1
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Chaudhary R, Goodman LS, Wang S, Asimakopoulos A, Weiskirchen R, Dooley S, Ehrlich M, Henis YI. Cholesterol modulates type I/II TGF-β receptor complexes and alters the balance between Smad and Akt signaling in hepatocytes. Commun Biol 2024; 7:8. [PMID: 38168942 PMCID: PMC10761706 DOI: 10.1038/s42003-023-05654-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 11/30/2023] [Indexed: 01/05/2024] Open
Abstract
Cholesterol mediates membrane compartmentalization, affecting signaling via differential distribution of receptors and signaling mediators. While excessive cholesterol and aberrant transforming growth factor-β (TGF-β) signaling characterize multiple liver diseases, their linkage to canonical vs. non-canonical TGF-β signaling remained unclear. Here, we subjected murine hepatocytes to cholesterol depletion (CD) or enrichment (CE), followed by biophysical studies on TGF-β receptor heterocomplex formation, and output to Smad2/3 vs. Akt pathways. Prior to ligand addition, raft-dependent preformed heteromeric receptor complexes were observed. Smad2/3 phosphorylation persisted following CD or CE. CD enhanced phospho-Akt (pAkt) formation by TGF-β or epidermal growth factor (EGF) at 5 min, while reducing it at later time points. Conversely, pAkt formation by TGF-β or EGF was inhibited by CE, suggesting a direct effect on the Akt pathway. The modulation of the balance between TGF-β signaling to Smad2/3 vs. pAkt (by TGF-β or EGF) has potential implications for hepatic diseases and malignancies.
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Affiliation(s)
- Roohi Chaudhary
- Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Laureen S Goodman
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Sai Wang
- Department of Medicine II, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, D-68167, Mannheim, Germany
| | - Anastasia Asimakopoulos
- Institute of Molecular Pathobiochemistry, Experimental Gene Therapy and Clinical Chemistry (IFMPEGKC), RWTH Aachen University Hospital, D-52074, Aachen, Germany
| | - Ralf Weiskirchen
- Institute of Molecular Pathobiochemistry, Experimental Gene Therapy and Clinical Chemistry (IFMPEGKC), RWTH Aachen University Hospital, D-52074, Aachen, Germany
| | - Steven Dooley
- Department of Medicine II, University Medical Center Mannheim, Medical Faculty Mannheim, Heidelberg University, D-68167, Mannheim, Germany
| | - Marcelo Ehrlich
- Shmunis School of Biomedicine and Cancer Research, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel.
| | - Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel.
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2
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Day CA, Kang M. The Utility of Fluorescence Recovery after Photobleaching (FRAP) to Study the Plasma Membrane. MEMBRANES 2023; 13:membranes13050492. [PMID: 37233553 DOI: 10.3390/membranes13050492] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 04/01/2023] [Accepted: 04/27/2023] [Indexed: 05/27/2023]
Abstract
The plasma membrane of mammalian cells is involved in a wide variety of cellular processes, including, but not limited to, endocytosis and exocytosis, adhesion and migration, and signaling. The regulation of these processes requires the plasma membrane to be highly organized and dynamic. Much of the plasma membrane organization exists at temporal and spatial scales that cannot be directly observed with fluorescence microscopy. Therefore, approaches that report on the membrane's physical parameters must often be utilized to infer membrane organization. As discussed here, diffusion measurements are one such approach that has allowed researchers to understand the subresolution organization of the plasma membrane. Fluorescence recovery after photobleaching (or FRAP) is the most widely accessible method for measuring diffusion in a living cell and has proven to be a powerful tool in cell biology research. Here, we discuss the theoretical underpinnings that allow diffusion measurements to be used in elucidating the organization of the plasma membrane. We also discuss the basic FRAP methodology and the mathematical approaches for deriving quantitative measurements from FRAP recovery curves. FRAP is one of many methods used to measure diffusion in live cell membranes; thus, we compare FRAP with two other popular methods: fluorescence correlation microscopy and single-particle tracking. Lastly, we discuss various plasma membrane organization models developed and tested using diffusion measurements.
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Affiliation(s)
- Charles A Day
- Hormel Institute, University of Minnesota, Austin, MN 55912, USA
- Mayo Clinic, Rochester, MN 55902, USA
| | - Minchul Kang
- Department of Mathematics, Texas A&M-Commerce, Commerce, TX 75428, USA
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3
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Ras Diffusion and Interactions with the Plasma Membrane Measured by FRAP Variations. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2021; 2262:185-197. [PMID: 33977477 DOI: 10.1007/978-1-0716-1190-6_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Ras proteins are non-integral membrane proteins, which bind to the plasma membrane by virtue of farnesylation and palmitoylation or a positively charged polybasic cluster at their C-terminus. Their membrane interactions and/or localization to membrane microdomains, which play important roles in signaling, are regulated by their lateral diffusion at the plasma membrane and their ability to exchange between the membrane and the cytoplasm (binding/unbinding kinetics). Here, using N-Ras as an example, we describe the use of variations of fluorescence recovery after photobleaching (FRAP) to measure the dynamics of the association of N-Ras with the plasma membrane of living cells and their dependence on several parameters (cholesterol, clustering of raft proteins, and palmitoylation/depalmitoylation).
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4
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Tzoneva R, Stoyanova T, Petrich A, Popova D, Uzunova V, Momchilova A, Chiantia S. Effect of Erufosine on Membrane Lipid Order in Breast Cancer Cell Models. Biomolecules 2020; 10:E802. [PMID: 32455962 PMCID: PMC7277205 DOI: 10.3390/biom10050802] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 05/15/2020] [Accepted: 05/19/2020] [Indexed: 12/11/2022] Open
Abstract
Alkylphospholipids are a novel class of antineoplastic drugs showing remarkable therapeutic potential. Among them, erufosine (EPC3) is a promising drug for the treatment of several types of tumors. While EPC3 is supposed to exert its function by interacting with lipid membranes, the exact molecular mechanisms involved are not known yet. In this work, we applied a combination of several fluorescence microscopy and analytical chemistry approaches (i.e., scanning fluorescence correlation spectroscopy, line-scan fluorescence correlation spectroscopy, generalized polarization imaging, as well as thin layer and gas chromatography) to quantify the effect of EPC3 in biophysical models of the plasma membrane, as well as in cancer cell lines. Our results indicate that EPC3 affects lipid-lipid interactions in cellular membranes by decreasing lipid packing and increasing membrane disorder and fluidity. As a consequence of these alterations in the lateral organization of lipid bilayers, the diffusive dynamics of membrane proteins are also significantly increased. Taken together, these findings suggest that the mechanism of action of EPC3 could be linked to its effects on fundamental biophysical properties of lipid membranes, as well as on lipid metabolism in cancer cells.
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Affiliation(s)
- Rumiana Tzoneva
- Bulgarian Academy of Sciences, Institute of Biophysics and Biomedical Engineering, 1113 Sofia, Bulgaria; (R.T.); (T.S.); (D.P.); (V.U.); (A.M.)
| | - Tihomira Stoyanova
- Bulgarian Academy of Sciences, Institute of Biophysics and Biomedical Engineering, 1113 Sofia, Bulgaria; (R.T.); (T.S.); (D.P.); (V.U.); (A.M.)
| | - Annett Petrich
- Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Street 24-25, 14476 Potsdam, Germany;
| | - Desislava Popova
- Bulgarian Academy of Sciences, Institute of Biophysics and Biomedical Engineering, 1113 Sofia, Bulgaria; (R.T.); (T.S.); (D.P.); (V.U.); (A.M.)
| | - Veselina Uzunova
- Bulgarian Academy of Sciences, Institute of Biophysics and Biomedical Engineering, 1113 Sofia, Bulgaria; (R.T.); (T.S.); (D.P.); (V.U.); (A.M.)
| | - Albena Momchilova
- Bulgarian Academy of Sciences, Institute of Biophysics and Biomedical Engineering, 1113 Sofia, Bulgaria; (R.T.); (T.S.); (D.P.); (V.U.); (A.M.)
| | - Salvatore Chiantia
- Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Street 24-25, 14476 Potsdam, Germany;
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5
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Curthoys NM, Mlodzianoski MJ, Parent M, Butler MB, Raut P, Wallace J, Lilieholm J, Mehmood K, Maginnis MS, Waters H, Busse B, Zimmerberg J, Hess ST. Influenza Hemagglutinin Modulates Phosphatidylinositol 4,5-Bisphosphate Membrane Clustering. Biophys J 2019; 116:893-909. [PMID: 30773293 DOI: 10.1016/j.bpj.2019.01.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 01/07/2019] [Accepted: 01/15/2019] [Indexed: 12/13/2022] Open
Abstract
The lipid phosphatidylinositol 4,5-bisphosphate (PIP2) forms nanoscopic clusters in cell plasma membranes; however, the processes determining PIP2 mobility and thus its spatial patterns are not fully understood. Using super-resolution imaging of living cells, we find that PIP2 is tightly colocalized with and modulated by overexpression of the influenza viral protein hemagglutinin (HA). Within and near clusters, HA and PIP2 follow a similar spatial dependence, which can be described by an HA-dependent potential gradient; PIP2 molecules move as if they are attracted to the center of clusters by a radial force of 0.079 ± 0.002 pN in HAb2 cells. The measured clustering and dynamics of PIP2 are inconsistent with the unmodified forms of the raft, tether, and fence models. Rather, we found that the spatial PIP2 distributions and how they change in time are explained via a novel, to our knowledge, dynamic mechanism: a radial gradient of PIP2 binding sites that are themselves mobile. This model may be useful for understanding other biological membrane domains whose distributions display gradients in density while maintaining their mobility.
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Affiliation(s)
- Nikki M Curthoys
- Department of Physics and Astronomy, University of Maine, Orono, Maine
| | | | - Matthew Parent
- Department of Physics and Astronomy, University of Maine, Orono, Maine
| | - Michael B Butler
- Department of Physics and Astronomy, University of Maine, Orono, Maine
| | - Prakash Raut
- Department of Physics and Astronomy, University of Maine, Orono, Maine
| | - Jaqulin Wallace
- Department of Physics and Astronomy, University of Maine, Orono, Maine
| | | | - Kashif Mehmood
- Department of Physics and Astronomy, University of Maine, Orono, Maine; Department of Molecular and Biomedical Sciences, University of Maine, Orono, Maine
| | - Melissa S Maginnis
- Department of Molecular and Biomedical Sciences, University of Maine, Orono, Maine
| | - Hang Waters
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Brad Busse
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Joshua Zimmerberg
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Samuel T Hess
- Department of Physics and Astronomy, University of Maine, Orono, Maine.
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6
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Kordyukova L. Structural and functional specificity of Influenza virus haemagglutinin and paramyxovirus fusion protein anchoring peptides. Virus Res 2017; 227:183-199. [DOI: 10.1016/j.virusres.2016.09.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 09/21/2016] [Accepted: 09/23/2016] [Indexed: 02/08/2023]
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7
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Gottlieb-Abraham E, Gutman O, Pai GM, Rubio I, Henis YI. The residue at position 5 of the N-terminal region of Src and Fyn modulates their myristoylation, palmitoylation, and membrane interactions. Mol Biol Cell 2016; 27:3926-3936. [PMID: 27733622 PMCID: PMC5170614 DOI: 10.1091/mbc.e16-08-0622] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 10/03/2016] [Accepted: 10/05/2016] [Indexed: 01/19/2023] Open
Abstract
Using biophysical methods in live cells and palmitoylation mutants of Src and Fyn, we show that palmitoylation stabilizes the interactions of SFKs with the plasma membrane. Moreover, we show that the amino acid at position 5 regulates the myristoylation and palmitoylation of these proteins, and thereby their targeting to raft domains. The interactions of Src family kinases (SFKs) with the plasma membrane are crucial for their activity. They depend on their fatty-acylated N-termini, containing N-myristate and either a polybasic cluster (in Src) or palmitoylation sites (e.g., Fyn). To investigate the roles of these moieties in SFK membrane association, we used fluorescence recovery after photobleaching beam-size analysis to study the membrane interactions of c-Src-GFP (green fluorescent protein) or Fyn-GFP fatty-acylation mutants. Our studies showed for the first time that the membrane association of Fyn is more stable than that of Src, an effect lost in a Fyn mutant lacking the palmitoylation sites. Unexpectedly, Src-S3C/S6C (containing cysteines at positions 3/6, which are palmitoylated in Fyn) exhibited fast cytoplasmic diffusion insensitive to palmitoylation inhibitors, suggesting defective fatty acylation. Further replacement of the charged Lys-5 by neutral Gln to resemble Fyn (Src-S3C/S6C/K5Q) restored Fyn-like membrane interactions, indicating that Lys-5 in the context of Src-S3C/S6C interferes with its myristoylation/palmitoylation. This was validated by direct myristoylation and palmitoylation studies, which indicated that the residue at position 5 regulates the membrane interactions of Src versus Fyn. Moreover, the palmitoylation levels correlated with targeting to detergent-resistant membranes (rafts) and to caveolin-1. Palmitoylation-dependent preferential containment of Fyn in rafts may contribute to its lower transformation potential.
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Affiliation(s)
- Efrat Gottlieb-Abraham
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Orit Gutman
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Govind M Pai
- Institute of Molecular Cell Biology, Center for Molecular Biomedicine, University Hospital, Jena 07745, Germany
| | - Ignacio Rubio
- Institute of Molecular Cell Biology, Center for Molecular Biomedicine, University Hospital, Jena 07745, Germany
| | - Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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8
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Chlanda P, Zimmerberg J. Protein-lipid interactions critical to replication of the influenza A virus. FEBS Lett 2016; 590:1940-54. [PMID: 26921878 DOI: 10.1002/1873-3468.12118] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 02/08/2016] [Accepted: 02/21/2016] [Indexed: 12/12/2022]
Abstract
Influenza A virus (IAV) assembles on the plasma membrane where viral proteins localize to form a bud encompassing the viral genome, which ultimately pinches off to give rise to newly formed infectious virions. Upon entry, the virus faces the opposite task-fusion with the endosomal membrane and disassembly to deliver the viral genome to the cytoplasm. There are at least four influenza proteins-hemagglutinin (HA), neuraminidase (NA), matrix 1 protein (M1), and the M2 ion channel-that are known to directly interact with the cellular membrane and modify membrane curvature in order to both assemble and disassemble membrane-enveloped virions. Here, we summarize and discuss current knowledge of the interactions of lipids and membrane proteins involved in the IAV replication cycle.
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Affiliation(s)
- Petr Chlanda
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Joshua Zimmerberg
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
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9
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PIP2Clustering: From model membranes to cells. Chem Phys Lipids 2015; 192:33-40. [DOI: 10.1016/j.chemphyslip.2015.07.021] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 07/26/2015] [Accepted: 07/27/2015] [Indexed: 11/23/2022]
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10
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Tazat K, Hector-Greene M, Blobe GC, Henis YI. TβRIII independently binds type I and type II TGF-β receptors to inhibit TGF-β signaling. Mol Biol Cell 2015; 26:3535-45. [PMID: 26269580 PMCID: PMC4591696 DOI: 10.1091/mbc.e15-04-0203] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 08/05/2015] [Indexed: 02/01/2023] Open
Abstract
Study of the TβRIII interaction with the signaling TGF-β receptors shows that TβRIII homo-oligomerization is indirect, depending largely on interactions with GIPC scaffolds. TβRI and II bind independently to TβRIII, competing with TβRI-TβRII complex formation and inhibiting Smad2/3 signaling by a mechanism independent of TβRIII ectodomain shedding. Transforming growth factor-β (TGF-β) receptor oligomerization has important roles in signaling. Complex formation among type I and type II (TβRI and TβRII) TGF-β receptors is well characterized and is essential for signal transduction. However, studies on their interactions with the type III TGF-β coreceptor (TβRIII) in live cells and their effects on TGF-β signaling are lacking. Here we investigated the homomeric and heteromeric interactions of TβRIII with TβRI and TβRII in live cells by combining IgG-mediated patching/immobilization of a given TGF-β receptor with fluorescence recovery after photobleaching studies on the lateral diffusion of a coexpressed receptor. Our studies demonstrate that TβRIII homo-oligomerization is indirect and depends on its cytoplasmic domain interactions with scaffold proteins (mainly GIPC). We show that TβRII and TβRI bind independently to TβRIII, whereas TβRIII augments TβRI/TβRII association, suggesting that TβRI and TβRII bind to TβRIII simultaneously but not as a complex. TβRIII expression inhibited TGF-β–mediated Smad2/3 signaling in MDA-MB-231 cell lines, an effect that depended on the TβRIII cytoplasmic domain and did not require TβRIII ectodomain shedding. We propose that independent binding of TβRI and TβRII to TβRIII competes with TβRI/TβRII signaling complex formation, thus inhibiting TGF-β–mediated Smad signaling.
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Affiliation(s)
- Keren Tazat
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | | | - Gerard C Blobe
- Department of Medicine, Duke University Medical Center, Durham, NC 27708 Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27708
| | - Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel )
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11
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Oxygen depletion speeds and simplifies diffusion in HeLa cells. Biophys J 2015; 107:1873-1884. [PMID: 25418168 DOI: 10.1016/j.bpj.2014.08.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 08/25/2014] [Accepted: 08/26/2014] [Indexed: 12/28/2022] Open
Abstract
Many cell types undergo a hypoxic response in the presence of low oxygen, which can lead to transcriptional, metabolic, and structural changes within the cell. Many biophysical studies to probe the localization and dynamics of single fluorescently labeled molecules in live cells either require or benefit from low-oxygen conditions. In this study, we examine how low-oxygen conditions alter the mobility of a series of plasma membrane proteins with a range of anchoring motifs in HeLa cells at 37°C. Under high-oxygen conditions, diffusion of all proteins is heterogeneous and confined. When oxygen is reduced with an enzymatic oxygen-scavenging system for ≥ 15 min, diffusion rates increase by > 2-fold, motion becomes unconfined on the timescales and distance scales investigated, and distributions of diffusion coefficients are remarkably consistent with those expected from Brownian motion. More subtle changes in protein mobility are observed in several other laboratory cell lines examined under both high- and low-oxygen conditions. Morphological changes and actin remodeling are observed in HeLa cells placed in a low-oxygen environment for 30 min, but changes are less apparent in the other cell types investigated. This suggests that changes in actin structure are responsible for increased diffusion in hypoxic HeLa cells, although superresolution localization measurements in chemically fixed cells indicate that membrane proteins do not colocalize with F-actin under either experimental condition. These studies emphasize the importance of controls in single-molecule imaging measurements, and indicate that acute response to low oxygen in HeLa cells leads to dramatic changes in plasma membrane structure. It is possible that these changes are either a cause or consequence of phenotypic changes in solid tumor cells associated with increased drug resistance and malignancy.
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12
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Reddy T, Shorthouse D, Parton DL, Jefferys E, Fowler PW, Chavent M, Baaden M, Sansom MSP. Nothing to sneeze at: a dynamic and integrative computational model of an influenza A virion. Structure 2015; 23:584-597. [PMID: 25703376 PMCID: PMC4353694 DOI: 10.1016/j.str.2014.12.019] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 12/09/2014] [Accepted: 12/17/2014] [Indexed: 11/28/2022]
Abstract
The influenza virus is surrounded by an envelope composed of a lipid bilayer and integral membrane proteins. Understanding the structural dynamics of the membrane envelope provides biophysical insights into aspects of viral function, such as the wide-ranging survival times of the virion in different environments. We have combined experimental data from X-ray crystallography, nuclear magnetic resonance spectroscopy, cryo-electron microscopy, and lipidomics to build a model of the intact influenza A virion. This is the basis of microsecond-scale coarse-grained molecular dynamics simulations of the virion, providing simulations at different temperatures and with varying lipid compositions. The presence of the Forssman glycolipid alters a number of biophysical properties of the virion, resulting in reduced mobility of bilayer lipid and protein species. Reduced mobility in the virion membrane may confer physical robustness to changes in environmental conditions. Our simulations indicate that viral spike proteins do not aggregate and thus are competent for multivalent immunoglobulin G interactions.
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Affiliation(s)
- Tyler Reddy
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - David Shorthouse
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Daniel L Parton
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Elizabeth Jefferys
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Philip W Fowler
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Matthieu Chavent
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Marc Baaden
- Institut de Biologie Physico-Chimique, Centre National de la Recherche Scientifique, UPR9080, Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
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13
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Fourrier M, Lester K, Thoen E, Mikalsen A, Evensen Ø, Falk K, Collet B, McBeath A. Deletions in the highly polymorphic region (HPR) of infectious salmon anaemia virus HPR0 haemagglutinin-esterase enhance viral fusion and influence the interaction with the fusion protein. J Gen Virol 2014; 95:1015-1024. [PMID: 24486627 DOI: 10.1099/vir.0.061648-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Since the discovery of a non-virulent infectious salmon anaemia virus (ISAV) HPR0 variant, many studies have speculated on the functional role of deletions within the highly polymorphic region (HPR) of genomic segment 6, which codes for the haemagglutinin-esterase (HE) protein. To address this issue, mutant HE proteins with deletions in their HPR were generated from the Scottish HPR0 template (NWM10) and fusion-inducing activity was measured using lipid (octadecyl rhodamine B) and content mixing assays (firefly luciferase). Segment six HPR was found to have a strong influence on ISAV fusion, and deletions in this near-membrane region predominantly increased the fusion-inducing ability of the resulting HE proteins. The position and length of the HPR deletions were not significant factors, suggesting that they may affect fusion non-specifically. In comparison, the amino acid composition of the associated fusion (F) protein was a more crucial criterion. Antibody co-patching and confocal fluorescence demonstrated that the HE and F proteins were highly co-localized, forming defined clusters on the cell surface post-transfection. The binding of erythrocyte ghosts on the attachment protein caused a reduction in the percentage of co-localization, suggesting that ISAV fusion might be triggered through physical separation of the F and HE proteins. In this process, HPR deletion appeared to modulate and reduce the strength of interaction between the two glycoproteins, causing more F protein to be released and activated. This work provides a first insight into the mechanism of virulence acquisition through HPR deletion, with fusion enhancement acting as a major contributing factor.
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Affiliation(s)
- Mickael Fourrier
- Marine Scotland Science, Marine Laboratory, 375 Victoria Road, Aberdeen AB11 9DB, UK
| | - Katherine Lester
- Marine Scotland Science, Marine Laboratory, 375 Victoria Road, Aberdeen AB11 9DB, UK
| | - Even Thoen
- Norwegian Veterinary Institute, Oslo, Norway
| | - Aase Mikalsen
- Norwegian School of Veterinary Science, Oslo, Norway
| | | | - Knut Falk
- Norwegian Veterinary Institute, Oslo, Norway
| | - Bertrand Collet
- Marine Scotland Science, Marine Laboratory, 375 Victoria Road, Aberdeen AB11 9DB, UK
| | - Alastair McBeath
- Marine Scotland Science, Marine Laboratory, 375 Victoria Road, Aberdeen AB11 9DB, UK
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14
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Gottlieb-Abraham E, Shvartsman DE, Donaldson JC, Ehrlich M, Gutman O, Martin GS, Henis YI. Src-mediated caveolin-1 phosphorylation affects the targeting of active Src to specific membrane sites. Mol Biol Cell 2013; 24:3881-95. [PMID: 24131997 PMCID: PMC3861084 DOI: 10.1091/mbc.e13-03-0163] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 10/07/2013] [Accepted: 10/08/2013] [Indexed: 01/29/2023] Open
Abstract
Src interactions with the plasma membrane are an important determinant of its activity. In turn, Src activity modulates its association with the membrane through binding of activated Src to phosphotyrosylated proteins. Caveolin-1 (Cav-1), a major component of caveolae, is a known Src phosphorylation target, and both were reported to regulate cell transformation. However, the nature of Src-Cav-1 interactions, a potential mechanism of their coregulation, remained unclear. Here we used fluorescence recovery after photobleaching beam-size analysis, coimmunoprecipitation, quantitative imaging, and far-Western studies with cells expressing wild type, as well as structural and activity mutants of Src-green fluorescent protein and Cav-1-monomeric red fluorescent protein, to measure their interactions with the membrane and with each other. We show dynamic Src-plasma membrane interactions, which are augmented and stabilized by Cav-1. The mechanism involves phosphorylation of Cav-1 at Tyr-14 by Src and subsequent binding of the Src SH2 domain to phospho-Cav-1, leading to accumulation of activated Src in focal adhesions. This novel Cav-1 function potentially modulates focal adhesion dynamics.
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Affiliation(s)
- Efrat Gottlieb-Abraham
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Dmitry E. Shvartsman
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - John C. Donaldson
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Marcelo Ehrlich
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Orit Gutman
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - G. Steven Martin
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720
| | - Yoav I. Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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15
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Formation of raft-like assemblies within clusters of influenza hemagglutinin observed by MD simulations. PLoS Comput Biol 2013; 9:e1003034. [PMID: 23592976 PMCID: PMC3623702 DOI: 10.1371/journal.pcbi.1003034] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 03/03/2013] [Indexed: 11/19/2022] Open
Abstract
The association of hemagglutinin (HA) with lipid rafts in the plasma membrane is an important feature of the assembly process of influenza virus A. Lipid rafts are thought to be small, fluctuating patches of membrane enriched in saturated phospholipids, sphingolipids, cholesterol and certain types of protein. However, raft-associating transmembrane (TM) proteins generally partition into Ld domains in model membranes, which are enriched in unsaturated lipids and depleted in saturated lipids and cholesterol. The reason for this apparent disparity in behavior is unclear, but model membranes differ from the plasma membrane in a number of ways. In particular, the higher protein concentration in the plasma membrane may influence the partitioning of membrane proteins for rafts. To investigate the effect of high local protein concentration, we have conducted coarse-grained molecular dynamics (CG MD) simulations of HA clusters in domain-forming bilayers. During the simulations, we observed a continuous increase in the proportion of raft-type lipids (saturated phospholipids and cholesterol) within the area of membrane spanned by the protein cluster. Lateral diffusion of unsaturated lipids was significantly attenuated within the cluster, while saturated lipids were relatively unaffected. On this basis, we suggest a possible explanation for the change in lipid distribution, namely that steric crowding by the slow-diffusing proteins increases the chemical potential for unsaturated lipids within the cluster region. We therefore suggest that a local aggregation of HA can be sufficient to drive association of the protein with raft-type lipids. This may also represent a general mechanism for the targeting of TM proteins to rafts in the plasma membrane, which is of functional importance in a wide range of cellular processes. The cell membrane is composed of a wide variety of lipids and proteins. Until recently, these were thought to be mixed evenly, but we now have evidence of the existence of “lipid rafts” — small, slow-moving areas of membrane in which certain types of lipid and protein accumulate. Rafts have many important biological functions in healthy cells, but also play a role in the assembly of influenza virus. For example, after the viral protein hemagglutinin is made inside the host cell, it accumulates in rafts. Exiting virus particles then take these portions of cell membrane with them as they leave the host cell. However, the mechanism by which proteins associate with lipid rafts is unclear. Here, we have used computers to simulate lipid membranes containing hemagglutinin. The simulations allow us to look in detail at the motions and interactions of individual proteins and lipids. We found that clusters of proteins altered the properties of nearby lipids, leading to accumulation of raft-type lipids. It therefore appears that aggregation of hemagglutinin may be enough to drive its association with rafts. This helps us to better understand both the influenza assembly process and the properties of lipid rafts.
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16
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Veit M, Engel S, Thaa B, Scolari S, Herrmann A. Lipid domain association of influenza virus proteins detected by dynamic fluorescence microscopy techniques. Cell Microbiol 2012; 15:179-89. [PMID: 23057766 DOI: 10.1111/cmi.12045] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 09/16/2012] [Accepted: 09/17/2012] [Indexed: 01/31/2023]
Abstract
Influenza virus is thought to assemble in raft domains of the plasma membrane, but many of the conclusions were based on (controversial) Triton extraction experiments. Here we review how sophisticated methods of fluorescence microscopy, such as FPALM, FRET and FRAP, contributed to our understanding of lipid domain association of the viral proteins HA and M2. The results are summarized in light of the current model for virus assembly and lipid domain organization. Finally, it is described how the signals that govern domain association in transfected cells affect replication of influenza virus.
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Affiliation(s)
- Michael Veit
- Institute of Immunology, Free University Berlin, Philippstr. 13, 10115 Berlin, Germany.
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17
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Schaap IAT, Eghiaian F, des Georges A, Veigel C. Effect of envelope proteins on the mechanical properties of influenza virus. J Biol Chem 2012; 287:41078-88. [PMID: 23048030 DOI: 10.1074/jbc.m112.412726] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The envelope of the influenza virus undergoes extensive structural change during the viral life cycle. However, it is unknown how lipid and protein components of the viral envelope contribute to its mechanical properties. Using atomic force microscopy, here we show that the lipid envelope of spherical influenza virions is ∼10 times softer (∼0.05 nanonewton nm(-1)) than a viral protein-capsid coat and sustains deformations of one-third of the virion's diameter. Compared with phosphatidylcholine liposomes, it is twice as stiff, due to membrane-attached protein components. We found that virus indentation resulted in a biphasic force-indentation response. We propose that the first phase, including a stepwise reduction in stiffness at ∼10-nm indentation and ∼100 piconewtons of force, is due to mobilization of membrane proteins by the indenting atomic force microscope tip, consistent with the glycoprotein ectodomains protruding ∼13 nm from the bilayer surface. This phase was obliterated for bromelain-treated virions with the ectodomains removed. Following pH 5 treatment, virions were as soft as pure liposomes, consistent with reinforcing proteins detaching from the lipid bilayer. We propose that the soft, pH-dependent mechanical properties of the envelope are critical for the pH-regulated life cycle and support the persistence of the virus inside and outside the host.
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Affiliation(s)
- Iwan A T Schaap
- National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom
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18
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Gulati V, Wallace R. Rafts, Nanoparticles and Neural Disease. NANOMATERIALS (BASEL, SWITZERLAND) 2012; 2:217-250. [PMID: 28348305 PMCID: PMC5304588 DOI: 10.3390/nano2030217] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Revised: 07/19/2012] [Accepted: 07/20/2012] [Indexed: 11/17/2022]
Abstract
This review examines the role of membrane rafts in neural disease as a rationale for drug targeting utilizing lipid-based nanoparticles. The article begins with an overview of methodological issues involving the existence, sizes, and lifetimes of rafts, and then examines raft function in the etiologies of three major neural diseases-epilepsy, Parkinson's disease, and Alzheimer's disease-selected as promising candidates for raft-based therapeutics. Raft-targeting drug delivery systems involving liposomes and solid lipid nanoparticles are then examined in detail.
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Affiliation(s)
- Vishal Gulati
- Ross University School of Medicine, Miami Beach Community Health Center, 11645 Biscayne Boulevard, North Miami, FL 33181, USA.
| | - Ron Wallace
- Department of Anthropology, University of Central Florida, Orlando, FL 32816, USA.
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19
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Hogue IB, Llewellyn GN, Ono A. Dynamic Association between HIV-1 Gag and Membrane Domains. Mol Biol Int 2012; 2012:979765. [PMID: 22830021 PMCID: PMC3399408 DOI: 10.1155/2012/979765] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2012] [Accepted: 06/01/2012] [Indexed: 12/18/2022] Open
Abstract
HIV-1 particle assembly is driven by the structural protein Gag. Gag binds to and multimerizes on the inner leaflet of the plasma membrane, eventually resulting in formation of spherical particles. During virus spread among T cells, Gag accumulates to the plasma membrane domain that, together with target cell membrane, forms a cell junction known as the virological synapse. While Gag association with plasma membrane microdomains has been implicated in virus assembly and cell-to-cell transmission, recent studies suggest that, rather than merely accumulating to pre-existing microdomains, Gag plays an active role in reorganizing the microdomains via its multimerization activity. In this paper, we will discuss this emerging view of Gag microdomain interactions. Relationships between Gag multimerization and microdomain association will be further discussed in the context of Gag localization to T-cell uropods and virological synapses.
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Affiliation(s)
- Ian B. Hogue
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - G. Nicholas Llewellyn
- Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Molecular Microbiology and Immunology, University of Southern California, Los Angeles, CA 90033, USA
| | - Akira Ono
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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20
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Soula HA, Coulon A, Beslon G. Membrane microdomains emergence through non-homogeneous diffusion. BMC BIOPHYSICS 2012; 5:6. [PMID: 22546236 PMCID: PMC3528627 DOI: 10.1186/2046-1682-5-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Accepted: 02/29/2012] [Indexed: 11/16/2022]
Abstract
Background In the classical view, cell membrane proteins undergo isotropic random motion, that is a 2D Brownian diffusion that should result in an homogeneous distribution of concentration. It is, however, far from the reality: Membrane proteins can assemble into so-called microdomains (sometimes called lipid rafts) which also display a specific lipid composition. We propose a simple mechanism that is able to explain the colocalization of protein and lipid rafts. Results Using very simple mathematical models and particle simulations, we show that a variation of membrane viscosity directly leads to variation of the local concentration of diffusive particles. Since specific lipid phases in the membrane can account for diffusion variation, we show that, in such a situation, the freely diffusing proteins (or any other component) still undergo a Brownian motion but concentrate in areas of lower diffusion. The amount of this so-called overconcentration at equilibrium issimply related to the ratio of diffusion coefficients between zones of high and low diffusion. Expanding the model to include particle interaction, we show that inhomogeneous diffusion can impact particles clusterization as well. The clusters of particles were more numerous and appear for a lower value of interaction strength in the zones of low diffusion compared to zones of high diffusion. Conclusion Provided we assume stable viscosity heterogeneity in the membrane, our model propose a simple mechanism to explain particle concentration heterogeneity. It has also a non-trivial impact on density of particles when interaction is added. This could potentially have an impact on membrane chemical reactions and oligomerization.
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Affiliation(s)
- Hédi A Soula
- Université de Lyon Inserm UMR1060, F-69621, Villeurbanne Cédex, France.
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21
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Abstract
The polarized distribution of proteins and lipids at the surface membrane of epithelial cells results in the formation of an apical and a basolateral domain, which are separated by tight junctions. The generation and maintenance of epithelial polarity require elaborate mechanisms that guarantee correct sorting and vectorial delivery of cargo molecules. This dynamic process involves the interaction of sorting signals with sorting machineries and the formation of transport carriers. Here we review the recent advances in the field of polarized sorting in epithelial cells. We especially highlight the role of lipid rafts in apical sorting.
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22
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Mechanisms underlying the confined diffusion of cholera toxin B-subunit in intact cell membranes. PLoS One 2012; 7:e34923. [PMID: 22511973 PMCID: PMC3325267 DOI: 10.1371/journal.pone.0034923] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2011] [Accepted: 03/10/2012] [Indexed: 11/19/2022] Open
Abstract
Multivalent glycolipid binding toxins such as cholera toxin have the capacity to cluster glycolipids, a process thought to be important for their functional uptake into cells. In contrast to the highly dynamic properties of lipid probes and many lipid-anchored proteins, the B-subunit of cholera toxin (CTxB) diffuses extremely slowly when bound to its glycolipid receptor GM(1) in the plasma membrane of living cells. In the current study, we used confocal FRAP to examine the origins of this slow diffusion of the CTxB/GM(1) complex at the cell surface, relative to the behavior of a representative GPI-anchored protein, transmembrane protein, and fluorescent lipid analog. We show that the diffusion of CTxB is impeded by actin- and ATP-dependent processes, but is unaffected by caveolae. At physiological temperature, the diffusion of several cell surface markers is unchanged in the presence of CTxB, suggesting that binding of CTxB to membranes does not alter the organization of the plasma membrane in a way that influences the diffusion of other molecules. Furthermore, diffusion of the B-subunit of another glycolipid-binding toxin, Shiga toxin, is significantly faster than that of CTxB, indicating that the confined diffusion of CTxB is not a simple function of its ability to cluster glycolipids. By identifying underlying mechanisms that control CTxB dynamics at the cell surface, these findings help to delineate the fundamental properties of toxin-receptor complexes in intact cell membranes.
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23
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Marquer C, Lévêque-Fort S, Potier MC. Determination of lipid raft partitioning of fluorescently-tagged probes in living cells by Fluorescence Correlation Spectroscopy (FCS). J Vis Exp 2012:e3513. [PMID: 22508446 DOI: 10.3791/3513] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
In the past fifteen years the notion that cell membranes are not homogenous and rely on microdomains to exert their functions has become widely accepted. Lipid rafts are membrane microdomains enriched in cholesterol and sphingolipids. They play a role in cellular physiological processes such as signalling, and trafficking but are also thought to be key players in several diseases including viral or bacterial infections and neurodegenerative diseases. Yet their existence is still a matter of controversy. Indeed, lipid raft size has been estimated to be around 20 nm, far under the resolution limit of conventional microscopy (around 200 nm), thus precluding their direct imaging. Up to now, the main techniques used to assess the partition of proteins of interest inside lipid rafts were Detergent Resistant Membranes (DRMs) isolation and co-patching with antibodies. Though widely used because of their rather easy implementation, these techniques were prone to artefacts and thus criticized. Technical improvements were therefore necessary to overcome these artefacts and to be able to probe lipid rafts partition in living cells. Here we present a method for the sensitive analysis of lipid rafts partition of fluorescently-tagged proteins or lipids in the plasma membrane of living cells. This method, termed Fluorescence Correlation Spectroscopy (FCS), relies on the disparity in diffusion times of fluorescent probes located inside or outside of lipid rafts. In fact, as evidenced in both artificial membranes and cell cultures, probes would diffuse much faster outside than inside dense lipid rafts. To determine diffusion times, minute fluorescence fluctuations are measured as a function of time in a focal volume (approximately 1 femtoliter), located at the plasma membrane of cells with a confocal microscope (Fig. 1). The auto-correlation curves can then be drawn from these fluctuations and fitted with appropriate mathematical diffusion models. FCS can be used to determine the lipid raft partitioning of various probes, as long as they are fluorescently tagged. Fluorescent tagging can be achieved by expression of fluorescent fusion proteins or by binding of fluorescent ligands. Moreover, FCS can be used not only in artificial membranes and cell lines but also in primary cultures, as described recently. It can also be used to follow the dynamics of lipid raft partitioning after drug addition or membrane lipid composition change.
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Affiliation(s)
- Catherine Marquer
- Centre de Recherche de l'Institut du Cerveau et de la Moelle Épinière, Hôpital de la Pitié-Salpêtrière.
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24
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Suzuki KGN. Lipid rafts generate digital-like signal transduction in cell plasma membranes. Biotechnol J 2012; 7:753-61. [PMID: 22488962 DOI: 10.1002/biot.201100360] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 02/13/2012] [Accepted: 02/24/2012] [Indexed: 11/10/2022]
Abstract
Lipid rafts are meso-scale (5-200 nm) cell membrane domains where signaling molecules assemble and function. However, due to their dynamic nature, it has been difficult to unravel the mechanism of signal transduction in lipid rafts. Recent advanced imaging techniques have revealed that signaling molecules are frequently, but transiently, recruited to rafts with the aid of protein-protein, protein-lipid, and/or lipid-lipid interactions. Individual signaling molecules within the raft are activated only for a short period of time. Immobilization of signaling molecules by cytoskeletal actin filaments and scaffold proteins may facilitate more efficient signal transmission from rafts. In this review, current opinions of how the transient nature of molecular interactions in rafts generates digital-like signal transduction in cell membranes, and the benefits this phenomenon provides, are discussed.
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Affiliation(s)
- Kenichi G N Suzuki
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto, Japan.
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25
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Caveolin 3, flotillin 1 and influenza virus hemagglutinin reside in distinct domains on the sarcolemma of skeletal myofibers. Biochem Res Int 2012; 2012:497572. [PMID: 22500232 PMCID: PMC3303869 DOI: 10.1155/2012/497572] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Revised: 10/14/2011] [Accepted: 10/21/2011] [Indexed: 11/17/2022] Open
Abstract
We examined the distribution of selected raft proteins on the sarcolemma of skeletal myofibers and the role of cholesterol environment in the distribution. Immunofluorescence staining showed that flotillin-1 and influenza hemagglutinin exhibited rafts that located in the domains deficient of the dystrophin glycoprotein complex, but the distribution patterns of the two proteins were different. Cholesterol depletion from the sarcolemma by means of methyl-β-cyclodextrin resulted in distorted caveolar morphology and redistribution of the caveolin 3 protein. Concomitantly, the water permeability of the sarcolemma increased significantly. However, cholesterol depletion did not reshuffle flotillin 1 or hemagglutinin. Furthermore, a hemagglutinin variant that lacked a raft-targeting signals exhibited a similar distribution pattern as the native raft protein. These findings indicate that each raft protein exhibits a strictly defined distribution in the sarcolemma. Only the distribution of caveolin 3 that binds cholesterol was exclusively dependent on cholesterol environment.
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26
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Gerl MJ, Sampaio JL, Urban S, Kalvodova L, Verbavatz JM, Binnington B, Lindemann D, Lingwood CA, Shevchenko A, Schroeder C, Simons K. Quantitative analysis of the lipidomes of the influenza virus envelope and MDCK cell apical membrane. ACTA ACUST UNITED AC 2012; 196:213-21. [PMID: 22249292 PMCID: PMC3265945 DOI: 10.1083/jcb.201108175] [Citation(s) in RCA: 214] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Analysis of the lipid composition of influenza virus–infected cells provides support for the membrane raft-based biogenesis model. The influenza virus (IFV) acquires its envelope by budding from host cell plasma membranes. Using quantitative shotgun mass spectrometry, we determined the lipidomes of the host Madin–Darby canine kidney cell, its apical membrane, and the IFV budding from it. We found the apical membrane to be enriched in sphingolipids (SPs) and cholesterol, whereas glycerophospholipids were reduced, and storage lipids were depleted compared with the whole-cell membranes. The virus membrane exhibited a further enrichment of SPs and cholesterol compared with the donor membrane at the expense of phosphatidylcholines. Our data are consistent with and extend existing models of membrane raft-based biogenesis of the apical membrane and IFV envelope.
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Affiliation(s)
- Mathias J Gerl
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
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27
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Itano MS, Neumann AK, Liu P, Zhang F, Gratton E, Parak WJ, Thompson NL, Jacobson K. DC-SIGN and influenza hemagglutinin dynamics in plasma membrane microdomains are markedly different. Biophys J 2011; 100:2662-70. [PMID: 21641311 DOI: 10.1016/j.bpj.2011.04.044] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Revised: 04/11/2011] [Accepted: 04/14/2011] [Indexed: 11/24/2022] Open
Abstract
DC-SIGN, a Ca(2+)-dependent transmembrane lectin, is found assembled in microdomains on the plasma membranes of dendritic cells. These microdomains bind a large variety of pathogens and facilitate their uptake for subsequent antigen presentation. In this study, DC-SIGN dynamics in microdomains were explored with several fluorescence microscopy methods and compared with dynamics for influenza hemagglutinin (HA), which is also found in plasma membrane microdomains. Fluorescence imaging indicated that DC-SIGN microdomains may contain other C-type lectins and that the DC-SIGN cytoplasmic region is not required for microdomain formation. Fluorescence recovery after photobleaching measurements showed that neither full-length nor cytoplasmically truncated DC-SIGN in microdomains appreciably exchanged with like molecules in other microdomains and the membrane surround, whereas HA in microdomains exchanged almost completely. Line-scan fluorescence correlation spectroscopy indicated an essentially undetectable lateral mobility for DC-SIGN but an appreciable mobility for HA within their respective domains. Single-particle tracking with defined-valency quantum dots confirmed that HA has significant mobility within microdomains, whereas DC-SIGN does not. By contrast, fluorescence recovery after photobleaching indicated that inner leaflet lipids are able to move through DC-SIGN microdomains. The surprising stability of DC-SIGN microdomains may reflect structural features that enhance pathogen uptake either by providing high-avidity platforms and/or by protecting against rapid microdomain endocytosis.
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Affiliation(s)
- Michelle S Itano
- Department of Cell and Developmental Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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28
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Gag induces the coalescence of clustered lipid rafts and tetraspanin-enriched microdomains at HIV-1 assembly sites on the plasma membrane. J Virol 2011; 85:9749-66. [PMID: 21813604 DOI: 10.1128/jvi.00743-11] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The HIV-1 structural protein Gag associates with two types of plasma membrane microdomains, lipid rafts and tetraspanin-enriched microdomains (TEMs), both of which have been proposed to be platforms for HIV-1 assembly. However, a variety of studies have demonstrated that lipid rafts and TEMs are distinct microdomains in the absence of HIV-1 infection. To measure the impact of Gag on microdomain behaviors, we took advantage of two assays: an antibody-mediated copatching assay and a Förster resonance energy transfer (FRET) assay that measures the clustering of microdomain markers in live cells without antibody-mediated patching. We found that lipid rafts and TEMs copatched and clustered to a greater extent in the presence of membrane-bound Gag in both assays, suggesting that Gag induces the coalescence of lipid rafts and TEMs. Substitutions in membrane binding motifs of Gag revealed that, while Gag membrane binding is necessary to induce coalescence of lipid rafts and TEMs, either acylation of Gag or binding of phosphatidylinositol-(4,5)-bisphosphate is sufficient. Finally, a Gag derivative that is defective in inducing membrane curvature appeared less able to induce lipid raft and TEM coalescence. A higher-resolution analysis of assembly sites by correlative fluorescence and scanning electron microscopy showed that coalescence of clustered lipid rafts and TEMs occurs predominantly at completed cell surface virus-like particles, whereas a transmembrane raft marker protein appeared to associate with punctate Gag fluorescence even in the absence of cell surface particles. Together, these results suggest that different membrane microdomain components are recruited in a stepwise manner during assembly.
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29
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Raft protein clustering alters N-Ras membrane interactions and activation pattern. Mol Cell Biol 2011; 31:3938-52. [PMID: 21807892 DOI: 10.1128/mcb.05570-11] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The trafficking, membrane localization, and lipid raft association of Ras proteins, which are crucial oncogenic mediators, dictate their isoform-specific biological responses. Accordingly, their spatiotemporal dynamics are tightly regulated. While extensively studied for H- and K-Ras, such information on N-Ras, an etiological oncogenic factor, is limited. Here, we report a novel mechanism regulating the activation-dependent spatiotemporal organization of N-Ras, its modulation by biologically relevant stimuli, and isoform-specific effects on signaling. We combined patching/immobilization of another membrane protein with fluorescence recovery after photobleaching (patch-FRAP) and FRAP beam size analysis to investigate N-Ras membrane interactions. Clustering of raft-associated proteins, either glycosylphosphatidylinositol-anchored influenza virus hemagglutinin (HA-GPI) or fibronectin receptors, selectively enhanced the plasma membrane-cytoplasm exchange of N-Ras-GTP (preferentially associated with raft domains) in a cholesterol-dependent manner. Electron microscopy (EM) analysis showed N-Ras-GTP localization in cholesterol-sensitive clusters, from which it preferentially detached upon HA-GPI cross-linking. HA-GPI clustering enhanced the Golgi compartment (GC) accumulation and signaling of epidermal growth factor (EGF)-stimulated N-Ras-GTP. Notably, the cross-linking-mediated enhancement of N-Ras-GTP exchange and GC accumulation depended strictly on depalmitoylation. We propose that the N-Ras activation pattern (e.g., by EGF) is altered by raft protein clustering, which enhances N-Ras-GTP raft localization and depalmitoylation, entailing its exchange and GC accumulation following repalmitoylation. This mechanism demonstrates a functional signaling role for the activation-dependent differential association of Ras isoforms with raft nanodomains.
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30
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Association of influenza virus proteins with membrane rafts. Adv Virol 2011; 2011:370606. [PMID: 22312341 PMCID: PMC3265303 DOI: 10.1155/2011/370606] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Accepted: 05/02/2011] [Indexed: 12/12/2022] Open
Abstract
Assembly and budding of influenza virus proceeds in the viral budozone, a domain in the plasma membrane with characteristics of cholesterol/sphingolipid-rich membrane rafts. The viral transmembrane glycoproteins hemagglutinin (HA) and neuraminidase (NA) are intrinsically targeted to these domains, while M2 is seemingly targeted to the edge of the budozone. Virus assembly is orchestrated by the matrix protein M1, binding to all viral components and the membrane. Budding progresses by protein- and lipid-mediated membrane bending and particle scission probably mediated by M2. Here, we summarize the experimental evidence for this model with emphasis on the raft-targeting features of HA, NA, and M2 and review the functional importance of raft domains for viral protein transport, assembly and budding, environmental stability, and membrane fusion.
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31
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LaRocca TJ, Crowley JT, Cusack BJ, Pathak P, Benach J, London E, Garcia-Monco JC, Benach JL. Cholesterol lipids of Borrelia burgdorferi form lipid rafts and are required for the bactericidal activity of a complement-independent antibody. Cell Host Microbe 2011; 8:331-42. [PMID: 20951967 DOI: 10.1016/j.chom.2010.09.001] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Revised: 07/20/2010] [Accepted: 09/01/2010] [Indexed: 10/18/2022]
Abstract
Borrelia burgdorferi, the agent of Lyme disease, is unusual as it contains free cholesterol and cholesterol glycolipids. It is also susceptible to complement-independent bactericidal antibodies, such as CB2, a monoclonal IgG1 against outer surface protein B (OspB). We find that the bactericidal action of CB2 requires the presence of cholesterol glycolipids and cholesterol. Ultrastructural, biochemical, and biophysical analysis revealed that the bacterial cholesterol glycolipids exist as lipid raft-like microdomains in the outer membrane of cultured and mouse-derived B. burgdorferi and in model membranes from B. burgdorferi lipids. The order and size of the microdomains are temperature sensitive and correlate with the bactericidal activity of CB2. This study demonstrates the existence of cholesterol-containing lipid raft-like microdomains in a prokaryote, and we suggest that the temperature dependence of B. burgdorferi lipid raft organization may have significant implications in the transmission cycle of the spirochetes which are exposed to a range of temperatures.
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Affiliation(s)
- Timothy J LaRocca
- Department of Molecular Genetics and Microbiology, and Center for Infectious Diseases, Stony Brook University, Stony Brook, NY 11794, USA
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Llewellyn GN, Hogue IB, Grover JR, Ono A. Nucleocapsid promotes localization of HIV-1 gag to uropods that participate in virological synapses between T cells. PLoS Pathog 2010; 6:e1001167. [PMID: 21060818 PMCID: PMC2965768 DOI: 10.1371/journal.ppat.1001167] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2010] [Accepted: 09/28/2010] [Indexed: 12/20/2022] Open
Abstract
T cells adopt a polarized morphology in lymphoid organs, where cell-to-cell transmission of HIV-1 is likely frequent. However, despite the importance of understanding virus spread in vivo, little is known about the HIV-1 life cycle, particularly its late phase, in polarized T cells. Polarized T cells form two ends, the leading edge at the front and a protrusion called a uropod at the rear. Using multiple uropod markers, we observed that HIV-1 Gag localizes to the uropod in polarized T cells. Infected T cells formed contacts with uninfected target T cells preferentially via HIV-1 Gag-containing uropods compared to leading edges that lack plasma-membrane-associated Gag. Cell contacts enriched in Gag and CD4, which define the virological synapse (VS), are also enriched in uropod markers. These results indicate that Gag-laden uropods participate in the formation and/or structure of the VS, which likely plays a key role in cell-to-cell transmission of HIV-1. Consistent with this notion, a myosin light chain kinase inhibitor, which disrupts uropods, reduced virus particle transfer from infected T cells to target T cells. Mechanistically, we observed that Gag copatches with antibody-crosslinked uropod markers even in non-polarized cells, suggesting an association of Gag with uropod-specific microdomains that carry Gag to uropods. Finally, we determined that localization of Gag to the uropod depends on higher-order clustering driven by its NC domain. Taken together, these results support a model in which NC-dependent Gag accumulation to uropods establishes a preformed platform that later constitutes T-cell-T-cell contacts at which HIV-1 virus transfer occurs. CD4+ T cells are natural targets of HIV-1. Efficient spread of HIV-1 from infected T cells to uninfected T cells is thought to occur via cell-cell contact structures. One of these structures is a virological synapse where both viral and cellular proteins have been shown to localize specifically. However, the steps leading to the formation of a virological synapse remain unknown. It has been observed that T cells adopt a polarized morphology in lymph nodes where cell-to-cell virus transmission is likely to occur frequently. In this study, we show that in polarized T cells, the primary viral structural protein Gag accumulates to the plasma membrane of a rear end structure called a uropod. We found that Gag multimerization, driven by its nucleocapsid domain, is essential for Gag localization to uropods and that HIV-1-laden uropods mediate contact with target cells and can become part of the virological synapse. Our findings elucidated a series of molecular events leading to formation of HIV-1-transferring cell contacts and support a model in which the uropod acts as a preformed platform that constitutes a virological synapse after cell-cell contact.
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Affiliation(s)
- G. Nicholas Llewellyn
- Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Ian B. Hogue
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Jonathan R. Grover
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Akira Ono
- Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
- * E-mail:
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Heterogeneous diffusion of a membrane-bound pHLIP peptide. Biophys J 2010; 98:2914-22. [PMID: 20550904 DOI: 10.1016/j.bpj.2010.03.050] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Revised: 02/24/2010] [Accepted: 03/19/2010] [Indexed: 11/20/2022] Open
Abstract
Lateral diffusion of cell membrane constituents is a prerequisite for many biological functions. However, the diffusivity (or mobility) of a membrane-bound species can be influenced by many factors. To provide a better understanding of how the conformation and location of a membrane-bound biological molecule affect its mobility, herein we study the diffusion properties of a pH low insertion peptide (pHLIP) in model membranes using fluorescence correlation spectroscopy. It is found that when the pHLIP peptide is located on the membrane surface, its lateral diffusion is characterized by a distribution of diffusion times, the characteristic of which depends on the peptide/lipid ratio. Whereas, under conditions where pHLIP adopts a well-defined transmembrane alpha-helical conformation the peptide still exhibits heterogeneous diffusion, the distribution of diffusion times is found to be independent of the peptide/lipid ratio. Taken together, these results indicate that the mobility of a membrane-bound species is sensitive to its conformation and location and that diffusion measurement could provide useful information regarding the conformational distribution of membrane-bound peptides. Furthermore, the observation that the mobility of a membrane-bound species depends on its concentration may have important implications for diffusion-controlled reactions taking place in membranes.
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Abstract
Advances in cell biology and biophysics revealed that cellular membranes consist of multiple microdomains with specific sets of components such as lipid rafts and TEMs (tetraspanin-enriched microdomains). An increasing number of enveloped viruses have been shown to utilize these microdomains during their assembly. Among them, association of HIV-1 (HIV type 1) and other retroviruses with lipid rafts and TEMs within the PM (plasma membrane) is well documented. In this review, I describe our current knowledge on interrelationships between PM microdomain organization and the HIV-1 particle assembly process. Microdomain association during virus particle assembly may also modulate subsequent virus spread. Potential roles played by microdomains will be discussed with regard to two post-assembly events, i.e., inhibition of virus release by a raft-associated protein BST-2/tetherin and cell-to-cell HIV-1 transmission at virological synapses.
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Chan RB, Tanner L, Wenk MR. Implications for lipids during replication of enveloped viruses. Chem Phys Lipids 2010; 163:449-59. [PMID: 20230810 PMCID: PMC7124286 DOI: 10.1016/j.chemphyslip.2010.03.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2009] [Accepted: 03/08/2010] [Indexed: 01/27/2023]
Abstract
Enveloped viruses, which include many medically important viruses such as human immunodeficiency virus, influenza virus and hepatitis C virus, are intracellular parasites that acquire lipid envelopes from their host cells. Success of replication is intimately linked to their ability to hijack host cell mechanisms, particularly those related to membrane dynamics and lipid metabolism. Despite recent progress, our knowledge of lipid mediated virus-host interactions remains highly incomplete. In addition, diverse experimental systems are used to study different stages of virus replication thus complicating comparisons. This review aims to present a unifying view of the widely diverse strategies used by enveloped viruses at distinct stages of their replication cycles.
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Affiliation(s)
- Robin B Chan
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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36
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FLIM-FRET and FRAP reveal association of influenza virus haemagglutinin with membrane rafts. Biochem J 2010; 425:567-73. [DOI: 10.1042/bj20091388] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
It has been supposed that the HA (haemagglutinin) of influenza virus must be recruited to membrane rafts to perform its function in membrane fusion and virus budding. In the present study, we aimed at substantiating this association in living cells by biophysical methods. To this end, we fused the cyan fluorescent protein Cer (Cerulean) to the cytoplasmic tail of HA. Upon expression in CHO (Chinese-hamster ovary) cells HA–Cer was glycosylated and transported to the plasma membrane in a similar manner to authentic HA. We measured FLIM-FRET (Förster resonance energy transfer by fluorescence lifetime imaging microscopy) and showed strong association of HA–Cer with Myr-Pal–YFP (myristoylated and palmitoylated peptide fused to yellow fluorescent protein), an established marker for rafts of the inner leaflet of the plasma membrane. Clustering was significantly reduced when rafts were disintegrated by cholesterol extraction and when the known raft-targeting signals of HA, the palmitoylation sites and amino acids in its transmembrane region, were removed. FRAP (fluorescence recovery after photobleaching) showed that removal of raft-targeting signals moderately increased the mobility of HA in the plasma membrane, indicating that the signals influence access of HA to slowly diffusing rafts. However, Myr-Pal–YFP exhibited a much faster mobility compared with HA–Cer, demonstrating that HA and the raft marker do not diffuse together in a stable raft complex for long periods of time.
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Baier CJ, Gallegos CE, Levi V, Barrantes FJ. Cholesterol modulation of nicotinic acetylcholine receptor surface mobility. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:213-27. [PMID: 19641915 DOI: 10.1007/s00249-009-0521-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2009] [Accepted: 07/06/2009] [Indexed: 12/26/2022]
Abstract
Nicotinic acetylcholine receptor (AChR) function and distribution are quite sensitive to cholesterol (Chol) levels in the plasma membrane (reviewed by Barrantes in J Neurochem 103 (suppl 1):72-80, 2007). Here we combined confocal fluorescence recovery after photobleaching (FRAP) and confocal fluorescence correlation spectroscopy (FCS) to examine the mobility of the AChR and its dependence on Chol content at the cell surface of a mammalian cell line. Plasma membrane AChR exhibited limited mobility and only ~55% of the fluorescence was recovered within 10 min after photobleaching. Depletion of membrane Chol by methyl-beta-cyclodextrin strongly affected the mobility of the AChR at the plasma membrane; the fraction of mobile AChR fell from 55 to 20% in Chol-depleted cells, whereas Chol enrichment by methyl-beta-cyclodextrin-Chol treatment did not reduce receptor mobility at the cell surface. Actin depolymerization caused by latrunculin A partially restored receptor mobility in Chol-depleted cells. In agreement with the FRAP data, scanning FCS experiments showed that the diffusion coefficient of the AChR was about 30% lower upon Chol depletion. Taken together, these results suggest that membrane Chol modulates AChR mobility at the plasma membrane through a Chol-dependent mechanism sensitive to cortical actin.
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Affiliation(s)
- Carlos J Baier
- UNESCO Chair of Biophysics and Molecular Neurobiology, Instituto de Investigaciones Bioquímicas de Bahía Blanca, C.C. 857, B8000FWB, Bahía Blanca, Argentina
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Denard J, Rundwasser S, Laroudie N, Gonnet F, Naldini L, Radrizzani M, Galy A, Merten OW, Danos O, Svinartchouk F. Quantitative proteomic analysis of lentiviral vectors using 2-DE. Proteomics 2009; 9:3666-76. [DOI: 10.1002/pmic.200800747] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Kalipatnapu S, Chattopadhyay A. Membrane organization of the human serotonin1Areceptor monitored by detergent insolubility using GFP fluorescence. Mol Membr Biol 2009; 22:539-47. [PMID: 16373325 DOI: 10.1080/09687860500421738] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Insolubility in non-ionic detergents such as Triton X-100 at low temperature is a widely used biochemical criterion for characterization of membrane domains. In view of the emerging role of membrane organization in the function of G-protein coupled receptors, we have examined detergent insolubility of the 5-HT(1A) receptor in CHO cells using a novel GFP fluorescence approach developed by us. Using this approach, we have explored the membrane organization of the serotonin(1A) receptor tagged to enhanced yellow fluorescent protein (5-HT(1A)R-EYFP) stably expressed in CHO-K1 cells under conditions of varying detergent concentration, reduced membrane cholesterol and agonist stimulation. Our results show that a small yet significant fraction of the 5-HT(1A) receptor exhibits detergent insolubility, which increases upon depletion of membrane cholesterol. Stimulation of 5-HT(1A)R-EYFP by its endogenous ligand, serotonin, did not cause a significant change in the detergent insolubility of the receptor. Taken together, our results on detergent insolubility of 5-HT(1A)R-EYFP provide new insights into the membrane organization of the 5-HT(1A) receptor and could be relevant in the analysis of membrane organization of other G-protein coupled receptors.
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40
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Waheed AA, Freed EO. Lipids and membrane microdomains in HIV-1 replication. Virus Res 2009; 143:162-76. [PMID: 19383519 DOI: 10.1016/j.virusres.2009.04.007] [Citation(s) in RCA: 126] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Revised: 04/01/2009] [Accepted: 04/03/2009] [Indexed: 10/20/2022]
Abstract
Several critical steps in the replication cycle of human immunodeficiency virus type 1 (HIV-1) - entry, assembly and budding - are complex processes that take place at the plasma membrane of the host cell. A growing body of data indicates that these early and late steps in HIV-1 replication take place in specialized plasma membrane microdomains, and that many of the viral and cellular components required for entry, assembly, and budding are concentrated in these microdomains. In particular, a number of studies have shown that cholesterol- and sphingolipid-enriched microdomains known as lipid rafts play important roles in multiple steps in the virus replication cycle. In this review, we provide an overview of what is currently known about the involvement of lipids and membrane microdomains in HIV-1 replication.
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Affiliation(s)
- Abdul A Waheed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, National Cancer Institute, Frederick, MD 21702, USA.
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41
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Chien MP, Lin CH, Chang DK. Recruitment of HIV-1 envelope occurs subsequent to lipid mixing: a fluorescence microscopic evidence. Retrovirology 2009; 6:20. [PMID: 19254359 PMCID: PMC2653015 DOI: 10.1186/1742-4690-6-20] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Accepted: 03/02/2009] [Indexed: 11/10/2022] Open
Abstract
Entry of the human immunodeficiency virus (HIV) into the target cell is initiated by fusion with the cell membrane, mediated through the envelope glycoproteins gp120 and gp41, following engagement to CD4 and the co-receptor. Previous fusion kinetics studies on the HXB2 envelope protein (Env) revealed that Env recruitment occurred at about 13 min concurrent with the lipid mixing. To resolve the temporal sequence of lipid mixing and recruitment, we employed an inhibitory assay monitored by fluorescence microscopy using a gp41 ectodomain (gp41e) fragment, which blocked Env recruitment in stark contrast to the lack of gp41e effect on the lipid mixing. In addition, to demonstrate the mode of action for the inhibition of gp41e, our results strongly suggested that lipid mixing precedes the Env recruitment because lipid mixing can proceed with Env recruitment inhibited by exogeneous gp41e molecules. Importantly, it was found that the random clustering of Env molecules on the membrane surface occurred at approximately 1 minute whereas the Env recruitment was observed at 13 minutes after the attachment of Env-expressing cell to the target cell. This > 10-fold temporal discrepancy highlights that the productive assembly of Env molecules leading to fusion requires spatio-temporal coordination of several adjacent Env trimers aggregated via directed movement.
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Affiliation(s)
- Miao-Ping Chien
- Institute of Chemistry, Academia Sinica, Taipei, Taiwan 11529, ROC.
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42
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Rechtman MM, Nakaryakov A, Shapira KE, Ehrlich M, Henis YI. Different domains regulate homomeric and heteromeric complex formation among type I and type II transforming growth factor-beta receptors. J Biol Chem 2009; 284:7843-52. [PMID: 19147499 DOI: 10.1074/jbc.m809215200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Transforming growth factor-beta (TGF-beta) binds to and signals via two serine-threonine kinase receptors, type I (TbetaRI) and type II (TbetaRII). The oligomerization of TGF-beta receptors modulates ligand binding and receptor trafficking and may contribute to signal diversification. However, numerous features of the molecular domains that determine the homo- and hetero-oligomerization of full-length receptors at the cell surface and the mode of these interactions remain unclear. Here, we address these questions through computerized immunofluorescence co-patching and patch/fluorescence recovery after photobleaching measurements of different combinations of epitope-tagged receptors and their mutants in live cells. We show that TbetaRI and TbetaRII are present on the plasma membrane both as monomers and homo- and hetero-oligomers. The homodimerization of TbetaRII depends on a cytoplasmic juxtamembrane region (amino acid residues 200-220). In contrast, the cytoplasmic domain of TbetaRI is dispensable for its homodimerization. TbetaRI.TbetaRII hetero-oligomerization depends on the cytoplasmic domain of TbetaRI and on a C-terminal region of TbetaRII (residues 419-565). TGF-beta1 elevates TbetaRII homodimerization to some degree and strongly enhances TbetaRI.TbetaRII heteromeric complex formation. Both ligand-induced effects depend on the region encompassed between residues 200-242 of TbetaRII. Furthermore, the kinase activity of TbetaRI is also necessary for the latter effect. All forms of the homo- and hetero-oligomers, whether constitutively present on the membrane or formed upon TGF-beta1 stimulation, were stable in the time-scale of our patch/FRAP measurements. We suggest that the different forms of receptor oligomerization may serve as a basis for the heterogeneity of TGF-beta signaling responses.
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Affiliation(s)
- Maya Mouler Rechtman
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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43
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Korade Z, Kenworthy AK. Lipid rafts, cholesterol, and the brain. Neuropharmacology 2008; 55:1265-73. [PMID: 18402986 DOI: 10.1016/j.neuropharm.2008.02.019] [Citation(s) in RCA: 223] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2007] [Revised: 02/15/2008] [Accepted: 02/26/2008] [Indexed: 01/11/2023]
Abstract
Lipid rafts are specialized membrane microdomains that serve as organizing centers for assembly of signaling molecules, influence membrane fluidity and trafficking of membrane proteins, and regulate different cellular processes such as neurotransmission and receptor trafficking. In this article, we provide an overview of current methods for studying lipid rafts and models for how lipid rafts might form and function. Next, we propose a potential mechanism for regulating lipid rafts in the brain via local control of cholesterol biosynthesis by neurotrophins and their receptors. Finally, we discuss evidence that altered cholesterol metabolism and/or lipid rafts play a critical role in the pathophysiology of multiple CNS disorders, including Smith-Lemli-Opitz syndrome, Huntington's, Alzheimer's, and Niemann-Pick Type C diseases.
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Affiliation(s)
- Zeljka Korade
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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44
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Both MHC class II and its GPI-anchored form undergo hop diffusion as observed by single-molecule tracking. Biophys J 2008; 95:435-50. [PMID: 18339737 DOI: 10.1529/biophysj.107.123018] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Previously, investigations using single-fluorescent-molecule tracking at frame rates of up to 65 Hz, showed that the transmembrane MHC class II protein and its GPI-anchored modified form expressed in CHO cells undergo simple Brownian diffusion, without any influence of actin depolymerization with cytochalasin D. These results are at apparent variance with the view that GPI-anchored proteins stay with cholesterol-enriched raft domains, as well as with the observation that both lipids and transmembrane proteins undergo short-term confined diffusion within a compartment and long-term hop diffusion between compartments. Here, this apparent discrepancy has been resolved by reexamining the same paradigm, by using both high-speed single-particle tracking (50 kHz) and single fluorescent-molecule tracking (30 Hz). Both molecules exhibited rapid hop diffusion between 40-nm compartments, with an average dwell time of 1-3 ms in each compartment. Cytochalasin D hardly affected the hop diffusion, consistent with previous observations, whereas latrunculin A increased the compartment sizes with concomitant decreases of the hop rates, which led to an approximately 50% increase in the median macroscopic diffusion coefficient. These results indicate that the actin-based membrane skeleton influences the diffusion of both transmembrane and GPI-anchored proteins.
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45
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Gould TJ, Hess ST. Chapter 12: Nanoscale biological fluorescence imaging: breaking the diffraction barrier. Methods Cell Biol 2008; 89:329-58. [PMID: 19118681 DOI: 10.1016/s0091-679x(08)00612-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Biological imaging has been limited by the finite resolution of light microscopy. Recent developments in ultra-high-resolution microscopy methods, many of which are based on fluorescence, are breaking the diffraction barrier; it is becoming possible to image intracellular protein distributions with resolution of tens of nanometers or better. Fluorescence photoactivation localization microscopy (FPALM) is an example of such an ultra-high-resolution method which can image living or fixed cells with demonstrated lateral resolution of better than 20 nm. A detailed description of the methods involved in FPALM imaging of biological samples is presented here, accompanied by comparison with existing methods from the literature.
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Affiliation(s)
- Travis J Gould
- Department of Physics and Astronomy and Institute for Molecular Biophysics, University of Maine, Orono, Maine 04469, USA
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46
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Wang X, Hinson ER, Cresswell P. The interferon-inducible protein viperin inhibits influenza virus release by perturbing lipid rafts. Cell Host Microbe 2007; 2:96-105. [PMID: 18005724 DOI: 10.1016/j.chom.2007.06.009] [Citation(s) in RCA: 359] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Revised: 05/16/2007] [Accepted: 06/12/2007] [Indexed: 12/24/2022]
Abstract
Interferons initiate the host antiviral response by inducing a number of genes, most with no defined antiviral function. Here we show that the interferon-induced protein viperin inhibits influenza A virus release from the plasma membrane of infected cells. Viperin expression altered plasma membrane fluidity by affecting the formation of lipid rafts, which are detergent-resistant membrane microdomains known to be the sites of influenza virus budding. Intracellular interaction of viperin with farnesyl diphosphate synthase (FPPS), an enzyme essential for isoprenoid biosynthesis, decreased the activity of the enzyme. Overexpression of FPPS reversed viperin-mediated inhibition of virus production and restored normal membrane fluidity, and reduction of FPPS levels by siRNA inhibited virus release and replication, indicating that the FPPS interaction underlies viperin's effects. These findings suggest that targeting the release stage of the life cycle may affect the replication of many enveloped viruses. Furthermore, FPPS may be an attractive target for antiviral therapy.
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Affiliation(s)
- Xiuyan Wang
- Department of Immunobiology, Yale University School of Medicine, 300 Cedar Street, New Haven, CT 06520-8011, USA
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47
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Abstract
The biological membrane is a complicated matrix wherein different lipid environments are thought to exist. The more ordered or raft environment has been perceived biochemically accessible via its relative resistance to detergent. This paper outlines the protocols developed in our laboratory for the analysis of such detergent-resistant membranes (DRMs). We stress the fact that DRMs are artifactual in nature and should not be equivocated to lipid rafts, their usefulness being limited to assigning raft-association potential most convincingly when changes in DRM composition are induced by biochemically/physiologically relevant events. These protocols are completed in 1-2 d.
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Affiliation(s)
- Daniel Lingwood
- Max Planck Institute for Molecular Cell Biology and Genetics, Dresden, Germany
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48
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Dynamic clustered distribution of hemagglutinin resolved at 40 nm in living cell membranes discriminates between raft theories. Proc Natl Acad Sci U S A 2007; 104:17370-5. [PMID: 17959773 DOI: 10.1073/pnas.0708066104] [Citation(s) in RCA: 282] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Organization in biological membranes spans many orders of magnitude in length scale, but limited resolution in far-field light microscopy has impeded distinction between numerous biomembrane models. One canonical example of a heterogeneously distributed membrane protein is hemagglutinin (HA) from influenza virus, which is associated with controversial cholesterol-rich lipid rafts. Using fluorescence photoactivation localization microscopy, we are able to image distributions of tens of thousands of HA molecules with subdiffraction resolution ( approximately 40 nm) in live and fixed fibroblasts. HA molecules form irregular clusters on length scales from approximately 40 nm up to many micrometers, consistent with results from electron microscopy. In live cells, the dynamics of HA molecules within clusters is observed and quantified to determine an effective diffusion coefficient. The results are interpreted in terms of several established models of biological membranes.
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49
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Shvartsman DE, Donaldson JC, Diaz B, Gutman O, Martin GS, Henis YI. Src kinase activity and SH2 domain regulate the dynamics of Src association with lipid and protein targets. ACTA ACUST UNITED AC 2007; 178:675-86. [PMID: 17698610 PMCID: PMC2064473 DOI: 10.1083/jcb.200701133] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Src functions depend on its association with the plasma membrane and with specific membrane-associated assemblies. Many aspects of these interactions are unclear. We investigated the functions of kinase, SH2, and SH3 domains in Src membrane interactions. We used FRAP beam-size analysis in live cells expressing a series of c-Src–GFP proteins with targeted mutations in specific domains together with biochemical experiments to determine whether the mutants can generate and bind to phosphotyrosyl proteins. Wild-type Src displays lipid-like membrane association, whereas constitutively active Src-Y527F interacts transiently with slower-diffusing membrane-associated proteins. These interactions require Src kinase activity and SH2 binding, but not SH3 binding. Furthermore, overexpression of paxillin, an Src substrate with a high cytoplasmic population, competes with membrane phosphotyrosyl protein targets for binding to activated Src. Our observations indicate that the interactions of Src with lipid and protein targets are dynamic and that the kinase and SH2 domain cooperate in the membrane targeting of Src.
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Affiliation(s)
- Dmitry E Shvartsman
- Department of Neurobiochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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50
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Kalipatnapu S, Chattopadhyay A. Membrane Organization and Function of the Serotonin1A Receptor. Cell Mol Neurobiol 2007; 27:1097-116. [PMID: 17710529 DOI: 10.1007/s10571-007-9189-2] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2007] [Accepted: 07/27/2007] [Indexed: 01/02/2023]
Abstract
(1) The serotonin(1A) receptor is a G-protein coupled receptor involved in several cognitive, behavioral, and developmental functions. It binds the neurotransmitter serotonin and signals across the membrane through its interactions with heterotrimeric G-proteins. (2) Lipid-protein interactions in membranes play an important role in the assembly, stability, and function of membrane proteins. The role of membrane environment in serotonin(1A) receptor function is beginning to be addressed by exploring the consequences of lipid manipulations on the ligand binding and G-protein coupling of serotonin(1A) receptors, the ability to functionally solubilize the serotonin(1A) receptor, and the factors influencing the membrane organization of the serotonin(1A) receptor. (3) Recent developments involving the application of detergent-based and detergent-free approaches to understand the membrane organization of the serotonin(1A) receptor under conditions of ligand activation and modulation of membrane lipid content, with an emphasis on membrane cholesterol, are described.
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Affiliation(s)
- Shanti Kalipatnapu
- Divisionof Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0377, USA
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