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Sofińska K, Lupa D, Chachaj-Brekiesz A, Czaja M, Kobierski J, Seweryn S, Skirlińska-Nosek K, Szymonski M, Wilkosz N, Wnętrzak A, Lipiec E. Revealing local molecular distribution, orientation, phase separation, and formation of domains in artificial lipid layers: Towards comprehensive characterization of biological membranes. Adv Colloid Interface Sci 2022; 301:102614. [PMID: 35190313 DOI: 10.1016/j.cis.2022.102614] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 01/28/2022] [Accepted: 02/01/2022] [Indexed: 01/01/2023]
Abstract
Lipids, together with molecules such as DNA and proteins, are one of the most relevant systems responsible for the existence of life. Selected lipids are able to assembly into various organized structures, such as lipid membranes. The unique properties of lipid membranes determine their complex functions, not only to separate biological environments, but also to participate in regulatory functions, absorption of nutrients, cell-cell communication, endocytosis, cell signaling, and many others. Despite numerous scientific efforts, still little is known about the reason underlying the variability within lipid membranes, and its biochemical significance. In this review, we discuss the structural complexity of lipid membranes, as well as the importance to simplify studied systems in order to understand phenomena occurring in natural, complex membranes. Such systems require a model interface to be analyzed. Therefore, here we focused on analytical studies of artificial systems at various interfaces. The molecular structure of lipid membranes, specifically the nanometric thickens of molecular bilayer, limits in a major extent the choice of highly sensitive methods suitable to study such structures. Therefore, we focused on methods that combine high sensitivity, and/or chemical selectivity, and/or nanometric spatial resolution, such as atomic force microscopy, nanospectroscopy (tip-enhanced Raman spectroscopy, infrared nanospectroscopy), phase modulation infrared reflection-absorption spectroscopy, sum-frequency generation spectroscopy. We summarized experimental and theoretical approaches providing information about molecular structure and composition, lipid spatial distribution (phase separation), organization (domain shape, molecular orientation) of lipid membranes, and real-time visualization of the influence of various molecules (proteins, drugs) on their integrity. An integral part of this review discusses the latest achievements in the field of lipid layer-based biosensors.
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Koklič T, Hrovat A, Guixà-González R, Rodríguez-Espigares I, Navio D, Frangež R, Uršič M, Kubale V, Plemenitaš A, Selent J, Šentjurc M, Vrecl M. Electron Paramagnetic Resonance Gives Evidence for the Presence of Type 1 Gonadotropin-Releasing Hormone Receptor (GnRH-R) in Subdomains of Lipid Rafts. Molecules 2021; 26:molecules26040973. [PMID: 33673080 PMCID: PMC7918721 DOI: 10.3390/molecules26040973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 02/02/2021] [Accepted: 02/08/2021] [Indexed: 11/16/2022] Open
Abstract
This study investigated the effect of type 1 gonadotropin releasing hormone receptor (GnRH-R) localization within lipid rafts on the properties of plasma membrane (PM) nanodomain structure. Confocal microscopy revealed colocalization of PM-localized GnRH-R with GM1-enriched raft-like PM subdomains. Electron paramagnetic resonance spectroscopy (EPR) of a membrane-partitioned spin probe was then used to study PM fluidity of immortalized pituitary gonadotrope cell line αT3-1 and HEK-293 cells stably expressing GnRH-R and compared it with their corresponding controls (αT4 and HEK-293 cells). Computer-assisted interpretation of EPR spectra revealed three modes of spin probe movement reflecting the properties of three types of PM nanodomains. Domains with an intermediate order parameter (domain 2) were the most affected by the presence of the GnRH-Rs, which increased PM ordering (order parameter (S)) and rotational mobility of PM lipids (decreased rotational correlation time (τc)). Depletion of cholesterol by methyl-β-cyclodextrin (methyl-β-CD) inhibited agonist-induced GnRH-R internalization and intracellular Ca2+ activity and resulted in an overall reduction in PM order; an observation further supported by molecular dynamics (MD) simulations of model membrane systems. This study provides evidence that GnRH-R PM localization may be related to a subdomain of lipid rafts that has lower PM ordering, suggesting lateral heterogeneity within lipid raft domains.
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Affiliation(s)
- Tilen Koklič
- Laboratory of Biophysics, Department of Condensed Matter Physics, Jožef Stefan Institute, 1000 Ljubljana, Slovenia; (T.K.); (M.Š.)
| | - Alenka Hrovat
- Veterinary Faculty, Institute of Preclinical Sciences, University of Ljubljana, Gerbičeva 60, 1000 Ljubljana, Slovenia; (A.H.); (R.F.); (M.U.); (V.K.)
| | - Ramon Guixà-González
- Research Programme on Biomedical Informatics (GRIB), Department of Experimental and Health Sciences, Hospital del Mar Medical Research Institute (IMIM), Pompeu Fabra University (UPF), 08003 Barcelona, Spain; (R.G.-G.); (I.R.-E.); (D.N.); (J.S.)
- Laboratory of Biomolecular Research, Paul Scherrer Institute (PSI), 5232 Villigen, Switzerland
- Condensed Matter Theory Group, PSI, 5232 Villigen, Switzerland
| | - Ismael Rodríguez-Espigares
- Research Programme on Biomedical Informatics (GRIB), Department of Experimental and Health Sciences, Hospital del Mar Medical Research Institute (IMIM), Pompeu Fabra University (UPF), 08003 Barcelona, Spain; (R.G.-G.); (I.R.-E.); (D.N.); (J.S.)
| | - Damaris Navio
- Research Programme on Biomedical Informatics (GRIB), Department of Experimental and Health Sciences, Hospital del Mar Medical Research Institute (IMIM), Pompeu Fabra University (UPF), 08003 Barcelona, Spain; (R.G.-G.); (I.R.-E.); (D.N.); (J.S.)
| | - Robert Frangež
- Veterinary Faculty, Institute of Preclinical Sciences, University of Ljubljana, Gerbičeva 60, 1000 Ljubljana, Slovenia; (A.H.); (R.F.); (M.U.); (V.K.)
| | - Matjaž Uršič
- Veterinary Faculty, Institute of Preclinical Sciences, University of Ljubljana, Gerbičeva 60, 1000 Ljubljana, Slovenia; (A.H.); (R.F.); (M.U.); (V.K.)
| | - Valentina Kubale
- Veterinary Faculty, Institute of Preclinical Sciences, University of Ljubljana, Gerbičeva 60, 1000 Ljubljana, Slovenia; (A.H.); (R.F.); (M.U.); (V.K.)
| | - Ana Plemenitaš
- Faculty of Medicine, Institute of Biochemistry and Molecular Genetics, University of Ljubljana, 1000 Ljubljana, Slovenia;
| | - Jana Selent
- Research Programme on Biomedical Informatics (GRIB), Department of Experimental and Health Sciences, Hospital del Mar Medical Research Institute (IMIM), Pompeu Fabra University (UPF), 08003 Barcelona, Spain; (R.G.-G.); (I.R.-E.); (D.N.); (J.S.)
| | - Marjeta Šentjurc
- Laboratory of Biophysics, Department of Condensed Matter Physics, Jožef Stefan Institute, 1000 Ljubljana, Slovenia; (T.K.); (M.Š.)
| | - Milka Vrecl
- Veterinary Faculty, Institute of Preclinical Sciences, University of Ljubljana, Gerbičeva 60, 1000 Ljubljana, Slovenia; (A.H.); (R.F.); (M.U.); (V.K.)
- Correspondence: ; Tel.: +386-1-477-9118
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Shrestha A, Kahraman O, Haselwandter CA. Regulation of membrane proteins through local heterogeneity in lipid bilayer thickness. Phys Rev E 2020; 102:060401. [PMID: 33465991 DOI: 10.1103/physreve.102.060401] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 11/06/2020] [Indexed: 11/07/2022]
Abstract
Cell membranes show an intricate organization of lipids and membrane proteins into domains with distinct composition and hydrophobic thickness. Using mechanosensitive ion channels as a model system, we employ the membrane elasticity theory of lipid-protein interactions together with the Landau-Ginzburg theory of lipid domain formation to quantify protein-induced lipid bilayer thickness deformations in lipid bilayers with heterogeneous hydrophobic thickness. We show that protein-induced lipid bilayer thickness deformations yield, without any assumptions about preferential interactions between particular lipid and protein species, organization of lipids and membrane proteins according to their preferred hydrophobic thickness, and couple the conformational states of membrane proteins to the local membrane composition. Our calculations suggest that protein-induced lipid bilayer thickness deformations endow proteins in cell membranes with diverse and controlled mechanical environments that, in turn, allow targeted regulation of membrane proteins.
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Affiliation(s)
- Ahis Shrestha
- Department of Physics & Astronomy and Department of Biological Sciences, University of Southern California, Los Angeles, California 90089, USA
| | - Osman Kahraman
- Department of Physics & Astronomy and Department of Biological Sciences, University of Southern California, Los Angeles, California 90089, USA
| | - Christoph A Haselwandter
- Department of Physics & Astronomy and Department of Biological Sciences, University of Southern California, Los Angeles, California 90089, USA
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Fabiani C, Antollini SS. Alzheimer's Disease as a Membrane Disorder: Spatial Cross-Talk Among Beta-Amyloid Peptides, Nicotinic Acetylcholine Receptors and Lipid Rafts. Front Cell Neurosci 2019; 13:309. [PMID: 31379503 PMCID: PMC6657435 DOI: 10.3389/fncel.2019.00309] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 06/25/2019] [Indexed: 12/17/2022] Open
Abstract
Biological membranes show lateral and transverse asymmetric lipid distribution. Cholesterol (Chol) localizes in both hemilayers, but in the external one it is mostly condensed in lipid-ordered microdomains (raft domains), together with saturated phosphatidyl lipids and sphingolipids (including sphingomyelin and glycosphingolipids). Membrane asymmetries induce special membrane biophysical properties and behave as signals for several physiological and/or pathological processes. Alzheimer’s disease (AD) is associated with a perturbation in different membrane properties. Amyloid-β (Aβ) plaques and neurofibrillary tangles of tau protein together with neuroinflammation and neurodegeneration are the most characteristic cellular changes observed in this disease. The extracellular presence of Aβ peptides forming senile plaques, together with soluble oligomeric species of Aβ, are considered the major cause of the synaptic dysfunction of AD. The association between Aβ peptide and membrane lipids has been extensively studied. It has been postulated that Chol content and Chol distribution condition Aβ production and posterior accumulation in membranes and, hence, cell dysfunction. Several lines of evidence suggest that Aβ partitions in the cell membrane accumulate mostly in raft domains, the site where the cleavage of the precursor AβPP by β- and γ- secretase is also thought to occur. The main consequence of the pathogenesis of AD is the disruption of the cholinergic pathways in the cerebral cortex and in the basal forebrain. In parallel, the nicotinic acetylcholine receptor has been extensively linked to membrane properties. Since its transmembrane domain exhibits extensive contacts with the surrounding lipids, the acetylcholine receptor function is conditioned by its lipid microenvironment. The nicotinic acetylcholine receptor is present in high-density clusters in the cell membrane where it localizes mainly in lipid-ordered domains. Perturbations of sphingomyelin or cholesterol composition alter acetylcholine receptor location. Therefore, Aβ processing, Aβ partitioning, and acetylcholine receptor location and function can be manipulated by changes in membrane lipid biophysics. Understanding these mechanisms should provide insights into new therapeutic strategies for prevention and/or treatment of AD. Here, we discuss the implications of lipid-protein interactions at the cell membrane level in AD.
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Affiliation(s)
- Camila Fabiani
- Instituto de Investigaciones Bioquímicas de Bahía Blanca CONICET-UNS, Bahía Blanca, Argentina.,Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, Bahía Blanca, Argentina
| | - Silvia S Antollini
- Instituto de Investigaciones Bioquímicas de Bahía Blanca CONICET-UNS, Bahía Blanca, Argentina.,Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, Bahía Blanca, Argentina
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5
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Differential Scanning Calorimetry of Protein-Lipid Interactions. Methods Mol Biol 2019. [PMID: 31218615 DOI: 10.1007/978-1-4939-9512-7_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
Differential scanning calorimetry (DSC) is a highly sensitive nonperturbing technique used for studying the thermodynamic properties of thermally induced transitions. Since these properties might be affected by ligand binding, DSC is particularly useful for the characterization of protein interactions with biomimetic membranes. The advantages of this technique over other methods consist in the direct measurement of intrinsic thermal properties of the samples, requiring no chemical modifications or extrinsic probes. This chapter describes the basic theory of DSC and provides the reader with an understanding of the capabilities of DSC instrumentation and the type of information that can be achieved from DSC studies of lipid-protein interactions. In particular, the chapter provides a detailed analysis of DSC data to assess the effects of proteins on biomimetic membranes.
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A Rationale for Mesoscopic Domain Formation in Biomembranes. Biomolecules 2018; 8:biom8040104. [PMID: 30274275 PMCID: PMC6316292 DOI: 10.3390/biom8040104] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 09/04/2018] [Accepted: 09/06/2018] [Indexed: 12/25/2022] Open
Abstract
Cell plasma membranes display a dramatically rich structural complexity characterized by functional sub-wavelength domains with specific lipid and protein composition. Under favorable experimental conditions, patterned morphologies can also be observed in vitro on model systems such as supported membranes or lipid vesicles. Lipid mixtures separating in liquid-ordered and liquid-disordered phases below a demixing temperature play a pivotal role in this context. Protein-protein and protein-lipid interactions also contribute to membrane shaping by promoting small domains or clusters. Such phase separations displaying characteristic length-scales falling in-between the nanoscopic, molecular scale on the one hand and the macroscopic scale on the other hand, are named mesophases in soft condensed matter physics. In this review, we propose a classification of the diverse mechanisms leading to mesophase separation in biomembranes. We distinguish between mechanisms relying upon equilibrium thermodynamics and those involving out-of-equilibrium mechanisms, notably active membrane recycling. In equilibrium, we especially focus on the many mechanisms that dwell on an up-down symmetry breaking between the upper and lower bilayer leaflets. Symmetry breaking is an ubiquitous mechanism in condensed matter physics at the heart of several important phenomena. In the present case, it can be either spontaneous (domain buckling) or explicit, i.e., due to an external cause (global or local vesicle bending properties). Whenever possible, theoretical predictions and simulation results are confronted to experiments on model systems or living cells, which enables us to identify the most realistic mechanisms from a biological perspective.
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Sreeja KK, Sunil Kumar PB. Lipid-protein interaction induced domains: Kinetics and conformational changes in multicomponent vesicles. J Chem Phys 2018; 148:134703. [PMID: 29626906 DOI: 10.1063/1.5022494] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The spatio-temporal organization of proteins and the associated morphological changes in membranes are of importance in cell signaling. Several mechanisms that promote the aggregation of proteins at low cell surface concentrations have been investigated in the past. We show, using Monte Carlo simulations, that the affinity of proteins for specific lipids can hasten their aggregation kinetics. The lipid membrane is modeled as a dynamically triangulated surface with the proteins defined as in-plane fields at the vertices. We show that, even at low protein concentrations, strong lipid-protein interactions can result in large protein clusters indicating a route to lipid mediated signal amplification. At high protein concentrations, the domains form buds similar to that seen in lipid-lipid interaction induced phase separation. Protein interaction induced domain budding is suppressed when proteins act as anisotropic inclusions and exhibit nematic orientational order. The kinetics of protein clustering and resulting conformational changes are shown to be significantly different for the isotropic and anisotropic curvature inducing proteins.
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Affiliation(s)
- K K Sreeja
- Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India
| | - P B Sunil Kumar
- Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India
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Al Khamici H, Hossain KR, Cornell BA, Valenzuela SM. Investigating Sterol and Redox Regulation of the Ion Channel Activity of CLIC1 Using Tethered Bilayer Membranes. MEMBRANES 2016; 6:membranes6040051. [PMID: 27941637 PMCID: PMC5192407 DOI: 10.3390/membranes6040051] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 12/04/2016] [Accepted: 12/05/2016] [Indexed: 12/03/2022]
Abstract
The Chloride Intracellular Ion Channel (CLIC) family consists of six conserved proteins in humans. These are a group of enigmatic proteins, which adopt both a soluble and membrane bound form. CLIC1 was found to be a metamorphic protein, where under specific environmental triggers it adopts more than one stable reversible soluble structural conformation. CLIC1 was found to spontaneously insert into cell membranes and form chloride ion channels. However, factors that control the structural transition of CLIC1 from being an aqueous soluble protein into a membrane bound protein have yet to be adequately described. Using tethered bilayer lipid membranes and electrical impedance spectroscopy system, herein we demonstrate that CLIC1 ion channel activity is dependent on the type and concentration of sterols in bilayer membranes. These findings suggest that membrane sterols play an essential role in CLIC1’s acrobatic switching from a globular soluble form to an integral membrane form, promoting greater ion channel conductance in membranes. What remains unclear is the precise nature of this regulation involving membrane sterols and ultimately determining CLIC1’s membrane structure and function as an ion channel. Furthermore, our impedance spectroscopy results obtained using CLIC1 mutants, suggest that the residue Cys24 is not essential for CLIC1’s ion channel function. However Cys24 does appear important for optimal ion channel activity. We also observe differences in conductance between CLIC1 reduced and oxidized forms when added to our tethered membranes. Therefore, we conclude that both membrane sterols and redox play a role in the ion channel activity of CLIC1.
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Affiliation(s)
- Heba Al Khamici
- School of Life Sciences, University of Technology Sydney, Sydney 2007, Australia.
| | - Khondher R Hossain
- School of Life Sciences, University of Technology Sydney, Sydney 2007, Australia.
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation (ANSTO), NSW 2234, Australia.
| | | | - Stella M Valenzuela
- School of Life Sciences, University of Technology Sydney, Sydney 2007, Australia.
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9
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Ho CS, Khadka NK, She F, Cai J, Pan J. Influenza M2 Transmembrane Domain Senses Membrane Heterogeneity and Enhances Membrane Curvature. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:6730-6738. [PMID: 27285399 PMCID: PMC5131574 DOI: 10.1021/acs.langmuir.6b00150] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Targeting host cell membranes by M2 of influenza A virus is important for virus invasion and replication. We study the transmembrane domain of M2 (M2TM) interacting with mica-supported planar bilayers and free-standing giant unilamellar vesicles (GUVs). Using solution atomic force microscopy (AFM), we show that the size of M2TM oligomers is dependent on lipid composition. The addition of M2TM to lipid bilayers containing liquid-ordered (Lo) and liquid-disordered (Ld) phases reveals that M2TM preferentially partitions into the Ld phase; phase-dependent partitioning results in a larger rigidity of the Ld phase. We next use fluorescence microscopy to study the effects of M2TM on phase-coexisting GUVs. In particular, M2TM is found to increase GUVs' miscibility transition temperature Tmix. The augmented thermodynamic stability can be accounted for by considering an enhanced energy barrier of lipid mixing between coexisting phases. Our GUV study also shows that M2TM can elicit an array of vesicle shapes mimicking virus budding. M2TM enhanced membrane curvature is consistent with our AFM data, which show altered membrane rigidity and consequently line tension at domain edges. Together, our results highlight that in addition to conducting protons, M2TM can actively regulate membrane heterogeneity and augment membrane curvature.
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Affiliation(s)
- Chian Sing Ho
- Department of Physics, University of South Florida, Tampa, FL 33620, United States
| | - Nawal K. Khadka
- Department of Physics, University of South Florida, Tampa, FL 33620, United States
| | - Fengyu She
- Department of Chemistry, University of South Florida, Tampa, FL 33620, United States
| | - Jianfeng Cai
- Department of Chemistry, University of South Florida, Tampa, FL 33620, United States
| | - Jianjun Pan
- Department of Physics, University of South Florida, Tampa, FL 33620, United States
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Lateral Distribution of Membrane Components and Transient Lipid-Protein Structures. MEMBRANE PROTEIN – LIPID INTERACTIONS: PHYSICS AND CHEMISTRY IN THE BILAYER 2016. [DOI: 10.1007/978-3-319-30277-5_3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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11
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Saka SK, Honigmann A, Eggeling C, Hell SW, Lang T, Rizzoli SO. Multi-protein assemblies underlie the mesoscale organization of the plasma membrane. Nat Commun 2014; 5:4509. [PMID: 25060237 PMCID: PMC4124874 DOI: 10.1038/ncomms5509] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 06/25/2014] [Indexed: 02/07/2023] Open
Abstract
Most proteins have uneven distributions in the plasma membrane. Broadly speaking, this may be caused by mechanisms specific to each protein, or may be a consequence of a general pattern that affects the distribution of all membrane proteins. The latter hypothesis has been difficult to test in the past. Here, we introduce several approaches based on click chemistry, through which we study the distribution of membrane proteins in living cells, as well as in membrane sheets. We found that the plasma membrane proteins form multi-protein assemblies that are long lived (minutes), and in which protein diffusion is restricted. The formation of the assemblies is dependent on cholesterol. They are separated and anchored by the actin cytoskeleton. Specific proteins are preferentially located in different regions of the assemblies, from their cores to their edges. We conclude that the assemblies constitute a basic mesoscale feature of the membrane, which affects the patterning of most membrane proteins, and possibly also their activity. Although many proteins adopt uneven distributions in the plasma membrane, it is not clear how these nanoscale heterogeneities relate to the general protein patterning of the membrane. Saka et al. use click chemistry to reveal the mesoscale organization of membrane proteins into multi-protein assemblies.
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Affiliation(s)
- Sinem K Saka
- 1] Department of Neuro- and Sensory Physiology, University of Göttingen Medical Centre, and Centre for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 37075 Göttingen, Germany [2] International Max Planck Research School Molecular Biology, 37077 Göttingen, Germany
| | - Alf Honigmann
- Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Christian Eggeling
- MRC Human Immunology Unit, Weatherall Institute of Molecular Medicine, Oxford OX3 9DS, UK
| | - Stefan W Hell
- Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Thorsten Lang
- Department of Membrane Biochemistry, Life and Medical Sciences (LIMES) Institute, University of Bonn, 53115 Bonn, Germany
| | - Silvio O Rizzoli
- Department of Neuro- and Sensory Physiology, University of Göttingen Medical Centre, and Centre for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 37075 Göttingen, Germany
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12
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Suárez-Germà C, Domènech Ò, Montero MT, Hernández-Borrell J. Effect of lactose permease presence on the structure and nanomechanics of two-component supported lipid bilayers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:842-52. [DOI: 10.1016/j.bbamem.2013.11.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 11/20/2013] [Accepted: 11/22/2013] [Indexed: 01/24/2023]
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13
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Olivera-Couto A, Aguilar PS. Eisosomes and plasma membrane organization. Mol Genet Genomics 2012; 287:607-20. [DOI: 10.1007/s00438-012-0706-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 06/29/2012] [Indexed: 12/16/2022]
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14
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Strandberg E, Esteban-Martín S, Ulrich AS, Salgado J. Hydrophobic mismatch of mobile transmembrane helices: Merging theory and experiments. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:1242-9. [PMID: 22326890 DOI: 10.1016/j.bbamem.2012.01.023] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Revised: 01/23/2012] [Accepted: 01/25/2012] [Indexed: 10/14/2022]
Abstract
Hydrophobic mismatch still represents a puzzle for transmembrane peptides, despite the apparent simplicity of this concept and its demonstrated validity in natural membranes. Using a wealth of available experimental ((2))H NMR data, we provide here a comprehensive explanation of the orientation and dynamics of model peptides in lipid bilayers, which shows how they can adapt to membranes of different thickness. The orientational adjustment of transmembrane α-helices can be understood as the result of a competition between the thermodynamically unfavorable lipid repacking associated with peptide tilting and the optimization of peptide/membrane hydrophobic coupling. In the positive mismatch regime (long-peptide/thin-membrane) the helices adapt mainly via changing their tilt angle, as expected from simple geometrical predictions. However, the adaptation mechanism varies with the peptide sequence in the flanking regions, suggesting additional effects that modulate hydrophobic coupling. These originate from re-adjustments of the peptide hydrophobic length and they depend on the hydrophobicity of the flanking region, the strength of interfacial anchoring, the structural flexibility of anchoring side-chains and the presence of alternative anchoring residues.
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Affiliation(s)
- Erik Strandberg
- Institute of Biological Interfaces (IBG-2), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
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15
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Picas L, Suárez-Germà C, Montero MT, Domènech Ò, Hernández-Borrell J. Miscibility behavior and nanostructure of monolayers of the main phospholipids of Escherichia coli inner membrane. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:701-6. [PMID: 22087507 DOI: 10.1021/la203795t] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
We report a thermodynamic study of the effect of calcium on the mixing properties at the air-water interface of two phospholipids that mimic the inner membrane of Escherichia coli: 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol. In this study, pure POPE and POPG monolayers and three mixed monolayers, χ(POPE) = 0.25, 0.5, and 0.75, were analyzed. We show that for χ(POPE) = 0.75, the values of the Gibbs energy of mixing were negative, which implies attractive interactions. We used atomic force microscopy to study the structural properties of Langmuir-Blodgett monolayers that were transferred onto mica substrate at lateral surface pressures of 25 and 30 mN m(-1). The topographic images of pure POPE and POPG monolayers exhibited two domains of differing size and morphology, showing a step height difference within the range expected for liquid-condensed and liquid-expanded phases. The images captured for χ(POPE) = 0.25 were featureless, and for χ(POPE) = 0.5 small microdomains were observed. The composition that mimics quantitatively the proportions found in the inner membrane of E. coli , χ(POPE) = 0.75, showed large liquid condensed domains in the liquid expanded phase. The extension of each domain was quantitatively analyzed. Because calcium is used in the formation of supported bilayers of negatively charged phospholipids, the possible influence of the nanostructure of the apical on the distal monolayer is discussed.
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Affiliation(s)
- Laura Picas
- Department of Physical-Chemistry, Faculty of Pharmacy and IN2UB, University of Barcelona, E-08028 Barcelona, Spain
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16
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β-Casein–phospholipid monolayers as model systems to understand lipid–protein interactions in the milk fat globule membrane. Int Dairy J 2012. [DOI: 10.1016/j.idairyj.2011.08.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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17
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Abstract
Prokaryotes are characterized by an extreme flexibility of their respiratory systems allowing them to cope with various extreme environments. To date, supramolecular organization of respiratory systems appears as a conserved evolutionary feature as supercomplexes have been isolated in bacteria, archaea, and eukaryotes. Most of the yet identified supercomplexes in prokaryotes are involved in aerobic respiration and share similarities with those reported in mitochondria. Supercomplexes likely reflect a snapshot of the cellular respiration in a given cell population. While the exact nature of the determinants for supramolecular organization in prokaryotes is not understood, lipids, proteins, and subcellular localization can be seen as key players. Owing to the well-reported supramolecular organization of the mitochondrial respiratory chain in eukaryotes, several hypotheses have been formulated to explain the consequences of such arrangement and can be tested in the context of prokaryotes. Considering the inherent metabolic flexibility of a number of prokaryotes, cellular distribution and composition of the supramolecular assemblies should be studied in regards to environmental signals. This would pave the way to new concepts in cellular respiration.
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Gröger T, Nathoo S, Ku T, Sikora C, Turner RJ, Prenner EJ. Real-time imaging of lipid domains and distinct coexisting membrane protein clusters. Chem Phys Lipids 2011; 165:216-24. [PMID: 22227110 DOI: 10.1016/j.chemphyslip.2011.12.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 12/15/2011] [Accepted: 12/19/2011] [Indexed: 12/20/2022]
Abstract
A detailed understanding of biomembrane architecture is still a challenging task. Many in vitro studies have shown lipid domains but much less information is known about the lateral organization of membrane proteins because their hydrophobic nature limits the use of many experimental methods. We examined lipid domain formation in biomimetic Escherichia coli membranes composed of phosphatidylethanolamine and phosphatidylglycerol in the absence and presence of 1% and 5% (mol/mol) membrane multidrug resistance protein, EmrE. Monolayer isotherms demonstrated protein insertion into the lipid monolayer. Subsequently, Brewster angle microscopy was applied to image domains in lipid matrices and lipid-protein mixtures. The images showed a concentration dependent impact of the protein on lipid domain size and shape and more interestingly distinct coexisting protein clusters. Whereas lipid domains varied in size (14-47μm), protein clusters exhibited a narrow size distribution (2.6-4.8μm) suggesting a non-random process of cluster formation. A 3-D display clearly indicates that these proteins clusters protrude from the membrane plane. These data demonstrate distinct co-existing lipid domains and membrane protein clusters as the monofilm is being compressed and illustrate the significant mutual impact of lipid-protein interactions on lateral membrane architecture.
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Affiliation(s)
- Thomas Gröger
- Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherbeg, Germany
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19
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Suárez-Germà C, Montero M, Ignés-Mullol J, Hernández-Borrell J, Domènech Ò. Acyl Chain Differences in Phosphatidylethanolamine Determine Domain Formation and LacY Distribution in Biomimetic Model Membranes. J Phys Chem B 2011; 115:12778-84. [DOI: 10.1021/jp206369k] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Carme Suárez-Germà
- Department of Physical Chemistry, Faculty of Pharmacy, and ‡Faculty of Chemistry, IN2UB, University of Barcelona, E-08028-Barcelona, Spain
| | - M.Teresa Montero
- Department of Physical Chemistry, Faculty of Pharmacy, and ‡Faculty of Chemistry, IN2UB, University of Barcelona, E-08028-Barcelona, Spain
| | - Jordi Ignés-Mullol
- Department of Physical Chemistry, Faculty of Pharmacy, and ‡Faculty of Chemistry, IN2UB, University of Barcelona, E-08028-Barcelona, Spain
| | - Jordi Hernández-Borrell
- Department of Physical Chemistry, Faculty of Pharmacy, and ‡Faculty of Chemistry, IN2UB, University of Barcelona, E-08028-Barcelona, Spain
| | - Òscar Domènech
- Department of Physical Chemistry, Faculty of Pharmacy, and ‡Faculty of Chemistry, IN2UB, University of Barcelona, E-08028-Barcelona, Spain
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20
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Olivera-Couto A, Graña M, Harispe L, Aguilar PS. The eisosome core is composed of BAR domain proteins. Mol Biol Cell 2011; 22:2360-72. [PMID: 21593205 PMCID: PMC3128537 DOI: 10.1091/mbc.e10-12-1021] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Revised: 05/02/2011] [Accepted: 05/06/2011] [Indexed: 11/30/2022] Open
Abstract
Eisosomes define sites of plasma membrane organization. In Saccharomyces cerevisiae, eisosomes delimit furrow-like plasma membrane invaginations that concentrate sterols, transporters, and signaling molecules. Eisosomes are static macromolecular assemblies composed of cytoplasmic proteins, most of which have no known function. In this study, we used a bioinformatics approach to analyze a set of 20 eisosome proteins. We found that the core components of eisosomes, paralogue proteins Pil1 and Lsp1, are distant homologues of membrane-sculpting Bin/amphiphysin/Rvs (BAR) proteins. Consistent with this finding, purified recombinant Pil1 and Lsp1 tubulated liposomes and formed tubules when the proteins were overexpressed in mammalian cells. Structural homology modeling and site-directed mutagenesis indicate that Pil1 positively charged surface patches are needed for membrane binding and liposome tubulation. Pil1 BAR domain mutants were defective in both eisosome assembly and plasma membrane domain organization. In addition, we found that eisosome-associated proteins Slm1 and Slm2 have F-BAR domains and that these domains are needed for targeting to furrow-like plasma membrane invaginations. Our results support a model in which BAR domain protein-mediated membrane bending leads to clustering of lipids and proteins within the plasma membrane.
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Affiliation(s)
| | - Martin Graña
- Institut Pasteur de Montevideo, Montevideo 11400, Uruguay
| | - Laura Harispe
- Institut Pasteur de Montevideo, Montevideo 11400, Uruguay
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21
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Fu M, Rao R, Sudhakar D, Hogue CP, Rutta Z, Morales S, Gordon LK, Braun J, Goodglick L, Wadehra M. Epithelial membrane protein-2 promotes endometrial tumor formation through activation of FAK and Src. PLoS One 2011; 6:e19945. [PMID: 21637765 PMCID: PMC3103522 DOI: 10.1371/journal.pone.0019945] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Accepted: 04/06/2011] [Indexed: 11/18/2022] Open
Abstract
Endometrial cancer is the most common gynecologic malignancy diagnosed among women in developed countries. One recent biomarker strongly associated with disease progression and survival is epithelial membrane protein-2 (EMP2), a tetraspan protein known to associate with and modify surface expression of certain integrin isoforms. In this study, we show using a xenograft model system that EMP2 expression is necessary for efficient endometrial tumor formation, and we have started to characterize the mechanism by which EMP2 contributes to this malignant phenotype. In endometrial cancer cells, the focal adhesion kinase (FAK)/Src pathway appears to regulate migration as measured through wound healing assays. Manipulation of EMP2 levels in endometrial cancer cells regulates the phosphorylation of FAK and Src, and promotes their distribution into lipid raft domains. Notably, cells with low levels of EMP2 fail to migrate and poorly form tumors in vivo. These findings reveal the pivotal role of EMP2 in endometrial cancer carcinogenesis, and suggest that the association of elevated EMP2 levels with endometrial cancer prognosis may be causally linked to its effect on integrin-mediated signaling.
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Affiliation(s)
- Maoyong Fu
- Department of Pathology and Laboratory Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Rajiv Rao
- Department of Pathology and Laboratory Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Deepthi Sudhakar
- Department of Pathology and Laboratory Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Claire P. Hogue
- Department of Pathology and Laboratory Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Zach Rutta
- Department of Pathology and Laboratory Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Shawn Morales
- Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, United States of America
| | - Lynn K. Gordon
- Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, United States of America
| | - Jonathan Braun
- Department of Pathology and Laboratory Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- Jonsson Comprehensive Cancer Center, University of California Los Angeles, Los Angeles, California, United States of America
| | - Lee Goodglick
- Department of Pathology and Laboratory Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- Jonsson Comprehensive Cancer Center, University of California Los Angeles, Los Angeles, California, United States of America
| | - Madhuri Wadehra
- Department of Pathology and Laboratory Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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22
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Meilhac N, Destainville N. Clusters of proteins in biomembranes: insights into the roles of interaction potential shapes and of protein diversity. J Phys Chem B 2011; 115:7190-9. [PMID: 21528886 DOI: 10.1021/jp1099865] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
It has recently been proposed that proteins embedded in lipidic biomembranes can spontaneously self-organize into stable small clusters, or membrane nanodomains, due to the competition between short-range attractive and longer-range repulsive forces between proteins, specific to these systems. In this paper, we carry on our investigation, by Monte Carlo simulations, of different aspects of cluster phases of proteins in biomembranes. First, we compare different long-range potentials (including notably three-body terms) to demonstrate that the existence of cluster phases should be quite generic. Furthermore, a real membrane contains hundreds of different protein species that are far from being randomly distributed in these nanodomains. We take this protein diversity into account by modulating protein-protein interaction potentials both at short and longer range. We confirm theoretical predictions in terms of biological cluster specialization by deciphering how clusters recruit only a few protein species. In this respect, we highlight that cluster phases can turn out to be an advantage at the biological level, for example by enhancing the cell response to external stimuli.
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Affiliation(s)
- Nicolas Meilhac
- Université de Toulouse, UPS, Laboratoire de Physique Théorique (IRSAMC), Toulouse, France
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23
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de Meyer FJM, Rodgers JM, Willems TF, Smit B. Molecular simulation of the effect of cholesterol on lipid-mediated protein-protein interactions. Biophys J 2011; 99:3629-38. [PMID: 21112287 DOI: 10.1016/j.bpj.2010.09.030] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Revised: 09/14/2010] [Accepted: 09/16/2010] [Indexed: 12/01/2022] Open
Abstract
Experiments and molecular simulations have shown that the hydrophobic mismatch between proteins and membranes contributes significantly to lipid-mediated protein-protein interactions. In this article, we discuss the effect of cholesterol on lipid-mediated protein-protein interactions as function of hydrophobic mismatch, protein diameter and protein cluster size, lipid tail length, and temperature. To do so, we study a mesoscopic model of a hydrated bilayer containing lipids and cholesterol in which proteins are embedded, with a hybrid dissipative particle dynamics-Monte Carlo method. We propose a mechanism by which cholesterol affects protein interactions: protein-induced, cholesterol-enriched, or cholesterol-depleted lipid shells surrounding the proteins affect the lipid-mediated protein-protein interactions. Our calculations of the potential of mean force between proteins and protein clusters show that the addition of cholesterol dramatically reduces repulsive lipid-mediated interactions between proteins (protein clusters) with positive mismatch, but does not affect attractive interactions between proteins with negative mismatch. Cholesterol has only a modest effect on the repulsive interactions between proteins with different mismatch.
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Affiliation(s)
- Frédérick J-M de Meyer
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California, USA.
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24
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Vats K, Knutson K, Hinderliter A, Sheets ED. Peripheral protein organization and its influence on lipid diffusion in biomimetic membranes. ACS Chem Biol 2010; 5:393-403. [PMID: 20175560 PMCID: PMC2855781 DOI: 10.1021/cb900303s] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein organization on biomembranes and their dynamics are essential for cellular function. It is not clear, however, how protein binding may influence the assembly of underlying lipids or how the membrane structure leads to functional protein organization. Toward this goal, we investigated the effects of annexin a5 binding to biomimetic membranes using fluorescence imaging and correlation spectroscopy. Annexin a5 (anx a5), a peripheral intracellular protein that plays a membrane remodeling role in addition to other functions, binds specifically and tightly to anionic (e.g., phosphatidylserine)-containing membranes in the presence of calcium ion. Our fluorescence microscopy reveals that annexin likely forms assemblies, along with a more dispersed population, upon binding to anionic biomembranes in the presence of calcium ion, which is reflected in its two-component Brownian motion. To investigate the effects of annexin binding on the underlying lipids, we used specific acyl chain labeled phospholipid analogues, NBD-phosphatidylcholine (NBD-PC) and NBD-phosphatidylserine (NBD-PS). We find that both NBD-labeled lipids cluster under anx a5 assemblies, as compared with when they are found under the dispersed annexin population, and NBD-PS exhibits two-component lateral diffusion under the annexin assemblies. In contrast, NBD-PC diffusion is slower by an order of magnitude under the annexin assemblies in contrast to its diffusion when not localized under anx a5 assemblies. Our results indicate that, upon binding to membranes, the peripheral protein annexin organizes the underlying lipids into domains, which may have functional implications in vivo.
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Affiliation(s)
- Kanika Vats
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
| | - Kristofer Knutson
- Department of Chemistry & Biochemistry, University of Minnesota, Duluth, MN 55812
| | - Anne Hinderliter
- Department of Chemistry & Biochemistry, University of Minnesota, Duluth, MN 55812
| | - Erin D. Sheets
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
- Department of Pharmacy Practice & Pharmaceutical Sciences, College of Pharmacy, University of Minnesota, Duluth, MN 55812
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25
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Picas L, Montero MT, Morros A, Vázquez-Ibar J, Hernández-Borrell J. Evidence of phosphatidylethanolamine and phosphatidylglycerol presence at the annular region of lactose permease of Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:291-6. [DOI: 10.1016/j.bbamem.2009.06.024] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2009] [Revised: 06/15/2009] [Accepted: 06/29/2009] [Indexed: 10/20/2022]
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26
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The interactions between phosphatidylglycerol and phosphatidylethanolamines in model bacterial membranes. Colloids Surf B Biointerfaces 2009; 72:32-9. [DOI: 10.1016/j.colsurfb.2009.03.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2008] [Revised: 03/08/2009] [Accepted: 03/17/2009] [Indexed: 11/24/2022]
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27
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Myelin, DIGs, and membrane rafts in the central nervous system. Prostaglandins Other Lipid Mediat 2009; 91:118-29. [PMID: 19379822 DOI: 10.1016/j.prostaglandins.2009.04.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Revised: 04/08/2009] [Accepted: 04/09/2009] [Indexed: 11/21/2022]
Abstract
Over the past 40 years our understanding of the organization of cell membranes has changed dramatically. Membranes are no longer viewed as a homogenous sea of phospholipids studded with randomly positioned islands of proteins. Our current view of the membrane involves the formation of small lipid clusters, comprised mainly of cholesterol and sphingolipids, known as membrane rafts. These lipid clusters apparently include and exclude specific proteins leading to the hypothesis that these domains (1) regulate cellular polarity and compartmentalization through trafficking and sorting, (2) provide platforms for cellular signaling and adhesion, and (3) function as cellular gate keepers. Tremendous controversy surrounds the concept of membrane rafts primarily because these small, highly dynamic entities are too small to be observed with traditional microscopic methods and the most utilized approach for raft analysis relies on poorly quantified, inconsistent biochemical extractions. New analytical approaches are being developed and applied to the study of membrane rafts and these techniques provide great promise for furthering our understanding of these enigmatic domains. In this review we will provide a brief summary of the current understanding of membrane rafts, utilizing the CNS myelin literature for illustrative purposes, and present caveats that should be considered when studying these domains.
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28
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Epand RM, Epand RF. Domains in bacterial membranes and the action of antimicrobial agents. MOLECULAR BIOSYSTEMS 2009; 5:580-7. [PMID: 19462015 DOI: 10.1039/b900278m] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A major advance in the concept of the fluid mosaic model of biological membranes in recent years has been the appreciation of the domain structure of membranes. This concept is now well developed with mammalian plasma membranes but is an emerging focus with regard to bacterial membranes. In addition to bacterial domains that form spontaneously, it is possible to induce the separation of anionic and zwitterionic lipids with certain cationic antimicrobial agents. As a consequence, the bacterial species for which these agents will be toxic can be predicted on the basis of the lipid composition of the bacterial membrane.
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Affiliation(s)
- Richard M Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
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29
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Calistri A, Salata C, Parolin C, Palù G. Role of multivesicular bodies and their components in the egress of enveloped RNA viruses. Rev Med Virol 2009; 19:31-45. [PMID: 18618839 DOI: 10.1002/rmv.588] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
As an enveloped virus buds, the nascent viral capsid becomes wrapped in a plasma membrane-derived lipid envelope, and a membrane fission event is thus necessary to separate the virion from the host cell. This membrane fission event is well characterised in the case of enveloped RNA viruses, where it is promoted by late assembly domains (L-domains) present at the level of specific viral structural proteins. Research conducted over the past 10 years has demonstrated that L-domains represent docking sites for cellular proteins essential for the biogenesis of a cellular organelle, the multivesicular body (MVB). In this way, enveloped RNA viruses hijack the MVB components to the cellular site where the budding is executed. This review will focus on the cellular machinery exploited by enveloped RNA viruses in order to be released from infected cells. The role of ubiquitin and lipids in viral budding will also be discussed.
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Affiliation(s)
- A Calistri
- Department of Histology, Microbiology and Medical Biotechnologies, University of Padova, Padova, Italy
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30
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Wenz JJ, Barrantes FJ. Resolution of complex fluorescence spectra of lipids and nicotinic acetylcholine receptor by multivariate analysis reveals protein-mediated effects on the receptor's immediate lipid microenvironment. PMC BIOPHYSICS 2008; 1:6. [PMID: 19351428 PMCID: PMC2666634 DOI: 10.1186/1757-5036-1-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Accepted: 12/18/2008] [Indexed: 11/29/2022]
Abstract
Analysis of fluorescent spectra from complex biological systems containing various fluorescent probes with overlapping emission bands is a challenging task. Valuable information can be extracted from the full spectra, however, by using multivariate analysis (MA) of measurements at different wavelengths. We applied MA to spectral data of purified Torpedo nicotinic acetylcholine receptor (AChR) protein reconstituted into liposomes made up of dioleoylphosphatidic acid (DOPA) and dioleoylphosphatidylcholine (DOPC) doped with two extrinsic fluorescent probes (NBD-cholesterol/pyrene-PC). Förster resonance energy transfer (FRET) was observed between the protein and pyrene-PC and between pyrene-PC and NBD-cholesterol, leading to overlapping emission bands. Partial least squares analysis was applied to fluorescence spectra of pyrene-PC in liposomes with different DOPC/DOPA ratios, generating a model that was tested by an internal validation (leave-one-out cross-validation) and was further used to predict the apparent lipid molar ratio in AChR-containing samples. The values predicted for DOPA, the lipid with the highest Tm, indicate that the protein exerts a rigidifying effect on its lipid microenvironment. A similar conclusion was reached from excimer formation of pyrene-PC, a collisional-dependent phenomenon. The excimer/monomer ratio (E/M) at different DOPC/DOPA molar ratios revealed the restricted diffusion of the probe in AChR-containing samples in comparison to pure lipid samples devoid of protein. FRET from the AChR (donor) to pyrene-PC (acceptor) as a function of temperature was found to increase with increasing temperature, suggesting a shorter distance between AChR and pyrene PC. Taken together, the results obtained by MA on complex spectra indicate that the AChR rigidifies its surrounding lipid and prefers DOPA rather than DOPC in its immediate microenvironment. PACS Codes: 32.50.+d, 33.50.Dq
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Affiliation(s)
- Jorge J Wenz
- UNESCO Chair of Biophysics and Molecular Neurobiology and Instituto de Investigaciones Bioquímicas de Bahía Blanca, B8000FWB Bahía Blanca, Argentina.
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31
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Epand RM. Proteins and cholesterol-rich domains. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:1576-82. [DOI: 10.1016/j.bbamem.2008.03.016] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2007] [Revised: 03/19/2008] [Accepted: 03/24/2008] [Indexed: 12/21/2022]
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