1
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Matveeva M, Lefebvre M, Chahinian H, Yahi N, Fantini J. Host Membranes as Drivers of Virus Evolution. Viruses 2023; 15:1854. [PMID: 37766261 PMCID: PMC10535233 DOI: 10.3390/v15091854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 08/29/2023] [Accepted: 08/30/2023] [Indexed: 09/29/2023] Open
Abstract
The molecular mechanisms controlling the adaptation of viruses to host cells are generally poorly documented. An essential issue to resolve is whether host membranes, and especially lipid rafts, which are usually considered passive gateways for many enveloped viruses, also encode informational guidelines that could determine virus evolution. Due to their enrichment in gangliosides which confer an electronegative surface potential, lipid rafts impose a first control level favoring the selection of viruses with enhanced cationic areas, as illustrated by SARS-CoV-2 variants. Ganglioside clusters attract viral particles in a dynamic electrostatic funnel, the more cationic viruses of a viral population winning the race. However, electrostatic forces account for only a small part of the energy of raft-virus interaction, which depends mainly on the ability of viruses to form a network of hydrogen bonds with raft gangliosides. This fine tuning of virus-ganglioside interactions, which is essential to stabilize the virus on the host membrane, generates a second level of selection pressure driven by a typical induced-fit mechanism. Gangliosides play an active role in this process, wrapping around the virus spikes through a dynamic quicksand-like mechanism. Viruses are thus in an endless race for access to lipid rafts, and they are bound to evolve perpetually, combining speed (electrostatic potential) and precision (fine tuning of amino acids) under the selective pressure of the immune system. Deciphering the host membrane guidelines controlling virus evolution mechanisms may open new avenues for the design of innovative antivirals.
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Affiliation(s)
| | | | | | | | - Jacques Fantini
- Department of Biology, Faculty of Medicine, University of Aix-Marseille, INSERM UMR_S 1072, 13015 Marseille, France; (M.M.); (M.L.); (H.C.); (N.Y.)
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2
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Hall D, Foster AS. Practical considerations for feature assignment in high-speed AFM of live cell membranes. Biophys Physicobiol 2022; 19:1-21. [PMID: 35797405 PMCID: PMC9173863 DOI: 10.2142/biophysico.bppb-v19.0016] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 04/13/2022] [Indexed: 12/01/2022] Open
Affiliation(s)
- Damien Hall
- WPI Nano Life Science Institute, Kanazawa University
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3
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Surface Sensitive Analysis Device using Model Membrane and Challenges for Biosensor-chip. BIOCHIP JOURNAL 2020. [DOI: 10.1007/s13206-019-4110-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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4
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Ryu YS, Yun H, Chung T, Suh JH, Kim S, Lee K, Wittenberg NJ, Oh SH, Lee B, Lee SD. Kinetics of lipid raft formation at lipid monolayer-bilayer junction probed by surface plasmon resonance. Biosens Bioelectron 2019; 142:111568. [PMID: 31442945 DOI: 10.1016/j.bios.2019.111568] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Revised: 07/27/2019] [Accepted: 08/02/2019] [Indexed: 02/06/2023]
Abstract
A label-free, non-dispruptive, and real-time analytical device to monitor the dynamic features of biomolecules and their interactions with neighboring molecules is an essential prerequisite for biochip- and diagonostic assays. To explore one of the central questions on the lipid-lipid interactions in the course of the liquid-ordered (lo) domain formation, called rafts, we developed a method of reconstituting continuous but spatially heterogeneous lipid membrane platforms with molayer-bilayer juntions (MBJs) that enable to form the lo domains in a spatiotemporally controlled manner. This allows us to detect the time-lapse dynamics of the lipid-lipid interactions during raft formation and resultant membrane phase changes together with the raft-associated receptor-ligand binding through the surface plasmon resonance (SPR). For cross-validation, using epifluorescence microscopy, we demonstrated the underlying mechanisms for raft formations that the infiltration of cholesterols into the sphingolipid-enriched domains plays a crucial roles in the membrane phase-separation. Our membrane platform, being capable of monitoring dynamic interactions among lipids and performing the systematic optical analysis, will unveil physiological roles of cholesterols in a variety of biological events.
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Affiliation(s)
- Yong-Sang Ryu
- School of Electrical and Computer Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea; Sensor System Research Center, Korea Institute of Science and Technology, Seongbuk-gu, Seoul, 02792, South Korea
| | - Hansik Yun
- School of Electrical and Computer Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea
| | - Taerin Chung
- Inter-University Semiconductor Research Center, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea
| | - Jeng-Hun Suh
- School of Electrical and Computer Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea
| | - Sungho Kim
- School of Electrical and Computer Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea
| | - Kyookeun Lee
- Inter-University Semiconductor Research Center, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea
| | - Nathan J Wittenberg
- Department of Electrical and Computer Engineering, University of Minnesota, 200 Union St SE, Minneapolis, MN, 55455, USA; Department of Chemistry, Lehigh University, Bethlehem, PA, 18015, USA
| | - Sang-Hyun Oh
- Department of Electrical and Computer Engineering, University of Minnesota, 200 Union St SE, Minneapolis, MN, 55455, USA
| | - Byoungho Lee
- School of Electrical and Computer Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea
| | - Sin-Doo Lee
- School of Electrical and Computer Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea; Inter-University Semiconductor Research Center, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea.
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5
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Bargen K, Scraba M, Krämer I, Ketterer M, Nehls C, Krokowski S, Repnik U, Wittlich M, Maaser A, Zapka P, Bunge M, Schlesinger M, Huth G, Klees A, Hansen P, Jeschke A, Bendas G, Utermöhlen O, Griffiths G, Gutsmann T, Wohlmann J, Haas A. Virulence‐associated protein A fromRhodococcus equiis an intercompartmental pH‐neutralising virulence factor. Cell Microbiol 2018; 21:e12958. [DOI: 10.1111/cmi.12958] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 08/17/2018] [Accepted: 09/04/2018] [Indexed: 12/26/2022]
Affiliation(s)
- Kristine Bargen
- Division of Biophysics, Cell Biology InstituteUniversity of Bonn Bonn Germany
| | - Mirella Scraba
- Division of Biophysics, Cell Biology InstituteUniversity of Bonn Bonn Germany
| | - Ina Krämer
- Division of Biophysics, Cell Biology InstituteUniversity of Bonn Bonn Germany
| | - Maren Ketterer
- Division of Biophysics, Cell Biology InstituteUniversity of Bonn Bonn Germany
| | | | - Sina Krokowski
- Division of Biophysics, Cell Biology InstituteUniversity of Bonn Bonn Germany
| | - Urska Repnik
- Department of BiosciencesUniversity of Oslo Oslo Norway
| | - Michaela Wittlich
- Division of Biophysics, Cell Biology InstituteUniversity of Bonn Bonn Germany
| | - Anna Maaser
- Division of Biophysics, Cell Biology InstituteUniversity of Bonn Bonn Germany
| | - Pia Zapka
- Division of Biophysics, Cell Biology InstituteUniversity of Bonn Bonn Germany
| | - Madeleine Bunge
- Division of Biophysics, Cell Biology InstituteUniversity of Bonn Bonn Germany
| | | | - Gitta Huth
- Division of Biophysics, Cell Biology InstituteUniversity of Bonn Bonn Germany
| | - Annette Klees
- Division of Biophysics, Cell Biology InstituteUniversity of Bonn Bonn Germany
| | - Philipp Hansen
- Division of Biophysics, Cell Biology InstituteUniversity of Bonn Bonn Germany
| | - Andreas Jeschke
- Division of Biophysics, Cell Biology InstituteUniversity of Bonn Bonn Germany
| | - Gerd Bendas
- Pharmaceutical InstituteUniversity of Bonn Bonn Germany
| | - Olaf Utermöhlen
- Institute for Medical Microbiology, Immunology and Hygiene, University Medical Center, and Center for Molecular Medicine Köln, and German Center for Infection Research (DCIF) Cologne Germany
| | | | | | - Jens Wohlmann
- Division of Biophysics, Cell Biology InstituteUniversity of Bonn Bonn Germany
- Department of BiosciencesUniversity of Oslo Oslo Norway
| | - Albert Haas
- Division of Biophysics, Cell Biology InstituteUniversity of Bonn Bonn Germany
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6
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Brazhe A. Shearlet-based measures of entropy and complexity for two-dimensional patterns. Phys Rev E 2018; 97:061301. [PMID: 30011571 DOI: 10.1103/physreve.97.061301] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Indexed: 11/07/2022]
Abstract
New spatial entropy and complexity measures for two-dimensional patterns are proposed. The approach is based on the notion of disequilibrium and is built on statistics of directional multiscale coefficients of the fast finite shearlet transform. Shannon entropy and Jensen-Shannon divergence measures are employed. Both local and global spatial complexity and entropy estimates can be obtained, thus allowing for spatial mapping of complexity in inhomogeneous patterns. The algorithm is validated in numerical experiments with a gradually decaying periodic pattern and Ising surfaces near critical state. It is concluded that the proposed algorithm can be instrumental in describing a wide range of two-dimensional imaging data, textures, or surfaces, where an understanding of the level of order or randomness is desired.
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Affiliation(s)
- Alexey Brazhe
- Department of Biophysics, Faculty of Biology, Moscow State University, Leninskie gory 1/24, 119234 Russia
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Garcia AF, Simão AMS, Bolean M, Hoylaerts MF, Millán JL, Ciancaglini P, Costa-Filho AJ. Effects of GPI-anchored TNAP on the dynamic structure of model membranes. Phys Chem Chem Phys 2016; 17:26295-301. [PMID: 26389140 DOI: 10.1039/c5cp02377g] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Tissue-nonspecific alkaline phosphatase (TNAP) plays a crucial role during skeletal mineralization, and TNAP deficiency leads to the soft bone disease hypophosphatasia. TNAP is anchored to the external surface of the plasma membranes by means of a GPI (glycosylphosphatidylinositol) anchor. Membrane-anchored and solubilized TNAP displays different kinetic properties against physiological substrates, indicating that membrane anchoring influences the enzyme function. Here, we used Electron Spin Resonance (ESR) measurements along with spin labeled phospholipids to probe the possible dynamic changes prompted by the interaction of GPI-anchored TNAP with model membranes. The goal was to systematically analyze the ESR data in terms of line shape changes and of alterations in parameters such as rotational diffusion rates and order parameters obtained from non-linear least-squares simulations of the ESR spectra of probes incorporated into DPPC liposomes and proteoliposomes. Overall, the presence of TNAP increased the dynamics and decreased the ordering in the three distinct regions probed by the spin labeled lipids DOPTC (headgroup), and 5- and 16-PCSL (acyl chains). The largest change was observed for 16-PCSL, thus suggesting that GPI-anchored TNAP can give rise to long reaching modifications that could influence membrane processes halfway through the bilayer.
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Affiliation(s)
- A F Garcia
- Laboratório de Biofísica Molecular, Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes, 3900, 14040-901, Ribeirão Preto, SP, Brazil.
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8
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Ryu YS, Wittenberg NJ, Suh JH, Lee SW, Sohn Y, Oh SH, Parikh AN, Lee SD. Continuity of Monolayer-Bilayer Junctions for Localization of Lipid Raft Microdomains in Model Membranes. Sci Rep 2016; 6:26823. [PMID: 27230411 PMCID: PMC4882513 DOI: 10.1038/srep26823] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 05/09/2016] [Indexed: 11/16/2022] Open
Abstract
We show that the selective localization of cholesterol-rich domains and associated ganglioside receptors prefer to occur in the monolayer across continuous monolayer-bilayer junctions (MBJs) in supported lipid membranes. For the MBJs, glass substrates were patterned with poly(dimethylsiloxane) (PDMS) oligomers by thermally-assisted contact printing, leaving behind 3 nm-thick PDMS patterns. The hydrophobicity of the transferred PDMS patterns was precisely tuned by the stamping temperature. Lipid monolayers were formed on the PDMS patterned surface while lipid bilayers were on the bare glass surface. Due to the continuity of the lipid membranes over the MBJs, essentially free diffusion of lipids was allowed between the monolayer on the PDMS surface and the upper leaflet of the bilayer on the glass substrate. The preferential localization of sphingomyelin, ganglioside GM1 and cholesterol in the monolayer region enabled to develop raft microdomains through coarsening of nanorafts. Our methodology provides a simple and effective scheme of non-disruptive manipulation of the chemical landscape associated with lipid phase separations, which leads to more sophisticated applications in biosensors and as cell culture substrates.
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Affiliation(s)
- Yong-Sang Ryu
- School of Electrical Engineering #032, Seoul National University, Kwanak P.O. Box 34, Seoul 151-600 Korea
| | - Nathan J. Wittenberg
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Jeng-Hun Suh
- School of Electrical Engineering #032, Seoul National University, Kwanak P.O. Box 34, Seoul 151-600 Korea
| | - Sang-Wook Lee
- School of Electrical Engineering #032, Seoul National University, Kwanak P.O. Box 34, Seoul 151-600 Korea
| | - Youngjoo Sohn
- Department of Anatomy, College of Korean Medicine, Institute of Oriental Medicine, Kyung Hee University, Seoul 130-701, Korea
| | - Sang-Hyun Oh
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Atul N. Parikh
- Departments of Biomedical Engineering and Chemical Engineering & Materials Science, University of California, Davis, California 95616, USA
| | - Sin-Doo Lee
- School of Electrical Engineering #032, Seoul National University, Kwanak P.O. Box 34, Seoul 151-600 Korea
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9
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Ryu YS, Lee IH, Suh JH, Park SC, Oh S, Jordan LR, Wittenberg NJ, Oh SH, Jeon NL, Lee B, Parikh AN, Lee SD. Reconstituting ring-rafts in bud-mimicking topography of model membranes. Nat Commun 2014; 5:4507. [PMID: 25058275 PMCID: PMC4124864 DOI: 10.1038/ncomms5507] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 06/25/2014] [Indexed: 01/30/2023] Open
Abstract
During vesicular trafficking and release of enveloped viruses, the budding and fission processes dynamically remodel the donor cell membrane in a protein- or a lipid-mediated manner. In all cases, in addition to the generation or relief of the curvature stress, the buds recruit specific lipids and proteins from the donor membrane through restricted diffusion for the development of a ring-type raft domain of closed topology. Here, by reconstituting the bud topography in a model membrane, we demonstrate the preferential localization of cholesterol- and sphingomyelin-enriched microdomains in the collar band of the bud-neck interfaced with the donor membrane. The geometrical approach to the recapitulation of the dynamic membrane reorganization, resulting from the local radii of curvatures from nanometre-to-micrometre scales, offers important clues for understanding the active roles of the bud topography in the sorting and migration machinery of key signalling proteins involved in membrane budding.
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Affiliation(s)
- Yong-Sang Ryu
- School of Electrical Engineering #032, Seoul National University, Kwanak P.O. Box 34, Seoul 151-600, Republic of Korea
| | - In-Ho Lee
- School of Electrical Engineering #032, Seoul National University, Kwanak P.O. Box 34, Seoul 151-600, Republic of Korea
| | - Jeng-Hun Suh
- School of Electrical Engineering #032, Seoul National University, Kwanak P.O. Box 34, Seoul 151-600, Republic of Korea
| | - Seung Chul Park
- School of Electrical Engineering #032, Seoul National University, Kwanak P.O. Box 34, Seoul 151-600, Republic of Korea
| | - Soojung Oh
- World Class University (WCU) Program of Multiscale Mechanical Design, School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-744, Republic of Korea
| | - Luke R. Jordan
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Nathan J. Wittenberg
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Sang-Hyun Oh
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Noo Li Jeon
- World Class University (WCU) Program of Multiscale Mechanical Design, School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-744, Republic of Korea
| | - Byoungho Lee
- School of Electrical Engineering #032, Seoul National University, Kwanak P.O. Box 34, Seoul 151-600, Republic of Korea
| | - Atul N. Parikh
- Department of Biomedical Engineering and Chemical Engineering and Materials Science, University of California, Davis, California 95616, USA
- Centre for Biomimetic Sensor Science, School of Materials Science and Engineering, Nanyang Technological University, Singapore 637553, Singapore
| | - Sin-Doo Lee
- School of Electrical Engineering #032, Seoul National University, Kwanak P.O. Box 34, Seoul 151-600, Republic of Korea
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10
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Zavala E, Marquez-Lago TT. The long and viscous road: uncovering nuclear diffusion barriers in closed mitosis. PLoS Comput Biol 2014; 10:e1003725. [PMID: 25032937 PMCID: PMC4102450 DOI: 10.1371/journal.pcbi.1003725] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 06/02/2014] [Indexed: 11/18/2022] Open
Abstract
Diffusion barriers are effective means for constraining protein lateral exchange in cellular membranes. In Saccharomyces cerevisiae, they have been shown to sustain parental identity through asymmetric segregation of ageing factors during closed mitosis. Even though barriers have been extensively studied in the plasma membrane, their identity and organization within the nucleus remains poorly understood. Based on different lines of experimental evidence, we present a model of the composition and structural organization of a nuclear diffusion barrier during anaphase. By means of spatial stochastic simulations, we propose how specialised lipid domains, protein rings, and morphological changes of the nucleus may coordinate to restrict protein exchange between mother and daughter nuclear lobes. We explore distinct, plausible configurations of these diffusion barriers and offer testable predictions regarding their protein exclusion properties and the diffusion regimes they generate. Our model predicts that, while a specialised lipid domain and an immobile protein ring at the bud neck can compartmentalize the nucleus during early anaphase; a specialised lipid domain spanning the elongated bridge between lobes would be entirely sufficient during late anaphase. Our work shows how complex nuclear diffusion barriers in closed mitosis may arise from simple nanoscale biophysical interactions. Spatial segregation of molecular contents is often necessary for an accurate, timely accomplishment of cellular functions, such as signal transduction and cell-fate decisions. For instance, budding yeast division requires the asymmetric segregation of proteins to distinguish a newborn cell from its parent. However, the strategies to achieve this parental identity are poorly understood. This holds especially true for key proteins and molecular complexes involved in mitosis that diffuse within the nuclear envelope. In fact, segregation within the nuclear envelope has been experimentally verified, but both the nature and configuration of any plausible diffusion barrier remain unknown. In this work, we built virtual models of the nucleus and carried out simulations testing the plausibility of specialised lipid domains and protein rings constituting the diffusion barrier. Moreover, we explored distinct barrier configurations in early and late stages of cell division, and verified our simulation results match experimental observations. Our work shows that the biophysical properties of these molecules, coordinated with morphological changes in the nucleus, make them suitable components of the nuclear diffusion barrier. Importantly, our research approach offers a novel avenue to study diffusion barriers in other biological membranes.
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Affiliation(s)
- Eder Zavala
- Integrative Systems Biology Unit, Okinawa Institute of Science and Technology, Okinawa, Japan
| | - Tatiana T. Marquez-Lago
- Integrative Systems Biology Unit, Okinawa Institute of Science and Technology, Okinawa, Japan
- * E-mail:
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11
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The productive entry pathway of HIV-1 in macrophages is dependent on endocytosis through lipid rafts containing CD4. PLoS One 2014; 9:e86071. [PMID: 24465876 PMCID: PMC3899108 DOI: 10.1371/journal.pone.0086071] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 12/05/2013] [Indexed: 12/20/2022] Open
Abstract
Macrophages constitute an important reservoir of HIV-1 infection, yet HIV-1 entry into these cells is poorly understood due to the difficulty in genetically manipulating primary macrophages. We developed an effective genetic approach to manipulate the sub-cellular distribution of CD4 in macrophages, and investigated how this affects the HIV-1 entry pathway. Pluripotent Stem Cells (PSC) were transduced with lentiviral vectors designed to manipulate CD4 location and were then differentiated into genetically modified macrophages. HIV-1 infection of these cells was assessed by performing assays that measure critical steps of the HIV-1 lifecycle (fusion, reverse transcription, and expression from HIV-1 integrants). Expression of LCK (which tethers CD4 to the surface of T cells, but is not normally expressed in macrophages) in PSC-macrophages effectively tethered CD4 at the cell surface, reducing its normal endocytic recycling route, and increasing surface CD4 expression 3-fold. This led to a significant increase in HIV-1 fusion and reverse transcription, but productive HIV-1 infection efficiency (as determined by reporter expression from DNA integrants) was unaffected. This implies that surface-tethering of CD4 sequesters HIV-1 into a pathway that is unproductive in macrophages. Secondly, to investigate the importance of lipid rafts (as detergent resistant membranes - DRM) in HIV-1 infection, we generated genetically modified PSC-macrophages that express CD4 mutants known to be excluded from DRM. These macrophages were significantly less able to support HIV-1 fusion, reverse-transcription and integration than engineered controls. Overall, these results support a model in which productive infection by HIV-1 in macrophages occurs via a CD4-raft-dependent endocytic uptake pathway.
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Naulin PA, Alveal NA, Barrera NP. Toward atomic force microscopy and mass spectrometry to visualize and identify lipid rafts in plasmodesmata. FRONTIERS IN PLANT SCIENCE 2014; 5:234. [PMID: 24910637 PMCID: PMC4038920 DOI: 10.3389/fpls.2014.00234] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2013] [Accepted: 05/11/2014] [Indexed: 05/08/2023]
Abstract
Plant cell-to-cell communication is mediated by nanopores called plasmodesmata (PDs) which are complex structures comprising plasma membrane (PM), highly packed endoplasmic reticulum and numerous membrane proteins. Although recent advances on proteomics have led to insights into mechanisms of transport, there is still an inadequate characterization of the lipidic composition of the PM where membrane proteins are inserted. It has been postulated that PDs could be formed by lipid rafts, however no structural evidence has shown to visualize and analyse their lipid components. In this perspective article, we discuss proposed experiments to characterize lipid rafts and proteins in the PDs. By using atomic force microscopy (AFM) and mass spectrometry (MS) of purified PD vesicles it is possible to determine the presence of lipid rafts, specific bound proteins and the lipidomic profile of the PD under physiological conditions and after changing transport permeability. In addition, MS can determine the stoichiometry of intact membrane proteins inserted in lipid rafts. This will give novel insights into the role of membrane proteins and lipid rafts on the PD structure.
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Affiliation(s)
| | | | - Nelson P. Barrera
- *Correspondence: Nelson P. Barrera, Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Alameda 340, Santiago 8331150, Chile e-mail:
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13
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Mencarelli C, Martinez–Martinez P. Ceramide function in the brain: when a slight tilt is enough. Cell Mol Life Sci 2013; 70:181-203. [PMID: 22729185 PMCID: PMC3535405 DOI: 10.1007/s00018-012-1038-x] [Citation(s) in RCA: 168] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Revised: 05/16/2012] [Accepted: 05/21/2012] [Indexed: 12/14/2022]
Abstract
Ceramide, the precursor of all complex sphingolipids, is a potent signaling molecule that mediates key events of cellular pathophysiology. In the nervous system, the sphingolipid metabolism has an important impact. Neurons are polarized cells and their normal functions, such as neuronal connectivity and synaptic transmission, rely on selective trafficking of molecules across plasma membrane. Sphingolipids are abundant on neural cellular membranes and represent potent regulators of brain homeostasis. Ceramide intracellular levels are fine-tuned and alteration of the sphingolipid-ceramide profile contributes to the development of age-related, neurological and neuroinflammatory diseases. The purpose of this review is to guide the reader towards a better understanding of the sphingolipid-ceramide pathway system. First, ceramide biology is presented including structure, physical properties and metabolism. Second, we describe the function of ceramide as a lipid second messenger in cell physiology. Finally, we highlight the relevance of sphingolipids and ceramide in the progression of different neurodegenerative diseases.
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Affiliation(s)
- Chiara Mencarelli
- Department of Neuroscience, School for Mental Health and Neuroscience, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands
| | - Pilar Martinez–Martinez
- Department of Neuroscience, School for Mental Health and Neuroscience, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands
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14
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Vieira FS, Corrêa G, Einicker-Lamas M, Coutinho-Silva R. Host-cell lipid rafts: a safe door for micro-organisms? Biol Cell 2010; 102:391-407. [PMID: 20377525 PMCID: PMC7161784 DOI: 10.1042/bc20090138] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Accepted: 02/10/2010] [Indexed: 12/20/2022]
Abstract
The lipid raft hypothesis proposed that these microdomains are small (10-200 nM), highly dynamic and enriched in cholesterol, glycosphingolipids and signalling phospholipids, which compartmentalize cellular processes. These membrane regions play crucial roles in signal transduction, phagocytosis and secretion, as well as pathogen adhesion/interaction. Throughout evolution, many pathogens have developed mechanisms to escape from the host immune system, some of which are based on the host membrane microdomain machinery. Thus lipid rafts might be exploited by pathogens as signalling and entry platforms. In this review, we summarize the role of lipid rafts as players in the overall invasion process used by different pathogens to escape from the host immune system.
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Affiliation(s)
- Flávia Sarmento Vieira
- Laboratório de Imunofisiologia, Universidade Federal do Rio de Janeiro, Instituto de Biofísica Carlos Chagas Filho, CCS, Rio de Janeiro, RJ, Brazil
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15
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Tresset G. The multiple faces of self-assembled lipidic systems. PMC BIOPHYSICS 2009; 2:3. [PMID: 19374753 PMCID: PMC2695813 DOI: 10.1186/1757-5036-2-3] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Accepted: 04/17/2009] [Indexed: 11/10/2022]
Abstract
Lipids, the building blocks of cells, common to every living organisms, have the propensity to self-assemble into well-defined structures over short and long-range spatial scales. The driving forces have their roots mainly in the hydrophobic effect and electrostatic interactions. Membranes in lamellar phase are ubiquitous in cellular compartments and can phase-separate upon mixing lipids in different liquid-crystalline states. Hexagonal phases and especially cubic phases can be synthesized and observed in vivo as well. Membrane often closes up into a vesicle whose shape is determined by the interplay of curvature, area difference elasticity and line tension energies, and can adopt the form of a sphere, a tube, a prolate, a starfish and many more. Complexes made of lipids and polyelectrolytes or inorganic materials exhibit a rich diversity of structural morphologies due to additional interactions which become increasingly hard to track without the aid of suitable computer models. From the plasma membrane of archaebacteria to gene delivery, self-assembled lipidic systems have left their mark in cell biology and nanobiotechnology; however, the underlying physics is yet to be fully unraveled.PACS Codes: 87.14.Cc, 82.70.Uv.
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Affiliation(s)
- Guillaume Tresset
- Laboratoire de Physique des Solides, Université Paris-Sud, CNRS, UMR 8502, F-91405 Orsay Cedex, France.
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Yuan J, Kiss A, Pramudya YH, Nguyen LT, Hirst LS. Solution synchrotron x-ray diffraction reveals structural details of lipid domains in ternary mixtures. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 79:031924. [PMID: 19391988 DOI: 10.1103/physreve.79.031924] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2008] [Revised: 12/22/2008] [Indexed: 05/27/2023]
Abstract
The influence of cholesterol on lipid bilayer structure is significant and the effect of cholesterol on lipid sorting and phase separation in lipid-raft-forming model membrane systems has been well investigated by microscopy methods on giant vesicles. An important consideration however is the influence of fluorescence illumination on the phase state of these lipids and this effect must be carefully minimized. In this paper, we show that synchrotron x-ray scattering on solution lipid mixtures is an effective alternative technique for the identification and characterization of the l_{o} (liquid ordered) and l_{d} (liquid disordered) phases. The high intensity of synchrotron x rays allows the observation of up to 5 orders of diffraction from the l_{o} phase, whereas only two are clearly visible when the l_{d} phase alone is present. This data can be collected in approximately 1 min/sample , allowing rapid generation of phase data. In this paper, we measure the lamellar spacing in both the liquid-ordered and liquid-disordered phases simultaneously, as a function of cholesterol concentration in two different ternary mixtures. We also observe evidence of a third gel-phaselike population at 10-12 mol % cholesterol and determine the thickness of the bilayer for this phase. Importantly we are able to look at phase coexistence in the membrane independent of photoeffects.
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Affiliation(s)
- Jing Yuan
- Department of Physics and MARTECH, Florida State University, Tallahassee, Florida 32306, USA
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17
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Gupta VR, Patel HK, Kostolansky SS, Ballivian RA, Eichberg J, Blanke SR. Sphingomyelin functions as a novel receptor for Helicobacter pylori VacA. PLoS Pathog 2008; 4:e1000073. [PMID: 18497859 PMCID: PMC2374909 DOI: 10.1371/journal.ppat.1000073] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Accepted: 04/15/2008] [Indexed: 12/18/2022] Open
Abstract
The vacuolating cytotoxin (VacA) of the gastric pathogen Helicobacter pylori binds and enters epithelial cells, ultimately resulting in cellular vacuolation. Several host factors have been reported to be important for VacA function, but none of these have been demonstrated to be essential for toxin binding to the plasma membrane. Thus, the identity of cell surface receptors critical for both toxin binding and function has remained elusive. Here, we identify VacA as the first bacterial virulence factor that exploits the important plasma membrane sphingolipid, sphingomyelin (SM), as a cellular receptor. Depletion of plasma membrane SM with sphingomyelinase inhibited VacA-mediated vacuolation and significantly reduced the sensitivity of HeLa cells, as well as several other cell lines, to VacA. Further analysis revealed that SM is critical for VacA interactions with the plasma membrane. Restoring plasma membrane SM in cells previously depleted of SM was sufficient to rescue both toxin vacuolation activity and plasma membrane binding. VacA association with detergent-resistant membranes was inhibited in cells pretreated with SMase C, indicating the importance of SM for VacA association with lipid raft microdomains. Finally, VacA bound to SM in an in vitro ELISA assay in a manner competitively inhibited by lysenin, a known SM-binding protein. Our results suggest a model where VacA may exploit the capacity of SM to preferentially partition into lipid rafts in order to access the raft-associated cellular machinery previously shown to be required for toxin entry into host cells. Sensitivity to toxins produced by pathogenic bacteria is largely dictated by the presence or absence of toxin receptors on the plasma membrane of host cells. VacA is an important toxin produced by the pathogenic bacterium Helicobacter pylori, which infects the human stomach and causes gastric ulcer disease and stomach cancer. VacA binds and enters human cells, and induces several changes resulting ultimately in the death of the intoxicated cells. However, the identity of the VacA receptor responsible for toxin binding and function has remained a topic of debate. In this paper, we demonstrate that sphingomyelin, a lipid on the surface of cells with important membrane structural and signaling properties, functions as a VacA receptor. We demonstrate that VacA binds to sphingomyelin, and that presence or absence of sphingomyelin on the plasma membrane dictates how much VacA binds to the cell surface, and therefore, how sensitive cells are to the toxin. The identification of sphingomyelin also provides a conceptual framework for how VacA may enter cells through specialized functional domains on the surface of cells. This is the first example of a bacterial toxin that exploits sphingomyelin as a receptor, and future work will focus on developing strategies to block VacA interactions with sphingomyelin, thereby protecting cells from the downstream consequences of toxin action.
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Affiliation(s)
- Vijay R. Gupta
- Department of Microbiology, Institute for Genomic Biology, University of Illinois, Urbana, Illinois, United States of America
| | - Hetal K. Patel
- Department of Microbiology, Institute for Genomic Biology, University of Illinois, Urbana, Illinois, United States of America
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Sean S. Kostolansky
- Department of Microbiology, Institute for Genomic Biology, University of Illinois, Urbana, Illinois, United States of America
| | - Roberto A. Ballivian
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Joseph Eichberg
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Steven R. Blanke
- Department of Microbiology, Institute for Genomic Biology, University of Illinois, Urbana, Illinois, United States of America
- * E-mail:
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Fan J, Sammalkorpi M, Haataja M. Domain formation in the plasma membrane: roles of nonequilibrium lipid transport and membrane proteins. PHYSICAL REVIEW LETTERS 2008; 100:178102. [PMID: 18518341 DOI: 10.1103/physrevlett.100.178102] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Indexed: 05/26/2023]
Abstract
Compositional lipid domains ("lipid rafts") in plasma membranes are believed to be important components of many cellular processes. The mechanisms by which cells regulate the sizes and lifetimes of these spatially extended domains are poorly understood at the moment. Here we show that the competition between phase separation in an immiscible lipid system and active cellular lipid transport processes naturally leads to the formation of such domains. Furthermore, we demonstrate that local interactions with immobile membrane proteins can spatially localize the rafts and lead to further clustering.
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Affiliation(s)
- Jun Fan
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, USA
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19
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Shahin V, Barrera NP. Providing Unique Insight into Cell Biology via Atomic Force Microscopy. INTERNATIONAL REVIEW OF CYTOLOGY 2008; 265:227-52. [DOI: 10.1016/s0074-7696(07)65006-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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20
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Elastic membrane heterogeneity of living cells revealed by stiff nanoscale membrane domains. Biophys J 2007; 94:1521-32. [PMID: 17981897 DOI: 10.1529/biophysj.107.112862] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Many approaches have been developed to characterize the heterogeneity of membranes in living cells. In this study, the elastic properties of specific membrane domains in living cells are characterized by atomic force microscopy. Our data reveal the existence of heterogeneous nanometric scale domains with specific biophysical properties. We focused on glycosylphosphatidylinositol (GPI)-anchored proteins, which play an important role in membrane trafficking and cell signaling under both physiological and pathological conditions and which are known to partition preferentially into cholesterol-rich microdomains. We demonstrate that these GPI-anchored proteins reside within domains that are stiffer than the surrounding membrane. In contrast, membrane domains containing the transferrin receptor, which does not associate with cholesterol-rich regions, manifest no such feature. The heightened stiffness of GPI domains is consistent with existing data relating to the specific condensation of lipids and the slow diffusion rates of lipids and proteins therein. Our quantitative data may forge the way to unveiling the links that exist between membrane stiffness, molecular diffusion, and signaling activation.
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Ma HP, Chou CF, Wei SP, Eaton DC. Regulation of the epithelial sodium channel by phosphatidylinositides: experiments, implications, and speculations. Pflugers Arch 2007; 455:169-80. [PMID: 17605040 DOI: 10.1007/s00424-007-0294-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2007] [Accepted: 05/18/2007] [Indexed: 10/23/2022]
Abstract
Recent studies suggest that the activity of epithelial sodium channels (ENaC) is increased by phosphatidylinositides, especially phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) and phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P(3)). Stimulation of phospholipase C by either adenosine triphosphate (ATP)-activation of purinergic P2Y receptors or epidermal growth factor (EGF)-activation of EGF receptors reduces membrane PI(4,5)P(2), and consequently decreases ENaC activity. Since ATP and EGF may be trapped in cysts formed by the distal tubule, it is possible that ENaC inhibition induced by ATP and EGF facilitates cyst formation in polycystic kidney diseases (PKD). However, some results suggest that ENaC activity is increased in PKD. In contrast to P2Y and EGF receptors, stimulation of insulin-like growth factor-1 (IGF-1) receptor by aldosterone or insulin produces PI(3,4,5)P(3), and consequently increases ENaC activity. The acute effect of aldosterone on ENaC activity through PI(3,4,5)P(3) possibly accounts for the initial feedback for blood volume recovery after hypovolemic hypotension. PI(4,5)P(2) and PI(3,4,5)P(3), respectively, interacts with the N terminus of beta-ENaC and the C terminus of gamma-ENaC. However, whether ENaC selectively binds to PI(4,5)P(2) and PI(3,4,5)P(3) over other anionic phospholipids remains unclear.
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Affiliation(s)
- He-Ping Ma
- Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, 1530 Third Avenue South, ZRB 510, Birmingham, AL, 35294, USA.
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22
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Corcoran JA, Salsman J, de Antueno R, Touhami A, Jericho MH, Clancy EK, Duncan R. The p14 fusion-associated small transmembrane (FAST) protein effects membrane fusion from a subset of membrane microdomains. J Biol Chem 2006; 281:31778-89. [PMID: 16936325 DOI: 10.1074/jbc.m602566200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The reovirus fusion-associated small transmembrane (FAST) proteins are a unique family of viral membrane fusion proteins. These nonstructural viral proteins induce efficient cell-cell rather than virus-cell membrane fusion. We analyzed the lipid environment in which the reptilian reovirus p14 FAST protein resides to determine the influence of the cell membrane on the fusion activity of the FAST proteins. Topographical mapping of the surface of fusogenic p14-containing liposomes by atomic force microscopy under aqueous conditions revealed that p14 resides almost exclusively in thickened membrane microdomains. In transfected cells, p14 was found in both Lubrol WX- and Triton X-100-resistant membrane complexes. Cholesterol depletion of donor cell membranes led to preferential disruption of p14 association with Lubrol WX (but not Triton X-100)-resistant membranes and decreased cell-cell fusion activity, both of which were reversed upon subsequent cholesterol repletion. Furthermore, co-patching analysis by fluorescence microscopy indicated that p14 did not co-localize with classical lipid-anchored raft markers. These data suggest that the p14 FAST protein associates with heterogeneous membrane microdomains, a distinct subset of which is defined by cholesterol-dependent Lubrol WX resistance and which may be more relevant to the membrane fusion process.
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Affiliation(s)
- Jennifer A Corcoran
- Departmentnof Microbiology, Dalhousie University, Halifax, Nova Scotia B3H 1X5, Canada
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23
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Abstract
Current models for cellular plasma membranes focus on spatial heterogeneity and how this heterogeneity relates to cell function. In particular, putative lipid raft membrane domains have been postulated to exist based in large part on the results that a significant fraction of the membrane is detergent insoluble and that molecules facilitating key membrane processes like signal transduction are often found in the detergent-resistant membrane fraction. Yet, the in vivo existence of lipid rafts remains extremely controversial because, despite being sought for more than a decade, evidence for their presence in intact cell membranes is inconclusive. In this review, a variety of experimental techniques that have been or might be used to look for lipid microdomains in intact cell membranes are described. Experimental results are highlighted and the strengths and limitations of different techniques for microdomain identification and characterization are assessed.
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Affiliation(s)
- B Christoffer Lagerholm
- Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA.
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24
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Shahin V, Ludwig Y, Schafer C, Nikova D, Oberleithner H. Glucocorticoids remodel nuclear envelope structure and permeability. J Cell Sci 2005; 118:2881-9. [PMID: 15976447 DOI: 10.1242/jcs.02429] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The present study describes glucocorticoid induced remodelling of nuclear envelope (NE) structure and permeability. A glucocorticoid analogue, triamcinolone acetonide (TA), is injected into Xenopus laevis oocytes that express an exogeneous glucocorticoid receptor (GR). Electrical, fluorescence and nano-imaging techniques are applied to study the permeability and the structure of the NE at 5 and 60 minutes after injection of TA. A remarkable dilation of nuclear pore complexes (NPCs), a rearrangement of NPC distribution and a significant increase of NE permeability for ions and fluorescent 20 kDa dextran are observed within 5 minutes of TA exposure. At regular distances on local NE patches, NPCs seem to adjoin forming clusters each consisting of several hundred NPCs. Interestingly, at the same time of exposure, hydrophobicity of NPC central channels and NPC-free NE surface increases. The changes in permeability and structure are transient as the NE permeability returns to its initial state within 60 minutes. In conclusion, the NE is a barrier of high plasticity sensitive to hydrophobic molecules. Remodelling of NE structure and permeability is a prerequisite for mediating physiological actions of glucocorticoids.
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Affiliation(s)
- Victor Shahin
- Institute of Physiology II, University of Münster, Robert-Koch Str. 27b, 48149 Münster, Germany.
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25
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Orädd G, Westerman PW, Lindblom G. Lateral diffusion coefficients of separate lipid species in a ternary raft-forming bilayer: a Pfg-NMR multinuclear study. Biophys J 2005; 89:315-20. [PMID: 15863478 PMCID: PMC1366530 DOI: 10.1529/biophysj.105.061762] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
By isotopical labeling lipid lateral diffusion coefficients for each of the membrane constituents, including cholesterol, have been measured by 1H, 2H, and 19F pulsed field gradient NMR spectroscopy in macroscopically oriented lipid bilayers. This provides a means of obtaining detailed dynamic and compositional information in raft-forming lipid bilayers without introducing foreign molecules into the systems. The raft systems studied contained dioleoylphosphatidylcholine/dipalmitoylphosphatidylcholine (DPPC)/cholesterol at the molar ratios of 42.5:42.5:15 and 35:35:30 in excess water. At temperatures below 30 degrees C the raft system forms large (>1 microm) domains of a liquid ordered (l(o)) phase, in which the lipid lateral diffusion was approximately 5 times slower than for the lipids in the surrounding liquid disordered (l(d)) phase. Within each domain all lipid species showed the same diffusion coefficient, despite the very different structures of cholesterol and phospholipids. DPPC partitions exclusively into the l(o) domains, whereas cholesterol and dioleoylphosphatidylcholine were distributed in both l(o) and l(d) phases. The cholesterol concentration was found to be 10-20 mol % in the l(d) domain and 30-40 mol % in the l(o) domain. Comparison of these results with data from sphingomyelin-containing systems suggests that DPPC interacts more weakly with cholesterol than does sphingomyelin.
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Affiliation(s)
- Greger Orädd
- Department of Chemistry: Biophysical Chemistry, Umeå University, Umeå, Sweden
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