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Epand RM. The scientific adventures of Richard Epand. Biophys Chem 2023; 292:106931. [PMID: 36434860 DOI: 10.1016/j.bpc.2022.106931] [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: 11/01/2022] [Accepted: 11/05/2022] [Indexed: 11/13/2022]
Abstract
This essay summarizes the many areas of science that my career has contributed to. It attempts to highlight some of the innovative concepts that developed from this work. The discussion encompasses studies I undertook from graduate school to the present but it will not attempt to be comprehensive. I apologize to individuals whose work I omitted. Because of space I cannot acknowledge all the contributions from other individuals that made these achievements possible.
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Affiliation(s)
- Richard M Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University, Health Sciences Centre, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada.
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2
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Billah MM, Saha SK, Or Rashid MM, Hossain F, Yamazaki M. Effect of Osmotic Pressure on Pore Formation in Lipid bilayers by the Antimicrobial Peptide Magainin 2. Phys Chem Chem Phys 2022; 24:6716-6731. [DOI: 10.1039/d1cp05764b] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Osmotic pressure (Π) induces membrane tension in cells and lipid vesicles, which may affect the activity of antimicrobial peptides (AMPs) by an unknown mechanism. We recently quantitated the membrane tension...
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3
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Controlled metabolic cascades for protein synthesis in an artificial cell. Biochem Soc Trans 2021; 49:2143-2151. [PMID: 34623386 DOI: 10.1042/bst20210175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 09/04/2021] [Accepted: 09/07/2021] [Indexed: 11/17/2022]
Abstract
In recent years, researchers have been pursuing a method to design and to construct life forms from scratch - in other words, to create artificial cells. In many studies, artificial cellular membranes have been successfully fabricated, allowing the research field to grow by leaps and bounds. Moreover, in addition to lipid bilayer membranes, proteins are essential factors required to construct any cellular metabolic reaction; for that reason, different cell-free expression systems under various conditions to achieve the goal of controlling the synthetic cascades of proteins in a confined area have been reported. Thus, in this review, we will discuss recent issues and strategies, enabling to control protein synthesis cascades that are being used, particularly in research on artificial cells.
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De Mel JU, Gupta S, Perera RM, Ngo L, Zolnierczuk P, Bleuel M, Pingali SV, Schneider GJ. Influence of External NaCl Salt on Membrane Rigidity of Neutral DOPC Vesicles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:9356-9367. [PMID: 32672981 DOI: 10.1021/acs.langmuir.0c01004] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Sodium chloride (NaCl) is a very common molecule in biotic and abiotic aqueous environments. In both cases, variation of ionic strength is inevitable. In addition to the osmotic variation posed by such perturbations, the question of whether the interactions of monovalent ions Na+ and Cl-, especially with the neutral head groups of phospholipid membranes are impactful enough to change the membrane rigidity, is still not entirely understood. We investigated the dynamics of 1,2-di-(octadecenoyl)-sn-glycero-3-phosphocholine (DOPC) vesicles with zwitterionic neutral head groups in the fluid phase with increasing external salt concentration. At higher salt concentrations, we observe an increase in bending rigidity from neutron spin echo (NSE) spectroscopy and an increase in bilayer thickness from small-angle X-ray scattering (SAXS). We compared different models to distinguish membrane undulations, lipid tail motions, and the translational diffusion of the vesicles. All of the models indicate an increase in bending rigidity by a factor of 1.3-3.6. We demonstrate that even down to t > 10 ns and for Q > 0.07 Å-1, the observed NSE relaxation spectra are influenced by translational diffusion of the vesicles. For t < 5 ns, the lipid tail motion dominates the intermediate dynamic structure factor. As the salt concentration increases, this contribution diminishes. We introduced a time-dependent analysis for the bending rigidity that highlights only a limited Zilman-Granek time window in which the rigidity is physically meaningful.
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Affiliation(s)
- Judith U De Mel
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Sudipta Gupta
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Rasangi M Perera
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Ly Ngo
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Piotr Zolnierczuk
- Jülich Centre for Neutron Science (JCNS), Outstation at SNS, POB 2008, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, United States
| | - Markus Bleuel
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8562, United States
| | - Sai Venkatesh Pingali
- Neutron Sciences Directorate, Oak Ridge National Laboratory (ORNL), POB 2008, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, United States
| | - Gerald J Schneider
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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5
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Saha SK, Alam Shibly SU, Yamazaki M. Membrane Tension in Negatively Charged Lipid Bilayers in a Buffer under Osmotic Pressure. J Phys Chem B 2020; 124:5588-5599. [DOI: 10.1021/acs.jpcb.0c03681] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Samiron Kumar Saha
- Integrated Bioscience Section, Graduate School of Science and Technology, Shizuoka University, Shizuoka 422-8529, Japan
| | - Sayed Ul Alam Shibly
- Integrated Bioscience Section, Graduate School of Science and Technology, Shizuoka University, Shizuoka 422-8529, Japan
| | - Masahito Yamazaki
- Integrated Bioscience Section, Graduate School of Science and Technology, Shizuoka University, Shizuoka 422-8529, Japan
- Nanomaterials Research Division, Research Institute of Electronics, Shizuoka University, Shizuoka 422-8529, Japan
- Department of Physics, Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan
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Flandez K, Bonardd S, Soto-Arriaza M. Physicochemical properties of L-alpha dipalmitoyl phosphatidylcholine large unilamellar vesicles: Effect of hydrophobic block (PLA/PCL) of amphipathic diblock copolymers. Chem Phys Lipids 2020; 230:104927. [PMID: 32454007 DOI: 10.1016/j.chemphyslip.2020.104927] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 04/27/2020] [Accepted: 05/09/2020] [Indexed: 10/24/2022]
Abstract
In the present work, we show how amphipathic diblock copolymers affect the physicochemical properties of the lipid bilayer of DPPC liposome. Diblock copolymers proposed for this study are focused in the difference between PLA and PCL hydrophobic block, because PLA and PCL differ in their glass transition temperature, where a higher ratio of PLA, lowers the flexibility of the diblock copolymer. On the contrary, a greater proportion of PCL makes the diblock copolymer more flexible. This flexibility difference between hydrophobic block would affect the physicochemical properties of lipid bilayer of DPPC. The difference of rigidity or flexibility of hydrophobic block and their interaction with DPPC large unilamellar vesicles (LUVs) was evaluated at low and high copolymers concentration. The copolymer concentrations used were chosen based on their respective cmc. We measure (a) Thermotropic behavior from GP of Laurdan and fluorescence anisotropy of DPH; (b) Relation between wavelength excitation and generalized polarization of Laurdan; (c) Time-resolved fluorescence anisotropy of DPH; (d) Water outflow through the lipid bilayer and (e) calcein release from DPPC LUVs. Furthermore, large unilamellar vesicles in the absence and in the presence of different copolymers were characterized by size and zeta-potential. The results show that the diblock copolymer at high PLA/PCL ratio, that is, greater rigidity of hydrophobic block produces an increase of the phase transition temperature (Tm). For DPPC LUVs, Tm increase 3.5 °C at low and about 4.5 °C at high copolymers concentration, sensed by Laurdan and DPH fluorescent probes, although the DPPC/copolymers molar ratio for Cop4 is higher than Cop3, Cop2 and Cop1. In addition, we observed a decrease in the polarity of microenvironments in the bilayer and an increase in the order of the acyl chains in the bilayer to a high proportion of PLA. Furthermore, the presence of diblock copolymer with high proportion of PLA, decreases water outflow from DPPC liposome and water efflux is slower; leading to a decrease in calcein release from DPPC liposomes. Our results clearly show that the greater the stiffness of the hydrophobic block, greater degree of packaging of the lipid bilayer, greater the order of the acyl chains, and greater retention of water and calcein inside the liposome. Therefore, the presence of AB-type diblock copolymers with a more rigid hydrophobic block, stabilizes the lipid bilayer and would allow a more controlled release of water, and encapsulated molecules inside of the DPPC liposome.
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Affiliation(s)
- Karina Flandez
- Laboratorio de Biocoloides y Biointerfaces, Departamento de Química-Física, Facultad de Química y de Farmacia, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Sebastian Bonardd
- Facultad de Ciencias, Centro de Nanotecnología Aplicada, Universidad Mayor, Camino la Pirámide 5750, 8580745, Santiago, Chile
| | - Marco Soto-Arriaza
- Laboratorio de Biocoloides y Biointerfaces, Departamento de Química-Física, Facultad de Química y de Farmacia, Pontificia Universidad Católica de Chile, Santiago, Chile; Centro de Investigación en Nanotecnología y Materiales Avanzados CIEN-UC, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Casilla 306, Correo 22, C.P. 7820436 Santiago, Chile.
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Wu IY, Bala S, Škalko-Basnet N, di Cagno MP. Interpreting non-linear drug diffusion data: Utilizing Korsmeyer-Peppas model to study drug release from liposomes. Eur J Pharm Sci 2019; 138:105026. [PMID: 31374254 DOI: 10.1016/j.ejps.2019.105026] [Citation(s) in RCA: 126] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 07/10/2019] [Accepted: 07/29/2019] [Indexed: 01/11/2023]
Abstract
The aim of this work was to clarify the dynamics behind the influence of ionic strength on the changes in drug release from large unilamellar vesicles (LUVs). For this purpose, we have investigated the transport of two different model drugs (caffeine and hydrocortisone) formulated into liposomes through different types of barriers with different retention properties (regenerated cellulose and the newly introduced biomimetic barrier, Permeapad®). Drug release from liposomes was studied utilizing the standard Franz diffusion cells. LUV dispersions were exposed to the isotonic, hypotonic and hypertonic environment (difference of 300 mOsm/kg between the initial LUVs and the environment) and experimental data treated with both linear and non-linear (Korsmeyer-Peppas) regression models. To alter the rigidity of the liposomal membranes, cholesterol was introduced in the liposomal barriers (up to 25% w/w). Korsmeyer-Peppas model was proven to be suited to analyse experimental data throughout the experimental time frame, providing important additive information in comparison to standard linear approximation. The obtained results are highly relevant as they improve the interpretation of drug release kinetics from LUVs under osmotic stress. Moreover, the findings can be utilized in the development of liposomal formulations intended for nose-to-brain targeted drug delivery.
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Affiliation(s)
- Iren Yeeling Wu
- Drug Transport and Delivery Research Group, Department of Pharmacy, University of Tromsø The Arctic University of Norway, Universitetsvegen 57, 9037 Tromsø, Norway
| | - Sonali Bala
- Drug Transport and Delivery Research Group, Department of Pharmacy, University of Tromsø The Arctic University of Norway, Universitetsvegen 57, 9037 Tromsø, Norway
| | - Nataša Škalko-Basnet
- Drug Transport and Delivery Research Group, Department of Pharmacy, University of Tromsø The Arctic University of Norway, Universitetsvegen 57, 9037 Tromsø, Norway
| | - Massimiliano Pio di Cagno
- Drug Transport and Delivery Research Group, Department of Pharmacy, University of Tromsø The Arctic University of Norway, Universitetsvegen 57, 9037 Tromsø, Norway; Department of Pharmacy, Faculty of Mathematics and Natural Sciences, University of Oslo, Sem Sælands vei 3, 0371 Oslo, Norway.
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Wu IY, Nikolaisen TE, Škalko-Basnet N, di Cagno MP. The Hypotonic Environmental Changes Affect Liposomal Formulations for Nose-to-Brain Targeted Drug Delivery. J Pharm Sci 2019; 108:2570-2579. [PMID: 30885660 DOI: 10.1016/j.xphs.2019.03.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 03/08/2019] [Accepted: 03/08/2019] [Indexed: 01/12/2023]
Abstract
Systemic administration of drugs is ineffective in the treatment of central nervous system disorders because of the blood-brain barrier. Nasal administration has been suggested as an alternative administration route as drugs absorbed in the olfactory epithelium bypass the blood-brain barrier and reach the brain within minutes. However, the nasal mucosa properties (e.g., tonicity, pH) are not constant because of physiological and environmental factors, and this might limit the therapeutic outcome of nanocarrier-based formulations. To shine light on the impact of environmental ionic strength on nanocarrier-based formulations, we have studied how liposomal formulations respond to the change of tonicity of the external environment. Large unilamellar vesicles loaded with 6 different drugs were exposed to different hypotonic environments, creating an osmotic gradient within the inner core and external environment of the liposomes up to 650 mOsm/kg. Both size and polydispersity of liposomes were significantly affected by tonicity changes. Moreover, the release kinetics of hydrophilic and lipophilic drugs were largely enhanced by hypotonic environments. These results clearly demonstrate that the environmental ionic strength has an impact on liposomal formulation stability and drug release kinetics and it should be considered when liposomal formulations for nose-to-brain targeted drug delivery are designed.
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Affiliation(s)
- Iren Yeeling Wu
- Drug Transport and Delivery Research Group, Department of Pharmacy, University of Tromsø-The Arctic University of Norway, Universitetsvegen 57, 9037 Tromsø, Norway
| | - Trygg Einar Nikolaisen
- Drug Transport and Delivery Research Group, Department of Pharmacy, University of Tromsø-The Arctic University of Norway, Universitetsvegen 57, 9037 Tromsø, Norway
| | - Nataša Škalko-Basnet
- Drug Transport and Delivery Research Group, Department of Pharmacy, University of Tromsø-The Arctic University of Norway, Universitetsvegen 57, 9037 Tromsø, Norway
| | - Massimiliano Pio di Cagno
- Drug Transport and Delivery Research Group, Department of Pharmacy, University of Tromsø-The Arctic University of Norway, Universitetsvegen 57, 9037 Tromsø, Norway; Department of Pharmacy, Faculty of Mathematics and Natural Sciences, University of Oslo, Sem Sælands vei 3, 0371 Oslo, Norway.
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Abstract
Leukocytes can completely reorganize their cytoskeletal architecture within minutes. This structural plasticity, which facilitates their migration and communicative function, also enables them to exert a substantial amount of mechanical force against the extracellular matrix and the surfaces of interacting cells. In recent years, it has become increasingly clear that these forces have crucial roles in immune cell activation and subsequent effector responses. Here, I review our current understanding of how mechanical force regulates cell-surface receptor activation, cell migration, intracellular signalling and intercellular communication, highlighting the biological ramifications of these effects in various immune cell types.
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Affiliation(s)
- Morgan Huse
- Immunology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York 10065, USA
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10
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Ahumada M, Calderon C, Lissi E, Alvarez C, Lanio M, Pazos F. The pore forming capacity of Sticholysin I in dipalmitoyl phosphatidyl vesicles is tuned by osmotic stress. Chem Phys Lipids 2017; 203:87-93. [DOI: 10.1016/j.chemphyslip.2016.12.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 12/28/2016] [Accepted: 12/28/2016] [Indexed: 11/25/2022]
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Recursive Alterations of the Relationship between Simple Membrane Geometry and Insertion of Amphiphilic Motifs. MEMBRANES 2017; 7:membranes7010006. [PMID: 28208740 PMCID: PMC5371967 DOI: 10.3390/membranes7010006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 12/23/2016] [Accepted: 01/05/2017] [Indexed: 11/30/2022]
Abstract
The shape and composition of a membrane directly regulate the localization, activity, and signaling properties of membrane associated proteins. Proteins that both sense and generate membrane curvature, e.g., through amphiphilic insertion motifs, potentially engage in recursive binding dynamics, where the recruitment of the protein itself changes the properties of the membrane substrate. Simple geometric models of membrane curvature interactions already provide prediction tools for experimental observations, however these models are treating curvature sensing and generation as separated phenomena. Here, we outline a model that applies both geometric and basic thermodynamic considerations. This model allows us to predict the consequences of recursive properties in such interaction schemes and thereby integrate the membrane as a dynamic substrate. We use this combined model to hypothesize the origin and properties of tubular carrier systems observed in cells. Furthermore, we pinpoint the coupling to a membrane reservoir as a factor that influences the membrane curvature sensing and generation properties of local curvatures in the cell in line with classic determinants such as lipid composition and membrane geometry.
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Basu R, Huse M. Mechanical Communication at the Immunological Synapse. Trends Cell Biol 2016; 27:241-254. [PMID: 27986534 DOI: 10.1016/j.tcb.2016.10.005] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 10/28/2016] [Accepted: 10/31/2016] [Indexed: 12/27/2022]
Abstract
T and B lymphocytes communicate by forming immunological synapses with antigen-presenting target cells. These highly dynamic contacts are characterized by continuous cytoskeletal remodeling events, which not only structure the interface but also exert a considerable amount of mechanical force. In recent years, it has become increasingly clear that synaptic forces influence information transfer both into and out of the lymphocyte. Here, we review our current understanding of synapse mechanics, focusing on its role as an avenue for intercellular communication.
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Affiliation(s)
- Roshni Basu
- Immunology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
| | - Morgan Huse
- Immunology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.
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Interaction between amphipathic triblock copolymers and L-α-dipalmitoyl phosphatidylcholine large unilamellar vesicles. Colloids Surf B Biointerfaces 2016; 148:30-40. [DOI: 10.1016/j.colsurfb.2016.08.038] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 08/19/2016] [Accepted: 08/22/2016] [Indexed: 11/24/2022]
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Basu R, Whitlock BM, Husson J, Le Floc'h A, Jin W, Oyler-Yaniv A, Dotiwala F, Giannone G, Hivroz C, Biais N, Lieberman J, Kam LC, Huse M. Cytotoxic T Cells Use Mechanical Force to Potentiate Target Cell Killing. Cell 2016; 165:100-110. [PMID: 26924577 DOI: 10.1016/j.cell.2016.01.021] [Citation(s) in RCA: 266] [Impact Index Per Article: 33.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 12/09/2015] [Accepted: 01/13/2016] [Indexed: 12/18/2022]
Abstract
The immunological synapse formed between a cytotoxic T lymphocyte (CTL) and an infected or transformed target cell is a physically active structure capable of exerting mechanical force. Here, we investigated whether synaptic forces promote the destruction of target cells. CTLs kill by secreting toxic proteases and the pore forming protein perforin into the synapse. Biophysical experiments revealed a striking correlation between the magnitude of force exertion across the synapse and the speed of perforin pore formation on the target cell, implying that force potentiates cytotoxicity by enhancing perforin activity. Consistent with this interpretation, we found that increasing target cell tension augmented pore formation by perforin and killing by CTLs. Our data also indicate that CTLs coordinate perforin release and force exertion in space and time. These results reveal an unappreciated physical dimension to lymphocyte function and demonstrate that cells use mechanical forces to control the activity of outgoing chemical signals.
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Affiliation(s)
- Roshni Basu
- Immunology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
| | - Benjamin M Whitlock
- Biochemistry and Molecular Biology Graduate Program, Weill-Cornell Medical College, New York, NY 10065, USA
| | - Julien Husson
- Hydrodynamics Laboratory (LadHyX), Department of Mechanics, Ecole Polytechnique, Palaiseau 91128, France
| | - Audrey Le Floc'h
- Immunology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
| | - Weiyang Jin
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | - Alon Oyler-Yaniv
- Computational Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
| | - Farokh Dotiwala
- Program in Cellular and Molecular Medicine, Harvard Medical School, Boston, MA 02115, USA
| | - Gregory Giannone
- CNRS, University of Bordeaux, Interdisciplinary Institute for Neuroscience, UMR 5297, Bordeaux 33000, France
| | - Claire Hivroz
- Institute Curie, INSERM U932, PSL Research University, Paris 75005, France
| | - Nicolas Biais
- Department of Biology, Brooklyn College of the City University of New York, New York, NY 11201, USA
| | - Judy Lieberman
- Program in Cellular and Molecular Medicine, Harvard Medical School, Boston, MA 02115, USA
| | - Lance C Kam
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | - Morgan Huse
- Immunology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.
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Response of unilamellar DPPC and DPPC:SM vesicles to hypo and hyper osmotic shocks: A comparison. Chem Phys Lipids 2015; 188:54-60. [DOI: 10.1016/j.chemphyslip.2015.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 04/30/2015] [Accepted: 05/02/2015] [Indexed: 11/17/2022]
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16
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Enyedi B, Niethammer P. Mechanisms of epithelial wound detection. Trends Cell Biol 2015; 25:398-407. [PMID: 25813429 DOI: 10.1016/j.tcb.2015.02.007] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2014] [Revised: 02/23/2015] [Accepted: 02/24/2015] [Indexed: 12/22/2022]
Abstract
Efficient wound healing requires the coordinated responses of various cell types within an injured tissue. To react to the presence of a wound, cells have to first detect it. Judging from their initial biochemical and morphological responses, many cells including leukocytes, epithelial cells, and endothelial cells detect wounds from over hundreds of micrometers within seconds-to-minutes. Wound detection involves the conversion of an injury-induced homeostatic perturbation, such as cell lysis, an unconstrained epithelial edge, or permeability barrier breakdown, into a chemical or physical signal. The signal is spatially propagated through the tissue to synchronize protective responses of cells near the wound site and at a distance. This review summarizes the triggers and mechanisms of wound detection in animals.
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Affiliation(s)
- Balázs Enyedi
- Cell Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Philipp Niethammer
- Cell Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.
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17
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Chen D, Santore MM. 1,2-Dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)-rich domain formation in binary phospholipid vesicle membranes: two-dimensional nucleation and growth. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:9484-9493. [PMID: 25084141 DOI: 10.1021/la502089t] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Decades of study have probed phase transitions in model phospholipid bilayers and vesicles, especially in the context of the equilibrium phase diagram. Critical to the response of vesicles to environmental triggers, to the ultimate domain morphology, and to the approach to equilibrium (or not), we present here a study of domain formation in vesicles, focusing on a mechanism by which the cooling rate, tension, and composition affect the first appearance (nucleation) and subsequent growth of solid membrane domains. Employing a popular mixed membrane model based on DOPC and DPPC (1,2-dioleoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, respectively), we examined phase separation in giant two-component vesicles that were cooled from the one-phase fluid (Lα) region of the phase diagram into a region of fluid (Lα)-solid coexistence. At moderate and low membrane tensions, cooling produced solid DPPC-rich domains appearing as compact patches or irregular hexagons and likely with a Pβ' (ripple) arrangement. (The compact solid domains in this study differed distinctly from striped domains in vesicles of the same composition, in terms of molecular organization and conditions of first appearance during cooling.) The amounts of these solid domains were shown to adhere to the lever arm rule for a tie line on the phase diagram, with a solid composition near 95 mol % DPPC. The nucleation of the compact solid domains occurred in a short period, followed by rapid addition of ordered molecules to the nucleated domains, excluding tracer dye. The two-dimensional nucleation density of these compact solid domains (in the range of 10(-2)-10(-1) μm(-2)) was found to increase with the cooling rate (equivalent to the quench depth) with a greater than linear dependence. The 2-D nucleation density was also seen to decrease with membrane tension, presumably because membrane tension increases the line tension around a domain that opposes nucleation. A sigmoidal dependence of the nucleation density on the DPPC concentration was also found. With cooling rates in excess of ∼1 °C/min, solid domains persisted down to room temperature, likely passing from a preferred equilibrium to a local equilibrium with continued cooling. As a result of the persistence of the originally nucleated domains and the conservation of DPPC in the membrane, we observed an increasingly greater number of smaller domains with increased cooling rates. The domains in these vesicles were compact or hexagonal-shaped in contrast to flower-shaped dendritic domains in the same membrane system in a supported membrane configuration.
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Affiliation(s)
- Dong Chen
- Department of Physics and ‡Department of Polymer Science and Engineering, University of Massachusetts , Amherst, Massachusetts 01003, United States
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Last NB, Schlamadinger DE, Miranker AD. A common landscape for membrane-active peptides. Protein Sci 2013; 22:870-82. [PMID: 23649542 DOI: 10.1002/pro.2274] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Revised: 04/23/2013] [Accepted: 04/24/2013] [Indexed: 10/26/2022]
Abstract
Three families of membrane-active peptides are commonly found in nature and are classified according to their initial apparent activity. Antimicrobial peptides are ancient components of the innate immune system and typically act by disruption of microbial membranes leading to cell death. Amyloid peptides contribute to the pathology of diverse diseases from Alzheimer's to type II diabetes. Preamyloid states of these peptides can act as toxins by binding to and permeabilizing cellular membranes. Cell-penetrating peptides are natural or engineered short sequences that can spontaneously translocate across a membrane. Despite these differences in classification, many similarities in sequence, structure, and activity suggest that peptides from all three classes act through a small, common set of physical principles. Namely, these peptides alter the Brownian properties of phospholipid bilayers, enhancing the sampling of intrinsic fluctuations that include membrane defects. A complete energy landscape for such systems can be described by the innate membrane properties, differential partition, and the associated kinetics of peptides dividing between surface and defect regions of the bilayer. The goal of this review is to argue that the activities of these membrane-active families of peptides simply represent different facets of what is a shared energy landscape.
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Affiliation(s)
- Nicholas B Last
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, USA
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Balleza D. Mechanical properties of lipid bilayers and regulation of mechanosensitive function: from biological to biomimetic channels. Channels (Austin) 2012; 6:220-33. [PMID: 22790280 DOI: 10.4161/chan.21085] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Material properties of lipid bilayers, including thickness, intrinsic curvature and compressibility regulate the function of mechanosensitive (MS) channels. This regulation is dependent on phospholipid composition, lateral packing and organization within the membrane. Therefore, a more complete framework to understand the functioning of MS channels requires insights into bilayer structure, thermodynamics and phospholipid structure, as well as lipid-protein interactions. Phospholipids and MS channels interact with each other mainly through electrostatic forces and hydrophobic matching, which are also crucial for antimicrobial peptides. They are excellent models for studying the formation and stabilization of membrane pores. Importantly, they perform equivalent responses as MS channels: (1) tilting in response to tension and (2) dissipation of osmotic gradients. Lessons learned from pore forming peptides could enrich our knowledge of mechanisms of action and evolution of these channels. Here, the current state of the art is presented and general principles of membrane regulation of mechanosensitive function are discussed.
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Affiliation(s)
- Daniel Balleza
- Unidad de Biofísica, CSIC, UPV/EHU, Universidad del País Vasco, Leioa, Spain.
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Binding of peptides corresponding to the carboxy-terminal region of human-β-defensins-1–3 with model membranes investigated by isothermal titration calorimetry. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:1386-94. [DOI: 10.1016/j.bbamem.2012.02.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Revised: 01/27/2012] [Accepted: 02/15/2012] [Indexed: 12/23/2022]
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Balleza D. Toward understanding protocell mechanosensation. ORIGINS LIFE EVOL B 2011; 41:281-304. [PMID: 21080073 DOI: 10.1007/s11084-010-9225-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Accepted: 10/20/2010] [Indexed: 01/11/2023]
Abstract
Mechanosensitive (MS) channels can prevent bacterial bursting during hypo-osmotic shocks by responding to increases in lateral tension at the membrane level through an integrated and coordinated opening mechanism. Mechanical regulation in protocells could have been one of the first mechanisms to evolve in order to preserve their integrity against changing environmental conditions. How has the rich functional diversity found in present cells been created throughout evolution, and what did the primordial MS channels look like? This review has been written with the aim of identifying which factors may have been important for the appearance of the first osmotic valve in a prebiotic context, and what this valve may have been like. It highlights the mechanical properties of lipid bilayers, the association of peptides as aggregates in membranes, and the conservation of sequence motifs as central aspects to understand the evolution of proteins that gate below the tension required for spontaneous pore formation and membrane rupture. The arguments developed here apply to both MscL and MscS homologs, but could be valid to mechano-susceptible proteins in general.
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Affiliation(s)
- Daniel Balleza
- Unidad de Biofísica, CSIC-UPV/EHU, Universidad del País Vasco, Barrio Sarriena s/n, Leioa, Spain.
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22
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Islet amyloid polypeptide demonstrates a persistent capacity to disrupt membrane integrity. Proc Natl Acad Sci U S A 2011; 108:9460-5. [PMID: 21606325 DOI: 10.1073/pnas.1102356108] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Amyloid fiber formation is correlated with pathology in many diseases, including Alzheimer's, Parkinson's, and type II diabetes. Although β-sheet-rich fibrillar protein deposits define this class of disorder, increasing evidence points toward small oligomeric species as being responsible for cell dysfunction and death. The molecular mechanism by which this occurs is unknown, but likely involves the interaction of these species with biological membranes, with a subsequent loss of integrity. Here, we investigate islet amyloid polypeptide, which is implicated in the loss of insulin-secreting cells in type II diabetics. We report the discovery of oligomeric species that arise through stochastic nucleation on membranes and result in disruption of the lipid bilayer. These species are stable, result in all-or-none leakage, and represent a definable protein/lipid phase that equilibrates over time. We characterize the reaction pathway of assembly through the use of an experimental design that includes both ensemble and single-particle evaluations. Complexity in the reaction pathway could not be satisfied using a two-state description of membrane-bound monomer and oligomeric species. We therefore put forward a three-state kinetic framework, one of which we conjecture represents a non-amyloid, non-β-sheet intermediate previously shown to be a candidate therapeutic target.
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Dominak LM, Omiatek DM, Gundermann EL, Heien ML, Keating CD. Polymeric crowding agents improve passive biomacromolecule encapsulation in lipid vesicles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:13195-200. [PMID: 20695558 PMCID: PMC2919175 DOI: 10.1021/la101903r] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Revised: 06/24/2010] [Indexed: 05/19/2023]
Abstract
Large solutes such as high molecular weight proteins can be difficult to encapsulate in lipid vesicles. Passive trapping of these macromolecular solutes during vesicle formation typically results in concentrations inside the vesicles that are much lower than in the external solution. Here, we investigated the effect of macromolecular crowding on passive encapsulation of biological macromolecules with molecular weights ranging from 52 kDa to 660 kDa within both individual giant lipid vesicles (GVs, > 3 microm diameter) and populations of 200 nm diameter large unilamellar vesicles (LUVs). Fluorescently labeled biomacromolecules were encapsulated during vesicle formation in the presence or absence of three weight percent poly(ethylene glycol) (PEG; 8 kDa) or dextran 500 kDa, which served as crowding agents. Encapsulation efficiency of the labeled biomolecules was higher for the lower molecular weight solutes, with internal concentrations essentially equal to external concentrations for labeled biomacromolecules with hydrodynamic radii (r(h)) less than 10 nm. In contrast, internal concentrations were reduced markedly for larger solutes with r(h) > or = 10 nm. Addition of PEG or dextran during vesicle formation improved encapsulation of these larger proteins up to the same levels as observed for the smaller proteins, such that internal and external concentrations were equal. This observation is consistent with PEG and dextran acting as volume excluders, reducing the hydrodynamic radius of the biomacromolecules and increasing their encapsulation. This work demonstrates a simple and general route to improved encapsulation of otherwise poorly encapsulated macromolecular solutes in both GV and LUVs up to their concentration in the solution present during vesicle formation.
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Affiliation(s)
- Lisa M. Dominak
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Donna M. Omiatek
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Erica L. Gundermann
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Michael L. Heien
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Christine D. Keating
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802
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24
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Quartz crystal microbalance with dissipation monitoring of supported lipid bilayers on various substrates. Nat Protoc 2010; 5:1096-106. [PMID: 20539285 DOI: 10.1038/nprot.2010.65] [Citation(s) in RCA: 386] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Supported lipid bilayers (SLBs) mimic biological membranes and are a versatile platform for a wide range of biophysical research fields including lipid-protein interactions, protein-protein interactions and membrane-based biosensors. The quartz crystal microbalance with dissipation monitoring (QCM-D) has had a pivotal role in understanding SLB formation on various substrates. As shown by its real-time kinetic monitoring of SLB formation, QCM-D can probe the dynamics of biomacromolecular interactions. We present a protocol for constructing zwitterionic SLBs supported on silicon oxide and titanium oxide, and discuss technical issues that need to be considered when working with charged lipid compositions. Furthermore, we explain a recently developed strategy that uses an amphipathic, alpha-helical (AH) peptide to form SLBs on gold and titanium oxide substrates. The protocols can be completed in less than 3 h.
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25
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Role of membrane lipids for the activity of pore forming peptides and proteins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 677:31-55. [PMID: 20687479 DOI: 10.1007/978-1-4419-6327-7_4] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Bilayer lipids, far from being passive elements, have multiple roles in polypeptide-dependent pore formation. Lipids participate at all stages of the formation of pores by providing the binding site for proteins and peptides, conditioning their active structure and modulating the molecular reorganization of the membrane complex. Such general functions of lipids superimpose to other particular roles, from electrostatic and curvature effects to more specific actions in cases like cholesterol, sphingolipids or cardiolipin. Pores are natural phenomena in lipid membranes. Driven by membrane fluctuations and packing defects, transient water pores are related to spontaneous lipid flip-flop and non-assisted ion permeation. In the absence ofproteins or peptides, these are rare short living events, with properties dependent on the lipid composition of the membrane. Their frequency increases under conditions of internal membrane disturbance of the lipid packing, like in the presence of membrane-bound proteins or peptides. These latter molecules, in fact, form dynamic supramolecular assemblies together with the lipids and transmembrane pores are one of the possible structures of the complex. Active peptides and proteins can thus be considered inducers or enhancers of pores which increase their probability and lifetime by modifying the thermodynamic membrane balance. This includes destabilizing the membrane lamellar structure, lowering the activation energy for pore formation and stabilizing the open pore structure.
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26
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Dominak LM, Keating CD. Macromolecular crowding improves polymer encapsulation within giant lipid vesicles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:13565-71. [PMID: 18980360 DOI: 10.1021/la8028403] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We report the effect of macromolecular crowding on encapsulation efficiency of fluorescently labeled poly(ethylene glycol) (PEG) and dextran polymers within individual giant lipid vesicles (GVs). Low concentrations of the fluorescently labeled polymers (82 nM to 186 pM) were mixed with varying concentrations of nonfluorescent polymers that served as crowding agents during vesicle formation by gentle hydration. Encapsulation efficiency of the fluorescently labeled polymers in individual GVs (EEind) was determined via confocal fluorescence microscopy. EEind for high molecular weight polymers (e.g., fluorescein isothiocyanate (FITC)-dextran 500 and 2000 kDa) increased substantially in the presence of several weight percent unlabeled PEG or dextran. For example, when 0.24 microM FITC dextran 500 kDa was encapsulated, addition of 3% PEG 8 kDa improved the mean concentration in the GVs from 0.14 microM (+/-50%) to 0.24 microM (+/-12%). Light scattering data indicate reduced hydrodynamic radii for polymers as a function of increasing polymer concentration, suggesting that the improvements in EEind result from polymer condensation due to macromolecular crowding. Polymeric cosolutes did not significantly impact EEind for lower molecular weight polymers (e.g., Alexa Fluor 488-PEG 20 kDa), which already encapsulated efficiently (EEind to approximately 1). However, for both the higher and lower molecular weight labeled polymers, cosolutes led to improved uniformity in EEind for vesicles within a batch. Methods for improving the value and homogeneity of EEind for polymeric solutes in lipid vesicles are important in a variety of applications, including the use of vesicles as microreactors and as vehicles for drug delivery.
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Affiliation(s)
- Lisa M Dominak
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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Fishkis M. Steps towards the formation of a protocell: the possible role of short peptides. ORIGINS LIFE EVOL B 2007; 37:537-53. [PMID: 17874202 DOI: 10.1007/s11084-007-9111-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2007] [Accepted: 08/15/2007] [Indexed: 10/22/2022]
Abstract
The paper deals with molecular self-organization leading to formation of a protocell. Plausible steps towards a protocell include: polymerization of peptides and oligonucleotides on mineral surfaces; coevolution of peptides and oligonucleotides with formation of collectively autocatalytic sets; self-organization of short peptides into vesicles; entrapment of the peptide/oligonucleotide systems in mixed peptide and simple amphiphile membranes; and formation of functioning protocells with metabolism and cell division. The established propensity of short peptides to self-ordering and to formation of vesicles makes this sequence plausible. We further suggest that evolution of a protocell produced cellular ancestors of viruses as well as ancestors of cellular organisms.
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Affiliation(s)
- Maya Fishkis
- Evolving Systems Technology, 95 Hawkfield Crescent NW, Calgary, Alberta, Canada.
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Dominak LM, Keating CD. Polymer encapsulation within giant lipid vesicles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:7148-54. [PMID: 17516666 DOI: 10.1021/la063687v] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We report encapsulation of polymers and small molecules within individual giant lipid vesicles (GVs; 3-80 microm), as determined by confocal fluorescence microscopy. Polymer-bound or free dyes were encapsulated within GVs by including these molecules in the aqueous solution during vesicle formation via gentle hydration. Encapsulation efficiencies of individual GVs (EE(ind)) were determined from the fluorescence intensity ratio inside vs outside the vesicle. EE(ind) varied considerably from vesicle to vesicle, with interior solute concentrations for GVs within the same batch ranging from much less than to slightly more than the initial concentration. The majority of GVs had high internal concentrations of polymer or small-molecule encapsulants equal to or slightly greater than the external concentration. EE(ind) decreased for high molecular weight polymers (e.g., dextran 500 000), but was relatively insensitive to the GV diameter, membrane composition, or incubation temperature in our experiments. Knowledge of EE(ind) is important for quantitative evaluation of reactions occurring within GVs (e.g., enzymatic processes) and for optimizing encapsulation conditions.
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Affiliation(s)
- Lisa M Dominak
- Department of Chemistry, Pennsylvania State University, University Park, PA 16802, USA
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29
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Rodriguez N, Cribier S, Pincet F. Transition from long- to short-lived transient pores in giant vesicles in an aqueous medium. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 74:061902. [PMID: 17280091 DOI: 10.1103/physreve.74.061902] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2006] [Revised: 08/24/2006] [Indexed: 05/13/2023]
Abstract
We have observed large pores in the membrane of giant vesicles in an aqueous medium. The lifetime of the pores can reach 2 min and their size (a few micrometers) enables their visualization by fluorescence microscopy. These pores are obtained thanks to a destabilization of the membrane due to the synergistic action of a cone-shaped and nitrobenzodiazole (NBD) labeled phospholipid illuminated in the presence of dithionite. The opening of the pore occurs immediately after illumination starts so that it can be accurately triggered. A concomitant decrease of the vesicle radius is observed; we interpret it as a solubilization of the membrane. Depending on the rate of this solubilization, long- or short-lived pores were observed. At the transition between both regimes for a 30 microm vesicle, the solubilization rate was about 1/300 s{-1} . In order to interpret these observations, we have revisited the current model of pore opening to take into account this solubilization. This proposed model along with simulations enables us to prove that solubilization explains why the large long-lived pores are observed even in an aqueous medium. The model also predicts the solubilization rate at the transition between a single long-lived pore and a cascade of short-lived pores.
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30
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Becucci L, León RR, Moncelli MR, Rovero P, Guidelli R. Electrochemical investigation of melittin reconstituted into a mercury-supported lipid bilayer. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:6644-50. [PMID: 16831008 DOI: 10.1021/la060681x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The channel-forming peptide melittin was incorporated into a biomimetic membrane consisting of a mercury electrode coated with a thiolipid monolayer, with a lipid monolayer self-assembled on top of it. The thiolipid consisted of a hydrophilic tetraethyleneoxy chain terminated at one end with a disulfide group, for anchoring to the mercury surface, and covalently linked at the other end to two diphytanyl chains, which formed a lipid bilayer with the overhanging lipid monolayer. The conductance of the lipid bilayer in contact with aqueous 0.1 M KCl was measured by electrochemical impedance spectroscopy over a frequency range from 1 x 10(-2) to 1 x 10(5) Hz and a potential range of 0.7 V for different compositions of the outer lipid monolayer. The conductance increases abruptly above the background level at sufficiently negative applied potentials, attaining a maximum value that increases with the composition of the outer monolayer in the order PC/chol (60:40) < PC < PC/SM/chol (59:15:26) < PS, with PC = phosphatidylcholine, chol = cholesterol, SM = sphingomyelin, and PS = phosphatidylserine. The higher the maximum conductance, the less negative the applied potential at which it is attained. This behavior is also discussed using a model of the electrified interphase.
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Affiliation(s)
- Lucia Becucci
- Department of Chemistry, Florence University, Via della Lastruccia 3, 50019 Sesto Fiorentino, Florence, Italy
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31
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Detergent-like actions of linear amphipathic cationic antimicrobial peptides. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:1529-39. [PMID: 16928357 DOI: 10.1016/j.bbamem.2006.07.001] [Citation(s) in RCA: 429] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2006] [Revised: 06/30/2006] [Accepted: 07/06/2006] [Indexed: 12/25/2022]
Abstract
Antimicrobial peptides have raised much interest as pathogens become resistant against conventional antibiotics. We review biophysical studies that have been performed to better understand the interactions of linear amphipathic cationic peptides such as magainins, cecropins, dermaseptin, delta-lysin or melittin. The amphipathic character of these peptides and their interactions with membranes resemble the properties of detergent molecules and analogies between membrane-active peptide and detergents are presented. Several models have been suggested to explain the pore-forming, membrane-lytic and antibiotic activities of these peptides. Here we suggest that these might be 'special cases' within complicated phase diagrams describing the morphological plasticity of peptide/lipid supramolecular assemblies.
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Livadaru L, Kovalenko A. Fundamental mechanism of translocation across liquidlike membranes: toward control over nanoparticle behavior. NANO LETTERS 2006; 6:78-83. [PMID: 16402791 DOI: 10.1021/nl052073s] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
We envision and theoretically investigate a novel behavior of a functionalized nanoparticle designed to translocate through a liquidlike membrane. We develop a statistical-mechanical approach to such a system. We predict a new mechanism for the opening of a circular energy-dominated pore on the membrane by a nanoparticle functionalized with a peptide aggregate. Following fluctuations in the position and orientation of the nanoparticle, the peptide aggregate incorporates into the membrane and locally destabilizes it. The nucleation of a pore centered at the peptide aggregate attached to the particle is a precursor to particle translocation. The subsequent opening of the pore is assisted by adhesion of the membrane to the particle. We determine the conditions in which thermal fluctuations in the membrane shape and the pore size can induce translocation of the particle. For different system parameters quantities such as the free energy, entropy, pore size, degree of particle wrapping, and the probability of spontaneous translocation are obtained.
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Affiliation(s)
- Lucian Livadaru
- National Institute for Nanotechnology, National Research Council of Canada, Edmonton, Alberta
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33
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Noireaux V, Libchaber A. A vesicle bioreactor as a step toward an artificial cell assembly. Proc Natl Acad Sci U S A 2004; 101:17669-74. [PMID: 15591347 PMCID: PMC539773 DOI: 10.1073/pnas.0408236101] [Citation(s) in RCA: 794] [Impact Index Per Article: 39.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
An Escherichia coli cell-free expression system is encapsulated in a phospholipid vesicle to build a cell-like bioreactor. Large unilamellar vesicles containing extracts are produced in an oil-extract emulsion. To form a bilayer the vesicles are transferred into a feeding solution that contains ribonucleotides and amino acids. Transcription-translation of plasmid genes is isolated in the vesicles. Whereas in bulk solution expression of enhanced GFP stops after 2 h, inside the vesicle permeability of the membrane to the feeding solution prolongs the expression for up to 5 h. To solve the energy and material limitations and increase the capacity of the reactor, the alpha-hemolysin pore protein from Staphylococcus aureus is expressed inside the vesicle to create a selective permeability for nutrients. The reactor can then sustain expression for up to 4 days with a protein production of 30 muM after 4 days. Oxygen diffusion and osmotic pressure are critical parameters to maintain expression and avoid vesicle burst.
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Affiliation(s)
- Vincent Noireaux
- Center for Studies in Physics and Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA
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McAnulty JF, Foley JD, Reid TW, Heath TD, Waller KR, Murphy CJ. Suppression of cold ischemic injury in stored kidneys by the antimicrobial peptide bactenecin. Cryobiology 2004; 49:230-40. [PMID: 15615609 DOI: 10.1016/j.cryobiol.2004.08.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2004] [Accepted: 08/19/2004] [Indexed: 11/23/2022]
Abstract
BACKGROUND Cold ischemic injury plays an important role in short- and long-term function of kidneys after transplant. Antimicrobial peptides have not previously been studied for their impact on cold ischemia in transplanted kidneys. METHODS Bactenecin (L- and D-forms) was added to University of Wisconsin (UW) preservation solution for 3-day cold storage of dog kidneys. Effects on membrane permeability were studied in synthetic liposomes and in kidney cortex tissue slices. The role of bactenecin as a tissue mitogen and direct cytoskeletal stabilizer were studied with cultured cells and in vitro. RESULTS Bactenecin (both L- and D- forms) resulted in significant decreases in postoperative serum creatinine and time required for return of creatinine to the normal range showing the effect was independent of chirality. Bactenecin permeabilized synthetic liposomes and altered kidney cortex tissue slice membrane permeability characteristics, irrespective of chirality. Neither did bactenecin act as a mitogen for either primary renal tubule or Madin-Darby canine kidney (MDCK) cells stored in UW solution, nor did it appear to directly affect cytoskeletal dynamics. CONCLUSIONS These results show that the antimicrobial peptide bactenecin can improve the quality of static cold storage of kidneys. The mechanism of its action is independent of receptor binding and does not appear to involve either an effect on the cytoskeleton or via activity as a mitogen. Current evidence best supports the hypothesis that bactenecin protects against cold ischemic injury by a controlled permeabilization of the membranes of the kidney during cold storage.
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Affiliation(s)
- Jonathan F McAnulty
- Department of Surgical Sciences, University of Wisconsin, 2015 Linden Dr., Madison, WI 53706, USA
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35
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Hull MC, Sauer DB, Hovis JS. Influence of Lipid Chemistry on the Osmotic Response of Cell Membranes: Effect of Non-Bilayer Forming Lipids. J Phys Chem B 2004. [DOI: 10.1021/jp049845d] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Marshall C. Hull
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2018
| | - David B. Sauer
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2018
| | - Jennifer S. Hovis
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2018
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Barrau C, Teissié J, Gabriel B. Osmotically induced membrane tension facilitates the triggering of living cell electropermeabilization. Bioelectrochemistry 2004; 63:327-32. [PMID: 15110297 DOI: 10.1016/j.bioelechem.2003.11.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2003] [Revised: 11/13/2003] [Accepted: 11/17/2003] [Indexed: 11/30/2022]
Abstract
Very little is known about the molecular mechanisms supporting living cell membrane electropermeabilization. This concept is based on the local membrane permeability induced by cell exposure to brief and intense external electric field pulses. During the electric field application, an electro-induced membrane electric potential difference is created that is locally associated with the dielectric properties of the plasma membrane. When the new membrane electric potential difference locally reaches a critical value, a local alteration of the membrane structure is induced and leads to reversible permeabilization. In our study, we attempted to determine whether mechanical tension could modulate the triggering of membrane electropermeabilization. Change in lateral tension of Chinese Hamster Ovary cell membrane has been osmotically induced. Cell electropermeabilization was performed in the minute time range after the osmotic stress, i.e., before the regulatory volume decrease being activated by the cell. Living cell electropermeabilization was analyzed on cell population using flow cytometry. We observed that electropermeabilization triggering was significantly facilitated when the lateral membrane tension was increased. The main conclusion is that the critical value of transmembrane potential needed to trigger membrane electropermeabilization, is smaller when the membrane is under lateral mechanical constraint. This supports the hypothesis that both mechanical and electrical constraints play a key role in transient membrane destabilization.
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Affiliation(s)
- C Barrau
- Institut de Pharmacologie et de Biologie Structurale-CNRS, UMR5089, 205 route de Narbonne, Toulouse cedex 4, F-31077 France
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Golantsova NE, Gorbunova EE, Mackow ER. Discrete domains within the rotavirus VP5* direct peripheral membrane association and membrane permeability. J Virol 2004; 78:2037-44. [PMID: 14747568 PMCID: PMC369428 DOI: 10.1128/jvi.78.4.2037-2044.2004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Cleavage of the rotavirus spike protein, VP4, is required for rotavirus-induced membrane permeability and viral entry into cells. The VP5* cleavage product selectively permeabilizes membranes and liposomes and contains an internal hydrophobic domain that is required for membrane permeability. Here we investigate VP5* domains (residues 248 to 474) that direct membrane binding. We determined that expressed VP5 fragments containing residues 248 to 474 or 265 to 474, including the internal hydrophobic domain, bind to cellular membranes but are not present in Triton X-100-resistant membrane rafts. Expressed VP5 partitions into aqueous but not detergent phases of Triton X-114, suggesting that VP5 is not integrally inserted into membranes. Since high-salt or alkaline conditions eluted VP5 from membranes, our findings demonstrate that VP5 is peripherally associated with membranes. Interestingly, mutagenesis of residue 394 (W-->R) within the VP5 hydrophobic domain, which abolishes VP5-directed permeability, had no effect on VP5's peripheral membrane association. In contrast, deletion of N-terminal VP5 residues (residues 265 to 279) abolished VP5 binding to membranes. Alanine mutagenesis of two positively charged residues within this domain (residues 274R and 276K) dramatically reduced (>95%) binding of VP5 to membranes and suggested their potential interaction with polar head groups of the lipid bilayer. Mutations in either the VP5 hydrophobic or basic domain blocked VP5-directed permeability of cells. These findings indicate that there are at least two discrete domains within VP5* required for pore formation: an N-terminal basic domain that permits VP5* to peripherally associate with membranes and an internal hydrophobic domain that is essential for altering membrane permeability. These results provide a fundamental understanding of interactions between VP5* and the membrane, which are required for rotavirus entry.
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Affiliation(s)
- Nina E Golantsova
- Department of Medicine, Stony Brook University, Stony Brook, New York 11794, USA
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Krishnakumari V, Sharadadevi A, Singh S, Nagaraj R. Single disulfide and linear analogues corresponding to the carboxy-terminal segment of bovine beta-defensin-2: effects of introducing the beta-hairpin nucleating sequence d-pro-gly on antibacterial activity and Biophysical properties. Biochemistry 2003; 42:9307-15. [PMID: 12899617 DOI: 10.1021/bi034403y] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mammalian defensins (alpha as well as beta forms) have a beta-hairpin structural motif spanning approximately 20 residues at the carboxy-terminal end. We have investigated the antibacterial activity and biophysical properties of synthetic peptides corresponding to the carboxy-terminal segment of bovine beta-defensin-2 (BNBD-2): VRNHVTC(1)RINRGFC(2)VPIRC(3)PGRTRQIGTC(4)FGPRIKC(5)C(6)RSW (positions of disulfide bonds are C(1)[bond]C(5), C(2)[bond]C(4), and C(3)[bond]C(6)). The parent sequence chosen was RCPGRTRQIGTIFGPRIKCRSW (P1), which spans the carboxy-terminal region of BNBD-2. Since the dipeptide sequence D-Pro-Gly favors nucleation of beta-hairpin structures even in acyclic peptides, analogues of P1 with one D-Pro-Gly at the central portion and two D-Pro-Gly segments near the N- and C-terminal ends were generated. An analogue in which GP (residues 14 and 15) in P1 was switched to PG was also synthesized. It was observed that the cyclic form as well as their linear forms exhibited antibacterial activity. Circular dichroism and theoretical studies indicated that while the beta-hairpin conformation is populated, there is conformational plasticity in the cyclic and linear peptides. The mode of bacterial killing was by membrane permeabilization. The entire mammalian defensin sequence does not appear to be essential for manifestation of antibacterial activity. Hence, short peptides corresponding to the C-terminal segments of mammalian defensins could have potential as therapeutic agents.
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Haro-Pérez C, Quesada-Pérez M, Callejas-Fernández J, Casals E, Estelrich J, Hidalgo-Álvarez R. Interplay between hydrodynamic and direct interactions using liposomes. J Chem Phys 2003. [DOI: 10.1063/1.1578628] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Johnson JM, Ha T, Chu S, Boxer SG. Early steps of supported bilayer formation probed by single vesicle fluorescence assays. Biophys J 2002; 83:3371-9. [PMID: 12496104 PMCID: PMC1302412 DOI: 10.1016/s0006-3495(02)75337-x] [Citation(s) in RCA: 183] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
We have developed a single vesicle assay to study the mechanisms of supported bilayer formation. Fluorescently labeled, unilamellar vesicles (30-100 nm diameter) were first adsorbed to a quartz surface at low enough surface concentrations to visualize single vesicles. Fusion and rupture events during the bilayer formation, induced by the subsequent addition of unlabeled vesicles, were detected by measuring two-color fluorescence signals simultaneously. Lipid-conjugated dyes monitored the membrane fusion while encapsulated dyes reported on the vesicle rupture. Four dominant pathways were observed, each exhibiting characteristic two-color fluorescence signatures: 1) primary fusion, in which an unlabeled vesicle fuses with a labeled vesicle on the surface, is signified by the dequenching of the lipid-conjugated dyes followed by rupture and final merging into the bilayer; 2) simultaneous fusion and rupture, in which a labeled vesicle on the surface ruptures simultaneously upon fusion with an unlabeled vesicle; 3) no dequenching, in which loss of fluorescence signal from both dyes occur simultaneously with the final merger into the bilayer; and 4) isolated rupture (pre-ruptured vesicles), in which a labeled vesicle on the surface spontaneously undergoes content loss, a process that occurs with high efficiency in the presence of a high concentration of Texas Red-labeled lipids. Vesicles that have undergone content loss appear to be more fusogenic than intact vesicles.
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Affiliation(s)
- Joseph M Johnson
- Department of Chemistry, Stanford University, Stanford, CA 94305-5080, USA
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Abstract
Cells exercise size homeostasis, and the origins of their ability to do so is the topic of this essay. Before there were cells, there were protocells. The most basic questions about protocells as objects are: What were they made of, and how big were they? Asking how big they were implies that the answer to the first part includes a boundary. The best candidate for that boundary is a self-assembling lipid bilayer. Therefore, protocells are defined here as Darwinian liposomes-bilayer vesicles with mutable on-board replicases linked to phenotypes. Because liposomes undergo spontaneous fission and fusion, and are subject to osmotic forces, size regulation in the earliest protocells would essentially have been liposome physics. For successful protocells, averting osmotic lysis would have been the first order of business. However, from the outset size mattered too, because of sex and reproduction (i.e., genome mixing and genome copying in entities with phenotypes). Protocell fission and fusion would have blended seamlessly into protocell sex and reproduction, making any gene product that furnished control over protocell size changes doubly adaptive. A recurrent theme is the feedback role of bilayer tension in protocell size control. Ways in which primitive peptides and their aggregates (e.g., channels) might have allowed liposomes to gain improved volume and surface area homeostasis are suggested. Domain-swapped proteins that polymerize as filaments are discussed as the origin of cytoskeleton structures that diversify and stabilize liposome shapes and sizes. Throughout, attention is paid to the question of set points for cell size.
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Affiliation(s)
- Catherine E Morris
- Department of Neuroscience, Ottawa Health Research Institute, Ottawa Hospital, Canada.
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