations and selective pressure drive protein adaptation to the changing demands of the environment. As a consequence, nature favors the evolution of protein diversity. A group of proteins subject to exceptional environmental stress and known for their widespread diversity are the pore-forming hemolytic proteins from sea anemones, known as actinoporins. In this study, we identified and isolated new isoforms of actinoporins from the sea anemone Actinia fragacea (fragaceatoxins). We characterized their hemolytic activity, examined their stability and structure, and performed a comparative analysis of their primary sequence. Sequence alignment reveals that most of the variability among actinoporins is associated with non-functional residues. The differences in the thermal behavior among fragaceatoxins suggest that these variability sites contribute to changes in protein stability. In addition, the protein-protein interaction region showed a very high degree of identity (92%) within fragaceatoxins, but only 25% among all actinoporins examined, suggesting some degree of specificity at the species level. Our findings support the mechanism of evolutionary adaptation in actinoporins and reflect common pathways conducive to protein variability.
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Affiliation(s)
- Koldo Morante
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
- Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain
- Instituto Biofisika (CSIC, UPV/EHU), Parque Científico de la UPV/EHU, Barrio Sarriena s/n, 48940 Leioa (Bizkaia), Spain
| | - Augusto Bellomio
- Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain
- Instituto Biofisika (CSIC, UPV/EHU), Parque Científico de la UPV/EHU, Barrio Sarriena s/n, 48940 Leioa (Bizkaia), Spain
- Instituto Superior de Investigaciones Biológicas (INSIBIO, CONICET-UNT) e Instituto de Química Biológica "Dr. Bernabé Bloj," Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, Chacabuco 461, T4000 San Miguel de Tucumán, Argentina
| | - Ana Rosa Viguera
- Instituto Biofisika (CSIC, UPV/EHU), Parque Científico de la UPV/EHU, Barrio Sarriena s/n, 48940 Leioa (Bizkaia), Spain
| | - Juan Manuel González-Mañas
- Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain
| | - Kouhei Tsumoto
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.
- Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, Japan.
| | - Jose M M Caaveiro
- Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.
- Department of Global Healthcare, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
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16
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Madio B, King GF, Undheim EAB. Sea Anemone Toxins: A Structural Overview. Mar Drugs 2019; 17:E325. [PMID: 31159357 PMCID: PMC6627431 DOI: 10.3390/md17060325] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 05/22/2019] [Accepted: 05/25/2019] [Indexed: 02/06/2023] Open
Abstract
Sea anemones produce venoms of exceptional molecular diversity, with at least 17 different molecular scaffolds reported to date. These venom components have traditionally been classified according to pharmacological activity and amino acid sequence. However, this classification system suffers from vulnerabilities due to functional convergence and functional promiscuity. Furthermore, for most known sea anemone toxins, the exact receptors they target are either unknown, or at best incomplete. In this review, we first provide an overview of the sea anemone venom system and then focus on the venom components. We have organised the venom components by distinguishing firstly between proteins and non-proteinaceous compounds, secondly between enzymes and other proteins without enzymatic activity, then according to the structural scaffold, and finally according to molecular target.
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Affiliation(s)
- Bruno Madio
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, 4072, Australia.
| | - Glenn F King
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, 4072, Australia.
| | - Eivind A B Undheim
- Centre for Advanced Imaging, The University of Queensland, St. Lucia, QLD 4072, Australia.
- Centre for Ecology and Evolutionary Synthesis, Department of Biosciences, University of Oslo, 0316 Oslo, Norway.
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17
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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.
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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.
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18
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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.
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