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Gabriel JM, Tan T, Rinauro DJ, Hsu CM, Buettner CJ, Gilmer M, Kaur A, McKenzie TL, Park M, Cohen S, Errico S, Wright AK, Chiti F, Vendruscolo M, Limbocker R. EGCG inactivates a pore-forming toxin by promoting its oligomerization and decreasing its solvent-exposed hydrophobicity. Chem Biol Interact 2023; 371:110307. [PMID: 36535315 DOI: 10.1016/j.cbi.2022.110307] [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: 09/18/2022] [Revised: 12/02/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022]
Abstract
Natural proteinaceous pore-forming agents can bind and permeabilize cell membranes, leading to ion dyshomeostasis and cell death. In the search for antidotes that can protect cells from peptide toxins, we discovered that the polyphenol epigallocatechin gallate (EGCG) interacts directly with melittin from honeybee venom, resulting in the elimination of its binding to the cell membrane and toxicity by markedly lowering the extent of its solvent-exposed hydrophobicity and promoting its oligomerization into larger species. These physicochemical parameters have also been shown to play a key role in the binding to cells of misfolded protein oligomers in a host of neurodegenerative diseases, where oligomer-membrane binding and associated toxicity have been shown to correlate negatively with oligomer size and positively with solvent-exposed hydrophobicity. For melittin, which is not an amyloid-forming protein and has a very distinct mechanism of toxicity compared to misfolded oligomers, we find that the size-hydrophobicity-toxicity relationship also rationalizes the pharmacological attenuation of melittin toxicity by EGCG. These results highlight the importance of the physicochemical properties of pore forming agents in mediating their interactions with cell membranes and suggest a possible therapeutic approach based on compounds with a similar mechanism of action as EGCG.
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Affiliation(s)
- Justus M Gabriel
- Department of Chemistry and Life Science, United States Military Academy, West Point, NY 10996, USA
| | - Thomas Tan
- Department of Chemistry and Life Science, United States Military Academy, West Point, NY 10996, USA
| | - Dillon J Rinauro
- Centre for Misfolding Diseases, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK
| | - Claire M Hsu
- Department of Chemistry and Life Science, United States Military Academy, West Point, NY 10996, USA
| | - Caleb J Buettner
- Department of Chemistry and Life Science, United States Military Academy, West Point, NY 10996, USA
| | - Marshall Gilmer
- Department of Chemistry and Life Science, United States Military Academy, West Point, NY 10996, USA
| | - Amrita Kaur
- Department of Chemistry and Life Science, United States Military Academy, West Point, NY 10996, USA
| | - Tristan L McKenzie
- Department of Chemistry and Life Science, United States Military Academy, West Point, NY 10996, USA
| | - Martin Park
- Department of Chemistry and Life Science, United States Military Academy, West Point, NY 10996, USA
| | - Sophie Cohen
- Department of Chemistry and Life Science, United States Military Academy, West Point, NY 10996, USA
| | - Silvia Errico
- Centre for Misfolding Diseases, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK; Department of Experimental and Clinical Biomedical Sciences, Section of Biochemistry, University of Florence, Florence, Italy
| | - Aidan K Wright
- Department of Chemistry and Life Science, United States Military Academy, West Point, NY 10996, USA
| | - Fabrizio Chiti
- Department of Experimental and Clinical Biomedical Sciences, Section of Biochemistry, University of Florence, Florence, Italy
| | - Michele Vendruscolo
- Centre for Misfolding Diseases, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK
| | - Ryan Limbocker
- Department of Chemistry and Life Science, United States Military Academy, West Point, NY 10996, USA.
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2
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Oncolytic peptide nanomachine circumvents chemo resistance of renal cell carcinoma. Biomaterials 2022; 284:121488. [DOI: 10.1016/j.biomaterials.2022.121488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Revised: 03/09/2022] [Accepted: 03/23/2022] [Indexed: 11/17/2022]
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3
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Sato W, Zajkowski T, Moser F, Adamala KP. Synthetic cells in biomedical applications. WILEY INTERDISCIPLINARY REVIEWS. NANOMEDICINE AND NANOBIOTECHNOLOGY 2022; 14:e1761. [PMID: 34725945 PMCID: PMC8918002 DOI: 10.1002/wnan.1761] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 08/23/2021] [Accepted: 08/30/2021] [Indexed: 12/12/2022]
Abstract
Synthetic cells are engineered vesicles that can mimic one or more salient features of life. These features include directed localization, sense-and-respond behavior, gene expression, metabolism, and high stability. In nanomedicine, many of these features are desirable capabilities of drug delivery vehicles but are difficult to engineer. In this focus article, we discuss where synthetic cells offer unique advantages over nanoparticle and living cell therapies. We review progress in the engineering of the above life-like behaviors and how they are deployed in nanomedicine. Finally, we assess key challenges synthetic cells face before being deployed as drugs and suggest ways to overcome these challenges. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Lipid-Based Structures.
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Affiliation(s)
- Wakana Sato
- 1 Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN US
| | - Tomasz Zajkowski
- Centre of New Technologies, University of Warsaw, S. Banacha 2c, 02-097 Warsaw, Poland
- USRA at NASA Ames Research Center, Mountain View, CA 94035
- Blue Marble Space Institute of Science, 600 1st Avenue, Seattle WA 98104
| | - Felix Moser
- Synlife, Inc., One Kendall Square Suite B4401, Cambridge, MA 20139
| | - Katarzyna P. Adamala
- 1 Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN US
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4
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Rangel K, Curty Lechuga G, Almeida Souza AL, Rangel da Silva Carvalho JP, Simões Villas Bôas MH, De Simone SG. Pan-Drug Resistant Acinetobacter baumannii, but Not Other Strains, Are Resistant to the Bee Venom Peptide Mellitin. Antibiotics (Basel) 2020; 9:antibiotics9040178. [PMID: 32295149 PMCID: PMC7235889 DOI: 10.3390/antibiotics9040178] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 12/09/2019] [Accepted: 12/14/2019] [Indexed: 12/20/2022] Open
Abstract
Acinetobacter baumannii is a prevalent pathogen in hospital settings with increasing importance in infections associated with biofilm production. Due to a rapid increase in its drug resistance and the failure of commonly available antibiotics to treat A. baumannii infections, this bacterium has become a critical public health issue. For these multi-drug resistant A. baumannii, polymyxin antibiotics are considered the only option for the treatment of severe infections. Concerning, several polymyxin-resistant A. baumannii strains have been isolated over the last few years. This study utilized pan drug-resistant (PDR) strains of A. baumannii isolated in Brazil, along with susceptible (S) and extreme drug-resistant (XDR) strains in order to evaluate the in vitro activity of melittin, an antimicrobial peptide, in comparison to polymyxin and another antibiotic, imipenem. From a broth microdilution method, the determined minimum inhibitory concentration showed that S and XDR strains were susceptible to melittin. In contrast, PDR A. baumannii was resistant to all treatments. Treatment with the peptide was also observed to inhibit biofilm formation of a susceptible strain and appeared to cause permanent membrane damage. A subpopulation of PDR showed membrane damage, however, it was not sufficient to stop bacterial growth, suggesting that alterations involved with antibiotic resistance could also influence melittin resistance. Presumably, mutations in the PDR that have arisen to confer resistance to widely used therapeutics also confer resistance to melittin. Our results demonstrate the potential of melittin to be used in the control of bacterial infections and suggest that antimicrobial peptides can serve as the basis for the development of new treatments.
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Affiliation(s)
- Karyne Rangel
- FIOCRUZ, Center for Technological, Development in Health (CDTS)/National, Institute of Science and Technology for Innovation in Neglected Population Diseases (INCT-IDPN), Rio de Janeiro 21040-900; (G.C.L.); (A.L.A.S.); (J.P.R.d.S.C.)
- Correspondence: (K.R.); (S.G.D.S.)
| | - Guilherme Curty Lechuga
- FIOCRUZ, Center for Technological, Development in Health (CDTS)/National, Institute of Science and Technology for Innovation in Neglected Population Diseases (INCT-IDPN), Rio de Janeiro 21040-900; (G.C.L.); (A.L.A.S.); (J.P.R.d.S.C.)
- FIOCRUZ, Oswaldo Cruz Institute, Laboratory of Cellular Ultrastructure, Rio de Janeiro 21040-900, Brazil
| | - André Luis Almeida Souza
- FIOCRUZ, Center for Technological, Development in Health (CDTS)/National, Institute of Science and Technology for Innovation in Neglected Population Diseases (INCT-IDPN), Rio de Janeiro 21040-900; (G.C.L.); (A.L.A.S.); (J.P.R.d.S.C.)
| | - João Pedro Rangel da Silva Carvalho
- FIOCRUZ, Center for Technological, Development in Health (CDTS)/National, Institute of Science and Technology for Innovation in Neglected Population Diseases (INCT-IDPN), Rio de Janeiro 21040-900; (G.C.L.); (A.L.A.S.); (J.P.R.d.S.C.)
| | - Maria Helena Simões Villas Bôas
- FIOCRUZ, Microbiology Department, National Institute for Quality Control in Health (INCQS), Rio de Janeiro 21040-900, Brazil;
| | - Salvatore Giovanni De Simone
- FIOCRUZ, Center for Technological, Development in Health (CDTS)/National, Institute of Science and Technology for Innovation in Neglected Population Diseases (INCT-IDPN), Rio de Janeiro 21040-900; (G.C.L.); (A.L.A.S.); (J.P.R.d.S.C.)
- FIOCRUZ, Federal Fluminense University, Biology Institute, Department of Molecular and Cellular Biology, Rio de Janeiro, Niterói 24020-140, Brazil
- Correspondence: (K.R.); (S.G.D.S.)
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Hong J, Lu X, Deng Z, Xiao S, Yuan B, Yang K. How Melittin Inserts into Cell Membrane: Conformational Changes, Inter-Peptide Cooperation, and Disturbance on the Membrane. Molecules 2019; 24:molecules24091775. [PMID: 31067828 PMCID: PMC6539814 DOI: 10.3390/molecules24091775] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 05/02/2019] [Accepted: 05/03/2019] [Indexed: 01/27/2023] Open
Abstract
Antimicrobial peptides (AMPs), as a key component of the immune defense systems of organisms, are a promising solution to the serious threat of drug-resistant bacteria to public health. As one of the most representative and extensively studied AMPs, melittin has exceptional broad-spectrum activities against microorganisms, including both Gram-positive and Gram-negative bacteria. Unfortunately, the action mechanism of melittin with bacterial membranes, especially the underlying physics of peptide-induced membrane poration behaviors, is still poorly understood, which hampers efforts to develop melittin-based drugs or agents for clinical applications. In this mini-review, we focus on recent advances with respect to the membrane insertion behavior of melittin mostly from a computational aspect. Membrane insertion is a prerequisite and key step for forming transmembrane pores and bacterial killing by melittin, whose occurrence is based on overcoming a high free-energy barrier during the transition of melittin molecules from a membrane surface-binding state to a transmembrane-inserting state. Here, intriguing simulation results on such transition are highlighted from both kinetic and thermodynamic aspects. The conformational changes and inter-peptide cooperation of melittin molecules, as well as melittin-induced disturbances to membrane structure, such as deformation and lipid extraction, are regarded as key factors influencing the insertion of peptides into membranes. The associated intermediate states in peptide conformations, lipid arrangements, membrane structure, and mechanical properties during this process are specifically discussed. Finally, potential strategies for enhancing the poration ability and improving the antimicrobial performance of AMPs are included as well.
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Affiliation(s)
- Jiajia Hong
- Center for Soft Condensed Matter Physics and Interdisciplinary Research & School of Physical Science and Technology, Soochow University, Suzhou 215006, China.
| | - Xuemei Lu
- Center for Soft Condensed Matter Physics and Interdisciplinary Research & School of Physical Science and Technology, Soochow University, Suzhou 215006, China.
| | - Zhixiong Deng
- Center for Soft Condensed Matter Physics and Interdisciplinary Research & School of Physical Science and Technology, Soochow University, Suzhou 215006, China.
| | - Shufeng Xiao
- Center for Soft Condensed Matter Physics and Interdisciplinary Research & School of Physical Science and Technology, Soochow University, Suzhou 215006, China.
| | - Bing Yuan
- Center for Soft Condensed Matter Physics and Interdisciplinary Research & School of Physical Science and Technology, Soochow University, Suzhou 215006, China.
| | - Kai Yang
- Center for Soft Condensed Matter Physics and Interdisciplinary Research & School of Physical Science and Technology, Soochow University, Suzhou 215006, China.
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Avci FG, Akbulut BS, Ozkirimli E. Membrane Active Peptides and Their Biophysical Characterization. Biomolecules 2018; 8:biom8030077. [PMID: 30135402 PMCID: PMC6164437 DOI: 10.3390/biom8030077] [Citation(s) in RCA: 92] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 08/08/2018] [Accepted: 08/13/2018] [Indexed: 12/12/2022] Open
Abstract
In the last 20 years, an increasing number of studies have been reported on membrane active peptides. These peptides exert their biological activity by interacting with the cell membrane, either to disrupt it and lead to cell lysis or to translocate through it to deliver cargos into the cell and reach their target. Membrane active peptides are attractive alternatives to currently used pharmaceuticals and the number of antimicrobial peptides (AMPs) and peptides designed for drug and gene delivery in the drug pipeline is increasing. Here, we focus on two most prominent classes of membrane active peptides; AMPs and cell-penetrating peptides (CPPs). Antimicrobial peptides are a group of membrane active peptides that disrupt the membrane integrity or inhibit the cellular functions of bacteria, virus, and fungi. Cell penetrating peptides are another group of membrane active peptides that mainly function as cargo-carriers even though they may also show antimicrobial activity. Biophysical techniques shed light on peptide–membrane interactions at higher resolution due to the advances in optics, image processing, and computational resources. Structural investigation of membrane active peptides in the presence of the membrane provides important clues on the effect of the membrane environment on peptide conformations. Live imaging techniques allow examination of peptide action at a single cell or single molecule level. In addition to these experimental biophysical techniques, molecular dynamics simulations provide clues on the peptide–lipid interactions and dynamics of the cell entry process at atomic detail. In this review, we summarize the recent advances in experimental and computational investigation of membrane active peptides with particular emphasis on two amphipathic membrane active peptides, the AMP melittin and the CPP pVEC.
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Affiliation(s)
- Fatma Gizem Avci
- Bioengineering Department, Marmara University, Kadikoy, 34722 Istanbul, Turkey.
| | | | - Elif Ozkirimli
- Chemical Engineering Department, Bogazici University, Bebek, 34342 Istanbul, Turkey.
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Picoli T, Peter CM, Zani JL, Waller SB, Lopes MG, Boesche KN, Vargas GD, Hübner SDO, Fischer G. Melittin and its potential in the destruction and inhibition of the biofilm formation by Staphylococcus aureus , Escherichia coli and Pseudomonas aeruginosa isolated from bovine milk. Microb Pathog 2017; 112:57-62. [DOI: 10.1016/j.micpath.2017.09.046] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 08/22/2017] [Accepted: 09/19/2017] [Indexed: 12/27/2022]
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Ayub M, Bayley H. Engineered transmembrane pores. Curr Opin Chem Biol 2016; 34:117-126. [PMID: 27658267 DOI: 10.1016/j.cbpa.2016.08.005] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Revised: 08/09/2016] [Accepted: 08/10/2016] [Indexed: 12/15/2022]
Abstract
Today, hundreds of researchers are working on nanopores, making an impact in both basic science and biotechnology. Proteins remain the most versatile sources of nanopores, based on our ability to engineer them with sub-nanometer precision. Recent work aimed at the construction and discovery of novel pores has included unnatural amino acid mutagenesis and the application of selection techniques. The diversity of structures has now been increased through the development of helix-based pores as well as the better-known β barrels. New developments also include truncated pores, which pierce bilayers through lipid rearrangement, and hybrid pores, which do away with bilayers altogether. Pore dimers, which span two lipid bilayers, have been constructed and pores based on DNA nanostructures are gaining in importance. While nanopore DNA sequencing has received enthusiastic attention, protein pores have a wider range of potential applications, requiring specifications that will require engineering efforts to continue for years to come.
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Affiliation(s)
- Mariam Ayub
- Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom
| | - Hagan Bayley
- Department of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom.
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9
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Balseiro-Gomez S, Flores JA, Acosta J, Ramirez-Ponce MP, Ales E. Transient fusion ensures granule replenishment to enable repeated release after IgE-mediated mast cell degranulation. J Cell Sci 2016; 129:3989-4000. [PMID: 27624612 DOI: 10.1242/jcs.194340] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 09/07/2016] [Indexed: 11/20/2022] Open
Abstract
To ensure normal immune function, mast cells employ different pathways to release mediators. Here, we report a thus far unknown capacity of mast cells to recycle and reuse secretory granules after an antigen-evoked degranulation process under physiological conditions; this phenomenon involves the existence of a recycling secretory granule pool that is available for release in a short time scale. Rapid endocytic modes contributed to the recycling of ∼60% of the total secretory granule population, which involved kiss-and-run and cavicapture mechanisms, causing retention of the intragranular matrix. We found the presence of normal-size granules and giant actomyosin- and dynamin-dependent granules, which were characterized by large quantal content. These large structures allowed the recovered mast cells to release a large amount of 5-HT, compensating for the decrease in the number of exocytosed secretory granules. This work uncovers a new physiological role of the exo-endocytosis cycle in the immunological plasticity of mast cells and reveals a new property of their biological secretion.
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Affiliation(s)
- Santiago Balseiro-Gomez
- Departamento Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de 41009 Sevilla, Spain
| | - Juan A Flores
- Departamento Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de 41009 Sevilla, Spain
| | - Jorge Acosta
- Departamento Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de 41009 Sevilla, Spain
| | - M Pilar Ramirez-Ponce
- Departamento Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de 41009 Sevilla, Spain
| | - Eva Ales
- Departamento Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de 41009 Sevilla, Spain
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10
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Gurnev PA, Nestorovich EM. Channel-forming bacterial toxins in biosensing and macromolecule delivery. Toxins (Basel) 2014; 6:2483-540. [PMID: 25153255 PMCID: PMC4147595 DOI: 10.3390/toxins6082483] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 08/08/2014] [Accepted: 08/08/2014] [Indexed: 12/19/2022] Open
Abstract
To intoxicate cells, pore-forming bacterial toxins are evolved to allow for the transmembrane traffic of different substrates, ranging from small inorganic ions to cell-specific polypeptides. Recent developments in single-channel electrical recordings, X-ray crystallography, protein engineering, and computational methods have generated a large body of knowledge about the basic principles of channel-mediated molecular transport. These discoveries provide a robust framework for expansion of the described principles and methods toward use of biological nanopores in the growing field of nanobiotechnology. This article, written for a special volume on "Intracellular Traffic and Transport of Bacterial Protein Toxins", reviews the current state of applications of pore-forming bacterial toxins in small- and macromolecule-sensing, targeted cancer therapy, and drug delivery. We discuss the electrophysiological studies that explore molecular details of channel-facilitated protein and polymer transport across cellular membranes using both natural and foreign substrates. The review focuses on the structurally and functionally different bacterial toxins: gramicidin A of Bacillus brevis, α-hemolysin of Staphylococcus aureus, and binary toxin of Bacillus anthracis, which have found their "second life" in a variety of developing medical and technological applications.
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Affiliation(s)
- Philip A Gurnev
- Physics Department, University of Massachusetts, Amherst, MA 01003, USA.
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11
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Flores JA, Balseiro-Gomez S, Cabeza JM, Acosta J, Ramirez-Ponce P, Ales E. A new role for myosin II in vesicle fission. PLoS One 2014; 9:e100757. [PMID: 24959909 PMCID: PMC4069105 DOI: 10.1371/journal.pone.0100757] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 05/28/2014] [Indexed: 11/19/2022] Open
Abstract
An endocytic vesicle is formed from a flat plasma membrane patch by a sequential process of invagination, bud formation and fission. The scission step requires the formation of a tubular membrane neck (the fission pore) that connects the endocytic vesicle with the plasma membrane. Progress in vesicle fission can be measured by the formation and closure of the fission pore. Live-cell imaging and sensitive biophysical measurements have provided various glimpses into the structure and behaviour of the fission pore. In the present study, the role of non-muscle myosin II (NM-2) in vesicle fission was tested by analyzing the kinetics of the fission pore with perforated-patch clamp capacitance measurements to detect single vesicle endocytosis with millisecond time resolution in peritoneal mast cells. Blebbistatin, a specific inhibitor of NM-2, dramatically increased the duration of the fission pore and also prevented closure during large endocytic events. Using the fluorescent markers FM1-43 and pHrodo Green dextran, we found that NM-2 inhibition greatly arrested vesicle fission in a late phase of the scission event when the pore reached a final diameter of ∼ 5 nm. Our results indicate that loss of the ATPase activity of myosin II drastically reduces the efficiency of membrane scission by making vesicle closure incomplete and suggest that NM-2 might be especially relevant in vesicle fission during compound endocytosis.
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Affiliation(s)
- Juan A. Flores
- Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
| | - Santiago Balseiro-Gomez
- Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
| | - Jose M. Cabeza
- Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
| | - Jorge Acosta
- Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
| | - Pilar Ramirez-Ponce
- Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
| | - Eva Ales
- Dpto. Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
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Abstract
Melittin is a prototype of the ubiquitous antimicrobial peptides that induce pores in membranes. It is commonly used as a molecular device for membrane permeabilization. Even at concentrations in the nanomolar range, melittin can induce transient pores that allow transmembrane conduction of atomic ions but not leakage of glucose or larger molecules. At micromolar concentrations, melittin induces stable pores allowing transmembrane leakage of molecules up to tens of kilodaltons, corresponding to its antimicrobial activities. Despite extensive studies, aspects of the molecular mechanism for pore formation remain unclear. To clarify the mechanism, one must know the states of the melittin-bound membrane before and after the process. By correlating experiments using giant unilamellar vesicles with those of peptide-lipid multilayers, we found that melittin bound on the vesicle translocated and redistributed to both sides of the membrane before the formation of stable pores. Furthermore, stable pores are formed only above a critical peptide-to-lipid ratio. The initial states for transient and stable pores are different, which implies different mechanisms at low and high peptide concentrations. To determine the lipidic structure of the pore, the pores in peptide-lipid multilayers were induced to form a lattice and examined by anomalous X-ray diffraction. The electron density distribution of lipid labels shows that the pore is formed by merging of two interfaces through a hole. The molecular property of melittin is such that it adsorbs strongly to the bilayer interface. Pore formation can be viewed as the bilayer adopting a lipid configuration to accommodate its excessive interfacial area.
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13
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Thresholds for phosphatidylserine externalization in Chinese hamster ovarian cells following exposure to nanosecond pulsed electrical fields (nsPEF). PLoS One 2013; 8:e63122. [PMID: 23658665 PMCID: PMC3639203 DOI: 10.1371/journal.pone.0063122] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 03/29/2013] [Indexed: 11/19/2022] Open
Abstract
High-amplitude, MV/m, nanosecond pulsed electric fields (nsPEF) have been hypothesized to cause nanoporation of the plasma membrane. Phosphatidylserine (PS) externalization has been observed on the outer leaflet of the membrane shortly after nsPEF exposure, suggesting local structural changes in the membrane. In this study, we utilized fluorescently-tagged Annexin V to observe the externalization of PS on the plasma membrane of isolated Chinese Hamster Ovary (CHO) cells following exposure to nsPEF. A series of experiments were performed to determine the dosimetric trends of PS expression caused by nsPEF as a function of pulse duration, τ, delivered field strength, ED, and pulse number, n. To accurately estimate dose thresholds for cellular response, data were reduced to a set of binary responses and ED50s were estimated using Probit analysis. Probit analysis results revealed that PS externalization followed the non-linear trend of (τ*ED2)−1 for high amplitudes, but failed to predict low amplitude responses. A second set of experiments was performed to determine the nsPEF parameters necessary to cause observable calcium uptake, using cells preloaded with calcium green (CaGr), and membrane permeability, using FM1-43 dye. Calcium influx and FM1-43 uptake were found to always be observed at lower nsPEF exposure parameters compared to PS externalization. These findings suggest that multiple, higher amplitude and longer pulse exposures may generate pores of larger diameter enabling lateral diffusion of PS; whereas, smaller pores induced by fewer, lower amplitude and short pulse width exposures may only allow extracellular calcium and FM1-43 uptake.
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14
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Properties of ribbon and non-ribbon release from rod photoreceptors revealed by visualizing individual synaptic vesicles. J Neurosci 2013; 33:2071-86. [PMID: 23365244 DOI: 10.1523/jneurosci.3426-12.2013] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Vesicle release from rod photoreceptors is regulated by Ca(2+) entry through L-type channels located near synaptic ribbons. We characterized sites and kinetics of vesicle release in salamander rods by using total internal reflection fluorescence microscopy to visualize fusion of individual synaptic vesicles. A small number of vesicles were loaded by brief incubation with FM1-43 or a dextran-conjugated, pH-sensitive form of rhodamine, pHrodo. Labeled organelles matched the diffraction-limited size of fluorescent microspheres and disappeared rapidly during stimulation. Consistent with fusion, depolarization-evoked vesicle disappearance paralleled electrophysiological release kinetics and was blocked by inhibiting Ca(2+) influx. Rods maintained tonic release at resting membrane potentials near those in darkness, causing depletion of membrane-associated vesicles unless Ca(2+) entry was inhibited. This depletion of release sites implies that sustained release may be rate limited by vesicle delivery. During depolarizing stimulation, newly appearing vesicles approached the membrane at ∼800 nm/s, where they paused for ∼60 ms before fusion. With fusion, vesicles advanced ∼18 nm closer to the membrane. Release events were concentrated near ribbons, but lengthy depolarization also triggered release from more distant non-ribbon sites. Consistent with greater contributions from non-ribbon sites during lengthier depolarization, damaging the ribbon by fluorophore-assisted laser inactivation (FALI) of Ribeye caused only weak inhibition of exocytotic capacitance increases evoked by 200-ms depolarizing test steps, whereas FALI more strongly inhibited capacitance increases evoked by 25 ms steps. Amplifying release by use of non-ribbon sites when rods are depolarized in darkness may improve detection of decrements in release when they hyperpolarize to light.
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Alabi AA, Tsien RW. Perspectives on Kiss-and-Run: Role in Exocytosis, Endocytosis, and Neurotransmission. Annu Rev Physiol 2013; 75:393-422. [DOI: 10.1146/annurev-physiol-020911-153305] [Citation(s) in RCA: 172] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- AbdulRasheed A. Alabi
- Department of Molecular and Cellular Physiology, Stanford Institute for Neuro-Innovation and Translational Neurosciences, Stanford Medical School, Stanford, California 94305;
| | - Richard W. Tsien
- Department of Physiology and Neuroscience, Center for Neural Science, NYU Neuroscience Institute, New York University, New York, NY 10016;
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Affiliation(s)
| | - Sergey M. Bezrukov
- Program in Physical Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, U.S.A
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Welzel O, Tischbirek CH, Kornhuber J, Groemer TW. Pool-independent labelling of synaptic vesicle exocytosis with single vesicle resolution in rat hippocampal neurons. J Neurosci Methods 2012; 205:258-64. [PMID: 22306057 DOI: 10.1016/j.jneumeth.2012.01.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Revised: 12/21/2011] [Accepted: 01/20/2012] [Indexed: 11/26/2022]
Abstract
FM dyes are an established tool to analyze synaptic vesicle pools. However, quantitative measurements using FM dyes are typically based on the re-release properties of previously labelled vesicles, which might vary depending on the experimental setup. An FM dye protocol independent of the previous labelling of vesicle membrane has not been applied for quantitative measurements of individual synaptic vesicles before. We therefore analyzed the direct staining of newly exocytosed vesicle membrane with FM dyes in cultured rat hippocampal neurons. In the presence of FM 1-43, stimulation-induced synaptic activity led to a stable fluorescence increase. The quantal release of synaptic vesicles was preserved and its amplitude correlated highly with the exocytic dye loss induced by a subsequent stimulation. Thus, the method presented here provides a tool for the pool-independent measurement of synaptic vesicle exocytosis.
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Affiliation(s)
- Oliver Welzel
- Department of Psychiatry and Psychotherapy, University of Erlangen-Nuremberg, Schwabachanlage 6, 91054 Erlangen, Germany
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