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Schmitt C, Lippert AH, Bonakdar N, Sandoghdar V, Voll LM. Compartmentalization and Transport in Synthetic Vesicles. Front Bioeng Biotechnol 2016; 4:19. [PMID: 26973834 PMCID: PMC4770187 DOI: 10.3389/fbioe.2016.00019] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Accepted: 02/11/2016] [Indexed: 12/03/2022] Open
Abstract
Nanoscale vesicles have become a popular tool in life sciences. Besides liposomes that are generated from phospholipids of natural origin, polymersomes fabricated of synthetic block copolymers enjoy increasing popularity, as they represent more versatile membrane building blocks that can be selected based on their specific physicochemical properties, such as permeability, stability, or chemical reactivity. In this review, we focus on the application of simple and nested artificial vesicles in synthetic biology. First, we provide an introduction into the utilization of multicompartmented vesosomes as compartmentalized nanoscale bioreactors. In the bottom-up development of protocells from vesicular nanoreactors, the specific exchange of pathway intermediates across compartment boundaries represents a bottleneck for future studies. To date, most compartmented bioreactors rely on unspecific exchange of substrates and products. This is either based on changes in permeability of the coblock polymer shell by physicochemical triggers or by the incorporation of unspecific porin proteins into the vesicle membrane. Since the incorporation of membrane transport proteins into simple and nested artificial vesicles offers the potential for specific exchange of substances between subcompartments, it opens new vistas in the design of protocells. Therefore, we devote the main part of the review to summarize the technical advances in the use of phospholipids and block copolymers for the reconstitution of membrane proteins.
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Affiliation(s)
- Christine Schmitt
- Division of Biochemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Anna H. Lippert
- Max-Planck-Institute for the Science of Light, Erlangen, Germany
| | - Navid Bonakdar
- Max-Planck-Institute for the Science of Light, Erlangen, Germany
| | - Vahid Sandoghdar
- Max-Planck-Institute for the Science of Light, Erlangen, Germany
| | - Lars M. Voll
- Division of Biochemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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Berthaud A, Quemeneur F, Deforet M, Bassereau P, Brochard-Wyart F, Mangenot S. Spreading of porous vesicles subjected to osmotic shocks: the role of aquaporins. SOFT MATTER 2016; 12:1601-1609. [PMID: 26662491 DOI: 10.1039/c5sm01654a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Aquaporin 0 (AQP0) is a transmembrane protein specific to the eye lens, involved as a water carrier across the lipid membranes. During eye lens maturation, AQP0s are truncated by proteolytic cleavage. We investigate in this work the capability of truncated AQP0 to conduct water across membranes. We developed a method to accurately determine water permeability across lipid membranes and across proteins from the deflation under osmotic pressure of giant unilamellar vesicles (GUVs) deposited on an adhesive substrate. Using reflection interference contrast microscopy (RICM), we measure the spreading area of GUVs during deswelling. We interpret these results using a model based on hydrodynamic, binder diffusion towards the contact zone, and Helfrich's law for the membrane tension, which allows us to relate the spread area to the vesicle internal volume. We first study the specific adhesion of vesicles coated with biotin spreading on a streptavidin substrate. We then determine the permeability of a single functional AQP0 and demonstrate that truncated AQP0 is no more a water channel.
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Affiliation(s)
- Alice Berthaud
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168, 75005, Paris, France.
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Gaul V, Lopez SG, Lentz BR, Moran N, Forster RJ, Keyes TE. The lateral diffusion and fibrinogen induced clustering of platelet integrin αIIbβ3 reconstituted into physiologically mimetic GUVs. Integr Biol (Camb) 2015; 7:402-11. [PMID: 25720532 DOI: 10.1039/c5ib00003c] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Platelet integrin αIIbβ3 is a key mediator of platelet activation and thrombosis. Upon activation αIIbβ3 undergoes significant conformational rearrangement, inducing complex bidirectional signalling and protein recruitment leading to platelet activation. Reconstituted lipid models of the integrin can enhance our understanding of the structural and mechanistic details of αIIbβ3 behaviour away from the complexity of the platelet machinery. Here, a novel method of αIIbβ3 insertion into Giant Unilamellar Vesicles (GUVs) is described that allows for effective integrin reconstitution unrestricted by lipid composition. αIIbβ3 was inserted into two GUV lipid compositions that seek to better mimic the platelet membrane. First, "nature's own", comprising 32% DOPC, 25% DOPE, 20% CH, 15% SM and 8% DOPS, intended to mimic the platelet cell membrane. Fluorescence Lifetime Correlation Spectroscopy (FLCS) reveals that exposure of the integrin to the activators Mn(2+) or DTT does not influence the diffusion coefficient of αIIbβ3. Similarly, exposure to αIIbβ3's primary ligand fibrinogen (Fg) alone does not affect αIIbβ3's diffusion coefficient. However, addition of Fg with either activator reduces the integrin diffusion coefficient from 2.52 ± 0.29 to μm(2) s(-1) to 1.56 ± 0.26 (Mn(2+)) or 1.49 ± 0.41 μm(2) s(-1) (DTT) which is consistent with aggregation of activated αIIbβ3 induced by fibrinogen binding. The Multichannel Scaler (MCS) trace shows that the integrin-Fg complex diffuses through the confocal volume in clusters. Using the Saffman-Delbrück model as a first approximation, the diffusion coefficient of the complex suggests at least a 20-fold increase in the radius of membrane bound protein, consistent with integrin clustering. Second, αIIbβ3 was also reconstituted into a "raft forming" GUV with well defined liquid disordered (Ld) and liquid ordered (Lo) phases. Using confocal microscopy and lipid partitioning dyes, αIIbβ3 showed an affinity for the DOPC rich Ld phase of the raft forming GUVs, and was effectively excluded from the cholesterol and sphingomyelin rich Lo phase. Activation and Fg binding of the integrin did not alter the distribution of αIIbβ3 between the lipid phases. This observation suggests partitioning of the activated fibrinogen bound αIIbβ3 into cholesterol rich domains is not responsible for the integrin clustering observed.
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Affiliation(s)
- Vinnie Gaul
- School of Chemical Sciences and National Biophotonics and Imaging Platform, Dublin City University, Dublin 9, Ireland.
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54
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Smeazzetto S, Tadini-Buoninsegni F, Thiel G, Berti D, Montis C. Phospholamban spontaneously reconstitutes into giant unilamellar vesicles where it generates a cation selective channel. Phys Chem Chem Phys 2015; 18:1629-36. [PMID: 26673394 DOI: 10.1039/c5cp05893g] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Phospholamban (PLN) is a small integral membrane protein, which modulates the activity of the Sarcoplasmic Reticulum Ca(2+)-ATPase (SERCA) of cardiac myocytes. PLN, as a monomer, can directly interact and tune SERCA activity, but the physiological function of the pentameric form is not yet fully understood and still debated. In this work, we reconstituted PLN in Giant Unilamellar Vesicles (GUVs), a simple and reliable experimental model system to monitor the activity of proteins in membranes. By Laser Scanning Confocal Microscopy (LSCM) and Fluorescence Correlation Spectroscopy (FCS) we verified a spontaneous reconstitution of PLN into the phospholipid bilayer. In parallel experiments, we measured with the patch clamp technique canonical ion channel fluctuations, which highlight a preference for Cs(+) over K(+) and do not conduct Ca(2+). The results prove that PLN forms, presumably in its pentameric form, a cation selective ion channel.
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Affiliation(s)
- S Smeazzetto
- Department of Chemistry "Ugo Schiff", University of Florence, Firenze, Italy
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Lagny TJ, Bassereau P. Bioinspired membrane-based systems for a physical approach of cell organization and dynamics: usefulness and limitations. Interface Focus 2015; 5:20150038. [PMID: 26464792 PMCID: PMC4590427 DOI: 10.1098/rsfs.2015.0038] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Being at the periphery of each cell compartment and enclosing the entire cell while interacting with a large part of cell components, cell membranes participate in most of the cell's vital functions. Biologists have worked for a long time on deciphering how membranes are organized, how they contribute to trafficking, motility, cytokinesis, cell-cell communication, information transport, etc., using top-down approaches and always more advanced techniques. In contrast, physicists have developed bottom-up approaches and minimal model membrane systems of growing complexity in order to build up general models that explain how cell membranes work and how they interact with proteins, e.g. the cytoskeleton. We review the different model membrane systems that are currently available, and how they can help deciphering cell functioning, but also list their limitations. Model membrane systems are also used in synthetic biology and can have potential applications beyond basic research. We discuss the possible synergy between the development of complex in vitro membrane systems in a biological context and for technological applications. Questions that could also be discussed are: what can we still do with synthetic systems, where do we stop building up and which are the alternative solutions?
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Affiliation(s)
- Thibaut J Lagny
- Institut Curie, PSL Research University , Laboratory PhysicoChimie Curie , 75248 Paris, Cedex 05 , France ; CNRS , UMR168, 75248 Paris, Cedex 05 , France ; Université Pierre et Marie Curie , 75252 Paris, Cedex 05 , France
| | - Patricia Bassereau
- Institut Curie, PSL Research University , Laboratory PhysicoChimie Curie , 75248 Paris, Cedex 05 , France ; CNRS , UMR168, 75248 Paris, Cedex 05 , France ; Université Pierre et Marie Curie , 75252 Paris, Cedex 05 , France
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Frohnmayer JP, Brüggemann D, Eberhard C, Neubauer S, Mollenhauer C, Boehm H, Kessler H, Geiger B, Spatz JP. Minimal synthetic cells to study integrin-mediated adhesion. Angew Chem Int Ed Engl 2015; 54:12472-8. [PMID: 26257266 PMCID: PMC4675076 DOI: 10.1002/anie.201503184] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Revised: 05/28/2015] [Indexed: 11/12/2022]
Abstract
To shed light on cell-adhesion-related molecular pathways, synthetic cells offer the unique advantage of a well-controlled model system with reduced molecular complexity. Herein, we show that liposomes with the reconstituted platelet integrin αIIb β3 as the adhesion-mediating transmembrane protein are a functional minimal cell model for studying cellular adhesion mechanisms in a defined environment. The interaction of these synthetic cells with various extracellular matrix proteins was analyzed using a quartz crystal microbalance with dissipation monitoring. The data indicated that integrin was functionally incorporated into the lipid vesicles, thus enabling integrin-specific adhesion of the engineered liposomes to fibrinogen- and fibronectin-functionalized surfaces. Then, we were able to initiate the detachment of integrin liposomes from these surfaces in the presence of the peptide GRGDSP, a process that is even faster with our newly synthesized peptide mimetic SN529, which specifically inhibits the integrin αIIb β3 .
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Affiliation(s)
- Johannes P Frohnmayer
- Department of New Materials and Biosystems, Max Planck Institute for Intelligent SystemsHeisenbergstrasse 3, 70569 Stuttgart (Germany)Department of Biophysical Chemistry, University of HeidelbergINF 253, 69120 Heidelberg (Germany) E-mail:
| | - Dorothea Brüggemann
- Department of New Materials and Biosystems, Max Planck Institute for Intelligent SystemsHeisenbergstrasse 3, 70569 Stuttgart (Germany)Department of Biophysical Chemistry, University of HeidelbergINF 253, 69120 Heidelberg (Germany) E-mail:
| | - Christian Eberhard
- Department of New Materials and Biosystems, Max Planck Institute for Intelligent SystemsHeisenbergstrasse 3, 70569 Stuttgart (Germany)Department of Biophysical Chemistry, University of HeidelbergINF 253, 69120 Heidelberg (Germany) E-mail:
| | - Stefanie Neubauer
- Institute for Advanced Study (IAS) and Center of Integrated Protein Science (CIPSM), Department Chemie, Technische Universität MünchenLichtenbergstrasse 4, 85747 Garching (Germany)
| | - Christine Mollenhauer
- Department of New Materials and Biosystems, Max Planck Institute for Intelligent SystemsHeisenbergstrasse 3, 70569 Stuttgart (Germany)Department of Biophysical Chemistry, University of HeidelbergINF 253, 69120 Heidelberg (Germany) E-mail:
- CSF Biomaterials and Cellular Biophysics, Max Planck Institute for Intelligent SystemsHeisenbergstrasse 3, 70569 Stuttgart (Germany)
| | - Heike Boehm
- Department of New Materials and Biosystems, Max Planck Institute for Intelligent SystemsHeisenbergstrasse 3, 70569 Stuttgart (Germany)Department of Biophysical Chemistry, University of HeidelbergINF 253, 69120 Heidelberg (Germany) E-mail:
- CSF Biomaterials and Cellular Biophysics, Max Planck Institute for Intelligent SystemsHeisenbergstrasse 3, 70569 Stuttgart (Germany)
| | - Horst Kessler
- Institute for Advanced Study (IAS) and Center of Integrated Protein Science (CIPSM), Department Chemie, Technische Universität MünchenLichtenbergstrasse 4, 85747 Garching (Germany)
| | - Benjamin Geiger
- The Weizmann Institute of Science, Department of Molecular Cell BiologyRehovot (Israel)
| | - Joachim P Spatz
- Department of New Materials and Biosystems, Max Planck Institute for Intelligent SystemsHeisenbergstrasse 3, 70569 Stuttgart (Germany)Department of Biophysical Chemistry, University of HeidelbergINF 253, 69120 Heidelberg (Germany) E-mail:
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Lou B, Zhou Z, Du Y, Dong S. Resistance-based logic aptamer sensor for CCRF-CEM and Ramos cells integrated on microfluidic chip. Electrochem commun 2015. [DOI: 10.1016/j.elecom.2015.07.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Motta I, Gohlke A, Adrien V, Li F, Gardavot H, Rothman JE, Pincet F. Formation of Giant Unilamellar Proteo-Liposomes by Osmotic Shock. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:7091-7099. [PMID: 26038815 PMCID: PMC4950989 DOI: 10.1021/acs.langmuir.5b01173] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Giant unilamellar vesicles (GUVs), composed of a phospholipid bilayer, are often used as a model system for cell membranes. However, the study of proteo-membrane interactions in this system is limited as the incorporation of integral and lipid-anchored proteins into GUVs remains challenging. Here, we present a simple generic method to incorporate proteins into GUVs. The basic principle is to break proteo-liposomes with an osmotic shock. They subsequently reseal into larger vesicles which, if necessary, can endure the same to obtain even larger proteo-GUVs. This process does not require specific lipids or reagents, works under physiological conditions with high concentrations of protein, the proteins remains functional after incorporation. The resulting proteo-GUVs can be micromanipulated. Moreover, our protocol is valid for a wide range of protein substrates. We have successfully reconstituted three structurally different proteins, two trans-membrane proteins (TolC and the neuronal t-SNARE), and one lipid-anchored peripheral protein (GABARAP-Like 1 (GL1)). In each case, we verified that the protein remains active after incorporation and in its correctly folded state. We also measured their mobility by performing diffusion measurements via fluorescence recovery after photobleaching (FRAP) experiments on micromanipulated single GUVs. The diffusion coefficients are in agreement with previous data.
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Affiliation(s)
- Isabelle Motta
- Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, UMR 8550, 24 rue Lhomond, 75005 Paris, France
| | - Andrea Gohlke
- Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, UMR 8550, 24 rue Lhomond, 75005 Paris, France
- Department of Cell Biology, Nanobiology Institute, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Vladimir Adrien
- Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, UMR 8550, 24 rue Lhomond, 75005 Paris, France
- Laboratoire de Cristallographie et RMN Biologiques, Université Paris Descartes, CNRS, UMR 8015, Paris, France
| | - Feng Li
- Department of Cell Biology, Nanobiology Institute, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Hélène Gardavot
- Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, UMR 8550, 24 rue Lhomond, 75005 Paris, France
| | - James E. Rothman
- Department of Cell Biology, Nanobiology Institute, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Frederic Pincet
- Laboratoire de Physique Statistique, Ecole Normale Supérieure de Paris, Université Pierre et Marie Curie, Université Paris Diderot, Centre National de la Recherche Scientifique, UMR 8550, 24 rue Lhomond, 75005 Paris, France
- Department of Cell Biology, Nanobiology Institute, School of Medicine, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
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60
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Barbot M, Jans DC, Schulz C, Denkert N, Kroppen B, Hoppert M, Jakobs S, Meinecke M. Mic10 oligomerizes to bend mitochondrial inner membranes at cristae junctions. Cell Metab 2015; 21:756-63. [PMID: 25955211 DOI: 10.1016/j.cmet.2015.04.006] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 03/06/2015] [Accepted: 04/01/2015] [Indexed: 11/25/2022]
Abstract
The mitochondrial inner membrane is highly folded and displays a complex molecular architecture. Cristae junctions are highly curved tubular openings that separate cristae membrane invaginations from the surrounding boundary membrane. Despite their central role in many vital cellular processes like apoptosis, the details of cristae junction formation remain elusive. Here we identify Mic10, a core subunit of the recently discovered MICOS complex, as an inner mitochondrial membrane protein with the ability to change membrane morphology in vitro and in vivo. We show that Mic10 spans the inner membrane in a hairpin topology and that its ability to sculpt membranes depends on oligomerization through a glycine-rich motif. Oligomerization mutants fail to induce curvature in model membranes, and when expressed in yeast, mitochondria display an altered inner membrane architecture characterized by drastically decreased numbers of cristae junctions. Thus, we demonstrate that membrane sculpting by Mic10 is essential for cristae junction formation.
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Affiliation(s)
- Mariam Barbot
- Department of Cellular Biochemistry, University Medical Center Göttingen, 37073 Göttingen, Germany
| | - Daniel C Jans
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany; Department of Neurology, University Medical Center, 37075 Göttingen, Germany
| | - Christian Schulz
- Department of Cellular Biochemistry, University Medical Center Göttingen, 37073 Göttingen, Germany
| | - Niels Denkert
- Department of Cellular Biochemistry, University Medical Center Göttingen, 37073 Göttingen, Germany
| | - Benjamin Kroppen
- Department of Cellular Biochemistry, University Medical Center Göttingen, 37073 Göttingen, Germany
| | - Michael Hoppert
- Institute of Microbiology and Genetics, Georg-August-University, 37077 Göttingen, Germany
| | - Stefan Jakobs
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany; Department of Neurology, University Medical Center, 37075 Göttingen, Germany
| | - Michael Meinecke
- Department of Cellular Biochemistry, University Medical Center Göttingen, 37073 Göttingen, Germany; European Neuroscience Institute Göttingen, 37077 Göttingen, Germany.
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61
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Miller DM, Gulbis JM. Engineering protocells: prospects for self-assembly and nanoscale production-lines. Life (Basel) 2015; 5:1019-53. [PMID: 25815781 PMCID: PMC4500129 DOI: 10.3390/life5021019] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2015] [Revised: 03/09/2015] [Accepted: 03/16/2015] [Indexed: 11/16/2022] Open
Abstract
The increasing ease of producing nucleic acids and proteins to specification offers potential for design and fabrication of artificial synthetic "organisms" with a myriad of possible capabilities. The prospects for these synthetic organisms are significant, with potential applications in diverse fields including synthesis of pharmaceuticals, sources of renewable fuel and environmental cleanup. Until now, artificial cell technology has been largely restricted to the modification and metabolic engineering of living unicellular organisms. This review discusses emerging possibilities for developing synthetic protocell "machines" assembled entirely from individual biological components. We describe a host of recent technological advances that could potentially be harnessed in design and construction of synthetic protocells, some of which have already been utilized toward these ends. More elaborate designs include options for building self-assembling machines by incorporating cellular transport and assembly machinery. We also discuss production in miniature, using microfluidic production lines. While there are still many unknowns in the design, engineering and optimization of protocells, current technologies are now tantalizingly close to the capabilities required to build the first prototype protocells with potential real-world applications.
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Affiliation(s)
- David M Miller
- The Walter and Eliza Hall Institute of Medical Research, Parkville VIC 3052, Australia.
- Department of Medical Biology, The University of Melbourne, Parkville VIC 3052, Australia.
| | - Jacqueline M Gulbis
- The Walter and Eliza Hall Institute of Medical Research, Parkville VIC 3052, Australia.
- Department of Medical Biology, The University of Melbourne, Parkville VIC 3052, Australia.
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62
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Garten M, Aimon S, Bassereau P, Toombes GES. Reconstitution of a transmembrane protein, the voltage-gated ion channel, KvAP, into giant unilamellar vesicles for microscopy and patch clamp studies. J Vis Exp 2015:52281. [PMID: 25650630 DOI: 10.3791/52281] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Giant Unilamellar Vesicles (GUVs) are a popular biomimetic system for studying membrane associated phenomena. However, commonly used protocols to grow GUVs must be modified in order to form GUVs containing functional transmembrane proteins. This article describes two dehydration-rehydration methods - electroformation and gel-assisted swelling - to form GUVs containing the voltage-gated potassium channel, KvAP. In both methods, a solution of protein-containing small unilamellar vesicles is partially dehydrated to form a stack of membranes, which is then allowed to swell in a rehydration buffer. For the electroformation method, the film is deposited on platinum electrodes so that an AC field can be applied during film rehydration. In contrast, the gel-assisted swelling method uses an agarose gel substrate to enhance film rehydration. Both methods can produce GUVs in low (e.g., 5 mM) and physiological (e.g., 100 mM) salt concentrations. The resulting GUVs are characterized via fluorescence microscopy, and the function of reconstituted channels measured using the inside-out patch-clamp configuration. While swelling in the presence of an alternating electric field (electroformation) gives a high yield of defect-free GUVs, the gel-assisted swelling method produces a more homogeneous protein distribution and requires no special equipment.
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Affiliation(s)
- Matthias Garten
- Institut Curie, Centre de Recherche, CNRS, UMR 168, PhysicoChimie Curie, Université Pierre et Marie Curie
| | - Sophie Aimon
- Kavli Institute for Brain and Mind, University of California, San Diego
| | - Patricia Bassereau
- Institut Curie, Centre de Recherche, CNRS, UMR 168, PhysicoChimie Curie, Université Pierre et Marie Curie;
| | - Gilman E S Toombes
- Molecular Physiology and Biophysics Section, National Institute for Neurological Disorders and Stroke, National Institute of Health
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63
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Beales PA, Ciani B, Cleasby AJ. Nature's lessons in design: nanomachines to scaffold, remodel and shape membrane compartments. Phys Chem Chem Phys 2015; 17:15489-507. [DOI: 10.1039/c5cp00480b] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Our understanding of the membrane sculpting capabilities of proteins from experimental model systems could be used to construct functional compartmentalised architectures for the engineering of synthetic cells.
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Affiliation(s)
- Paul A. Beales
- School of Chemistry and Astbury Centre for Structural Molecular Biology
- University of Leeds
- Leeds LS2 9JT
- UK
| | - Barbara Ciani
- Centre for Membrane Interaction and Dynamics
- Department of Chemistry
- University of Sheffield
- Sheffield S3 7HF
- UK
| | - Alexa J. Cleasby
- Centre for Membrane Interaction and Dynamics
- Department of Chemistry
- University of Sheffield
- Sheffield S3 7HF
- UK
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64
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Horger KS, Liu H, Rao DK, Shukla S, Sept D, Ambudkar SV, Mayer M. Hydrogel-assisted functional reconstitution of human P-glycoprotein (ABCB1) in giant liposomes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:643-53. [PMID: 25450342 DOI: 10.1016/j.bbamem.2014.10.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 09/17/2014] [Accepted: 10/20/2014] [Indexed: 11/24/2022]
Abstract
This paper describes the formation of giant proteoliposomes containing P-glycoprotein (P-gp) from a solution of small proteoliposomes that had been deposited and partially dried on a film of agarose. This preparation method generated a significant fraction of giant proteoliposomes that were free of internalized vesicles, making it possible to determine the accessible liposome volume. Measuring the intensity of the fluorescent substrate rhodamine 123 (Rho123) inside and outside these giant proteoliposomes determined the concentration of transported substrates of P-gp. Fitting a kinetic model to the fluorescence data revealed the rate of passive diffusion as well as active transport by reconstituted P-gp in the membrane. This approach determined estimates for the membrane permeability coefficient (Ps) of passive diffusion and rate constants of active transport (kT) by P-gp as a result of different experimental conditions. The Ps value for Rho123 was larger in membranes containing P-gp under all assay conditions than in membranes without P-gp indicating increased leakiness in the presence of reconstituted transmembrane proteins. For P-gp liposomes, the kT value was significantly higher in the presence of ATP than in its absence or in the presence of ATP and the competitive inhibitor verapamil. This difference in kT values verified that P-gp was functionally active after reconstitution and quantified the rate of active transport. Lastly, patch clamp experiments on giant proteoliposomes showed ion channel activity consistent with a chloride ion channel protein that co-purified with P-gp. Together, these results demonstrate several advantages of using giant rather than small proteoliposomes to characterize transport properties of transport proteins and ion channels.
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Affiliation(s)
- Kim S Horger
- Department of Chemical Engineering, University of Michigan, 2300 Hayward Street, Ann Arbor, MI 48109, USA
| | - Haiyan Liu
- Department of Biomedical Engineering, University of Michigan, 1101 Beal Avenue, Ann Arbor, MI 48109, USA
| | - Divya K Rao
- Department of Biomedical Engineering, University of Michigan, 1101 Beal Avenue, Ann Arbor, MI 48109, USA
| | - Suneet Shukla
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 37 Convent Drive, Bethesda, MD 20814, USA
| | - David Sept
- Department of Biomedical Engineering, University of Michigan, 1101 Beal Avenue, Ann Arbor, MI 48109, USA; Center for Computational Medicine and Bioinformatics, University of Michigan, 2800 Plymouth Road, Ann Arbor, MI 48109, USA
| | - Suresh V Ambudkar
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 37 Convent Drive, Bethesda, MD 20814, USA
| | - Michael Mayer
- Department of Chemical Engineering, University of Michigan, 2300 Hayward Street, Ann Arbor, MI 48109, USA; Department of Biomedical Engineering, University of Michigan, 1101 Beal Avenue, Ann Arbor, MI 48109, USA.
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X-ray structure of the mouse serotonin 5-HT3 receptor. Nature 2014; 512:276-81. [PMID: 25119048 DOI: 10.1038/nature13552] [Citation(s) in RCA: 303] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2014] [Accepted: 06/02/2014] [Indexed: 01/03/2023]
Abstract
Neurotransmitter-gated ion channels of the Cys-loop receptor family mediate fast neurotransmission throughout the nervous system. The molecular processes of neurotransmitter binding, subsequent opening of the ion channel and ion permeation remain poorly understood. Here we present the X-ray structure of a mammalian Cys-loop receptor, the mouse serotonin 5-HT3 receptor, at 3.5 Å resolution. The structure of the proteolysed receptor, made up of two fragments and comprising part of the intracellular domain, was determined in complex with stabilizing nanobodies. The extracellular domain reveals the detailed anatomy of the neurotransmitter binding site capped by a nanobody. The membrane domain delimits an aqueous pore with a 4.6 Å constriction. In the intracellular domain, a bundle of five intracellular helices creates a closed vestibule where lateral portals are obstructed by loops. This 5-HT3 receptor structure, revealing part of the intracellular domain, expands the structural basis for understanding the operating mechanism of mammalian Cys-loop receptors.
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66
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Brüggemann D, Frohnmayer JP, Spatz JP. Model systems for studying cell adhesion and biomimetic actin networks. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2014; 5:1193-202. [PMID: 25161853 PMCID: PMC4142981 DOI: 10.3762/bjnano.5.131] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 06/25/2014] [Indexed: 05/28/2023]
Abstract
Many cellular processes, such as migration, proliferation, wound healing and tumor progression are based on cell adhesion. Amongst different cell adhesion molecules, the integrin receptors play a very significant role. Over the past decades the function and signalling of various such integrins have been studied by incorporating the proteins into lipid membranes. These proteolipid structures lay the foundation for the development of artificial cells, which are able to adhere to substrates. To build biomimetic models for studying cell shape and spreading, actin networks can be incorporated into lipid vesicles, too. We here review the mechanisms of integrin-mediated cell adhesion and recent advances in the field of minimal cells towards synthetic adhesion. We focus on reconstituting integrins into lipid structures for mimicking cell adhesion and on the incorporation of actin networks and talin into model cells.
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Affiliation(s)
- Dorothea Brüggemann
- Department of New Materials and Biosystems, Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
- Department of Biophysical Chemistry, University of Heidelberg, INF 253, D-69120 Heidelberg, Germany
| | - Johannes P Frohnmayer
- Department of New Materials and Biosystems, Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
- Department of Biophysical Chemistry, University of Heidelberg, INF 253, D-69120 Heidelberg, Germany
| | - Joachim P Spatz
- Department of New Materials and Biosystems, Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
- Department of Biophysical Chemistry, University of Heidelberg, INF 253, D-69120 Heidelberg, Germany
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67
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Bassereau P, Sorre B, Lévy A. Bending lipid membranes: experiments after W. Helfrich's model. Adv Colloid Interface Sci 2014; 208:47-57. [PMID: 24630341 DOI: 10.1016/j.cis.2014.02.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 02/02/2014] [Accepted: 02/03/2014] [Indexed: 10/25/2022]
Abstract
Current description of biomembrane mechanics originates for a large part from W. Helfrich's model. Based on his continuum theory, many experiments have been performed in the past four decades on simplified membranes in order to characterize the mechanical properties of lipid membranes and the contribution of polymers or proteins. The long-term goal was to develop a better understanding of the mechanical properties of cell membranes. In this paper, we will review representative experimental approaches that were developed during this period and the main results that were obtained.
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68
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Wu T, Shi Z, Baumgart T. Mutations in BIN1 associated with centronuclear myopathy disrupt membrane remodeling by affecting protein density and oligomerization. PLoS One 2014; 9:e93060. [PMID: 24755653 PMCID: PMC3995651 DOI: 10.1371/journal.pone.0093060] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2013] [Accepted: 03/02/2014] [Indexed: 11/18/2022] Open
Abstract
The regulation of membrane shapes is central to many cellular phenomena. Bin/Amphiphysin/Rvs (BAR) domain-containing proteins are key players for membrane remodeling during endocytosis, cell migration, and endosomal sorting. BIN1, which contains an N-BAR domain, is assumed to be essential for biogenesis of plasma membrane invaginations (T-tubules) in muscle tissues. Three mutations, K35N, D151N and R154Q, have been discovered so far in the BAR domain of BIN1 in patients with centronuclear myopathy (CNM), where impaired organization of T-tubules has been reported. However, molecular mechanisms behind this malfunction have remained elusive. None of the BIN1 disease mutants displayed a significantly compromised curvature sensing ability. However, two mutants showed impaired membrane tubulation both in vivo and in vitro, and displayed characteristically different behaviors. R154Q generated smaller membrane curvature compared to WT N-BAR. Quantification of protein density on membranes revealed a lower membrane-bound density for R154Q compared to WT and the other mutants, which appeared to be the primary reason for the observation of impaired deformation capacity. The D151N mutant was unable to tubulate liposomes under certain experimental conditions. At medium protein concentrations we found 'budding' structures on liposomes that we hypothesized to be intermediates during the tubulation process except for the D151N mutant. Chemical crosslinking assays suggested that the D151N mutation impaired protein oligomerization upon membrane binding. Although we found an insignificant difference between WT and K35N N-BAR in in vitro assays, depolymerizing actin in live cells allowed tubulation of plasma membranes through the K35N mutant. Our results provide insights into the membrane-involved pathophysiological mechanisms leading to human disease.
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Affiliation(s)
- Tingting Wu
- Department of Chemistry, School of Arts & Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Zheng Shi
- Department of Chemistry, School of Arts & Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Tobias Baumgart
- Department of Chemistry, School of Arts & Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
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69
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Aimon S, Callan-Jones A, Berthaud A, Pinot M, Toombes GES, Bassereau P. Membrane shape modulates transmembrane protein distribution. Dev Cell 2014; 28:212-8. [PMID: 24480645 DOI: 10.1016/j.devcel.2013.12.012] [Citation(s) in RCA: 158] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Revised: 07/22/2013] [Accepted: 12/19/2013] [Indexed: 01/01/2023]
Abstract
Although membrane shape varies greatly throughout the cell, the contribution of membrane curvature to transmembrane protein targeting is unknown because of the numerous sorting mechanisms that take place concurrently in cells. To isolate the effect of membrane shape, we used cell-sized giant unilamellar vesicles (GUVs) containing either the potassium channel KvAP or the water channel AQP0 to form membrane nanotubes with controlled radii. Whereas the AQP0 concentrations in flat and curved membranes were indistinguishable, KvAP was enriched in the tubes, with greater enrichment in more highly curved membranes. Fluorescence recovery after photobleaching measurements showed that both proteins could freely diffuse through the neck between the tube and GUV, and the effect of each protein on membrane shape and stiffness was characterized using a thermodynamic sorting model. This study establishes the importance of membrane shape for targeting transmembrane proteins and provides a method for determining the effective shape and flexibility of membrane proteins.
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Affiliation(s)
- Sophie Aimon
- Centre de Recherche, Institut Curie, Paris F-75248, France; CNRS, PhysicoChimie Curie, UMR168, Paris F-75248, France; Université Pierre et Marie Curie, Paris F-75252, France; Kavli Institute for Brain and Mind, UCSD, La Jolla, CA 92093, USA
| | - Andrew Callan-Jones
- Laboratoire Matière et Systèmes Complexes, CNRS/Université Paris-Diderot, UMR 7057, 75205 Paris Cedex 13, France
| | - Alice Berthaud
- Centre de Recherche, Institut Curie, Paris F-75248, France; CNRS, PhysicoChimie Curie, UMR168, Paris F-75248, France; Université Pierre et Marie Curie, Paris F-75252, France; CelTisPhyBio Labex, Paris Sciences et Lettres, 75005 Paris, France
| | - Mathieu Pinot
- Centre de Recherche, Institut Curie, Paris F-75248, France; CelTisPhyBio Labex, Paris Sciences et Lettres, 75005 Paris, France; CNRS, Subcellular Structure and Cellular Dynamics, UMR144, Paris F-75248, France
| | - Gilman E S Toombes
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-3017, USA.
| | - Patricia Bassereau
- Centre de Recherche, Institut Curie, Paris F-75248, France; CNRS, PhysicoChimie Curie, UMR168, Paris F-75248, France; Université Pierre et Marie Curie, Paris F-75252, France; CelTisPhyBio Labex, Paris Sciences et Lettres, 75005 Paris, France
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70
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Abstract
The lateral mobility of proteins within cell membranes is usually thought to be dependent on their size and modulated by local heterogeneities of the membrane. Experiments using single-particle tracking on reconstituted membranes demonstrate that protein diffusion is significantly influenced by the interplay of membrane curvature, membrane tension, and protein shape. We find that the curvature-coupled voltage-gated potassium channel (KvAP) undergoes a significant increase in protein mobility under tension, whereas the mobility of the curvature-neutral water channel aquaporin 0 (AQP0) is insensitive to it. Such observations are well explained in terms of an effective friction coefficient of the protein induced by the local membrane deformation.
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71
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Springer S, Malkus P, Borchert B, Wellbrock U, Duden R, Schekman R. Regulated Oligomerization Induces Uptake of a Membrane Protein into COPII Vesicles Independent of Its Cytosolic Tail. Traffic 2014; 15:531-45. [DOI: 10.1111/tra.12157] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Revised: 01/07/2014] [Accepted: 01/30/2014] [Indexed: 12/22/2022]
Affiliation(s)
| | - Per Malkus
- Department of Systems Biology; Harvard Medical School; Boston MA 02115 USA
| | - Britta Borchert
- Biochemistry and Cell Biology; Jacobs University Bremen; Bremen Germany
| | - Ursula Wellbrock
- Biochemistry and Cell Biology; Jacobs University Bremen; Bremen Germany
| | - Rainer Duden
- Centre for Structural and Cell Biology in Medicine, Institute of Biology; University of Lübeck; Lübeck Germany
| | - Randy Schekman
- Howard Hughes Medical Institute and Department of Molecular and Cell Biology; University of California, Berkeley; Berkeley CA 94720 USA
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72
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Chiaruttini N, Letellier L, Viasnoff V. A novel method to couple electrophysiological measurements and fluorescence imaging of suspended lipid membranes: the example of T5 bacteriophage DNA ejection. PLoS One 2013; 8:e84376. [PMID: 24376806 PMCID: PMC3871697 DOI: 10.1371/journal.pone.0084376] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Accepted: 11/22/2013] [Indexed: 12/21/2022] Open
Abstract
We present an innovative method to couple electrophysiological measurements with fluorescence imaging of functionalized suspended bilayers. Our method combines several advantages: it is well suited to study transmembrane proteins that are difficult to incorporate in suspended bilayers, it allows single molecule resolution both in terms of electrophysiological measurements and fluorescence imaging, and it enables mechanical stimulations of the membrane. The approach comprises of two steps: first the reconstitution of membrane proteins in giant unilamellar vesicles; then the formation of a suspended bilayer spanning a 5 to 15 micron-wide aperture that can be visualized by high NA microscope objectives. We exemplified how the technique can be used to detect in real time the translocation of T5 DNA across the bilayer during its ejection from the bacteriophage capsid.
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Affiliation(s)
- Nicolas Chiaruttini
- ESPCI Paristech, CNRS, Paris, France
- Aurélien Roux Lab, Biochemistry Department, University of Geneva, Geneva, Switzerland
| | - Lucienne Letellier
- Institut de Biochimie et Biophysique Moléculaire et Cellulaire, Université Paris Sud-11, CNRS, Orsay, France
| | - Virgile Viasnoff
- ESPCI Paristech, CNRS, Paris, France
- Aurélien Roux Lab, Biochemistry Department, University of Geneva, Geneva, Switzerland
- Institut de Biochimie et Biophysique Moléculaire et Cellulaire, Université Paris Sud-11, CNRS, Orsay, France
- MechanoBiology Institute of Singapore, Singapore, Singapore
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73
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Capretto L, Carugo D, Mazzitelli S, Nastruzzi C, Zhang X. Microfluidic and lab-on-a-chip preparation routes for organic nanoparticles and vesicular systems for nanomedicine applications. Adv Drug Deliv Rev 2013; 65:1496-532. [PMID: 23933616 DOI: 10.1016/j.addr.2013.08.002] [Citation(s) in RCA: 140] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 07/10/2013] [Accepted: 08/01/2013] [Indexed: 01/02/2023]
Abstract
In recent years, advancements in the fields of microfluidic and lab-on-a-chip technologies have provided unique opportunities for the implementation of nanomaterial production processes owing to the miniaturisation of the fluidic environment. It has been demonstrated that microfluidic reactors offer a range of advantages compared to conventional batch reactors, including improved controllability and uniformity of nanomaterial characteristics. In addition, the fast mixing achieved within microchannels, and the predictability of the laminar flow conditions, can be leveraged to investigate the nanomaterial formation dynamics. In this article recent developments in the field of microfluidic production of nanomaterials for drug delivery applications are reviewed. The features that make microfluidic reactors a suitable technological platform are discussed in terms of controllability of nanomaterials production. An overview of the various strategies developed for the production of organic nanoparticles and colloidal assemblies is presented, focusing on those nanomaterials that could have an impact on nanomedicine field such as drug nanoparticles, polymeric micelles, liposomes, polymersomes, polyplexes and hybrid nanoparticles. The effect of microfluidic environment on nanomaterials formation dynamics, as well as the use of microdevices as tools for nanomaterial investigation is also discussed.
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74
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Liu YJ, Hansen GPR, Venancio-Marques A, Baigl D. Cell-free preparation of functional and triggerable giant proteoliposomes. Chembiochem 2013; 14:2243-7. [PMID: 24115581 DOI: 10.1002/cbic.201300501] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Indexed: 01/15/2023]
Abstract
Heat, we leak: We express a membrane protein outside well-defined giant liposomes obtained by gravity-transferred sucrose-in-oil droplets into a cell-free, reconstituted expression system. We show that the presence of the liposome is necessary during expression for efficient protein insertion into the membrane and that temperature can trigger the resulting membrane function.
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Affiliation(s)
- Yan-Jun Liu
- Department of Chemistry, Ecole Normale Superieure, 24 rue Lhomond, 75005 Paris (France) http://www.baigllab.com/; Université Pierre et Marie Curie Paris 6, 4 place Jussieu, 75005 Paris (France); UMR 8640, CNRS, 3 rue Michel-Ange, 75016 Paris (France)
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75
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Hughes LD, Boxer SG. DNA-based patterning of tethered membrane patches. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:12220-7. [PMID: 23992147 PMCID: PMC3815428 DOI: 10.1021/la402537p] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Solid-supported lipid bilayers are useful model systems for mimicking cellular membranes; however, the interaction of the bilayer with the surface can disrupt the function of integral membrane proteins and impede topological transformations such as membrane fusion. As a result, a variety of tethered or cushioned lipid bilayer architectures have been described, which retain the proximity to the surface, enabling surface-sensitive techniques, but physically distance the bilayer from the surface. We have recently developed a method for spatially separating a lipid bilayer from a solid support using DNA lipids. In this system, a DNA strand is covalently attached to a glass slide or SiO2 wafer, and giant unilamellar vesicles (GUVs) displaying the complement rupture to form a planar lipid bilayer tethered above the surface. However, the location of the patch is random, determined by where the DNA-GUV initially binds to its complement. To allow greater versatility and control, we sought a way to pattern tethered membrane patches. We present a method for creating spatially distinct tethered membrane patches on a glass slide using microarray printing. Surface-reactive DNA sequences are spotted onto the slide, incubated to covalently link the DNA to the surface, and DNA-GUVs patches are formed selectively on the printed DNA. By interfacing the bilayers with microfluidic flow cells, materials can be added on top of or fused into the membrane to change the composition of the bilayers. With further development, this approach would enable rapid screening of different patches in protein binding assays and would enable interfacing patches with electrical detectors.
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Affiliation(s)
- Laura D. Hughes
- Department of Chemistry, Stanford University, Stanford, California 94305-5012, United States
| | - Steven G. Boxer
- Department of Chemistry, Stanford University, Stanford, California 94305-5012, United States
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76
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Collins MD, Gordon SE. Giant liposome preparation for imaging and patch-clamp electrophysiology. J Vis Exp 2013. [PMID: 23851612 DOI: 10.3791/50227] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The reconstitution of ion channels into chemically defined lipid membranes for electrophysiological recording has been a powerful technique to identify and explore the function of these important proteins. However, classical preparations, such as planar bilayers, limit the manipulations and experiments that can be performed on the reconstituted channel and its membrane environment. The more cell-like structure of giant liposomes permits traditional patch-clamp experiments without sacrificing control of the lipid environment. Electroformation is an efficient mean to produce giant liposomes >10 μm in diameter which relies on the application of alternating voltage to a thin, ordered lipid film deposited on an electrode surface. However, since the classical protocol calls for the lipids to be deposited from organic solvents, it is not compatible with less robust membrane proteins like ion channels and must be modified. Recently, protocols have been developed to electroform giant liposomes from partially dehydrated small liposomes, which we have adapted to protein-containing liposomes in our laboratory. We present here the background, equipment, techniques, and pitfalls of electroformation of giant liposomes from small liposome dispersions. We begin with the classic protocol, which should be mastered first before attempting the more challenging protocols that follow. We demonstrate the process of controlled partial dehydration of small liposomes using vapor equilibrium with saturated salt solutions. Finally, we demonstrate the process of electroformation itself. We will describe simple, inexpensive equipment that can be made in-house to produce high-quality liposomes, and describe visual inspection of the preparation at each stage to ensure the best results.
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Affiliation(s)
- Marcus D Collins
- Department of Physiology and Biophysics, University of Washington
| | - Sharona E Gordon
- Department of Physiology and Biophysics, University of Washington;
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77
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Detergent-mediated incorporation of transmembrane proteins in giant unilamellar vesicles with controlled physiological contents. Proc Natl Acad Sci U S A 2013; 110:7276-81. [PMID: 23589883 DOI: 10.1073/pnas.1303857110] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Giant unilamellar vesicles (GUVs) are convenient biomimetic systems of the same size as cells that are increasingly used to quantitatively address biophysical and biochemical processes related to cell functions. However, current approaches to incorporate transmembrane proteins in the membrane of GUVs are limited by the amphiphilic nature or proteins. Here, we report a method to incorporate transmembrane proteins in GUVs, based on concepts developed for detergent-mediated reconstitution in large unilamellar vesicles. Reconstitution is performed either by direct incorporation from proteins purified in detergent micelles or by fusion of purified native vesicles or proteoliposomes in preformed GUVs. Lipid compositions of the membrane and the ionic, protein, or DNA compositions in the internal and external volumes of GUVs can be controlled. Using confocal microscopy and functional assays, we show that proteins are unidirectionally incorporated in the GUVs and keep their functionality. We have successfully tested our method with three types of transmembrane proteins. GUVs containing bacteriorhodopsin, a photoactivable proton pump, can generate large transmembrane pH and potential gradients that are light-switchable and stable for hours. GUVs with FhuA, a bacterial porin, were used to follow the DNA injection by T5 phage upon binding to its transmembrane receptor. GUVs incorporating BmrC/BmrD, a bacterial heterodimeric ATP-binding cassette efflux transporter, were used to demonstrate the protein-dependent translocation of drugs and their interactions with encapsulated DNA. Our method should thus apply to a wide variety of membrane or peripheral proteins for producing more complex biomimetic GUVs.
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78
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Abstract
Liposome structures have a wide range of applications in biology, biochemistry, and biophysics. As a result, several methods for forming liposomes have been developed. This review provides a critical comparison of existing microfluidic technologies for forming liposomes and, when applicable, a comparison with their analogous macroscale counterparts. The properties of the generated liposomes, including size, size distribution, lamellarity, membrane composition, and encapsulation efficiency, form the basis for comparison. We hope that this critique will allow the reader to make an informed decision as to which method should be used for a given biological application.
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Affiliation(s)
- Dirk van Swaay
- Institute for Chemical and Bioengineering, ETH Zurich, Zurich, Switzerland
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79
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Reigada R. Atomistic study of lipid membranes containing chloroform: looking for a lipid-mediated mechanism of anesthesia. PLoS One 2013; 8:e52631. [PMID: 23300982 PMCID: PMC3534722 DOI: 10.1371/journal.pone.0052631] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 11/20/2012] [Indexed: 01/29/2023] Open
Abstract
The molecular mechanism of general anesthesia is still a controversial issue. Direct effect by linking of anesthetics to proteins and indirect action on the lipid membrane properties are the two hypotheses in conflict. Atomistic simulations of different lipid membranes subjected to the effect of small volatile organohalogen compounds are used to explore plausible lipid-mediated mechanisms. Simulations of homogeneous membranes reveal that electrostatic potential and lateral pressure transversal profiles are affected differently by chloroform (anesthetic) and carbon tetrachloride (non-anesthetic). Simulations of structured membranes that combine ordered and disordered regions show that chloroform molecules accumulate preferentially in highly disordered lipid domains, suggesting that the combination of both lateral and transversal partitioning of chloroform in the cell membrane could be responsible of its anesthetic action.
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Affiliation(s)
- Ramon Reigada
- Departament de Química Física and Institut de Química Teòrica i Computacional, Universitat de Barcelona, Barcelona, Spain.
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80
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Abstract
Lipid bilayers are natural barriers of biological cells and cellular compartments. Membrane proteins integrated in biological membranes enable vital cell functions such as signal transduction and the transport of ions or small molecules. In order to determine the activity of a protein of interest at defined conditions, the membrane protein has to be integrated into artificial lipid bilayers immobilized on a surface. For the fabrication of such biosensors expertise is required in material science, surface and analytical chemistry, molecular biology and biotechnology. Specifically, techniques are needed for structuring surfaces in the micro- and nanometer scale, chemical modification and analysis, lipid bilayer formation, protein expression, purification and solubilization, and most importantly, protein integration into engineered lipid bilayers. Electrochemical and optical methods are suitable to detect membrane activity-related signals. The importance of structural knowledge to understand membrane protein function is obvious. Presently only a few structures of membrane proteins are solved at atomic resolution. Functional assays together with known structures of individual membrane proteins will contribute to a better understanding of vital biological processes occurring at biological membranes. Such assays will be utilized in the discovery of drugs, since membrane proteins are major drug targets.
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81
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Slingenbergh W, de Boer SK, Cordes T, Browne WR, Feringa BL, Hoogenboom JP, De Hosson JTM, van Dorp WF. Selective functionalization of tailored nanostructures. ACS NANO 2012; 6:9214-9220. [PMID: 22994624 DOI: 10.1021/nn303571p] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The controlled positioning of nanostructures with active molecular components is of importance throughout nanoscience and nanotechnology. We present a novel three-step method to produce nanostructures that are selectively decorated with functional molecules. We use fluorophores and nanoparticles to functionalize SiO features with defined shapes and with sizes ranging from micrometers to 25 nm. The method is called MACE-ID: molecular assembly controlled by electron-beam-induced deposition. In the first step, SiO nanostructures are written with focused electron-beam-induced deposition, a direct-writing technique. In the second step, the deposits are selectively silanized. In the final step, the silanes are functionalized with fluorescent dyes, polystyrene spheres, or gold nanoparticles. This recipe gives exciting new possibilities for combining the highly accurate control of top-down patterning (e-beam direct writing) with the rich variety of the bottom-up approach (self-assembly), leading to active or responsive surfaces. An important advantage of MACE-ID is that it can be used on substrates that already contain complex features, such as plasmonic structures, nanoantennas, and cavities.
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Affiliation(s)
- Winand Slingenbergh
- Applied Physics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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82
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Abstract
Tremendous progress has been made in recent years in understanding the working of the living cell, including its micro-anatomy, signalling networks, and regulation of genes. However, an understanding of cellular phenomena using fundamental laws starting from first principles is still very far away. Part of the reason is that a cell is an active and exquisitely complex system where every part is linked to the other. Thus, it is difficult or even impossible to design experiments that selectively and exclusively probe a chosen aspect of the cell. Various kinds of idealised systems and cell models have been used to circumvent this problem. An important example is a giant unilamellar vesicle (GUV, also called giant liposome), which provides a cell-sized confined volume to study biochemical reactions as well as self-assembly processes that occur on the membrane. The GUV membrane can be designed suitably to present selected, correctly-oriented cell-membrane proteins, whose mobility is confined to two dimensions. Here, we present recent advances in GUV design and the use of GUVs as cell models that enable quantitative testing leading to insight into the working of real cells. We briefly recapitulate important classical concepts in membrane biophysics emphasising the advantages and limitations of GUVs. We then present results obtained over the last decades using GUVs, choosing the formation of membrane domains and cell adhesion as examples for in-depth treatment. Insight into cell adhesion obtained using micro-interferometry is treated in detail. We conclude by summarising the open questions and possible future directions.
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Affiliation(s)
- Susanne F Fenz
- Leiden Institute of Physics: Physics of Life Processes, Leiden University, The Netherlands
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83
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Kooijmans SAA, Vader P, van Dommelen SM, van Solinge WW, Schiffelers RM. Exosome mimetics: a novel class of drug delivery systems. Int J Nanomedicine 2012; 7:1525-41. [PMID: 22619510 PMCID: PMC3356169 DOI: 10.2147/ijn.s29661] [Citation(s) in RCA: 219] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The identification of extracellular phospholipid vesicles as conveyors of cellular information has created excitement in the field of drug delivery. Biological therapeutics, including short interfering RNA and recombinant proteins, are prone to degradation, have limited ability to cross biological membranes, and may elicit immune responses. Therefore, delivery systems for such drugs are under intensive investigation. Exploiting extracellular vesicles as carriers for biological therapeutics is a promising strategy to overcome these issues and to achieve efficient delivery to the cytosol of target cells. Exosomes are a well studied class of extracellular vesicles known to carry proteins and nucleic acids, making them especially suitable for such strategies. However, the considerable complexity and the related high chance of off-target effects of these carriers are major barriers for translation to the clinic. Given that it is well possible that not all components of exosomes are required for their proper functioning, an alternative strategy would be to mimic these vesicles synthetically. By assembly of liposomes harboring only crucial components of natural exosomes, functional exosome mimetics may be created. The low complexity and use of well characterized components strongly increase the pharmaceutical acceptability of such systems. However, exosomal components that would be required for the assembly of functional exosome mimetics remain to be identified. This review provides insights into the composition and functional properties of exosomes, and focuses on components which could be used to enhance the drug delivery properties of exosome mimetics.
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Affiliation(s)
- Sander A A Kooijmans
- Department of Clinical Chemistry and Haematology, University Medical Center Utrecht, Utrecht, The Netherlands
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