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Bacalum M, Radu M, Osella S, Knippenberg S, Ameloot M. Generalized polarization and time-resolved fluorescence provide evidence for different populations of Laurdan in lipid vesicles. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2024; 250:112833. [PMID: 38141326 DOI: 10.1016/j.jphotobiol.2023.112833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 11/29/2023] [Accepted: 12/18/2023] [Indexed: 12/25/2023]
Abstract
The solvatochromic dye Laurdan is widely used in sensing the lipid packing of both model and biological membranes. The fluorescence emission maximum shifts from about 440 nm (blue channel) in condensed membranes (So) to about 490 nm (green channel) in the liquid-crystalline phase (Lα). Although the fluorescence intensity based generalized polarization (GP) is widely used to characterize lipid membranes, the fluorescence lifetime of Laurdan, in the blue and the green channel, is less used for that purpose. Here we explore the correlation between GP and fluorescence lifetimes by spectroscopic measurements on the So and Lα phases of large unilamellar vesicles of DMPC and DPPC. A positive correlation between GP and the lifetimes is observed in each of the optical channels for the two lipid phases. Microfluorimetric determinations on giant unilamellar vesicles of DPPC and DOPC at room temperature are performed under linearly polarized two-photon excitation to disentangle possible subpopulations of Laurdan at a scale below the optical resolution. Fluorescence intensities, GP and fluorescence lifetimes depend on the angle between the orientation of the linear polarization of the excitation light and the local normal to the membrane of the optical cross-section. This angular variation depends on the lipid phase and the emission channel. GP and fluorescence intensities in the blue and green channel in So and in the blue channel in Lα exhibit a minimum near 90o. Surprisingly, the intensity in the green channel in Lα reaches a maximum near 90o. The fluorescence lifetimes in the two optical channels also reach a pronounced minimum near 90o in So and Lα, apart from the lifetime in the blue channel in Lα where the lifetime is short with minimal angular variation. To our knowledge, these experimental observations are the first to demonstrate the existence of a bent conformation of Laurdan in lipid membranes, as previously suggested by molecular dynamics calculations.
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Affiliation(s)
- Mihaela Bacalum
- Department of Life and Environmental Physics, Horia Hulubei National Institute for Physics and Nuclear Engineering, Reactorului, 30, Măgurele 077125, Romania
| | - Mihai Radu
- Department of Life and Environmental Physics, Horia Hulubei National Institute for Physics and Nuclear Engineering, Reactorului, 30, Măgurele 077125, Romania
| | - Silvio Osella
- Chemical and Biological Systems Simulation Lab, Centre of New Technologies, University of Warsaw, Banacha 2C, 02-097 Warsaw, Poland
| | - Stefan Knippenberg
- Biomedical Research Institute, Hasselt University, Agoralaan Bldg. C, 3590 Diepenbeek, Belgium; Theory Lab, Hasselt University, Agoralaan Bldg. D, 3590 Diepenbeek, Belgium
| | - Marcel Ameloot
- Biomedical Research Institute, Hasselt University, Agoralaan Bldg. C, 3590 Diepenbeek, Belgium.
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2
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Mayor S, Bhat A, Kusumi A. A Survey of Models of Cell Membranes: Toward a New Understanding of Membrane Organization. Cold Spring Harb Perspect Biol 2023; 15:a041394. [PMID: 37643877 PMCID: PMC10547391 DOI: 10.1101/cshperspect.a041394] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
The cell membrane, the boundary that separates living cells from their environment, has been the subject of study for over a century. The fluid-mosaic model of Singer and Nicolson in 1972 proposed the plasma membrane as a two-dimensional fluid composed of lipids and proteins. Fifty years hence, advances in biophysical and biochemical tools, particularly optical imaging techniques, have allowed for a better understanding of the physical nature, organization, and composition of cell membranes. This has been made possible by visualizing membrane heterogeneities and their dynamics and appreciating the asymmetrical arrangement of lipids in living cell membranes. Despite these advances, mechanisms underlying the local spatiotemporal organization of membrane components remain unclear. This review surveys various models of membrane organization, culminating in a new model that incorporates nonequilibrium processes and forces exerted by interactions with extramembrane elements such as the actin cytoskeleton. The proposed model provides a comprehensive understanding of membrane organization, taking into account the dynamic nature of the cell membrane and its interactions with its immediate environment.
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Affiliation(s)
- Satyajit Mayor
- National Centre for Biological Science, TIFR, Bangalore 560065, India
| | - Abrar Bhat
- National Centre for Biological Science, TIFR, Bangalore 560065, India
| | - Akihiro Kusumi
- Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904-0495, Japan; Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, Kyoto 606-8501, Japan
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3
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Zhukov A, Popov V. Eukaryotic Cell Membranes: Structure, Composition, Research Methods and Computational Modelling. Int J Mol Sci 2023; 24:11226. [PMID: 37446404 DOI: 10.3390/ijms241311226] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 07/03/2023] [Accepted: 07/06/2023] [Indexed: 07/15/2023] Open
Abstract
This paper deals with the problems encountered in the study of eukaryotic cell membranes. A discussion on the structure and composition of membranes, lateral heterogeneity of membranes, lipid raft formation, and involvement of actin and cytoskeleton networks in the maintenance of membrane structure is included. Modern methods for the study of membranes and their constituent domains are discussed. Various simplified models of biomembranes and lipid rafts are presented. Computer modelling is considered as one of the most important methods. This is stated that from the study of the plasma membrane structure, it is desirable to proceed to the diverse membranes of all organelles of the cell. The qualitative composition and molar content of individual classes of polar lipids, free sterols and proteins in each of these membranes must be considered. A program to create an open access electronic database including results obtained from the membrane modelling of individual cell organelles and the key sites of the membranes, as well as models of individual molecules composing the membranes, has been proposed.
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Affiliation(s)
- Anatoly Zhukov
- Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya Street 35, 127276 Moscow, Russia
| | - Valery Popov
- Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya Street 35, 127276 Moscow, Russia
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4
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Fabiunke S, Fillafer C, Schneider MF. Unitary Response of Solvatochromic Dye to Pulse Excitation in Lipid and Cell Membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:12408-12413. [PMID: 36154016 DOI: 10.1021/acs.langmuir.2c02261] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The existence of acoustic pulse propagation in lipid monolayers at the air-water interface is well known. These pulses are controlled by the thermodynamic state of the lipid membrane. Nevertheless, the role of acoustic pulses for intra- and inter-cellular communication is still a matter of debate. Herein, we used the dye di-4-ANEPPDHQ, which is known to be sensitive to the physical state and transmembrane potential of membranes, in order to gain insights into compression waves in lipid-based membrane interfaces. The dye was incorporated into lipid monolayers made of phosphatidylserine or phosphatidylcholine at the air-water-interface. A significant blue shift of the emission spectrum was detected when the state of the monolayer was changed from the liquid-expanded (LE) to the liquid-condensed (LC) phase. This "transition sensitivity" of di-4-ANEPPDHQ was generalized in experiments with the bulk solvent dimethyl sulfoxide (DMSO). Upon crystallization of solvent, the emission spectrum also underwent a blue shift. During compression pulses in lipid monolayers, a significant fluorescence response was only observed when the main transition is crossed. The optical signature of these waves─in terms of sign and magnitude─was identical to the response of di-4-ANEPPDHQ during action potentials in neurons and excitable plant cells. These findings corroborated the suggestion that action potentials are nonlinear state changes that propagate in the cell membrane.
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Affiliation(s)
- Simon Fabiunke
- Department of Medical and Biological Physics, Technical University Dortmund, 44227 Dortmund, Germany
| | - Christian Fillafer
- Department of Medical and Biological Physics, Technical University Dortmund, 44227 Dortmund, Germany
| | - Matthias F Schneider
- Department of Medical and Biological Physics, Technical University Dortmund, 44227 Dortmund, Germany
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5
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Biocompatible and optically stable hydrophobic fluorescent carbon dots for isolation and imaging of lipid rafts in model membrane. Anal Bioanal Chem 2022; 414:6055-6067. [PMID: 35697813 DOI: 10.1007/s00216-022-04165-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 05/06/2022] [Accepted: 06/02/2022] [Indexed: 11/01/2022]
Abstract
Lateral heterogeneity in cell membranes features a variety of compositions that influence their inherent properties. One such biophysical variation is the formation of a membrane or lipid raft, which plays important roles in many cellular processes. The lipid rafts on the cell membrane are mostly identified by specific dyes and heavy metal quantum dots, which have their own drawbacks, such as cytotoxicity, photostability, and incompatibility. To this end, we synthesized special, hydrophobic, fluorescent, photostable, and non-cytotoxic carbon dots (CDs) by solvent-free thermal treatment using non-cytotoxic materials and incorporated into the lipid bilayers of giant unilamellar vesicles (GUVs) made from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and dipalmitoylphosphatidylcholine (DPPC) lipids. A 2:2:1 mixture of DOPC, DPPC, and cholesterol (Chol) develops lipid rafts on the membrane by phase separation. The photophysical properties of the CDs get modulated on incorporation into the lipid rafts that identifies the membrane heterogeneity. The main attempt in this work is to develop a new, simple, cost-effective, and bio-friendly lipid raft marker, which can be used in biological applications, alongside other conventional raft markers, with more advantages.
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6
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Zapata-Mercado E, Azarova EV, Hristova K. Effect of reversible osmotic stress on live cell plasma membranes, probed via Laurdan general polarization measurements. Biophys J 2022; 121:2411-2418. [PMID: 35596525 DOI: 10.1016/j.bpj.2022.05.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 09/10/2021] [Accepted: 05/16/2022] [Indexed: 11/02/2022] Open
Abstract
Here we seek to gain insight into changes in the plasma membrane of live cells upon the application of osmotic stress using Laurdan, a fluorescent probe that reports on membrane organization, hydration, and dynamics. It is known that the application of osmotic stress to lipid vesicles causes a decrease in Laurdan's generalized polarization (GP), which has been interpreted as an indication of membrane stretching. In cells, we see the opposite effects, as GP increases when the osmolarity of the solution is decreased. This increase in GP is associated with the presence of caveolae, which are known to disassemble and flatten in response to osmotic stress.
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Affiliation(s)
- Elmer Zapata-Mercado
- Department of Materials Science and Engineering, Institute for NanoBioTechnology, and Program in Molecular Biophysics, Johns Hopkins University, Baltimore, MD 21218
| | - Evgenia V Azarova
- Department of Materials Science and Engineering, Institute for NanoBioTechnology, and Program in Molecular Biophysics, Johns Hopkins University, Baltimore, MD 21218
| | - Kalina Hristova
- Department of Materials Science and Engineering, Institute for NanoBioTechnology, and Program in Molecular Biophysics, Johns Hopkins University, Baltimore, MD 21218.
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Levitan I. Evaluating membrane structure by Laurdan imaging: Disruption of lipid packing by oxidized lipids. CURRENT TOPICS IN MEMBRANES 2021; 88:235-256. [PMID: 34862028 DOI: 10.1016/bs.ctm.2021.10.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Impact of different lipids on membrane structure/lipid order is critical for multiple biological processes. Laurdan microscopy provides a unique tool to assess this property in heterogeneous biological membranes. This review describes the general principles of the approach and its application in model membranes and cells. It also provides an in-depth discussion of the insights obtained using Laurdan microscopy to evaluate the differential effects of cholesterol, oxysterols and oxidized phospholipids on lipid packing of ordered and disordered domains in vascular endothelial cells.
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Affiliation(s)
- Irena Levitan
- Division of Pulmonary and Critical Care, Department of Medicine, University of Illinois at Chicago, Chicago, IL, United States.
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8
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Minnelli C, Laudadio E, Fiorini R, Galeazzi R, Armeni T, Stipa P, Rusciano D, Mobbili G. Influence of a lipophilic edaravone on physical state and activity of antioxidant liposomes: An experimental and in silico study. Colloids Surf B Biointerfaces 2021; 210:112217. [PMID: 34836703 DOI: 10.1016/j.colsurfb.2021.112217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 11/10/2021] [Accepted: 11/11/2021] [Indexed: 11/16/2022]
Abstract
The influence of a lipophilic derivative of Edaravone (C18Edv) on a POPC liposomal bilayer has been investigated by a combined computational-experimental approach. The order and hydration degree of three different systems composed by 10%, 20% and 40% in w/w percentage of C18Edv respect to POPC were investigated through Molecular Dynamics (MD) simulations and fluorescence spectroscopy experiments. Dynamic Light Scattering measurements showed how the presence of different amounts of C18EdV determines differences on liposome size and stability. The survey revealed that the content of lipophilic antioxidant tunes liposome rigidity and influences cellular uptake and antioxidant activity which are maximized for formulation containing 20% of C18Edv.
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Affiliation(s)
- Cristina Minnelli
- Dipartimento di Scienze della Vita e dell'Ambiente (DISVA), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy
| | - Emiliano Laudadio
- Dipartimento di Scienze e Ingegneria della Materia, dell'Ambiente e Urbanistica (SIMAU), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy
| | - Rosamaria Fiorini
- Dipartimento di Scienze della Vita e dell'Ambiente (DISVA), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy
| | - Roberta Galeazzi
- Dipartimento di Scienze della Vita e dell'Ambiente (DISVA), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy
| | - Tatiana Armeni
- Dipartimento Scienze Cliniche Specialistiche ed Odontostomatologiche, Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy
| | - Pierluigi Stipa
- Dipartimento di Scienze e Ingegneria della Materia, dell'Ambiente e Urbanistica (SIMAU), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy
| | | | - Giovanna Mobbili
- Dipartimento di Scienze della Vita e dell'Ambiente (DISVA), Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy.
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9
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Amiar S, Husby ML, Wijesinghe KJ, Angel S, Bhattarai N, Gerstman BS, Chapagain PP, Li S, Stahelin RV. Lipid-specific oligomerization of the Marburg virus matrix protein VP40 is regulated by two distinct interfaces for virion assembly. J Biol Chem 2021; 296:100796. [PMID: 34019871 PMCID: PMC8191294 DOI: 10.1016/j.jbc.2021.100796] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 05/12/2021] [Accepted: 05/14/2021] [Indexed: 02/03/2023] Open
Abstract
Marburg virus (MARV) is a lipid-enveloped virus harboring a negative-sense RNA genome, which has caused sporadic outbreaks of viral hemorrhagic fever in sub-Saharan Africa. MARV assembles and buds from the host cell plasma membrane where MARV matrix protein (mVP40) dimers associate with anionic lipids at the plasma membrane inner leaflet and undergo a dynamic and extensive self-oligomerization into the structural matrix layer. The MARV matrix layer confers the virion filamentous shape and stability but how host lipids modulate mVP40 oligomerization is mostly unknown. Using in vitro and cellular techniques, we present a mVP40 assembly model highlighting two distinct oligomerization interfaces: the (N-terminal domain [NTD] and C-terminal domain [CTD]) in mVP40. Cellular studies of NTD and CTD oligomerization interface mutants demonstrate the importance of each interface in matrix assembly. The assembly steps include protein trafficking to the plasma membrane, homo-multimerization that induced protein enrichment, plasma membrane fluidity changes, and elongations at the plasma membrane. An ascorbate peroxidase derivative (APEX)-transmission electron microscopy method was employed to closely assess the ultrastructural localization and formation of viral particles for wildtype mVP40 and NTD and CTD oligomerization interface mutants. Taken together, these studies present a mechanistic model of mVP40 oligomerization and assembly at the plasma membrane during virion assembly that requires interactions with phosphatidylserine for NTD–NTD interactions and phosphatidylinositol-4,5-bisphosphate for proper CTD–CTD interactions. These findings have broader implications in understanding budding of lipid-enveloped viruses from the host cell plasma membrane and potential strategies to target protein–protein or lipid–protein interactions to inhibit virus budding.
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Affiliation(s)
- Souad Amiar
- Department of Medicinal Chemistry & Molecular Pharmacology, Purdue University, West Lafayette, Indiana, USA
| | - Monica L Husby
- Department of Medicinal Chemistry & Molecular Pharmacology, Purdue University, West Lafayette, Indiana, USA
| | - Kaveesha J Wijesinghe
- Department of Medicinal Chemistry & Molecular Pharmacology, Purdue University, West Lafayette, Indiana, USA; Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
| | - Stephanie Angel
- Department of Medicinal Chemistry & Molecular Pharmacology, Purdue University, West Lafayette, Indiana, USA
| | - Nisha Bhattarai
- Department of Physics, Florida International University, Miami, Florida, USA
| | - Bernard S Gerstman
- Department of Physics, Florida International University, Miami, Florida, USA; Biomolecular Sciences Institute, Florida International University, Miami, Florida, USA
| | - Prem P Chapagain
- Department of Physics, Florida International University, Miami, Florida, USA; Biomolecular Sciences Institute, Florida International University, Miami, Florida, USA
| | - Sheng Li
- Department of Medicine, University of California San Diego, La Jolla, California, USA
| | - Robert V Stahelin
- Department of Medicinal Chemistry & Molecular Pharmacology, Purdue University, West Lafayette, Indiana, USA.
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10
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Hedde PN, Malacrida L, Barylko B, Binns DD, Albanesi JP, Jameson DM. Membrane Remodeling by Arc/Arg3.1. Front Mol Biosci 2021; 8:630625. [PMID: 33763452 PMCID: PMC7982473 DOI: 10.3389/fmolb.2021.630625] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 01/11/2021] [Indexed: 11/13/2022] Open
Abstract
The activity-regulated cytoskeletal-associated protein (Arc, also known as Arg3.1) is an immediate early gene product induced by activity/experience and required for multiple modes of synaptic plasticity. Both long-term potentiation (LTP) and long-term depression (LTD) are impaired upon Arc deletion, as well as the ability to form long-term spatial, taste and fear memories. The best-characterized cellular function of Arc is enhancement of the endocytic internalization of AMPA receptors (AMPARs) in dendritic spines. Solution of the crystal structure of a C-terminal segment of Arc revealed a striking similarity to the capsid domain of HIV Gag. It was subsequently shown that Arc assembles into viral capsid-like structures that enclose Arc mRNA, are released into the extracellular space, and are internalized by neighboring cells. Thus, Arc is unique in participating in plasma membrane budding both into and out of the cell. In this report we study the interaction of Arc with membranes using giant unilamellar vesicles (GUVs). Using the fluorescent lipid probe LAURDAN, we find that Arc promotes the formation of smaller vesicles that penetrate into the GUV interior. Our results suggest that Arc induces negative membrane curvature and may therefore facilitate the formation of mRNA-containing extracellular vesicles from the plasma membrane.
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Affiliation(s)
- Per Niklas Hedde
- Department of Cell and Molecular Biology, University of Hawaii at Manoa, Honolulu, HI, United States.,Laboratory for Fluorescence Dynamics, University of California, Irvine , CA, United States
| | - Leonel Malacrida
- Departamento de Fisiopatología, Hospital de Clínicas, Facultad de Medicina, Universidad de la República, Montevideo , Uruguay.,Advanced Bioimaging Unit, Institute Pasteur of Montevideo-Universidad de la República, Montevideo, Uruguay
| | - Barbara Barylko
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Derk D Binns
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Joseph P Albanesi
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - David M Jameson
- Department of Cell and Molecular Biology, University of Hawaii at Manoa, Honolulu, HI, United States
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11
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Hedde PN, Malacrida L, Barylko B, Binns DD, Albanesi JP, Jameson DM. Membrane Remodeling by Arc/Arg3.1. Front Mol Biosci 2021; 8:630625. [PMID: 33763452 DOI: 10.3389/fmolb.2021.630625/full] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 01/11/2021] [Indexed: 05/23/2023] Open
Abstract
The activity-regulated cytoskeletal-associated protein (Arc, also known as Arg3.1) is an immediate early gene product induced by activity/experience and required for multiple modes of synaptic plasticity. Both long-term potentiation (LTP) and long-term depression (LTD) are impaired upon Arc deletion, as well as the ability to form long-term spatial, taste and fear memories. The best-characterized cellular function of Arc is enhancement of the endocytic internalization of AMPA receptors (AMPARs) in dendritic spines. Solution of the crystal structure of a C-terminal segment of Arc revealed a striking similarity to the capsid domain of HIV Gag. It was subsequently shown that Arc assembles into viral capsid-like structures that enclose Arc mRNA, are released into the extracellular space, and are internalized by neighboring cells. Thus, Arc is unique in participating in plasma membrane budding both into and out of the cell. In this report we study the interaction of Arc with membranes using giant unilamellar vesicles (GUVs). Using the fluorescent lipid probe LAURDAN, we find that Arc promotes the formation of smaller vesicles that penetrate into the GUV interior. Our results suggest that Arc induces negative membrane curvature and may therefore facilitate the formation of mRNA-containing extracellular vesicles from the plasma membrane.
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Affiliation(s)
- Per Niklas Hedde
- Department of Cell and Molecular Biology, University of Hawaii at Manoa, Honolulu, HI, United States
- Laboratory for Fluorescence Dynamics, University of California, Irvine , CA, United States
| | - Leonel Malacrida
- Departamento de Fisiopatología, Hospital de Clínicas, Facultad de Medicina, Universidad de la República, Montevideo , Uruguay
- Advanced Bioimaging Unit, Institute Pasteur of Montevideo-Universidad de la República, Montevideo, Uruguay
| | - Barbara Barylko
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Derk D Binns
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Joseph P Albanesi
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - David M Jameson
- Department of Cell and Molecular Biology, University of Hawaii at Manoa, Honolulu, HI, United States
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12
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Gunther G, Malacrida L, Jameson DM, Gratton E, Sánchez SA. LAURDAN since Weber: The Quest for Visualizing Membrane Heterogeneity. Acc Chem Res 2021; 54:976-987. [PMID: 33513300 PMCID: PMC8552415 DOI: 10.1021/acs.accounts.0c00687] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Any chemist studying the interaction of molecules with lipid assemblies will eventually be confronted by the topic of membrane bilayer heterogeneity and may ultimately encounter the heterogeneity of natural membranes. In artificial bilayers, heterogeneity is defined by phase segregation that can be in the nano- and micrometer range. In biological bilayers, heterogeneity is considered in the context of small (10-200 nm) sterol and sphingolipid-enriched heterogeneous and highly dynamic domains. Several techniques can be used to assess membrane heterogeneity in living systems. Our approach is to use a fluorescent reporter molecule immersed in the bilayer, which, by changes in its spectroscopic properties, senses physical-chemistry aspects of the membrane. This dye in combination with microscopy and fluctuation techniques can give information about membrane heterogeneity at different temporal and spatial levels: going from average fluidity to number and diffusion coefficient of nanodomains. LAURDAN (6-dodecanoyl-2-(dimethylamino) naphthalene), is a fluorescent probe designed and synthesized in 1979 by Gregorio Weber with the purpose to study the phenomenon of dipolar relaxation. The spectral displacement observed when LAURDAN is either in fluid or gel phase permitted the use of the technique in the field of membrane dynamics. The quantitation of the spectral displacement was first addressed by the generalized polarization (GP) function in the cuvette, a ratio of the difference in intensity at two wavelengths divided by their sum. In 1997, GP measurements were done for the first time in the microscope, adding to the technique the spatial resolution and allowing the visualization of lipid segregation both in liposomes and cells. A new prospective to the membrane heterogeneity was obtained when LAURDAN fluorescent lifetime measurements were done in the microscope. Two channel lifetime imaging provides information on membrane polarity and dipole relaxation (the two parameters responsible for the spectral shift of LAURDAN), and the application of phasor analysis allows pixel by pixel understanding of these two parameters in the membrane. To increase temporal resolution, LAURDAN GP was combined with fluctuation correlation spectroscopy (FCS) and the motility of nanometric highly packed structures in biological membranes was registered. Lately the application of phasor analysis to spectral images from membranes labeled with LAURDAN allows us to study the full spectra pixel by pixel in an image. All these methodologies, using LAURDAN, offer the possibility to address different properties of membranes depending on the question being asked. In this Account, we will focus on the principles, advantages, and limitations of different approaches to orient the reader to select the most appropriate technique for their research.
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Affiliation(s)
- German Gunther
- Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Sergio Livingstone P. 1007, Santiago 8380492, Chile
| | - Leonel Malacrida
- Advanced Microscopy and Biophotonics Unit, Hospital de Clínicas, Universidad de la República, Montevideo-Uruguay. Advanced Bioimaging Unit, Institut Pasteur Montevideo, Av. Italia s/n, 90600 Montevideo, Uruguay
| | - David M Jameson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, 651 Ilalo Street, Biosciences 222, Honolulu, Hawaii 96813, United States
| | - Enrico Gratton
- Laboratory for Fluorescence Dynamics, 3210 Natural Sciences II, University of California, Irvine, Irvine, California 92697-2725, United States
| | - Susana A Sánchez
- Departamento de Polímeros, Facultad de Ciencias Químicas, Universidad de Concepción, Edmundo Larenas 129, Concepción 4070371, Chile
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13
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Fabiunke S, Fillafer C, Paeger A, Schneider MF. Optical studies of membrane state during action potential propagation. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2020; 162:69-78. [DOI: 10.1016/j.pbiomolbio.2020.11.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 10/05/2020] [Accepted: 11/13/2020] [Indexed: 10/23/2022]
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14
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Miles SM, Hofstetter S, Edwards T, Dlusskaya E, Cologgi DL, Gänzle M, Ulrich AC. Tolerance and cytotoxicity of naphthenic acids on microorganisms isolated from oil sands process-affected water. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 695:133749. [PMID: 31419688 DOI: 10.1016/j.scitotenv.2019.133749] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/31/2019] [Accepted: 08/01/2019] [Indexed: 06/10/2023]
Abstract
The expansion of oil sands has made remediation of oil sands process-affected water (OSPW) critical. As naphthenic acids (NAs) are the primary contributors to toxicity, remediation is required. Bioremediation by native microorganisms is potentially effective, however, toxicity of NAs towards native microorganisms is poorly understood. The aim of this study was to isolate microorganisms from OSPW, assess tolerance to stressors, including naturally sourced NAs and examine exposure effect of NAs on cell membranes. Microorganisms were isolated from OSPW, including the first reported isolation of a fungus (Trichoderma harzianum) and yeast (Rhodotorula mucilaginosa). Isolates tolerated alkaline pH, high salinity, and NA concentrations far exceeding those typical of OSPW indicating toxic effects of OSPW are likely the result of interactions between OSPW components. Comparisons of toxicity determined that OSPW exhibited higher cytotoxicity than NAs. The fungal isolate was able to grow using commercial NAs as its sole carbon source, indicating high resistance to NAs' cytotoxic effects. Future studies will focus on the organisms' ability to degrade NAs, and subsequent effects on toxicity. Characterization of OSPW constituents should be investigated with focus on the synergistic toxic effects of dissolved compounds. A better understanding of OSPW toxicity would enable more effective and targeted bioremediation schemes by native microorganisms.
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Affiliation(s)
- Sarah M Miles
- University of Alberta, Department of Civil and Environmental Engineering, Edmonton, Alberta, Canada
| | - Simmon Hofstetter
- University of Alberta, Department of Civil and Environmental Engineering, Edmonton, Alberta, Canada
| | - Timothy Edwards
- University of Alberta, Department of Civil and Environmental Engineering, Edmonton, Alberta, Canada
| | - Elena Dlusskaya
- University of Alberta, Department of Civil and Environmental Engineering, Edmonton, Alberta, Canada
| | - Dena L Cologgi
- University of Alberta, Department of Civil and Environmental Engineering, Edmonton, Alberta, Canada
| | - Michael Gänzle
- University of Alberta, Department of Agricultural, Food, and Nutrition Science, Edmonton, Alberta, Canada
| | - Ania C Ulrich
- University of Alberta, Department of Civil and Environmental Engineering, Edmonton, Alberta, Canada.
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15
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Osella S, Knippenberg S. Laurdan as a Molecular Rotor in Biological Environments. ACS APPLIED BIO MATERIALS 2019; 2:5769-5778. [DOI: 10.1021/acsabm.9b00789] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Silvio Osella
- Chemical and Biological Systems Simulation Lab, Centre of New Technologies, University of Warsaw, Banacha 2C, 02-097 Warsaw, Poland
| | - Stefan Knippenberg
- RCPTM, Department of Physical Chemistry, Fac. Sciences, Palacký University, 771 46 Olomouc, Czech Republic
- Theoretical Physics, Hasselt University, Agoralaan Building D, 3590 Diepenbeek, Belgium
- Department of Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, SE-10691 Stockholm, Sweden
- Research Group PLASMANT, Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium
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16
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Haiping L, Pei Z, Shuhai Z, Dengyun Z, Herong F, Yi S, Xinqian W. Protective effect of polysaccharides from Pholiota nameko on Lactobacillus casei ATCC 334 subjected to freeze-drying. Lebensm Wiss Technol 2019. [DOI: 10.1016/j.lwt.2019.108463] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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17
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Calori IR, Pazin WM, Brunaldi K, Pellosi DS, Caetano W, Tedesco AC, Hioka N. Laurdan as fluorescent probe to determinate the critical micelle temperature of polymers from Pluronic®-coated fluid phase liposomes. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2019.111562] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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18
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Measuring the Impact of Bile Acids on the Membrane Order of Primary Hepatocytes and Isolated Mitochondria by Fluorescence Imaging and Spectroscopy. Methods Mol Biol 2019; 1981:99-115. [PMID: 31016650 DOI: 10.1007/978-1-4939-9420-5_7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
Cholestasis is characterized by impaired secretion of bile flow that can result in the accumulation of highly abnormal levels of bile acids causing hepatocyte and biliary injury. As amphipathic molecules, bile acids can intercalate in lipid membranes, and pathophysiologic concentrations of bile acids have the potential to induce marked changes in the biophysical properties of biomembranes, including membrane ordering. These effects, particularly on the mitochondrial and plasma membranes, have been proposed to trigger toxicity of bile acids. This chapter details different fluorescence-based methods (fluorescence polarization, and spectroscopy/imaging of solvatochromic dyes) to evaluate the impact of different bile acids on membrane order. Protocols are described for the application of these methods to biomimetic vesicles, isolated mitochondria, and hepatocytes, following a bottom-up approach.
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19
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Osella S, Di Meo F, Murugan NA, Fabre G, Ameloot M, Trouillas P, Knippenberg S. Combining (Non)linear Optical and Fluorescence Analysis of DiD To Enhance Lipid Phase Recognition. J Chem Theory Comput 2018; 14:5350-5359. [DOI: 10.1021/acs.jctc.8b00553] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Silvio Osella
- Centre of New Technologies, University of Warsaw, Banacha 2C, 02-097 Warsaw, Poland
- Department of Theoretical Chemistry and Biology, School of Engineering Sciences in Chemistry, Biotechnology and Health, Royal Institute of Technology, SE-10691 Stockholm, Sweden
| | - Florent Di Meo
- Faculty of Pharmacy, UMR 1248 INSERM, Limoges University, 2 rue du Docteur Marcland, 87025 Limoges Cedex, France
| | - N. Arul Murugan
- Department of Theoretical Chemistry and Biology, School of Engineering Sciences in Chemistry, Biotechnology and Health, Royal Institute of Technology, SE-10691 Stockholm, Sweden
| | - Gabin Fabre
- LCSN-EA1069, Faculty of Pharmacy, Limoges University, 2, rue du Dr. Marcland, 87025 Limoges Cedex, France
| | - Marcel Ameloot
- Biomedical Research Institute, Hasselt University, B-3590, Diepenbeek, Belgium
| | - Patrick Trouillas
- Faculty of Pharmacy, UMR 1248 INSERM, Limoges University, 2 rue du Docteur Marcland, 87025 Limoges Cedex, France
- Centre of Advanced Technologies and Materials, Faculty of Science, Palacký University, tř. 17 listopadu 12, 771 46 Olomouc, Czech Republic
| | - Stefan Knippenberg
- Department of Theoretical Chemistry and Biology, School of Engineering Sciences in Chemistry, Biotechnology and Health, Royal Institute of Technology, SE-10691 Stockholm, Sweden
- Biomedical Research Institute, Hasselt University, B-3590, Diepenbeek, Belgium
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20
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Slenders E, Seneca S, Pramanik SK, Smisdom N, Adriaensens P, vandeVen M, Ethirajan A, Ameloot M. Dynamics of the phospholipid shell of microbubbles: a fluorescence photoselection and spectral phasor approach. Chem Commun (Camb) 2018; 54:4854-4857. [DOI: 10.1039/c8cc01012a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The lipid organization of microbubbles is important in many applications.
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Affiliation(s)
- Eli Slenders
- Biomedical Research Institute (BIOMED)
- Hasselt University
- Agoralaan Bldg. C
- 3590 Diepenbeek
- Belgium
| | - Senne Seneca
- Institute for Materials Research (IMO)
- Hasselt University
- Wetenschapspark 1 and Agoralaan Bldg. D
- 3590 Diepenbeek
- Belgium
| | - Sumit Kumar Pramanik
- Institute for Materials Research (IMO)
- Hasselt University
- Wetenschapspark 1 and Agoralaan Bldg. D
- 3590 Diepenbeek
- Belgium
| | - Nick Smisdom
- Biomedical Research Institute (BIOMED)
- Hasselt University
- Agoralaan Bldg. C
- 3590 Diepenbeek
- Belgium
| | - Peter Adriaensens
- Institute for Materials Research (IMO)
- Hasselt University
- Wetenschapspark 1 and Agoralaan Bldg. D
- 3590 Diepenbeek
- Belgium
| | - Martin vandeVen
- Biomedical Research Institute (BIOMED)
- Hasselt University
- Agoralaan Bldg. C
- 3590 Diepenbeek
- Belgium
| | - Anitha Ethirajan
- Institute for Materials Research (IMO)
- Hasselt University
- Wetenschapspark 1 and Agoralaan Bldg. D
- 3590 Diepenbeek
- Belgium
| | - Marcel Ameloot
- Biomedical Research Institute (BIOMED)
- Hasselt University
- Agoralaan Bldg. C
- 3590 Diepenbeek
- Belgium
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21
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Cornell CE, McCarthy NLC, Levental KR, Levental I, Brooks NJ, Keller SL. n-Alcohol Length Governs Shift in L o-L d Mixing Temperatures in Synthetic and Cell-Derived Membranes. Biophys J 2017; 113:1200-1211. [PMID: 28801104 PMCID: PMC5607138 DOI: 10.1016/j.bpj.2017.06.066] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 06/07/2017] [Accepted: 06/29/2017] [Indexed: 11/30/2022] Open
Abstract
A persistent challenge in membrane biophysics has been to quantitatively predict how membrane physical properties change upon addition of new amphiphiles (e.g., lipids, alcohols, peptides, or proteins) in order to assess whether the changes are large enough to plausibly result in biological ramifications. Because of their roles as general anesthetics, n-alcohols are perhaps the best-studied amphiphiles of this class. When n-alcohols are added to model and cell membranes, changes in membrane parameters tend to be modest. One striking exception is found in the large decrease in liquid-liquid miscibility transition temperatures (Tmix) observed when short-chain n-alcohols are incorporated into giant plasma membrane vesicles (GPMVs). Coexisting liquid-ordered and liquid-disordered phases are observed at temperatures below Tmix in GPMVs as well as in giant unilamellar vesicles (GUVs) composed of ternary mixtures of a lipid with a low melting temperature, a lipid with a high melting temperature, and cholesterol. Here, we find that when GUVs of canonical ternary mixtures are formed in aqueous solutions of short-chain n-alcohols (n ≤ 10), Tmix increases relative to GUVs in water. This shift is in the opposite direction from that reported for cell-derived GPMVs. The increase in Tmix is robust across GUVs of several types of lipids, ratios of lipids, types of short-chain n-alcohols, and concentrations of n-alcohols. However, as chain lengths of n-alcohols increase, nonmonotonic shifts in Tmix are observed. Alcohols with chain lengths of 10-14 carbons decrease Tmix in ternary GUVs of dioleoyl-PC/dipalmitoyl-PC/cholesterol, whereas 16 carbons increase Tmix again. Gray et al. observed a similar influence of the length of n-alcohols on the direction of the shift in Tmix. These results are consistent with a scenario in which the relative partitioning of n-alcohols between liquid-ordered and liquid-disordered phases evolves as the chain length of the n-alcohol increases.
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Affiliation(s)
- Caitlin E Cornell
- University of Washington, Department of Chemistry, Seattle, Washington
| | | | - Kandice R Levental
- Department of Integrative Biology and Pharmacology, McGovern Medical School at The University of Texas Medical Center, Houston, Texas
| | - Ilya Levental
- Department of Integrative Biology and Pharmacology, McGovern Medical School at The University of Texas Medical Center, Houston, Texas
| | - Nicholas J Brooks
- Department of Chemistry, Imperial College London, London, United Kingdom
| | - Sarah L Keller
- University of Washington, Department of Chemistry, Seattle, Washington.
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22
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Mazeres S, Fereidouni F, Joly E. Using spectral decomposition of the signals from laurdan-derived probes to evaluate the physical state of membranes in live cells. F1000Res 2017; 6:763. [PMID: 28663788 PMCID: PMC5473435 DOI: 10.12688/f1000research.11577.2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 07/28/2017] [Indexed: 01/22/2023] Open
Abstract
Background: We wanted to investigate the physical state of biological membranes in live cells under the most physiological conditions possible. Methods: For this we have been using laurdan, C-laurdan or M-laurdan to label a variety of cells, and a biphoton microscope equipped with both a thermostatic chamber and a spectral analyser. We also used a flow cytometer to quantify the 450/530 nm ratio of fluorescence emissions by whole cells. Results: We find that using all the information provided by spectral analysis to perform spectral decomposition dramatically improves the imaging resolution compared to using just two channels, as commonly used to calculate generalized polarisation (GP). Coupled to a new plugin called Fraction Mapper, developed to represent the fraction of light intensity in the first component in a stack of two images, we obtain very clear pictures of both the intra-cellular distribution of the probes, and the polarity of the cellular environments where the lipid probes are localised. Our results lead us to conclude that, in live cells kept at 37°C, laurdan, and M-laurdan to a lesser extent, have a strong tendency to accumulate in the very apolar environment of intra-cytoplasmic lipid droplets, but label the plasma membrane (PM) of mammalian cells ineffectively. On the other hand, C-laurdan labels the PM very quickly and effectively, and does not detectably accumulate in lipid droplets. Conclusions: From using these probes on a variety of mammalian cell lines, as well as on cells from
Drosophila and
Dictyostelium discoideum, we conclude that, apart from the lipid droplets, which are very apolar, probes in intracellular membranes reveal a relatively polar and hydrated environment, suggesting a very marked dominance of liquid disordered states. PMs, on the other hand, are much more apolar, suggesting a strong dominance of liquid ordered state, which fits with their high sterol contents.
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Affiliation(s)
- Serge Mazeres
- Membrane and DNA Dynamics Team, Institut de Pharmacologie et de Biologie Structurale, CNRS, Université de Toulouse, Toulouse, F-31077, France
| | - Farzad Fereidouni
- Department of Pathology and Laboratory Medicine, University of California Davis Medical Center, CA 95817, CA, 4400, USA
| | - Etienne Joly
- Membrane and DNA Dynamics Team, Institut de Pharmacologie et de Biologie Structurale, CNRS, Université de Toulouse, Toulouse, F-31077, France
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23
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Mazeres S, Fereidouni F, Joly E. Using spectral decomposition of the signals from laurdan-derived probes to evaluate the physical state of membranes in live cells. F1000Res 2017; 6:763. [PMID: 28663788 DOI: 10.12688/f1000research.11577.1] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/26/2017] [Indexed: 12/13/2022] Open
Abstract
Background: We wanted to investigate the physical state of biological membranes in live cells under the most physiological conditions possible. Methods: For this we have been using laurdan, C-laurdan or M-laurdan to label a variety of cells, and a biphoton microscope equipped with both a thermostatic chamber and a spectral analyser. We also used a flow cytometer to quantify the 450/530 nm ratio of fluorescence emissions by whole cells. Results: We find that using all the information provided by spectral analysis to perform spectral decomposition dramatically improves the imaging resolution compared to using just two channels, as commonly used to calculate generalized polarisation (GP). Coupled to a new plugin called Fraction Mapper, developed to represent the fraction of light intensity in the first component in a stack of two images, we obtain very clear pictures of both the intra-cellular distribution of the probes, and the polarity of the cellular environments where the lipid probes are localised. Our results lead us to conclude that, in live cells kept at 37°C, laurdan, and M-laurdan to a lesser extent, have a strong tendency to accumulate in the very apolar environment of intra-cytoplasmic lipid droplets, but label the plasma membrane (PM) of mammalian cells ineffectively. On the other hand, C-laurdan labels the PM very quickly and effectively, and does not detectably accumulate in lipid droplets. Conclusions: From using these probes on a variety of mammalian cell lines, as well as on cells from Drosophila and Dictyostelium discoideum, we conclude that, apart from the lipid droplets, which are very apolar, probes in intracellular membranes reveal a relatively polar and hydrated environment, suggesting a very marked dominance of liquid disordered states. PMs, on the other hand, are much more apolar, suggesting a strong dominance of liquid ordered state, which fits with their high sterol contents.
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Affiliation(s)
- Serge Mazeres
- Membrane and DNA Dynamics Team, Institut de Pharmacologie et de Biologie Structurale, CNRS, Université de Toulouse, Toulouse, F-31077, France
| | - Farzad Fereidouni
- Department of Pathology and Laboratory Medicine, University of California Davis Medical Center, CA 95817, CA, 4400, USA
| | - Etienne Joly
- Membrane and DNA Dynamics Team, Institut de Pharmacologie et de Biologie Structurale, CNRS, Université de Toulouse, Toulouse, F-31077, France
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24
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Sezgin E, Levental I, Mayor S, Eggeling C. The mystery of membrane organization: composition, regulation and roles of lipid rafts. Nat Rev Mol Cell Biol 2017; 18:361-374. [PMID: 28356571 PMCID: PMC5500228 DOI: 10.1038/nrm.2017.16] [Citation(s) in RCA: 1225] [Impact Index Per Article: 175.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Cellular plasma membranes are laterally heterogeneous, featuring a variety of distinct subcompartments that differ in their biophysical properties and composition. A large number of studies have focused on understanding the basis for this heterogeneity and its physiological relevance. The membrane raft hypothesis formalized a physicochemical principle for a subtype of such lateral membrane heterogeneity, in which the preferential associations between cholesterol and saturated lipids drive the formation of relatively packed (or ordered) membrane domains that selectively recruit certain lipids and proteins. Recent studies have yielded new insights into this mechanism and its relevance in vivo, owing primarily to the development of improved biochemical and biophysical technologies.
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Affiliation(s)
- Erdinc Sezgin
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford OX3 9DS, UK
| | - Ilya Levental
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, 6431 Fannin Street, Houston, Texas 77030, USA
| | - Satyajit Mayor
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, Bellary Road, Bangalore 560065, India
| | - Christian Eggeling
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford OX3 9DS, UK
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25
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Arumugam S, Kaur A. The Lipids of the Early Endosomes: Making Multimodality Work. Chembiochem 2017; 18:1053-1060. [PMID: 28374483 DOI: 10.1002/cbic.201700046] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Indexed: 01/21/2023]
Abstract
Early endosomes are dynamic intracellular compartments that fuse with incoming endocytic carrier vesicles and associated cargoes from the plasma membrane. It has been long known that the chemical structures of lipids confer striking properties and rich biochemistry on bilayers. Although the organisational principles of the plasma membrane are relatively better understood, understanding endosomal membranes has been challenging. It has become increasingly apparent that endosomal membranes, because of their lipid compositions and interactions, use distinct lipid chemistries. We discuss the biochemical and biophysical phenomena in play at the early endosomal membrane. We focus on cholesterol, phosphoinositides, and phosphatidylserine and their clear roles in endosome functions. We discuss the various principles and mechanisms underpinning how these lipids are implicated at the functional level in the working of endosomes, and we summarise early endosomes as a multimodal organelle employing distinct lipid-specific mechanisms.
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Affiliation(s)
- Senthil Arumugam
- European Molecular Biology Laboratory Australia Node for Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, University of New South Wales, Sydney, 2052, New South Wales, Australia
| | - Amandeep Kaur
- European Molecular Biology Laboratory Australia Node for Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, University of New South Wales, Sydney, 2052, New South Wales, Australia
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26
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Amaro M, Reina F, Hof M, Eggeling C, Sezgin E. Laurdan and Di-4-ANEPPDHQ probe different properties of the membrane. JOURNAL OF PHYSICS D: APPLIED PHYSICS 2017; 50:134004. [PMID: 29449744 PMCID: PMC5802044 DOI: 10.1088/1361-6463/aa5dbc] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 01/02/2017] [Accepted: 02/02/2017] [Indexed: 05/22/2023]
Abstract
Lipid packing is a crucial feature of cellular membranes. Quantitative analysis of membrane lipid packing can be achieved using polarity sensitive probes whose emission spectrum depends on the lipid packing. However, detailed insights into the exact mechanisms that cause the changes in the spectra are necessary to interpret experimental fluorescence emission data correctly. Here, we analysed frequently used polarity sensitive probes, Laurdan and di-4-ANEPPDHQ, to test whether the underlying physical mechanisms of their spectral changes are the same and, thus, whether they report on the same physico-chemical properties of the cell membrane. Steady-state spectra as well as time-resolved emission spectra of the probes in solvents and model membranes revealed that they probe different properties of the lipid membrane. Our findings are important for the application of these dyes in cell biology.
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Affiliation(s)
- Mariana Amaro
- Department of Biophysical Chemistry, J. Heyrovský Institute of Physical Chemistry of the C.A.S, v.v.i., Dolejskova 3, 182 23 Prague, Czechia
| | - Francesco Reina
- MRC Human Immunology Unit, OX39DS, University of Oxford, Oxford, United Kingdom
| | - Martin Hof
- Department of Biophysical Chemistry, J. Heyrovský Institute of Physical Chemistry of the C.A.S, v.v.i., Dolejskova 3, 182 23 Prague, Czechia
| | - Christian Eggeling
- MRC Human Immunology Unit, OX39DS, University of Oxford, Oxford, United Kingdom
| | - Erdinc Sezgin
- MRC Human Immunology Unit, OX39DS, University of Oxford, Oxford, United Kingdom
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27
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Sánchez-Maldonado AF, Schieber A, Gänzle MG. Antifungal activity of secondary plant metabolites from potatoes (Solanum tuberosum L.): Glycoalkaloids and phenolic acids show synergistic effects. J Appl Microbiol 2016; 120:955-65. [PMID: 26786886 DOI: 10.1111/jam.13056] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 12/20/2015] [Accepted: 12/26/2015] [Indexed: 12/29/2022]
Abstract
AIMS To study the antifungal effects of the potato secondary metabolites α-solanine, α-chaconine, solanidine and caffeic acid, alone or combined. METHODS AND RESULTS Resistance to glycoalkaloids varied among the fungal species tested, as derived from minimum inhibitory concentrations assays. Synergistic antifungal activity between glycoalkaloids and phenolic compounds was found. Changes in the fluidity of fungal membranes caused by potato secondary plant metabolites were determined by calculation of the generalized polarization values. The results partially explained the synergistic effect between caffeic acid and α-chaconine and supported findings on membrane disruption mechanisms from previous studies on artificial membranes. LC/MS analysis was used to determine variability and relative amounts of sterols in the different fungal species. Results suggested that the sterol pattern of fungi is related to their resistance to potato glycoalkaloids and to their taxonomy. CONCLUSION Fungal resistance to α-chaconine and possibly other glycoalkaloids is species dependent. α-Chaconine and caffeic acid show synergistic antifungal activity. The taxonomic classification and the sterol pattern play a role in fungal resistance to glycoalkaloids. SIGNIFICANCE AND IMPACT OF THE STUDY Results improve the understanding of the antifungal mode of action of potato secondary metabolites, which is essential for their potential utilization as antifungal agents in nonfood systems.
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Affiliation(s)
- A F Sánchez-Maldonado
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada
| | - A Schieber
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada.,Institute of Nutritional and Food Sciences, Chair of Food Technology and Food Biotechnology, University of Bonn, Bonn, Germany
| | - M G Gänzle
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada
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28
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LPS-Induced Macrophage Activation and Plasma Membrane Fluidity Changes are Inhibited Under Oxidative Stress. J Membr Biol 2016; 249:789-800. [PMID: 27619206 DOI: 10.1007/s00232-016-9927-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 08/30/2016] [Indexed: 10/21/2022]
Abstract
Macrophage activation is essential for a correct and efficient response of innate immunity. During oxidative stress membrane receptors and/or membrane lipid dynamics can be altered, leading to dysfunctional cell responses. Our aim is to analyze membrane fluidity modifications and cell function under oxidative stress in LPS-activated macrophages. Membrane fluidity of individual living THP-1 macrophages was evaluated by the technique two-photon microscopy. LPS-activated macrophage function was determined by TNFα secretion. It was shown that LPS activation causes fluidification of macrophage plasma membrane and production of TNFα. However, oxidative stress induces rigidification of macrophage plasma membrane and inhibition of cell activation, which is evidenced by a decrease of TNFα secretion. Thus, under oxidative conditions macrophage proinflammatory response might develop in an inefficient manner.
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29
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Viitala L, Pajari S, Lajunen T, Kontturi LS, Laaksonen T, Kuosmanen P, Viitala T, Urtti A, Murtomäki L. Photothermally Triggered Lipid Bilayer Phase Transition and Drug Release from Gold Nanorod and Indocyanine Green Encapsulated Liposomes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:4554-4563. [PMID: 27089512 DOI: 10.1021/acs.langmuir.6b00716] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In light-activated liposomal drug delivery systems (DDSs), the light sensitivity can be obtained by a photothermal agent that converts light energy into heat. Excess heat increases the drug permeability of the lipid bilayer, and drug is released as a result. In this work, two near-IR responsive photothermal agents in a model drug delivery system are studied: either gold nanorods (GNRs) encapsulated inside the liposomes or indocyanine green (ICG) embedded into the lipid bilayer. The liposome system is exposed to light, and the heating effect is studied with fluorescent thermometers: laurdan and CdSe quantum dots (QDs). Both photothermal agents are shown to convert light into heat in an extent to cause a phase transition in the surrounding lipid bilayer. This phase transition is also proven with laurdan generalized polarization (GP). In addition to the heating results, we show that the model drug (calcein) is released from the liposomal cavity with both photothermal agents when the light power is sufficient to cause a phase transition in the lipid bilayer.
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Affiliation(s)
- Lauri Viitala
- Department of Chemistry, Aalto University , P.O. Box 16100, FI-00076 Aalto, Finland
| | - Saija Pajari
- Department of Chemistry, Aalto University , P.O. Box 16100, FI-00076 Aalto, Finland
| | - Tatu Lajunen
- Faculty of Pharmacy, University of Helsinki , P.O. Box 56, FI-00014 Helsinki, Finland
| | - Leena-Stiina Kontturi
- Faculty of Pharmacy, University of Helsinki , P.O. Box 56, FI-00014 Helsinki, Finland
- Department of Pharmaceutics, Utrecht University , Universiteitsweg 99, 3584 CG, Utrecht, The Netherlands
| | - Timo Laaksonen
- Faculty of Pharmacy, University of Helsinki , P.O. Box 56, FI-00014 Helsinki, Finland
| | - Päivi Kuosmanen
- Department of Chemistry, Aalto University , P.O. Box 16100, FI-00076 Aalto, Finland
| | - Tapani Viitala
- Faculty of Pharmacy, University of Helsinki , P.O. Box 56, FI-00014 Helsinki, Finland
| | - Arto Urtti
- Faculty of Pharmacy, University of Helsinki , P.O. Box 56, FI-00014 Helsinki, Finland
- School of Pharmacy, University of Eastern Finland , P.O. Box 1627, FI-70211 Kuopio, Finland
| | - Lasse Murtomäki
- Department of Chemistry, Aalto University , P.O. Box 16100, FI-00076 Aalto, Finland
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Carquin M, D'Auria L, Pollet H, Bongarzone ER, Tyteca D. Recent progress on lipid lateral heterogeneity in plasma membranes: From rafts to submicrometric domains. Prog Lipid Res 2015; 62:1-24. [PMID: 26738447 DOI: 10.1016/j.plipres.2015.12.004] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 12/22/2015] [Accepted: 12/22/2015] [Indexed: 12/29/2022]
Abstract
The concept of transient nanometric domains known as lipid rafts has brought interest to reassess the validity of the Singer-Nicolson model of a fluid bilayer for cell membranes. However, this new view is still insufficient to explain the cellular control of surface lipid diversity or membrane deformability. During the past decades, the hypothesis that some lipids form large (submicrometric/mesoscale vs nanometric rafts) and stable (>min vs s) membrane domains has emerged, largely based on indirect methods. Morphological evidence for stable submicrometric lipid domains, well-accepted for artificial and highly specialized biological membranes, was further reported for a variety of living cells from prokaryot es to yeast and mammalian cells. However, results remained questioned based on limitations of available fluorescent tools, use of poor lipid fixatives, and imaging artifacts due to non-resolved membrane projections. In this review, we will discuss recent evidence generated using powerful and innovative approaches such as lipid-specific toxin fragments that support the existence of submicrometric domains. We will integrate documented mechanisms involved in the formation and maintenance of these domains, and provide a perspective on their relevance on membrane deformability and regulation of membrane protein distribution.
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Affiliation(s)
- Mélanie Carquin
- CELL Unit, de Duve Institute & Université Catholique de Louvain, UCL B1.75.05, Avenue Hippocrate, 75, B-1200 Brussels, Belgium
| | - Ludovic D'Auria
- The Myelin Regeneration Group at the Dept. Anatomy & Cell Biology, College of Medicine, University of Illinois, 808 S. Wood St. MC512, Chicago, IL. 60612. USA
| | - Hélène Pollet
- CELL Unit, de Duve Institute & Université Catholique de Louvain, UCL B1.75.05, Avenue Hippocrate, 75, B-1200 Brussels, Belgium
| | - Ernesto R Bongarzone
- The Myelin Regeneration Group at the Dept. Anatomy & Cell Biology, College of Medicine, University of Illinois, 808 S. Wood St. MC512, Chicago, IL. 60612. USA
| | - Donatienne Tyteca
- CELL Unit, de Duve Institute & Université Catholique de Louvain, UCL B1.75.05, Avenue Hippocrate, 75, B-1200 Brussels, Belgium.
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Sezgin E, Can FB, Schneider F, Clausen MP, Galiani S, Stanly TA, Waithe D, Colaco A, Honigmann A, Wüstner D, Platt F, Eggeling C. A comparative study on fluorescent cholesterol analogs as versatile cellular reporters. J Lipid Res 2015; 57:299-309. [PMID: 26701325 DOI: 10.1194/jlr.m065326] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Indexed: 12/12/2022] Open
Abstract
Cholesterol (Chol) is a crucial component of cellular membranes, but knowledge of its intracellular dynamics is scarce. Thus, it is of utmost interest to develop tools for visualization of Chol organization and dynamics in cells and tissues. For this purpose, many studies make use of fluorescently labeled Chol analogs. Unfortunately, the introduction of the label may influence the characteristics of the analog, such as its localization, interaction, and trafficking in cells; hence, it is important to get knowledge of such bias. In this report, we compared different fluorescent lipid analogs for their performance in cellular assays: 1) plasma membrane incorporation, specifically the preference for more ordered membrane environments in phase-separated giant unilamellar vesicles and giant plasma membrane vesicles; 2) cellular trafficking, specifically subcellular localization in Niemann-Pick type C disease cells; and 3) applicability in fluorescence correlation spectroscopy (FCS)-based and super-resolution stimulated emission depletion-FCS-based measurements of membrane diffusion dynamics. The analogs exhibited strong differences, with some indicating positive performance in the membrane-based experiments and others in the intracellular trafficking assay. However, none showed positive performance in all assays. Our results constitute a concise guide for the careful use of fluorescent Chol analogs in visualizing cellular Chol dynamics.
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Affiliation(s)
- Erdinc Sezgin
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, OX39DS Oxford, United Kingdom
| | - Fatma Betul Can
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, OX39DS Oxford, United Kingdom
| | - Falk Schneider
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, OX39DS Oxford, United Kingdom
| | - Mathias P Clausen
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, OX39DS Oxford, United Kingdom MEMPHYS-Center for Biomembrane Physics, Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, 5230 Odense M, Denmark
| | - Silvia Galiani
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, OX39DS Oxford, United Kingdom
| | - Tess A Stanly
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, OX39DS Oxford, United Kingdom
| | - Dominic Waithe
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, OX39DS Oxford, United Kingdom
| | - Alexandria Colaco
- Department of Pharmacology, University of Oxford, OX13QT Oxford, United Kingdom
| | - Alf Honigmann
- Max Planck Institute of Cell Biology and Genetics, 01307 Dresden, Germany
| | - Daniel Wüstner
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, 5230 Odense M, Denmark
| | - Frances Platt
- Department of Pharmacology, University of Oxford, OX13QT Oxford, United Kingdom
| | - Christian Eggeling
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, OX39DS Oxford, United Kingdom
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Reales E, Bernabé-Rubio M, Casares-Arias J, Rentero C, Fernández-Barrera J, Rangel L, Correas I, Enrich C, Andrés G, Alonso MA. The MAL protein is crucial for proper membrane condensation at the ciliary base, which is required for primary cilium elongation. J Cell Sci 2015; 128:2261-70. [DOI: 10.1242/jcs.164970] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 04/30/2015] [Indexed: 01/11/2023] Open
Abstract
ABSTRACT
The base of the primary cilium contains a zone of condensed membranes whose importance is not known. Here, we have studied the involvement of MAL, a tetraspanning protein that exclusively partitions into condensed membrane fractions, in the condensation of membranes at the ciliary base and investigated the importance of these membranes in primary cilium formation. We show that MAL accumulates at the ciliary base of epithelial MDCK cells. Knockdown of MAL expression resulted in a drastic reduction in the condensation of membranes at the ciliary base, the percentage of ciliated cells and the length of the cilia, but did not affect the docking of the centrosome to the plasma membrane or produce missorting of proteins to the pericentriolar zone or to the membrane of the remaining cilia. Rab8 (for which there are two isoforms, Rab8A and Rab8b), IFT88 and IFT20, which are important components of the machinery of ciliary growth, were recruited normally to the ciliary base of MAL-knockdown cells but were unable to elongate the primary cilium correctly. MAL, therefore, is crucial for the proper condensation of membranes at the ciliary base, which is required for efficient primary cilium extension.
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Affiliation(s)
- Elena Reales
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain
| | - Miguel Bernabé-Rubio
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain
| | - Javier Casares-Arias
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain
| | - Carles Rentero
- Departament de Biologia Cel·lular, Immunologia i Neurociències, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, Barcelona 08036, Spain
| | - Jaime Fernández-Barrera
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain
| | - Laura Rangel
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain
| | - Isabel Correas
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain
| | - Carlos Enrich
- Departament de Biologia Cel·lular, Immunologia i Neurociències, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, Barcelona 08036, Spain
| | - Germán Andrés
- Electron Microscopy Unit, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain
| | - Miguel A. Alonso
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain
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Sezgin E, Waithe D, Bernardino de la Serna J, Eggeling C. Spectral imaging to measure heterogeneity in membrane lipid packing. Chemphyschem 2015; 16:1387-94. [PMID: 25755090 PMCID: PMC4539592 DOI: 10.1002/cphc.201402794] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Revised: 02/18/2015] [Indexed: 12/03/2022]
Abstract
Physicochemical properties of the plasma membrane have been shown to play an important role in cellular functionality. Among those properties, the molecular order of the lipids, or the lipid packing, is of high importance. Changes in lipid packing are believed to compartmentalize cellular signaling by initiating coalescence and conformational changes of proteins. A common way to infer membrane lipid packing is by using membrane-embedded polarity-sensitive dyes, whose emission spectrum is dependent on the molecular order of the immediate membrane environment. Here, we report on an improved determination of such spectral shifts in the emission spectrum of the polarity-sensitive dyes. This improvement is based on the use of spectral imaging on a scanning confocal fluorescence microscope in combination with an improved analysis, which considers the whole emission spectrum instead of just single wavelength ranges. Using this approach and the polarity-sensitive dyes C-Laurdan or Di-4-ANEPPDHQ, we were able to image-with high accuracy-minute differences in the lipid packing of model and cellular membranes.
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Affiliation(s)
- Erdinc Sezgin
- MRC Human Immunology Unit and Wolfson Imaging Centre Oxford, Weatherall Institute of Molecular Medicine, University of OxfordHeadley Way, Oxford, OX3 9DS (United Kingdom) E-mail:
| | - Dominic Waithe
- MRC Human Immunology Unit and Wolfson Imaging Centre Oxford, Weatherall Institute of Molecular Medicine, University of OxfordHeadley Way, Oxford, OX3 9DS (United Kingdom) E-mail:
| | - Jorge Bernardino de la Serna
- MRC Human Immunology Unit and Wolfson Imaging Centre Oxford, Weatherall Institute of Molecular Medicine, University of OxfordHeadley Way, Oxford, OX3 9DS (United Kingdom) E-mail:
| | - Christian Eggeling
- MRC Human Immunology Unit and Wolfson Imaging Centre Oxford, Weatherall Institute of Molecular Medicine, University of OxfordHeadley Way, Oxford, OX3 9DS (United Kingdom) E-mail:
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Curthoys NM, Parent M, Mlodzianoski M, Nelson AJ, Lilieholm J, Butler MB, Valles M, Hess ST. Dances with Membranes: Breakthroughs from Super-resolution Imaging. CURRENT TOPICS IN MEMBRANES 2015; 75:59-123. [PMID: 26015281 PMCID: PMC5584789 DOI: 10.1016/bs.ctm.2015.03.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Biological membrane organization mediates numerous cellular functions and has also been connected with an immense number of human diseases. However, until recently, experimental methodologies have been unable to directly visualize the nanoscale details of biological membranes, particularly in intact living cells. Numerous models explaining membrane organization have been proposed, but testing those models has required indirect methods; the desire to directly image proteins and lipids in living cell membranes is a strong motivation for the advancement of technology. The development of super-resolution microscopy has provided powerful tools for quantification of membrane organization at the level of individual proteins and lipids, and many of these tools are compatible with living cells. Previously inaccessible questions are now being addressed, and the field of membrane biology is developing rapidly. This chapter discusses how the development of super-resolution microscopy has led to fundamental advances in the field of biological membrane organization. We summarize the history and some models explaining how proteins are organized in cell membranes, and give an overview of various super-resolution techniques and methods of quantifying super-resolution data. We discuss the application of super-resolution techniques to membrane biology in general, and also with specific reference to the fields of actin and actin-binding proteins, virus infection, mitochondria, immune cell biology, and phosphoinositide signaling. Finally, we present our hopes and expectations for the future of super-resolution microscopy in the field of membrane biology.
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Affiliation(s)
- Nikki M. Curthoys
- Department of Physics and Astronomy, University of Maine, Orono, ME, USA
| | - Matthew Parent
- Department of Physics and Astronomy, University of Maine, Orono, ME, USA
| | | | - Andrew J. Nelson
- Department of Physics and Astronomy, University of Maine, Orono, ME, USA
| | - Jennifer Lilieholm
- Department of Physics and Astronomy, University of Maine, Orono, ME, USA
| | - Michael B. Butler
- Department of Physics and Astronomy, University of Maine, Orono, ME, USA
| | - Matthew Valles
- Department of Physics and Astronomy, University of Maine, Orono, ME, USA
| | - Samuel T. Hess
- Department of Physics and Astronomy, University of Maine, Orono, ME, USA
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Cholesterol-dependent membrane fusion induced by the gp41 membrane-proximal external region-transmembrane domain connection suggests a mechanism for broad HIV-1 neutralization. J Virol 2014; 88:13367-77. [PMID: 25210180 DOI: 10.1128/jvi.02151-14] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The HIV-1 glycoprotein 41 promotes fusion of the viral membrane with that of the target cell. Structural, biochemical, and biophysical studies suggest that its membrane-proximal external region (MPER) may interact with the HIV-1 membrane and induce its disruption and/or deformation during the process. However, the high cholesterol content of the envelope (ca. 40 to 50 mol%) imparts high rigidity, thereby acting against lipid bilayer restructuring. Here, based on the outcome of vesicle stability assays, all-atom molecular dynamics simulations, and atomic force microscopy observations, we propose that the conserved sequence connecting the MPER with the N-terminal residues of the transmembrane domain (TMD) is involved in HIV-1 fusion. This junction would function by inducing phospholipid protrusion and acyl-chain splay in the cholesterol-enriched rigid envelope. Supporting the functional relevance of such a mechanism, membrane fusion was inhibited by the broadly neutralizing 4E10 antibody but not by a nonneutralizing variant with the CDR-H3 loop deleted. We conclude that the MPER-TMD junction embodies an envelope-disrupting C-terminal fusion peptide that can be targeted by broadly neutralizing antibodies. IMPORTANCE Fusion of the cholesterol-enriched viral envelope with the cell membrane marks the beginning of the infectious HIV-1 replicative cycle. Consequently, the Env glycoprotein-mediated fusion function constitutes an important clinical target for inhibitors and preventive vaccines. Antibodies 4E10 and 10E8 bind to one Env vulnerability site located at the gp41 membrane-proximal external region (MPER)-transmembrane domain (TMD) junction and block infection. These antibodies display broad viral neutralization, which underscores the conservation and functionality of the MPER-TMD region. In this work, we combined biochemical assays with molecular dynamics simulations and microscopy observations to characterize the unprecedented fusogenic activity of the MPER-TMD junction. The fact that such activity is dependent on cholesterol and inhibited by the broadly neutralizing 4E10 antibody emphasizes its physiological relevance. Discovery of this functional element adds to our understanding of the mechanisms underlying HIV-1 infection and its blocking by antibodies.
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Sezgin E, Sadowski T, Simons K. Measuring lipid packing of model and cellular membranes with environment sensitive probes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:8160-6. [PMID: 24905799 DOI: 10.1021/la501226v] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The extent of lipid packing is one of the key physicochemical features of biological membranes and is involved in many membrane processes. Polarity sensitive fluorescent probes are commonly used tools to measure membrane lipid packing in both artificial and biological membranes. In this paper, we have systematically compared eight different probes to measure membrane lipid ordering. We investigated how these probes behave in small unilamellar liposomes, phase-separated giant unilamellar vesicles, cell-derived giant plasma membrane vesicles, and live cells. We have tested the order sensitivity of a variety of measurable parameters, including generalized polarization, peak shift, or intensity shift. We also investigated internalization and photostability of the probes to assess probe potential for time-lapse live cell imaging. These results provide a catalogue of properties to facilitate the choice of probe according to need.
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Affiliation(s)
- Erdinc Sezgin
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
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37
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Jaureguiberry MS, Tricerri MA, Sanchez SA, Finarelli GS, Montanaro MA, Prieto ED, Rimoldi OJ. Role of plasma membrane lipid composition on cellular homeostasis: learning from cell line models expressing fatty acid desaturases. Acta Biochim Biophys Sin (Shanghai) 2014; 46:273-82. [PMID: 24473084 DOI: 10.1093/abbs/gmt155] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Experimental evidence has suggested that plasma membrane (PM)-associated signaling and hence cell metabolism and viability depend on lipid composition and organization. The aim of the present work is to develop a cell model to study the endogenous polyunsaturated fatty acids (PUFAs) effect on PM properties and analyze its influence on cholesterol (Chol) homeostasis. We have previously shown that by using a cell line over-expressing stearoyl-CoA-desaturase, membrane composition and organization coordinate cellular pathways involved in Chol efflux and cell viability by different mechanisms. Now, we expanded our studies to a cell model over-expressing both Δ5 and Δ6 desaturases, which resulted in a permanently higher PUFA content in PM. Furthermore, this cell line showed increased PM fluidity, Chol storage, and mitochondrial activity. In addition, human apolipoprotein A-I-mediated Chol removal was less efficient in these cells than in the corresponding control. Taken together, our results suggested that the cell functionality is preserved by regulating PM organization and Chol exportation and homeostasis.
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Affiliation(s)
- María S Jaureguiberry
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), La Plata 1900, Buenos Aires, Argentina
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Méndez-Barbero N, Esteban V, Villahoz S, Escolano A, Urso K, Alfranca A, Rodríguez C, Sánchez SA, Osawa T, Andrés V, Martínez-González J, Minami T, Redondo JM, Campanero MR. A major role for RCAN1 in atherosclerosis progression. EMBO Mol Med 2013; 5:1901-17. [PMID: 24127415 PMCID: PMC3914525 DOI: 10.1002/emmm.201302842] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Revised: 08/08/2013] [Accepted: 09/03/2013] [Indexed: 01/19/2023] Open
Abstract
Atherosclerosis is a complex inflammatory disease involving extensive vascular vessel remodelling and migration of vascular cells. As RCAN1 is implicated in cell migration, we investigated its contribution to atherosclerosis. We show RCAN1 induction in atherosclerotic human and mouse tissues. Rcan1 was expressed in lesional macrophages, endothelial cells and vascular smooth muscle cells and was induced by treatment of these cells with oxidized LDLs (oxLDLs). Rcan1 regulates CD36 expression and its genetic inactivation reduced atherosclerosis extension and severity in Apoe−/− mice. This effect was mechanistically linked to diminished oxLDL uptake, resistance to oxLDL-mediated inhibition of macrophage migration and increased lesional IL-10 and mannose receptor expression. Moreover, Apoe−/−Rcan1−/− macrophages expressed higher-than-Apoe−/− levels of anti-inflammatory markers. We previously showed that Rcan1 mediates aneurysm development and that its expression is not required in haematopoietic cells for this process. However, transplantation of Apoe−/−Rcan1−/− bone-marrow (BM) cells into Apoe−/− recipients confers atherosclerosis resistance. Our data define a major role for haematopoietic Rcan1 in atherosclerosis and suggest that therapies aimed at inhibiting RCAN1 expression or function might significantly reduce atherosclerosis burden.
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Affiliation(s)
- Nerea Méndez-Barbero
- Department of Vascular Biology and Inflammation, Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain
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de la Haba C, Palacio JR, Palkovics T, Szekeres-Barthó J, Morros A, Martínez P. Oxidative stress effect on progesterone-induced blocking factor (PIBF) binding to PIBF-receptor in lymphocytes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:148-57. [PMID: 23954806 DOI: 10.1016/j.bbamem.2013.08.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 07/23/2013] [Accepted: 08/08/2013] [Indexed: 10/26/2022]
Abstract
Receptor-ligand binding is an essential interaction for biological function. Oxidative stress can modify receptors and/or membrane lipid dynamics, thus altering cell physiological functions. The aim of this study is to analyze how oxidative stress may alter receptor-ligand binding and lipid domain distribution in the case of progesterone-induced blocking factor/progesterone-induced blocking factor-receptor. For membrane fluidity regionalization analysis of MEC-1 lymphocytes, two-photon microscopy was used in individual living cells. Lymphocytes were also double stained with AlexaFluor647/progesterone-induced blocking factor and Laurdan to evaluate -induced blocking factor/progesterone-induced blocking factor-receptor distribution in the different membrane domains, under oxidative stress. A new procedure has been developed which quantitatively analyzes the regionalization of a membrane receptor among the lipid domains of different fluidity in the plasma membrane. We have been able to establish a new tool which detects and evaluates lipid raft clustering from two-photon microscopy images of individual living cells. We show that binding of progesterone-induced blocking factor to progesterone-induced blocking factor-receptor causes a rigidification of plasma membrane which is related to an increase of lipid raft clustering. However, this clustering is inhibited under oxidative stress conditions. In conclusion, oxidative stress decreases membrane fluidity, impairs receptor-ligand binding and reduces lipid raft clustering.
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Affiliation(s)
- Carlos de la Haba
- Unitat de Biofísica, Departament de Bioquímica i de Biologia Molecular, Centre d'Estudis en Biofísica (CEB), Facultat de Medicina, Universitat Autònoma de Barcelona (UAB), 08193 Bellaterra, Barcelona, Spain; Unitat d'Immunologia, Institut de Biotecnologia i de Biomedicina (IBB), Universitat Autònoma de Barcelona (UAB), 08193 Bellaterra, Barcelona, Spain
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Marty NJ, Holman CL, Abdullah N, Johnson CP. The C2 domains of otoferlin, dysferlin, and myoferlin alter the packing of lipid bilayers. Biochemistry 2013; 52:5585-92. [PMID: 23859474 DOI: 10.1021/bi400432f] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Ferlins are large multi-C2 domain membrane proteins involved in membrane fusion and fission events. In this study, we investigate the effects of binding of the C2 domains of otoferlin, dysferlin, and myoferlin on the structure of lipid bilayers. Fluorescence measurements indicate that multi-C2 domain constructs of myoferlin, dysferlin, and otoferlin change the lipid packing of both small unilamellar vesicles and giant plasma membrane vesicles. The activities of these proteins were enhanced in the presence of calcium and required negatively charged lipids like phosphatidylserine or phosphatidylglycerol for activity. Experiments with individual domains uncovered functional differences between the C2A domain of otoferlin and those of dysferlin and myoferlin, and truncation studies suggest that the effects of each subsequent C2 domain on lipid ordering appear to be additive. Finally, we demonstrate that the activities of these proteins on membranes are insensitive to high salt concentrations, suggesting a nonelectrostatic component to the interaction between ferlin C2 domains and lipid bilayers. Together, the data indicate that dysferlin, otoferlin, and myoferlin do not merely passively adsorb to membranes but actively sculpt lipid bilayers, which would result in highly curved or distorted membrane regions that could facilitate membrane fusion, membrane fission, or recruitment of other membrane-trafficking proteins.
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Affiliation(s)
- Naomi J Marty
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331, USA
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Ben-Dov N, Korenstein R. Proton-induced endocytosis is dependent on cell membrane fluidity, lipid-phase order and the membrane resting potential. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:2672-81. [PMID: 23911577 DOI: 10.1016/j.bbamem.2013.07.027] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 07/20/2013] [Accepted: 07/22/2013] [Indexed: 01/13/2023]
Abstract
Recently it has been shown that decreasing the extracellular pH of cells stimulates the formation of inward membrane invaginations and vesicles, accompanied by an enhanced uptake of macromolecules. This type of endocytosis was coined as proton-induced uptake (PIU). Though the initial induction of inward membrane curvature was rationalized in terms of proton-based increase of charge asymmetry across the membrane, the dependence of the phenomenon on plasma membrane characteristics is still unknown. The present study shows that depolarization of the membrane resting potential elevates PIU by 25%, while hyperpolarization attenuates it by 25%. Comparison of uptake in suspended and adherent cells implicates that the resting-potential affects PIU through remodeling the actin-cytoskeleton. The pH at the external interface of the cell membrane rather than the pH gradient across it determines the extent of PIU. PIU increases linearly upon temperature increase in the range of 4-36°C, in correlation with the membrane fluidity. The plasma membrane fluidity and the lipid phase order are modulated by enriching the cell's membrane with cholesterol, tergitol, dimethylsulfoxide, 6-ketocholestanol and phloretin and by cholesterol depletion. These treatments are shown to alter the extent of PIU and are better correlated with membrane fluidity than with the lipid phase order. We suggest that the lipid phase order and fluidity influence PIU by regulating the lipid order gradient across the perimeter of the lipid-condensed microdomains (rafts) and alter the characteristic tension line that separates the higher ordered lipid-domains from the lesser ordered ones.
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Affiliation(s)
- Nadav Ben-Dov
- Department of Physiology and Pharmacology, Faculty of Medicine, Tel-Aviv University, 69978 Tel-Aviv, Israel.
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Effects of surfactin on membrane models displaying lipid phase separation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:801-15. [DOI: 10.1016/j.bbamem.2012.11.007] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 10/19/2012] [Accepted: 11/05/2012] [Indexed: 01/02/2023]
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43
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de la Haba C, Palacio JR, Martínez P, Morros A. Effect of oxidative stress on plasma membrane fluidity of THP-1 induced macrophages. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:357-64. [DOI: 10.1016/j.bbamem.2012.08.013] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Revised: 07/26/2012] [Accepted: 08/17/2012] [Indexed: 01/11/2023]
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44
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Funkhouser CM, Mayer M, Solis FJ, Thornton K. Effects of interleaflet coupling on the morphologies of multicomponent lipid bilayer membranes. J Chem Phys 2013; 138:024909. [DOI: 10.1063/1.4773856] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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45
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Hofstetter S, Denter C, Winter R, McMullen LM, Gänzle MG. Use of the fluorescent probe LAURDAN to label and measure inner membrane fluidity of endospores of Clostridium spp. J Microbiol Methods 2012; 91:93-100. [PMID: 22884687 DOI: 10.1016/j.mimet.2012.07.023] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Revised: 07/17/2012] [Accepted: 07/17/2012] [Indexed: 11/29/2022]
Abstract
A method for measuring the fluidity of inner membranes of populations of endospores of Clostridium spp. with a fluorescent dye was developed. Cells of Clostridium beijerinckii ATCC 8260 and Clostridium sporogenes ATCC 7955 were allowed to sporulate in the presence of 6-dodecanoyl-2-dimethylaminonaphthalene (LAURDAN) on a soil-based media. Labeling of endospores with LAURDAN did not affect endospore viability. Removal of the outer membranes of endospores was done using a chemical treatment and confirmed using transmission electron microscopy (TEM). Two-photon confocal laser scanning microscopy (CLSM), and generalized polarization (GP) measurements were used to assess fluorescence of endospores. Lipid composition analysis of cells and endospores was done to determine whether differences in GP values are attributable to differences in membrane composition. Removal of the outer membranes of endospores did not significantly impact GP values. Decoated, labeled endospores of C. sporogenes ATCC 7955 and C. beijerinckii ATCC 8260 exhibited GP values of 0.77±0.031 and 0.74±0.027 respectively. Differences in ratios of fatty acids between cells and endospores are unlikely to be responsible for high GP values observed in endospores. These GP values indicate high levels of lipid order and the exclusion of water from within inner membranes of endospores.
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Affiliation(s)
- Simmon Hofstetter
- University of Alberta, Department of Agricultural, Food and Nutritional Science, Edmonton, Alberta, Canada, T6G 2P5.
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46
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Sezgin E, Schwille P. Model membrane platforms to study protein-membrane interactions. Mol Membr Biol 2012; 29:144-54. [DOI: 10.3109/09687688.2012.700490] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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47
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Dodes Traian MM, Flecha FLG, Levi V. Imaging lipid lateral organization in membranes with C-laurdan in a confocal microscope. J Lipid Res 2012; 53:609-616. [PMID: 22184757 PMCID: PMC3276485 DOI: 10.1194/jlr.d021311] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Revised: 12/01/2011] [Indexed: 11/20/2022] Open
Abstract
Lateral organization of biological membranes is frequently studied using fluorescence microscopy. One of the most widely used probes for these studies is 2-dimethylamino-6-lauroylnaphthalene (laurdan). The fluorescence of this probe is sensitive to the environment polarity, and thus laurdan reports the local penetration of water when inserted in membranes. Unfortunately, this probe can only be used under two-photon excitation due to its low photostability. This is a very important limitation, because there are not too many laboratories with capability for two-photon microscopy. In this work, we explored the performance of 6-dodecanoyl-2-[N-methyl-N-(carboxymethyl)amino]naphthalene (C-laurdan), a carboxyl-modified version of laurdan, for imaging biological membranes using a conventional confocal microscopy setup. We acquired generalized polarization (GP) images of C-laurdan inserted in giant unillamelar vesicles composed of binary mixtures of lipids and verified that the probe allows observing the coexistence of different phases. We also tested the performance of the probe for measurement with living cells and registered GP images of melanophore cells labeled with C-laurdan in which we could observe highly ordered regions such as filopodia. These findings show that C-laurdan can be successfully employed for studies of membrane lateral organization using a conventional confocal microscope and can open the possibility of studying a wide variety of membrane-related processes.
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Affiliation(s)
- Martín M Dodes Traian
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, CP 1428 Ciudad de Buenos Aires, Argentina; Laboratorio de Biofísica Molecular, Instituto de Química y Fisicoquímica Biológicas, Universidad de Buenos Aires, CONICET, Buenos Aires, Argentina
| | - F Luis González Flecha
- Laboratorio de Biofísica Molecular, Instituto de Química y Fisicoquímica Biológicas, Universidad de Buenos Aires, CONICET, Buenos Aires, Argentina
| | - Valeria Levi
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, CP 1428 Ciudad de Buenos Aires, Argentina.
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48
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Bending Rigidities of Lipid Bilayers. ACTA ACUST UNITED AC 2012. [DOI: 10.1016/b978-0-12-396533-2.00006-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Bagatolli LA. LAURDAN Fluorescence Properties in Membranes: A Journey from the Fluorometer to the Microscope. SPRINGER SERIES ON FLUORESCENCE 2012. [DOI: 10.1007/4243_2012_42] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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50
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An epifluorescence microscopy method for generalized polarization imaging. Biochem Biophys Res Commun 2011; 415:686-90. [PMID: 22079294 DOI: 10.1016/j.bbrc.2011.10.138] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 10/28/2011] [Indexed: 12/17/2022]
Abstract
Generalized polarization (GP) microscopy represents an excellent tool to study lipid-lipid and lipid-protein interactions in situ and in vitro. Here, we present an efficient and cost effective method to perform GP microscopy using a standard light-emitting diode (LED) epifluorescence microscope equipped with a digital color camera.
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