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Sakamoto K, Kitano T, Kuwahara H, Tedani M, Aburai K, Futaki S, Abe M, Sakai H, Ohtaka H, Yamashita Y. Effect of Vesicle Size on the Cytolysis of Cell-Penetrating Peptides (CPPs). Int J Mol Sci 2020; 21:E7405. [PMID: 33036492 PMCID: PMC7582850 DOI: 10.3390/ijms21197405] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 09/20/2020] [Accepted: 10/05/2020] [Indexed: 12/29/2022] Open
Abstract
A specific series of peptides, called a cell-penetrating peptide (CPP), is known to be free to directly permeate through cell membranes into the cytosol (cytolysis); hence, this CPP would be a potent carrier for a drug delivery system (DDS). Previously, we proposed the mechanism of cytolysis as a temporal and local phase transfer of membrane lipid caused by positive membrane curvature generation. Moreover, we showed how to control the CPP cytolysis. Here, we investigate the phospholipid vesicle's size effect on CPP cytolysis because this is the most straightforward way to control membrane curvature. Contrary to our expectation, we found that the smaller the vesicle diameter (meaning a higher membrane curvature), the more cytolysis was suppressed. Such controversial findings led us to seek the reason for the unexpected results, and we ended up finding out that the mobility of membrane lipids as a liquid crystal is the key to cytolysis. As a result, we could explain the cause of cytolysis suppression by reducing the vesicle size (because of the restriction of lipid mobility); osmotic pressure reduction to enhance positive curvature generation works as long as the membrane is mobile enough to modulate the local structure. Taking all the revealed vital factors and their effects as a tool, we will further explore how to control CPP cytolysis for developing a DDS system combined with appropriate cargo selection to be tagged with CPPs.
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Affiliation(s)
- Kazutami Sakamoto
- Tokyo University of Science, Noda, Chiba 278-8510, Japan; (T.K.); (H.K.); (K.A.); (M.A.); (H.S.)
| | - Takeshi Kitano
- Tokyo University of Science, Noda, Chiba 278-8510, Japan; (T.K.); (H.K.); (K.A.); (M.A.); (H.S.)
| | - Haruka Kuwahara
- Tokyo University of Science, Noda, Chiba 278-8510, Japan; (T.K.); (H.K.); (K.A.); (M.A.); (H.S.)
| | - Megumi Tedani
- Chiba Institute of Science, Choshi, Chiba 288-0025, Japan; (M.T.); (H.O.); (Y.Y.)
| | - Kenichi Aburai
- Tokyo University of Science, Noda, Chiba 278-8510, Japan; (T.K.); (H.K.); (K.A.); (M.A.); (H.S.)
| | - Shiroh Futaki
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan;
| | - Masahiko Abe
- Tokyo University of Science, Noda, Chiba 278-8510, Japan; (T.K.); (H.K.); (K.A.); (M.A.); (H.S.)
| | - Hideki Sakai
- Tokyo University of Science, Noda, Chiba 278-8510, Japan; (T.K.); (H.K.); (K.A.); (M.A.); (H.S.)
| | - Hiroyasu Ohtaka
- Chiba Institute of Science, Choshi, Chiba 288-0025, Japan; (M.T.); (H.O.); (Y.Y.)
| | - Yuji Yamashita
- Chiba Institute of Science, Choshi, Chiba 288-0025, Japan; (M.T.); (H.O.); (Y.Y.)
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2
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Takatori SC, Sahu A. Active Contact Forces Drive Nonequilibrium Fluctuations in Membrane Vesicles. Phys Rev Lett 2020; 124:158102. [PMID: 32357050 DOI: 10.1103/physrevlett.124.158102] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Accepted: 03/20/2020] [Indexed: 05/24/2023]
Abstract
We analyze the nonequilibrium shape fluctuations of giant unilamellar vesicles encapsulating motile bacteria. Owing to bacteria-membrane collisions, we experimentally observe a significant increase in the magnitude of membrane fluctuations at low wave numbers, compared to the well-known thermal fluctuation spectrum. We interrogate these results by numerically simulating membrane height fluctuations via a modified Langevin equation, which includes bacteria-membrane contact forces. Taking advantage of the lengthscale and timescale separation of these contact forces and thermal noise, we further corroborate our results with an approximate theoretical solution to the dynamical membrane equations. Our theory and simulations demonstrate excellent agreement with nonequilibrium fluctuations observed in experiments. Moreover, our theory reveals that the fluctuation-dissipation theorem is not broken by the bacteria; rather, membrane fluctuations can be decomposed into thermal and active components.
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Affiliation(s)
- Sho C Takatori
- Department of Chemical Engineering, University of California, Santa Barbara, California 93106, USA
| | - Amaresh Sahu
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, USA
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3
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Abstract
Abnormal shapes of red blood cells (RBC) have been associated with various diseases. Diverse RBC shapes have also been intriguing for membrane biophysics. Here we focus on sickle shaped RBC which form due to abnormal growth of semi-rigid hemoglobin (HbS) fibers confined in RBC. Using the area difference elasticity (ADE) model for RBC and worm-like chain model for the confined HbS fibers, we explore shape deformations at equilibrium using Monte-Carlo simulations. We show that while a single HbS fiber is not rigid enough to produce sickle like deformation, a fiber bundle can do so. We also consider multiple disjoint filaments and find that confinement can generate multipolar RBC shapes and can even promote helical filament conformations which have not been discussed before. We show that the same model, when applied to microtubules confined in phospholipid vesicles, predicts vesicle tubulation. In addition we reproduce the tube collapse transition and tennis racket type vesicle shapes, as reported in experiments. We conclude that with a decrease in the surface area to volume ratio, and membrane rigidity, the vesicles prefer tubulation over sickling. The highlight of this work is several important non-axisymmetric RBC and vesicle shapes, which have never been explored in simulations.
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Affiliation(s)
- Arabinda Behera
- Indian Institute Of Technology Bombay, Powai-400076, Mumbai, India.
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4
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Luo C, Hu X, Peng R, Huang H, Liu Q, Tan W. Biomimetic Carriers Based on Giant Membrane Vesicles for Targeted Drug Delivery and Photodynamic/Photothermal Synergistic Therapy. ACS Appl Mater Interfaces 2019; 11:43811-43819. [PMID: 31670932 DOI: 10.1021/acsami.9b11223] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Membrane vesicles derived from live cells show great potential in biological applications due to their preserved cell membrane properties. Here, we demonstrate that cell-derived giant membrane vesicles can be used as vectors to deliver multiple therapeutic drugs and carry out combinational phototherapy for targeted cancer treatment. We show that therapeutic drugs can be efficiently encapsulated into giant membrane vesicles and delivered to target cells by membrane fusion, resulting in synergistic photodynamic/photothermal therapy under light irradiation. This study highlights biomimetic giant membrane vesicles for drug delivery with potential biomedical application in cancer therapeutics.
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Affiliation(s)
- Can Luo
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province , Hunan University , Changsha , Hunan 410082 , China
| | - Xiaoxiao Hu
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province , Hunan University , Changsha , Hunan 410082 , China
| | - Ruizi Peng
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province , Hunan University , Changsha , Hunan 410082 , China
| | - Huidong Huang
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province , Hunan University , Changsha , Hunan 410082 , China
| | - Qiaoling Liu
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province , Hunan University , Changsha , Hunan 410082 , China
| | - Weihong Tan
- Molecular Science and Biomedicine Laboratory (MBL), State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, College of Biology, College of Chemistry and Chemical Engineering, Aptamer Engineering Center of Hunan Province , Hunan University , Changsha , Hunan 410082 , China
- Institute of Molecular Medicine (IMM), Renji Hospital, Shanghai Jiao Tong University School of Medicine, and College of Chemistry and Chemical Engineering , Shanghai Jiao Tong University , Shanghai 200240 , China
- Institute of Cancer and Basic Medicine (IBMC), Chinese Academy of Sciences , The Cancer Hospital of the University of Chinese Academy of Sciences , Hangzhou , Zhejiang 310022 , China
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5
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Bell CL, Shakespeare TI, Smith AR, Murray SA. Visualization of Annular Gap Junction Vesicle Processing: The Interplay Between Annular Gap Junctions and Mitochondria. Int J Mol Sci 2018; 20:ijms20010044. [PMID: 30583492 PMCID: PMC6337258 DOI: 10.3390/ijms20010044] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 12/15/2018] [Accepted: 12/20/2018] [Indexed: 11/16/2022] Open
Abstract
It is becoming clear that in addition to gap junctions playing a role in cell⁻cell communication, gap junction proteins (connexins) located in cytoplasmic compartments may have other important functions. Mitochondrial connexin 43 (Cx43) is increased after ischemic preconditioning and has been suggested to play a protective role in the heart. How Cx43 traffics to the mitochondria and the interactions of mitochondria with other Cx43-containing structures are unclear. In this study, immunocytochemical, super-resolution, and transmission electron microscopy were used to detect cytoplasmic Cx43-containing structures and to demonstrate their interactions with other cytoplasmic organelles. The most prominent cytoplasmic Cx43-containing structures-annular gap junctions-were demonstrated to form intimate associations with lysosomes as well as with mitochondria. Surprisingly, the frequency of associations between mitochondria and annular gap junctions was greater than that between lysosomes and annular gap junctions. The benefits of annular gap junction/mitochondrial associations are not known. However, it is tempting to suggest, among other possibilities, that the contact between annular gap junction vesicles and mitochondria facilitates Cx43 delivery to the mitochondria. Furthermore, it points to the need for investigating annular gap junctions as more than only vesicles destined for degradation.
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Affiliation(s)
- Cheryl L Bell
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA.
| | | | - Amber R Smith
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA.
| | - Sandra A Murray
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA.
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6
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Abstract
Biomechanical properties of cells such as cellular stiffness have been increasingly considered as biomarkers for diseases. For instance, stiffness of cancer cells has been correlated to the malignant potential in certain cell lines. In cells, the cholesterol content plays a crucial role in determining stiffness. Changes in the cholesterol content in cellular membranes can be an indication of pathological disorders. Acoustophoresis as a separation and diagnostic tool is well positioned to help in the separation and diagnosis of cells taking advantage of its unique separation criteria of density and compressibility. However, under the same conditions, cells and vesicles secreted by these cells often have a positive contrast factor sign and thus do not yield simple separations. Thermally-assisted acoustophoresis, also referred to as thermo-acoustophoresis, solves this problem by adding a temperature dimension to the separation. In this work, we evaluate the acoustic contrast temperature (TΦ) of vesicles at different cholesterol molar ratios (Xchol) and develop a multi-stage lab-on-a-chip method to accomplish for the first time the separation of a three-vesicle mixture. Using Xchol = 0.1, 0.2, and 0.3 vesicles, we have obtained separation efficiencies exceeding 93%. The simplicity, rapidity, and label-free nature of this approach holds promise as a diagnostic and separation tool for cells and extracellular vesicles such as exosomes and microvesicles.
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Affiliation(s)
- Ata Dolatmoradi
- Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174, USA.
| | - Elnaz Mirtaheri
- Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174, USA.
| | - Bilal El-Zahab
- Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174, USA.
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7
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Holdbrook DA, Huber RG, Piggot TJ, Bond PJ, Khalid S. Dynamics of Crowded Vesicles: Local and Global Responses to Membrane Composition. PLoS One 2016; 11:e0156963. [PMID: 27310814 PMCID: PMC4910979 DOI: 10.1371/journal.pone.0156963] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 05/22/2016] [Indexed: 11/22/2022] Open
Abstract
The bacterial cell envelope is composed of a mixture of different lipids and proteins, making it an inherently complex organelle. The interactions between integral membrane proteins and lipids are crucial for their respective spatial localization within bacterial cells. We have employed microsecond timescale coarse-grained molecular dynamics simulations of vesicles of varying sizes and with a range of protein and lipid compositions, and used novel approaches to measure both local and global system dynamics, the latter based on spherical harmonics analysis. Our results suggest that both hydrophobic mismatch, enhanced by embedded membrane proteins, and curvature based sorting, due to different modes of undulation, may drive assembly in vesicular systems. Interestingly, the modes of undulation of the vesicles were found to be altered by the specific protein and lipid composition of the vesicle. Strikingly, lipid dynamics were shown to be coupled to proteins up to 6 nm from their surface, a substantially larger distance than has previously been observed, resulting in multi-layered annular rings enriched with particular types of phospholipid. Such large protein-lipid complexes may provide a mechanism for long-range communication. Given the complexity of bacterial membranes, our results suggest that subtle changes in lipid composition may have major implications for lipid and protein sorting under a curvature-based membrane-sorting model.
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Affiliation(s)
- Daniel A. Holdbrook
- Bioinformatics Institute (A*STAR), 30 Biopolis Str, #07–01 Matrix, Singapore 138671, Singapore
- School of Chemistry, University of Southampton, Southampton, SO17 1BJ, United Kingdom
| | - Roland G. Huber
- Bioinformatics Institute (A*STAR), 30 Biopolis Str, #07–01 Matrix, Singapore 138671, Singapore
| | - Thomas J. Piggot
- The Defence Science and Technology Laboratory, Porton Down, Salisbury, SP4 0JQ, United Kingdom
- School of Chemistry, University of Southampton, Southampton, SO17 1BJ, United Kingdom
| | - Peter J. Bond
- Bioinformatics Institute (A*STAR), 30 Biopolis Str, #07–01 Matrix, Singapore 138671, Singapore
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore
| | - Syma Khalid
- School of Chemistry, University of Southampton, Southampton, SO17 1BJ, United Kingdom
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8
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Kim S, Hilgenfeldt S. Heterogeneous vesicles: an analytical approach to equilibrium shapes. Soft Matter 2015; 11:8920-8929. [PMID: 26482343 DOI: 10.1039/c5sm02245b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We develop an analytical model to predict equilibrium shapes of two-component heterogeneous vesicles or capsules. Using a free energy functional including the bending energies of the two components and line tension contributions, the model describes shape transitions between spherical and polyhedral (faceted) states, complementing and extending results of previous numerical simulations. In the parameter space of relative area fraction, bending modulus ratio, and line tension, a region of polyhedral shapes occurs for weak line tension and large bending modulus ratio and is very robust towards changes in the modeling assumptions. At large enough line tension, the spherical shape fragments into two components. Within the polyhedral region, we compare the energies of all regular and semiregular polyhedra, as well as those of arbitrary prismatic shapes. We find that the largest bending modulus contrasts together with larger line tension favor polyhedra with small face number as optimal shapes. In this region, we also demonstrate the counter-intuitive result that the most symmetric polyhedra are not energetically optimal, with specific Archimedean solids and specific prismatic shapes beating more isotropic (e.g. Platonic) polyhedra. Furthermore, all polyhedra of lowest energy are found to be three-fold coordinated. The shape transition boundary for polyhedra can be computed analytically. The model can be utilized to predict heterogeneous vesicle shapes and to estimate physical properties of the components constituting observed vesicles.
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Affiliation(s)
- Sangwoo Kim
- Mechanical Science and Engineering, University of Illinois, Urbana-Champaign, USA.
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9
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Abstract
We investigate the diffusio-phoretic motion of a deformable vesicle. A vesicle is built from the linked catalytic and noncatalytic vertices that consumes fuel in the environment and utilize the resulting self-generated concentration gradient to exhibit propulsive motion. Under nonequilibrium conditions it is found that the self-propulsion velocity of the vesicle depends on its shape, which in turn is controlled by the bending rigidity of the membrane and solvent density around it. The self-propulsion velocity of the vesicle for different shapes has been calculated and the factors which affect the velocity are identified.
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Affiliation(s)
- Shivam Gupta
- Department of Physics, Indian Institute of Science Education and Research Bhopal, Bhopal, India
| | - K K Sreeja
- Department of Physics, Indian Institute of Technology Madras, Chennai, India
| | - Snigdha Thakur
- Department of Physics, Indian Institute of Science Education and Research Bhopal, Bhopal, India
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10
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Chen YH, Du W, Hagemeijer MC, Takvorian PM, Pau C, Cali A, Brantner CA, Stempinski ES, Connelly PS, Ma HC, Jiang P, Wimmer E, Altan-Bonnet G, Altan-Bonnet N. Phosphatidylserine vesicles enable efficient en bloc transmission of enteroviruses. Cell 2015; 160:619-630. [PMID: 25679758 PMCID: PMC6704014 DOI: 10.1016/j.cell.2015.01.032] [Citation(s) in RCA: 332] [Impact Index Per Article: 36.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 12/13/2014] [Accepted: 01/12/2015] [Indexed: 12/17/2022]
Abstract
A central paradigm within virology is that each viral particle largely behaves as an independent infectious unit. Here, we demonstrate that clusters of enteroviral particles are packaged within phosphatidylserine (PS) lipid-enriched vesicles that are non-lytically released from cells and provide greater infection efficiency than free single viral particles. We show that vesicular PS lipids are co-factors to the relevant enterovirus receptors in mediating subsequent infectivity and transmission, in particular to primary human macrophages. We demonstrate that clustered packaging of viral particles within vesicles enables multiple viral RNA genomes to be collectively transferred into single cells. This study reveals a novel mode of viral transmission, where enteroviral genomes are transmitted from cell-to-cell en bloc in membrane-bound PS vesicles instead of as single independent genomes. This has implications for facilitating genetic cooperativity among viral quasispecies as well as enhancing viral replication.
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Affiliation(s)
- Ying-Han Chen
- Laboratory of Host-Pathogen Dynamics, National Heart Lung and Blood Institute, NIH, Bethesda, MD 20892, USA; Federated Department of Biological Sciences, Rutgers University, Newark, NJ 07102, USA
| | - WenLi Du
- Laboratory of Host-Pathogen Dynamics, National Heart Lung and Blood Institute, NIH, Bethesda, MD 20892, USA
| | - Marne C Hagemeijer
- Laboratory of Host-Pathogen Dynamics, National Heart Lung and Blood Institute, NIH, Bethesda, MD 20892, USA
| | - Peter M Takvorian
- Federated Department of Biological Sciences, Rutgers University, Newark, NJ 07102, USA
| | - Cyrilla Pau
- Federated Department of Biological Sciences, Rutgers University, Newark, NJ 07102, USA
| | - Ann Cali
- Federated Department of Biological Sciences, Rutgers University, Newark, NJ 07102, USA
| | - Christine A Brantner
- Electron Microscopy Core Facility, National Heart Lung and Blood Institute, NIH, Bethesda, MD 20892, USA
| | - Erin S Stempinski
- Electron Microscopy Core Facility, National Heart Lung and Blood Institute, NIH, Bethesda, MD 20892, USA
| | - Patricia S Connelly
- Electron Microscopy Core Facility, National Heart Lung and Blood Institute, NIH, Bethesda, MD 20892, USA
| | - Hsin-Chieh Ma
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794, USA
| | - Ping Jiang
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794, USA
| | - Eckard Wimmer
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794, USA
| | - Grégoire Altan-Bonnet
- Program in Computational Biology and Immunology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Nihal Altan-Bonnet
- Laboratory of Host-Pathogen Dynamics, National Heart Lung and Blood Institute, NIH, Bethesda, MD 20892, USA.
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11
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Vidavsky N, Addadi S, Mahamid J, Shimoni E, Ben-Ezra D, Shpigel M, Weiner S, Addadi L. Initial stages of calcium uptake and mineral deposition in sea urchin embryos. Proc Natl Acad Sci U S A 2014; 111:39-44. [PMID: 24344263 PMCID: PMC3890786 DOI: 10.1073/pnas.1312833110] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sea urchin larvae have an endoskeleton consisting of two calcitic spicules. We reconstructed various stages of the formation pathway of calcium carbonate from calcium ions in sea water to mineral deposition and integration into the forming spicules. Monitoring calcium uptake with the fluorescent dye calcein shows that calcium ions first penetrate the embryo and later are deposited intracellularly. Surprisingly, calcium carbonate deposits are distributed widely all over the embryo, including in the primary mesenchyme cells and in the surface epithelial cells. Using cryo-SEM, we show that the intracellular calcium carbonate deposits are contained in vesicles of diameter 0.5-1.5 μm. Using the newly developed airSEM, which allows direct correlation between fluorescence and energy dispersive spectroscopy, we confirmed the presence of solid calcium carbonate in the vesicles. This mineral phase appears as aggregates of 20-30-nm nanospheres, consistent with amorphous calcium carbonate. The aggregates finally are introduced into the spicule compartment, where they integrate into the growing spicule.
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Affiliation(s)
- Netta Vidavsky
- Department of Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel
| | | | - Julia Mahamid
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Eyal Shimoni
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel; and
| | - David Ben-Ezra
- Israel Oceanographic and Limnological Research, National Center for Mariculture, Eilat 88112, Israel
| | - Muki Shpigel
- Israel Oceanographic and Limnological Research, National Center for Mariculture, Eilat 88112, Israel
| | - Steve Weiner
- Department of Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Lia Addadi
- Department of Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel
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12
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DasSarma S, Karan R, DasSarma P, Barnes S, Ekulona F, Smith B. An improved genetic system for bioengineering buoyant gas vesicle nanoparticles from Haloarchaea. BMC Biotechnol 2013; 13:112. [PMID: 24359319 PMCID: PMC3878110 DOI: 10.1186/1472-6750-13-112] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 12/17/2013] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Gas vesicles are hollow, buoyant organelles bounded by a thin and extremely stable protein membrane. They are coded by a cluster of gvp genes in the halophilic archaeon, Halobacterium sp. NRC-1. Using an expression vector containing the entire gvp gene cluster, gas vesicle nanoparticles (GVNPs) have been successfully bioengineered for antigen display by constructing gene fusions between the gvpC gene and coding sequences from bacterial and viral pathogens. RESULTS To improve and streamline the genetic system for bioengineering of GVNPs, we first constructed a strain of Halobacterium sp. NRC-1 deleted solely for the gvpC gene. The deleted strain contained smaller, more spindle-shaped nanoparticles observable by transmission electron microscopy, confirming a shape-determining role for GvpC in gas vesicle biogenesis. Next, we constructed expression plasmids containing N-terminal coding portions or the complete gvpC gene. After introducing the expression plasmids into the Halobacterium sp. NRC-1 ΔgvpC strain, GvpC protein and variants were localized to the GVNPs by Western blotting analysis and their effects on increasing the size and shape of nanoparticles established by electron microscopy. Finally, a synthetic gene coding for Gaussia princeps luciferase was fused to the gvpC gene fragments on expression plasmids, resulting in an enzymatically active GvpC-luciferase fusion protein bound to the buoyant nanoparticles from Halobacterium. CONCLUSION GvpC protein and its N-terminal fragments expressed from plasmid constructs complemented a Halobacterium sp. NRC-1 ΔgvpC strain and bound to buoyant GVNPs. Fusion of the luciferase reporter gene from Gaussia princeps to the gvpC gene derivatives in expression plasmids produced GVNPs with enzymatically active luciferase bound. These results establish a significantly improved genetic system for displaying foreign proteins on Halobacterium gas vesicles and extend the bioengineering potential of these novel nanoparticles to catalytically active enzymes.
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Affiliation(s)
- Shiladitya DasSarma
- Institute of Marine and Environmental Technology and Department of Microbiology and Immunology, University of Maryland School of Medicine, 701 E Pratt Street, Baltimore, MD 21202, USA
| | - Ram Karan
- Institute of Marine and Environmental Technology and Department of Microbiology and Immunology, University of Maryland School of Medicine, 701 E Pratt Street, Baltimore, MD 21202, USA
| | - Priya DasSarma
- Institute of Marine and Environmental Technology and Department of Microbiology and Immunology, University of Maryland School of Medicine, 701 E Pratt Street, Baltimore, MD 21202, USA
| | - Susan Barnes
- Institute of Marine and Environmental Technology and Department of Microbiology and Immunology, University of Maryland School of Medicine, 701 E Pratt Street, Baltimore, MD 21202, USA
| | - Folasade Ekulona
- Institute of Marine and Environmental Technology and Department of Microbiology and Immunology, University of Maryland School of Medicine, 701 E Pratt Street, Baltimore, MD 21202, USA
| | - Barbara Smith
- Johns Hopkins School of Medicine Microscope Facility, Baltimore, MD 21205, USA
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13
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Abstract
In this study, we observed the intracellular behavior of recombinant invasin, a 103-kDa outer membrane protein of Yersinia pseudotuberculosis. To mimic the in vivo behavior of bacterial invasin, a polyvalent form of invasin was generated by incubation of biotinylated GST-fused invasin C-terminal portion protein (GST-INVS) with avidin. Several experiments confirmed that the recombinant invasin could consistently reproduce the invasin-mediated entry to mammalian epithelial cells. We analyzed the molecular kinetics of polyvalent INVS by western blotting, (125) I-uptake, and immunofluorescent microscopy. The internalized polyvalent INVS was rapidly translocated to the RIPA-insoluble (polymerized-actin enriched) fraction and formed cytoplasmic vesicles, while monovalent invasin did not show such kinetics. From these observations, we concluded that our bacterial-free system is able to analyze the action of invasin for Yersinia pseudotuberculosis entry.
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Affiliation(s)
- Hisashi Koga
- Department of Tumor Genetics and Biology, Graduate School of Medical Science Kumamoto University, Kumamoto, Japan.
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14
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Abstract
Biological cells are highly dynamic, and continually move material around their own volume and between their interior and exterior. Much of this transport encapsulates the material inside phospholipid vesicles that shuttle to and from, fusing with, and budding from, other membranes. A feature of vesicles that is crucial for this transport is their ability to fuse to target membranes and release their contents to the distal side. In industry, some personal care products contain vesicles to help transport reagents across the skin, and research on drug formulation shows that packaging active compounds inside vesicles delays their clearance from the blood stream. In this chapter, we survey the biological role and physicochemical properties of phospholipids, and describe progress in coarse-grained simulations of vesicles and vesicle fusion. Because coarse-grained simulations retain only those molecular details that are thought to influence the large-scale processes of interest, they act as a model embodying our current understanding. Comparing the predictions of these models with experiments reveals the importance of the retained microscopic details and also the deficiencies that can suggest missing details, thereby furthering our understanding of the complex dynamic world of vesicles.
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15
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Stockert JC, Blázquez-Castro A, Cañete M, Horobin RW, Villanueva A. MTT assay for cell viability: Intracellular localization of the formazan product is in lipid droplets. Acta Histochem 2012; 114:785-96. [PMID: 22341561 DOI: 10.1016/j.acthis.2012.01.006] [Citation(s) in RCA: 356] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2011] [Revised: 01/20/2012] [Accepted: 01/22/2012] [Indexed: 01/01/2023]
Abstract
Although MTT is widely used to assess cytotoxicity and cell viability, the precise localization of its reduced formazan product is still unclear. In the present study the localization of MTT formazan was studied by direct microscopic observation of living HeLa cells and by colocalization analysis with organelle-selective fluorescent probes. MTT formazan granules did not colocalize with mitochondria as revealed by rhodamine 123 labeling or autofluorescence. Likewise, no colocalization was observed between MTT formazan granules and lysosomes labeled by neutral red. Taking into account the lipophilic character and lipid solubility of MTT formazan, an evaluation of the MTT reaction was performed after treatment of cells with sunflower oil emulsions to induce a massive occurrence of lipid droplets. Under this condition, lipid droplets revealed a large amount of MTT formazan deposits. Kinetic studies on the viability of MTT-treated cells showed no harmful effects at short times. Quantitative structure-activity relations (QSAR) models were used to predict and explain the localization of both the MTT tetrazolium salt and its formazan product. These predictions were in agreement with experimental observations on the accumulation of MTT formazan product in lipid droplets.
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Affiliation(s)
- Juan C Stockert
- Department of Biology, Faculty of Sciences, Autonomous University of Madrid, Spain.
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16
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Katsman D, Stackpole EJ, Domin DR, Farber DB. Embryonic stem cell-derived microvesicles induce gene expression changes in Müller cells of the retina. PLoS One 2012; 7:e50417. [PMID: 23226281 PMCID: PMC3511553 DOI: 10.1371/journal.pone.0050417] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Accepted: 10/19/2012] [Indexed: 12/20/2022] Open
Abstract
Cell-derived microvesicles (MVs), recognized as important components of cell-cell communication, contain mRNAs, miRNAs, proteins and lipids and transfer their bioactive contents from parent cells to cells of other origins. We have studied the effect that MVs released from embryonic stem cells (ESMVs) have on retinal progenitor Müller cells. Cultured human Müller cells were exposed to mouse ESMVs every 48 hours for a total of 9 treatments. Morphological changes were observed by light microscopy in the treated cells, which grew as individual heterogeneous cells, compared to the uniform, spindle-like adherent cellular sheets of untreated cells. ESMVs transferred to Müller cells embryonic stem cell (ESC) mRNAs involved in the maintenance of pluripotency, including Oct4 and Sox2, and the miRNAs of the 290 cluster, important regulators of the ESC-specific cell cycle. Moreover, ESMV exposure induced up-regulation of the basal levels of endogenous human Oct4 mRNA in Müller cells. mRNA and miRNA microarrays of ESMV-treated vs. untreated Müller cells revealed the up-regulation of genes and miRNAs involved in the induction of pluripotency, cellular proliferation, early ocular genes and genes important for retinal protection and remodeling, as well as the down-regulation of inhibitory and scar-related genes and miRNAs involved in differentiation and cell cycle arrest. To further characterize the heterogeneous cell population of ESMV-treated Müller cells, their expression of retinal cell markers was compared to that in untreated control cells by immunocytochemistry. Markers for amacrine, ganglion and rod photoreceptors were present in treated but not in control Müller cells. Together, our findings indicate that ESMs induce de-differentiation and pluripotency in their target Müller cells, which may turn on an early retinogenic program of differentiation.
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Affiliation(s)
- Diana Katsman
- Jules Stein Eye Institute and Department of Ophthalmology, University of California Los Angeles, Los Angeles, California, United States of America
- Molecular Biology Institute, University of California Los Angeles, Los Angeles, California, United States of America
| | - Emma J. Stackpole
- Jules Stein Eye Institute and Department of Ophthalmology, University of California Los Angeles, Los Angeles, California, United States of America
| | - Daniel R. Domin
- Jules Stein Eye Institute and Department of Ophthalmology, University of California Los Angeles, Los Angeles, California, United States of America
| | - Debora B. Farber
- Jules Stein Eye Institute and Department of Ophthalmology, University of California Los Angeles, Los Angeles, California, United States of America
- Molecular Biology Institute, University of California Los Angeles, Los Angeles, California, United States of America
- Brain Research Institute, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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17
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Lopes da Silva M, Thieleke-Matos C, Cabrita-Santos L, Ramalho JS, Wavre-Shapton ST, Futter CE, Barral DC, Seabra MC. The host endocytic pathway is essential for Plasmodium berghei late liver stage development. Traffic 2012; 13:1351-63. [PMID: 22780869 DOI: 10.1111/j.1600-0854.2012.01398.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 07/06/2012] [Accepted: 07/10/2012] [Indexed: 12/27/2022]
Abstract
The obligate intracellular liver stage of the Plasmodium parasite represents a bottleneck in the parasite life cycle and remains a promising target for therapeutic intervention. During this stage, parasites undergo dramatic morphological changes and achieve one of the fastest replication rates among eukaryotic species. Nevertheless, relatively little is known about the parasite interactions with the host hepatocyte. Using immunofluorescence, live cell imaging and electron microscopy, we show that Plasmodium berghei parasites are surrounded by vesicles from the host late endocytic pathway. We found that these vesicles are acidic and contain the membrane markers Rab7a, CD63 and LAMP1. When host cell vesicle acidification was disrupted using ammonium chloride or Concanamycin A during the late liver stage of infection, parasite survival was not affected, but schizont size was significantly decreased. Furthermore, when the host cell endocytic pathway was loaded with BSA-gold, gold particles were found within the parasite cytoplasm, showing the transport of material from the host endocytic pathway toward the parasite interior. These observations reveal a novel Plasmodium-host interaction and suggest that vesicles from the host endolysosomal pathway could represent an important source of nutrients exploited by the fast-growing late liver stage parasites.
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Affiliation(s)
- Mafalda Lopes da Silva
- CEDOC, Faculdade de Ciências Médicas, FCM, Universidade Nova de Lisboa, Lisboa, 1169-056, Portugal; Instituto Gulbenkian de Ciência, Oeiras, 2780-156, Portugal
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18
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Wu YY, Ye XJ. [Roles of microvesicles in tumor progress and its clinical application]. Zhejiang Da Xue Xue Bao Yi Xue Ban 2012; 41:105-110. [PMID: 22419473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Microvesicles transport special proteins, micro RNA and DNA segments, which provides new access to intercellular communication. Tumor-derived membrane microvesicles (TMV) are involved in the tumor progress by transporting tumor-derived proteins, delivering microRNA to surrounding normal cells to alter their phenotype and promoting reverse transcription to interfere gene stability and to create tumor microenvironment. TMV also play crucial roles in tumor angiogenesis and matrix degradation, which facilitates malignant cell metastasis. TMVs are also involved in escaping immunological surveillance by intensifying the function of suppressor T cell and inducing apoptosis of cytotoxic T cells. On the other hand, microvesicles carry tumor antigens and can be used for development of tumor vaccines; some new vaccines such as AEX and DEX are under early clinical trials. Circulating microRNA and DNA segments in body fluid can be a new potential biomarker for cancer diagnosis and prognosis. Purification of microvesicles needs to be further improved, which is important for identification of microvesicles and their subtypes.
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Affiliation(s)
- Ying-ying Wu
- Center of Bone Marrow Ttransplantation, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China
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19
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Šuštar V, Bedina-Zavec A, Štukelj R, Frank M, Bobojević G, Janša R, Ogorevc E, Kruljc P, Mam K, Šimunič B, Manček-Keber M, Jerala R, Rozman B, Veranič P, Hägerstrand H, Kralj-Iglič V. Nanoparticles isolated from blood: a reflection of vesiculability of blood cells during the isolation process. Int J Nanomedicine 2011; 6:2737-48. [PMID: 22128248 PMCID: PMC3225219 DOI: 10.2147/ijn.s24537] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Shedding of nanoparticles from the cell membrane is a common process in all cells. These nanoparticles are present in body fluids and can be harvested by isolation. To collect circulating nanoparticles from blood, a standard procedure consisting of repeated centrifugation and washing is applied to the blood samples. Nanoparticles can also be shed from blood cells during the isolation process, so it is unclear whether nanoparticles found in the isolated material are present in blood at sampling or if are they created from the blood cells during the isolation process. We addressed this question by determination of the morphology and identity of nanoparticles harvested from blood. METHODS The isolates were visualized by scanning electron microscopy, analyzed by flow cytometry, and nanoparticle shapes were determined theoretically. RESULTS The average size of nanoparticles was about 300 nm, and numerous residual blood cells were found in the isolates. The shapes of nanoparticles corresponded to the theoretical shapes obtained by minimization of the membrane free energy, indicating that these nanoparticles can be identified as vesicles. The concentration and size of nanoparticles in blood isolates was sensitive to the temperature during isolation. We demonstrated that at lower temperatures, the nanoparticle concentration was higher, while the nanoparticles were on average smaller. CONCLUSION These results indicate that a large pool of nanoparticles is produced after blood sampling. The shapes of deformed blood cells found in the isolates indicate how fragmentation of blood cells may take place. The results show that the contents of isolates reflect the properties of blood cells and their interaction with the surrounding solution (rather than representing only nanoparticles present in blood at sampling) which differ in different diseases and may therefore present a relevant clinical parameter.
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Affiliation(s)
- Vid Šuštar
- Laboratory of Clinical Biophysics, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Apolonija Bedina-Zavec
- Laboratory of Clinical Biophysics, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
- Laboratory of Biosynthesis and Biotransformation, National Institute of Chemistry, Ljubljana, Slovenia
| | - Roman Štukelj
- Laboratory of Clinical Biophysics, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Mojca Frank
- Department of Rheumatology, Ljubljana University Medical Centre, Ljubljana, Slovenia
| | - Goran Bobojević
- Laboratory of Clinical Biophysics, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Rado Janša
- Department of Gastroenterology, Ljubljana University Medical Centre, Ljubljana, Slovenia
| | - Eva Ogorevc
- Laboratory of Biophysics, Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia
| | - Peter Kruljc
- Clinics for Reproduction and Horses, Faculty of Veterinary Medicine, University of Ljubljana, Ljubljana, Slovenia
| | | | - Boštjan Šimunič
- Laboratory of Biotechnology, National Institute of Chemistry, Ljubljana, Slovenia
| | - Mateja Manček-Keber
- University of Primorska, Science and Research Centre of Koper, Koper, Slovenia
| | - Roman Jerala
- University of Primorska, Science and Research Centre of Koper, Koper, Slovenia
| | - Blaž Rozman
- Department of Rheumatology, Ljubljana University Medical Centre, Ljubljana, Slovenia
| | - Peter Veranič
- Institute of Cell Biology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Henry Hägerstrand
- Department of Biosciences, Biocity, Åbo Akademi University, Åbo/Turku, Finland
| | - Veronika Kralj-Iglič
- Laboratory of Clinical Biophysics, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
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20
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Storey SM, McIntosh AL, Senthivinayagam S, Moon KC, Atshaves BP. The phospholipid monolayer associated with perilipin-enriched lipid droplets is a highly organized rigid membrane structure. Am J Physiol Endocrinol Metab 2011; 301:E991-E1003. [PMID: 21846905 PMCID: PMC3213997 DOI: 10.1152/ajpendo.00109.2011] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The significance of lipid droplets (LD) in lipid metabolism, cell signaling, and membrane trafficking is increasingly recognized, yet the role of the LD phospholipid monolayer in LD protein targeting and function remains unknown. To begin to address this issue, two populations of LD were isolated by ConA sepharose affinity chromatography: 1) functionally active LD enriched in perilipin, caveolin-1, and several lipolytic proteins, including ATGL and HSL; and 2) LD enriched in ADRP and TIP47 that contained little to no lipase activity. Coimmunoprecipitation experiments confirmed the close association of caveolin and perilipin and lack of interaction between caveolin and ADRP, in keeping with the separation observed with the ConA procedure. The phospholipid monolayer structure was evaluated to reveal that the perilipin-enriched LD exhibited increased rigidity (less fluidity), as shown by increased cholesterol/phospholipid, Sat/Unsat, and Sat/MUFA ratios. These results were confirmed by DPH-TMA, NBD-cholesterol, and NBD-sphingomyelin fluorescence polarization studies. By structure and organization, the perilipin-enriched LD most closely resembled the adipocyte PM. In contrast, the ADRP/TIP47-enriched LD contained a more fluid monolayer membrane, reflecting decreased polarizations and lipid order based on phospholipid fatty acid analysis. Taken together, results indicate that perilipin and associated lipolytic enzymes target areas in the phospholipid monolayer that are highly organized and rigid, similar in structure to localized areas of the PM where cholesterol and fatty acid uptake and efflux occur.
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Affiliation(s)
- Stephen M Storey
- Department of Physiology and Pharmacology, Texas A & M University, Texas Veterinary Medical Center, College Station, Texas, USA
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21
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Abstract
We investigate double-walled vesicles as a simple model system for multi-vesicular structures, where the inner membrane is confined within the outer membrane. Various shapes of double-walled vesicles in two dimensions are obtained by means of our recently-developed discrete space variation method, and the shapes of each layer are found to be interdependent. Confined within the outer membrane, an inner membrane with a larger surface area always shows a cristae shape. As previous simulations and theoretical analyses of a single-walled vesicle have been done before, the geometric properties of double-walled vesicles, including the mean square radius of gyration and volume within the vesicle membrane, are studied in detail as functions of the pressure and surface area. It is found that due to the inter-space restriction of each layer, double-walled vesicles exhibit different behaviors compared with the previously-observed scaling laws of single-walled vesicles. It is straightforward to extend this study to more complicated and realistic biological systems, such as those including electrostatic interactions between membranes and solvent, phase separation, and cooperative interactions between multicomponent membranes.
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Affiliation(s)
- Kunkun Guo
- College of Materials Science and Engineering, Hunan University, Changsha, People's Republic of China.
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22
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Idema T, Storm C. Analytical expressions for the shape of axisymmetric membranes with multiple domains. Eur Phys J E Soft Matter 2011; 34:67. [PMID: 21751093 DOI: 10.1140/epje/i2011-11067-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 06/09/2011] [Accepted: 06/21/2011] [Indexed: 05/31/2023]
Abstract
Based on the Canham-Helfrich free energy, we derive analytical expressions for the shapes of axisymmetric membranes consisting of multiple domains. We give explicit equations for both closed vesicles and almost cylindrical tubes. Using these expressions, we also find the shape of a tube attached to a spherical vesicle. The resulting shapes compare well to numerical data, and our expressions can be used to easily determine membrane parameters from experimentally obtained shapes.
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Affiliation(s)
- T Idema
- Department of Physics and Astronomy, University of Pennsylvania, 209 S 33rd street, 19104 Philadelphia, Pennsylvania, USA.
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23
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Božič AL, Šiber A, Podgornik R. Electrostatic self-energy of a partially formed spherical shell in salt solution: application to stability of tethered and fluid shells as models for viruses and vesicles. Phys Rev E Stat Nonlin Soft Matter Phys 2011; 83:041916. [PMID: 21599209 DOI: 10.1103/physreve.83.041916] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Revised: 01/02/2011] [Indexed: 05/30/2023]
Abstract
We investigate the electrostatics of a partially formed, charged spherical shell in a salt solution. We solve the problem numerically at the Poisson-Boltzmann level and analytically in the Debye-Hückel regime. From the results on energetics of partially formed shells we examine the stability of tethered (crystalline) and fluid shells toward rupture. We delineate different regimes of stability, where, for fluid shells, we also include the effects of bending elasticity of the shells. Our analysis shows how charging of the shell induces its instability toward rupture but also provides insight regarding growth of charged shells.
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Affiliation(s)
- Anže Lošdorfer Božič
- Department of Theoretical Physics, Jožef Stefan Institute, SI-1000 Ljubljana, Slovenia
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24
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Schrempf H, Koebsch I, Walter S, Engelhardt H, Meschke H. Extracellular Streptomyces vesicles: amphorae for survival and defence. Microb Biotechnol 2011; 4:286-99. [PMID: 21342473 PMCID: PMC3818868 DOI: 10.1111/j.1751-7915.2011.00251.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Accepted: 01/12/2011] [Indexed: 11/27/2022] Open
Abstract
Blue-pigmented exudates arise as droplets on sporulated lawns of Streptomyces coelicolor M110 grown on agar plates. Our electron microscopical and biochemical studies suggest that droplets contain densely packed vesicles with large assemblies of different protein types and/or the polyketide antibiotic actinorhodin. Frozen-hydrated vesicles were unilamellar with a typical bilayer membrane, and ranged from 80 to 400 nm in diameter with a preferred width of 150-300 nm. By means of cryo-electron tomography, three types were reconstructed three-dimensionally: vesicles that were filled with particulate material, likely protein assemblies, those that contained membrane-bound particles, and a vesicle that showed a higher contrast inside, but lacked particles. Our LC/MS analyses of generated tryptic peptides led to the identification of distinct proteins that carry often a predicted N-terminal signal peptide with a twin-arginine motif or lack a canonical signal sequence. The proteins are required for a range of processes: the acquisition of inorganic as well as organic phosphate, iron ions, and of distinct carbon sources, energy metabolism and redox balance, defence against oxidants and tellurites, the tailoring of actinorhodin, folding and assembly of proteins, establishment of turgor, and different signalling cascades. Our novel findings have immense implications for understanding new avenues of environmental biology of streptomycetes and for biotechnological applications.
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Affiliation(s)
- Hildgund Schrempf
- FB Biology/Chemistry, Applied Genetics of Microorganisms, University Osnabrück, Barbarastr. 13, D-49069 Osnabrück, Germany.
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25
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Ghigliotti G, Rahimian A, Biros G, Misbah C. Vesicle migration and spatial organization driven by flow line curvature. Phys Rev Lett 2011; 106:028101. [PMID: 21405252 DOI: 10.1103/physrevlett.106.028101] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Indexed: 05/30/2023]
Abstract
Cross-streamline migration of deformable entities is essential in many problems such as industrial particulate flows, DNA sorting, and blood rheology. Using two-dimensional numerical experiments, we have discovered that vesicles suspended in a flow with curved flow lines migrate towards regions of high flowline curvature, which are regions of high shear rates. The migration velocity of a vesicle is found to be a universal function of the normal stress difference and the flow curvature. This finding quantitatively demonstrates a direct coupling between a microscopic quantity (migration) and a macroscopic one (normal stress difference). Furthermore, simulations with multiple vesicles revealed a self-organization, which corresponds to segregation, in a rim closer to the inner cylinder, resulting from a subtle interaction among vesicles. Such segregation effects could have a significant impact on the rheology of vesicle flows.
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Affiliation(s)
- Giovanni Ghigliotti
- Université Joseph Fourier and CNRS (UMR5588), Laboratoire de Spectrométrie Physique, 140 Avenue de la Physique, 38402 Saint Martin d'Hères, France
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26
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Reggiori F, Monastyrska I, Verheije MH, Calì T, Ulasli M, Bianchi S, Bernasconi R, de Haan CAM, Molinari M. Coronaviruses Hijack the LC3-I-positive EDEMosomes, ER-derived vesicles exporting short-lived ERAD regulators, for replication. Cell Host Microbe 2010; 7:500-8. [PMID: 20542253 PMCID: PMC7103375 DOI: 10.1016/j.chom.2010.05.013] [Citation(s) in RCA: 310] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Revised: 04/09/2010] [Accepted: 05/11/2010] [Indexed: 12/21/2022]
Abstract
Coronaviruses (CoV), including SARS and mouse hepatitis virus (MHV), are enveloped RNA viruses that induce formation of double-membrane vesicles (DMVs) and target their replication and transcription complexes (RTCs) on the DMV-limiting membranes. The DMV biogenesis has been connected with the early secretory pathway. CoV-induced DMVs, however, lack conventional endoplasmic reticulum (ER) or Golgi protein markers, leaving their membrane origins in question. We show that MHV co-opts the host cell machinery for COPII-independent vesicular ER export of a short-living regulator of ER-associated degradation (ERAD), EDEM1, to derive cellular membranes for replication. MHV infection causes accumulation of EDEM1 and OS-9, another short-living ER chaperone, in the DMVs. DMVs are coated with the nonlipidated LC3/Atg8 autophagy marker. Downregulation of LC3, but not inactivation of host cell autophagy, protects cells from CoV infection. Our study identifies the host cellular pathway hijacked for supplying CoV replication membranes and describes an autophagy-independent role for nonlipidated LC3-I.
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Affiliation(s)
- Fulvio Reggiori
- Department of Cell Biology, University Medical Centre Utrecht, 3584 CX Utrecht, The Netherlands.
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27
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Chen LZ, Liang GM, Zhang J, Wu KM, Guo YY, Rector BG. Proteomic analysis of novel Cry1Ac binding proteins in Helicoverpa armigera (Hübner). Arch Insect Biochem Physiol 2010; 73:61-73. [PMID: 19847794 DOI: 10.1002/arch.20340] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Aminopeptidase N (APN) and cadherin-like proteins have been previously identified as Cry1Ac-binding proteins in Helicoverpa armigera (Hübner). In this study, a proteomic approach was used to identify novel Cry1Ac-binding proteins in H. armigera. Brush border membrane vesicles (BBMV) of H. armigera were extracted and separated by two-dimensional gel electrophoresis (2-DE). Cry1Ac-binding proteins were detected using antisera against Cry1Ac. Peptide mass fingerprinting (PMF) was used to identify Cry1Ac-binding proteins. In total, four proteins were identified as candidate Cry1Ac-binding proteins in H. armigera: vacuolar ATP synthase (V-ATPase) subunit B, actin, heat shock cognate protein (HSCP), and a novel protein.
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Affiliation(s)
- Li-Zhen Chen
- Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, P.R. China
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28
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Bohinc K, Lombardo D, Kraljiglič V, Fošnarič M, May S, Pernuš F, Hägerstrand H, Iglič A. Shape variation of bilayer membrane daughter vesicles induced by anisotropic membrane inclusions. Cell Mol Biol Lett 2009; 11:90-101. [PMID: 16847752 PMCID: PMC6275760 DOI: 10.2478/s11658-006-0009-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2005] [Accepted: 01/06/2006] [Indexed: 11/20/2022] Open
Abstract
A theoretical model of a two-component bilayer membrane was used in order to describe the influence of anisotropic membrane inclusions on shapes of membrane daughter micro and nano vesicles. It was shown that for weakly anisotropic inclusions the stable vesicle shapes are only slightly out-of-round. In contrast, for strongly anisotropic inclusions the stable vesicle shapes may significantly differ from spheres, i.e. they have a flattened oblate shape at small numbers of inclusions in the membrane, and an elongated cigar-like prolate shape at high numbers of inclusions in the vesicle membrane.
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Affiliation(s)
- Klemen Bohinc
- Laboratory of Physics, Faculty of Electrical Engineering, University of Ljubljana, Tržaška 25, SI-1000 Ljubljana, Slovenia
- University College for Health Studies, University of Ljubljana, Poljanska 26a, SI-1000 Ljubljana, Slovenia
| | - Darko Lombardo
- Laboratory of Physics, Faculty of Electrical Engineering, University of Ljubljana, Tržaška 25, SI-1000 Ljubljana, Slovenia
| | - Veronika Kraljiglič
- Laboratory of Physics, Faculty of Electrical Engineering, University of Ljubljana, Tržaška 25, SI-1000 Ljubljana, Slovenia
- Institute of Biophysics, Faculty of Medicine, University of Ljubljana, Lipičeva 2, 1000 Ljubljana, Slovenia
| | - Miha Fošnarič
- Laboratory of Physics, Faculty of Electrical Engineering, University of Ljubljana, Tržaška 25, SI-1000 Ljubljana, Slovenia
| | - Sylvio May
- Department of Physics, North Dakota State University, Fargo, ND 58105-5566 USA
| | - Franjo Pernuš
- Laboratory of Physics, Faculty of Electrical Engineering, University of Ljubljana, Tržaška 25, SI-1000 Ljubljana, Slovenia
| | - Henry Hägerstrand
- Department of Biology, Åbo Akademi University, Abo/Turku, FIN-20520 Finland
| | - Aleš Iglič
- Laboratory of Physics, Faculty of Electrical Engineering, University of Ljubljana, Tržaška 25, SI-1000 Ljubljana, Slovenia
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29
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Jamet D, Misbah C. Thermodynamically consistent picture of the phase-field model of vesicles: elimination of the surface tension. Phys Rev E Stat Nonlin Soft Matter Phys 2008; 78:041903. [PMID: 18999451 DOI: 10.1103/physreve.78.041903] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Indexed: 05/27/2023]
Abstract
In two recent papers [D. Jamet and C. Misbah, Phys. Rev. E 76, 051907 (2007); 78, 031902 (2008)], we considered a thermodynamically consistent model for vesicles and membranes, where we dealt, in the first paper, with the membrane local incompressibility condition, while in the second one with the bending energy and the derivation of a constitutive law of the composite fluid: ambient fluid+membrane . This is the last paper of this series and focuses on the elimination of surface tension (inherent in phase-field models), retaining the thermodynamically consistent model. We write down the complete set of equations and the full constitutive law for membranes embedded in a Newtonian fluid.
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Affiliation(s)
- D Jamet
- DEN/DER/SSTH/LMDL, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France.
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Esseling-Ozdoba A, Vos JW, van Lammeren AAM, Emons AMC. Synthetic lipid (DOPG) vesicles accumulate in the cell plate region but do not fuse. Plant Physiol 2008; 147:1699-709. [PMID: 18583535 PMCID: PMC2492608 DOI: 10.1104/pp.108.119842] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2008] [Accepted: 06/19/2008] [Indexed: 05/23/2023]
Abstract
The cell plate is the new cell wall, with bordering plasma membrane, that is formed between two daughter cells in plants, and it is formed by fusion of vesicles (approximately 60 nm). To start to determine physical properties of cell plate forming vesicles for their transport through the phragmoplast, and fusion with each other, we microinjected fluorescent synthetic lipid vesicles that were made of 1,2-dioleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DOPG) into Tradescantia virginiana stamen hair cells. During interphase, the 60-nm wide DOPG vesicles moved inside the cytoplasm comparably to organelles. During cytokinesis, they were transported through the phragmoplast and accumulated in the cell plate region together with the endogenous vesicles, even inside the central cell plate region. Because at this stage microtubules are virtually absent from that region, while actin filaments are present, actin filaments may have a role in the transport of vesicles toward the cell plate. Unlike the endogenous vesicles, the synthetic DOPG vesicles did not fuse with the developing cell plate. Instead, they redistributed into the cytoplasm of the daughter cells upon completion of cytokinesis. Because the redistribution of the vesicles occurs when actin filaments disappear from the phragmoplast, actin filaments may be involved in keeping the vesicles inside the developing cell plate region.
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Abstract
Lipid droplets are depots of neutral lipids that exist virtually in any kind of cell. Recent studies have revealed that the lipid droplet is not a mere lipid blob, but a major contributor not only to lipid homeostasis but also to diverse cellular functions. Because of the unique structure as well as the functional importance in relation to obesity, steatosis, and other prevailing diseases, the lipid droplet is now reborn as a brand new organelle, attracting interests from researchers of many disciplines.
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Affiliation(s)
- Toyoshi Fujimoto
- Department of Anatomy and Molecular Cell Biology, Graduate School of Medicine, Nagoya University, 65 Tsurumai, Showa, Nagoya, 466-8550, Japan.
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Winkler K, Leneweit G, Schubert R. Characterization of membrane vesicles in plant extracts. Colloids Surf B Biointerfaces 2008; 45:57-65. [PMID: 16125916 DOI: 10.1016/j.colsurfb.2005.07.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Revised: 07/18/2005] [Accepted: 07/18/2005] [Indexed: 10/25/2022]
Abstract
During the preparation of plant extracts by a press-slit technique, membranes of cell walls and cell organelles of the plant material form vesicles, which are colloidally dispersed. It was assumed that chlorophyll-containing green extracts enclose lipoidic structures. Vesicles in aqueous mistletoe extracts (extracts of Viscum album L.) were analyzed by cryo-transmission electron microscopy (cryo-TEM) without fixation. For the first time, it was possible to analyze unfixed vesicles in the mistletoe extract. Micrographs of cryo-TEM showed predominantly unilamellar vesicles of different sizes. The quantification of vesicles was established through the analysis of phospholipids, which are major components of membranes. The method was validated mainly according to ICH guidelines for the validation of analytical methods (Q2A and Q2B). For further characterization of the vesicle size, a method was developed which is based on the separation of the vesicles from low molecular weight substances by size exclusion chromatography. Fractions were collected and average sizes were determined by multi-angle laser light scattering (MALLS). Furthermore, the UV-vis absorbance and phospholipid concentration were analyzed. Phospholipid quantification was in agreement with photometrical data. Sizes determined by cryo-TEM and by light scattering showed consistent results.
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Affiliation(s)
- Karin Winkler
- Institut für Pharmazeutische Wissenschaften, Hermann-Herder-Strasse 9, D-79104 Freiburg, Germany
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Abstract
Exosomes are nanometer particles (50-100 nm) secreted by most living cells. The first description of exosomes was made in 1987 by Rose Johnstone, who described a vesicle formation during the maturation process of reticulocytes. At this time it has been suggested that exosome release could represent a major route for the externalization of obsolete membrane proteins. A renewed vision of exosome function was raised when Graça Raposo demonstrated in 1996 that exosomes derived from B cells could have immunogenic capacities. Since then, exosomes have been described in numerous cell types IN VITRO, including hematopoietic and nonhematopoietic cells. The physiological relevance of exosomes IN VIVO still remains unclear. Studies have demonstrated that exosomes can play a role in the physiology of originating cells (i.e., reticulocyte-derived exosomes). Furthermore, exosomes can act on intercellular communication by allowing exchange of proteins, lipids, and also mRNA between cells. Finally, exosomes have been shown to modulate the immune system (i.e., dendritic cells, B cells, and tumor cells). In the present review, we have focused on the potential therapeutic role of exosomes as a cell free vaccine in cancer.
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Affiliation(s)
- S Viaud
- Institut National de la Santé Et de la Recherche Médicale, INSERM U805, Institut Gustave Roussy, Villejuif, France
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Abstract
Dendritic cells (DC) are crucial components of the early events of HIV infection. Dendritic cells capture and internalize HIV at mucosal surfaces and efficiently transfer the virus to CD4+ T cells in trans through infectious synapses (trans-infection pathway). Alternatively, HIV-1 replicates in DC (R5-HIV-1) (cis-infection pathway). Here, we analyzed HIV trafficking in DC during the trans-infection pathway as well as the cis-infection pathway. Confocal immunofluorescence microscopy demonstrated that after capture by DC, R5-HIV-1 and HIV-1 pseudotyped with vesicular stomatitis virus protein G colocalized in a viral compartment enriched in tetraspanins including CD81, CD82 and CD9, although at different levels, indicating a role of the viral envelope in targeting to the tetraspanin-rich compartment. Replication of R5-HIV-1 in DC (cis-infection pathway) also led to the accumulation, in an envelope-independent manner, of mature viral particles in a tetraspanin-rich compartment. A fraction of the HIV-1-containing compartments appeared directly accessible from the cell surface. In sharp contrast with the trans-infection pathway, the delta-subunit of the adaptor protein 3 (AP-3) complex was enriched on the HIV-1-containing compartment during R5-HIV-1 replication in DC (cis-infection pathway). Downregulation of AP-3 delta-adaptin reduced significantly viral particle release from HIV-1-infected DC. Together, these studies demonstrate a role for AP-3 in HIV replication in a tetraspanin-rich compartment in DC and contribute to the elucidation of the trafficking pathways required for DC-T cell transfer of HIV-1 infection, a critical step during the early events of HIV infection.
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Affiliation(s)
- Eduardo Garcia
- Department of Dermatology and Venereology, University Hospital and Medical School of Geneva, 1211 Geneva, Switzerland
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Abstract
Recent experiments by Kantsler et al. [Phys. Rev. Lett. 99, 178102 (2007)10.1103/PhysRevLett.99.178102] have shown that the relaxational dynamics of a vesicle in external elongation flow is accompanied by the formation of wrinkles on a membrane. Motivated by these experiments we present a theory describing the dynamics of a wrinkled membrane. The formation of wrinkles is related to the dynamical instability induced by negative surface tension of the membrane. For quasispherical vesicles we perform analytical study of the wrinkle structure dynamics. We derive the expression for the instability threshold and identify three stages of the dynamics. The scaling laws for the temporal evolution of wrinkling wavelength and surface tension are established, confirmed numerically, and compared to experimental results.
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Affiliation(s)
- K S Turitsyn
- James Franck Institute, University of Chicago, Chicago, Illinois 60637, USA
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Jiang H, Huber G, Pelcovits RA, Powers TR. Vesicle shape, molecular tilt, and the suppression of necks. Phys Rev E Stat Nonlin Soft Matter Phys 2007; 76:031908. [PMID: 17930272 DOI: 10.1103/physreve.76.031908] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2007] [Indexed: 05/25/2023]
Abstract
Can the presence of molecular-tilt order significantly affect the shapes of lipid bilayer membranes, particularly membrane shapes with narrow necks? Motivated by the propensity for tilt order and the common occurrence of narrow necks in the intermediate stages of biological processes such as endocytosis and vesicle trafficking, we examine how tilt order inhibits the formation of necks in the equilibrium shapes of vesicles. For vesicles with a spherical topology, point defects in the molecular order with a total strength of +2 are required. We study axisymmetric shapes and suppose that there is a unit-strength defect at each pole of the vesicle. The model is further simplified by the assumption of tilt isotropy: invariance of the energy with respect to rotations of the molecules about the local membrane normal. This isotropy condition leads to a minimal coupling of tilt order and curvature, giving a high energetic cost to regions with Gaussian curvature and tilt order. Minimizing the elastic free energy with constraints of fixed area and fixed enclosed volume determines the allowed shapes. Using numerical calculations, we find several branches of solutions and identify them with the branches previously known for fluid membranes. We find that tilt order changes the relative energy of the branches, suppressing thin necks by making them costly, leading to elongated prolate vesicles as a generic family of tilt-ordered membrane shapes.
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Affiliation(s)
- Hongyuan Jiang
- Division of Engineering, Box D, Brown University, Providence, Rhode Island 02912, USA
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Cenedella RJ, Sexton PS, Brako L, Lo WK, Jacob RF. Status of caveolin-1 in various membrane domains of the bovine lens. Exp Eye Res 2007; 85:473-81. [PMID: 17669400 DOI: 10.1016/j.exer.2007.05.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Revised: 04/17/2007] [Accepted: 05/24/2007] [Indexed: 01/29/2023]
Abstract
Recent studies of the distribution and relative concentration of caveolin-1 in fractions of bovine lens epithelial and fiber cells have led to the novel concept that caveolin-1 may largely exist as a peripheral membrane protein in some cells. Caveolin-1 is typically viewed as a scaffolding protein for caveolae in plasma membrane. In this study, membrane from cultured bovine lens epithelial cells and bovine lens fiber cells were divided into urea soluble and insoluble fractions. Cytosolic lipid vesicles were also recovered from the lens epithelial cells. Lipid-raft domains were recovered from fiber cells following treatment with detergents and examined for caveolin and lipid content. Aliquots of all fractions were Western blotted for caveolin-1. Fluorescence microscopy and double immunofluorescence labeling were used to examine the distribution of caveolin-1 in cultured epithelial cells. Electron micrographs revealed an abundance of caveolae in plasma membrane of cultured lens epithelial cells. About 60% of the caveolin-1 in the epithelial-crude membrane was soluble in urea, a characteristic of peripheral membrane proteins. About 30% of the total was urea-insoluble membrane protein that likely supports the structure of caveolae. The remaining caveolin was part of cytosolic lipid vesicles. By contrast, most caveolin in the bovine lens fiber cell membrane was identified as intrinsic protein, being present at relatively low concentrations in caveolae-free lipid raft domains enriched in cholesterol and sphingomyelin. We estimate that these domains occupied 25-30% of the fiber cell membrane surface. Thus, the status of caveolin-1 in lens epithelial cells appears markedly different from that in fiber cells.
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Affiliation(s)
- Richard J Cenedella
- Department of Biochemistry, A.T. Still University of Health Sciences, Kirksville, MO 63501, USA.
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Abstract
In the cell, the plasma membrane is often densely decorated by transmembrane proteins. The morphology and dynamics of the membrane are strongly influenced by the presence of proteins. In this paper, we use a coarse-grained model to explore the composite membrane-protein system and develop a simulation methodology based on thermodynamic integration to examine free energy changes during membrane shape transitions. The authors show that a critical concentration of conical membrane proteins or proteins with nonzero spontaneous curvature can drive the formation of small vesicles. The driving force of vesicle budding stems from the preference of proteins to gather in regions of high curvature. A sufficiently high concentration of proteins therefore can influence the topology of the membrane. The biological significance of our results is discussed.
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Affiliation(s)
- Erdinç Atilgan
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA
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Uetsuka K, Nishikawa S, Isobe K, Nakayama H. Histopathological Characteristics of Kupffer Cells and Ito Cells in the Porcine and Bovine Liver. J Vet Med Sci 2007; 69:767-70. [PMID: 17675812 DOI: 10.1292/jvms.69.767] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We previously reported that no Kupffer cells reacted with the antibody against lysozyme, and Ito cells contained a large cytoplasmic vacuole in the feline liver. In this report, we further examined the characteristics of porcine and bovine hepatic non-parenchymal cells. In the liver of both animals, Kupffer cells were positive for lysozyme, and cytoplasmic vacuoles in Ito cells were small. The histopathological characteristics of porcine and bovine hepatic non-parenchymal cells were different from those of the feline liver.
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Affiliation(s)
- Koji Uetsuka
- Department of Veterinary Pathology, Graduated School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
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Wikström A, Deinum J. Probing the interaction of coagulation factors with phospholipid vesicle surfaces by surface plasma resonance. Anal Biochem 2006; 362:98-107. [PMID: 17239338 DOI: 10.1016/j.ab.2006.12.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2006] [Revised: 12/04/2006] [Accepted: 12/05/2006] [Indexed: 10/23/2022]
Abstract
The dynamics of the binding of human coagulation factor Xa (FXa) and prothrombin to small unilamellar vesicles (25% phosphatidylserine, 75% phosphatidylcholine) were compared and quantified by Biacore, using two immobilization techniques. The vesicles were either tagged with different molar ratios of cholesterol-DNA and attached on Au chips or fused directly on L1 chips. The diameter in solution was 145 nm, but the more DNA tags/vesicle the more compressed the immobilized vesicles became; with 30 DNA tags the calculated thickness was 88 nm and with 1 DNA tag it was 138 nm. In both models the affinity for the vesicles was higher for the activated coagulation factors than for the corresponding zymogens. FXa and prothrombin had the highest affinities. The affinity was dependent on the vesicle preparation since overall K(D) values were up to 10 times lower for N(2)-dried than for vacuum-dried phospholipids, although with apparently fewer binding sites. However, compression of the vesicles had no effect on the K(D). In contrast, the rate constants were dependent on the number of DNA tags; thus deformation of the vesicles was observed. The k(a) and k(d) for FXa were similar for vesicles attached with 30 DNA tags or fused on the L1 chip but higher with fewer tags and approximately 10 times higher if attached with 1 tag. Thus for controlled kinetic studies immobilized DNA-tagged vesicles should be used.
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Affiliation(s)
- Angelica Wikström
- Department of Applied Physics, Chalmers University of Technology, S-431 90 Göteborg, Sweden
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41
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Williams JN, Skipp PJ, Humphries HE, Christodoulides M, O'Connor CD, Heckels JE. Proteomic analysis of outer membranes and vesicles from wild-type serogroup B Neisseria meningitidis and a lipopolysaccharide-deficient mutant. Infect Immun 2006; 75:1364-72. [PMID: 17158897 PMCID: PMC1828559 DOI: 10.1128/iai.01424-06] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Current experimental vaccines against serogroup B Neisseria meningitidis are based on meningococcal outer membrane (OM) proteins present in outer membrane vesicles (OMV) in which toxic lipopolysaccharide is depleted by detergent extraction. Knowledge of the composition of OM and OMV is essential for developing new meningococcal vaccines based on defined antigens. In the current study, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and nanocapillary liquid chromatography-tandem mass spectrometry were used to investigate the proteomes of OM and OMV from meningococcal strain MC58 and OM from a lipopolysaccharide-deficient mutant. The analysis of OM revealed a composition that was much more complex than the composition that has been reported previously; a total of 236 proteins were identified, only 6.4% of which were predicted to be located in the outer membrane. The most abundant proteins included not only the well-established major OM proteins (PorA, PorB, Opc, Rmp, and Opa) but also other proteins, such as pilus-associated protein Q (PilQ) and a putative macrophage infectivity protein. All of these proteins were also present in OMV obtained by extraction of the OM with deoxycholate. There were markedly increased levels of some additional proteins in OM from the lipopolysaccharide-deficient mutant, including enzymes that contribute to the tricarboxylic acid cycle. In all the preparations, the proteins not predicted to have an OM location were predominantly periplasmic or cytoplasmic or had an unknown location, and relatively few cytoplasmic membrane proteins were detected. However, several proteins that have previously been identified as potential vaccine candidates were not detected in either OM preparations or in OMV. These results have important implications for the development and use of vaccines based on outer membrane proteins.
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Affiliation(s)
- Jeannette N Williams
- Molecular Microbiology Group, Division of Infection Inflammation and Repair, University of Southampton Medical School, Southampton General Hospital, Southampton SO16 6YD, United Kingdom
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Ohashi M, Horie K, Hoshikawa Y, Nagata K, Osaki M, Ito H, Sairenji T. Accumulation of Epstein-Barr virus (EBV) BMRF1 protein EA-D during latent EBV activation of Burkitt's lymphoma cell line Raji. Microbes Infect 2006; 9:150-9. [PMID: 17223371 DOI: 10.1016/j.micinf.2006.11.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2006] [Revised: 10/29/2006] [Accepted: 11/06/2006] [Indexed: 11/25/2022]
Abstract
As a new model to elucidate molecular mechanisms in Epstein-Barr virus (EBV) activation, we tested the tetracycline-inducible (Tet-On)/BZLF1-oriP plasmid system in Raji cells. Cells transfected with this Tet-On plasmid did not activate EBV by doxycycline and surprisingly EBV latency was disrupted with large amounts of BMRF1 protein (EA-D) being accumulated in the cells. Brilliant EA-D fluorescence was markedly condensed in small sized cells, intra-cellular vesicles, and extra-cellular particles. Scanning electron microscopy demonstrated the extra-cellular particles to be covered with a membrane. EA-D molecules of 58, 50, 48, and 44kDa were expressed in the cells. The high (58 and 50kDa) and low (48 and 44kDa) EA-D molecules appeared in the early and late stages, respectively. Low EA-D molecules were detected mostly in EA-D positive cells separated into the heaviest density layer of a discontinuous Percoll gradient. Such molecules could be created from high EA-D molecules by protein phosphatase treatment. The EA-D molecules that appeared similar were detected in EBV-activated P3HR-1 and Akata cells. Several hypotheses concerning the accumulation of EA-D molecules of various polymorphic forms and their phosphorylation/dephosphorylation in this model system are presented, with possible biological and clinical relevance.
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Affiliation(s)
- Makoto Ohashi
- Division of Biosignaling, Department of Biomedical Science, School of Life Science, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago 683-8503, Japan
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Perkumas KM, Hoffman EA, McKay BS, Allingham RR, Stamer WD. Myocilin-associated exosomes in human ocular samples. Exp Eye Res 2006; 84:209-12. [PMID: 17094967 PMCID: PMC1780107 DOI: 10.1016/j.exer.2006.09.020] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2006] [Revised: 09/08/2006] [Accepted: 09/26/2006] [Indexed: 11/17/2022]
Abstract
Mutations in myocilin result in ocular hypertension, likely due to decreased drainage of aqueous humor through the trabecular meshwork. Since less myocilin is found in the aqueous humor of those with disease-causing mutations, understanding myocilin's role in the aqueous humor is of clinical importance. Recently, myocilin was shown to exit cultured trabecular meshwork cells in association with shed vesicles called exosomes. To examine relevance of this finding in a physiological setting, the present study examined three different types of ocular samples for the presence of myocilin-associated exosomes. Using differential centrifugation steps, we found myocilin associated with exosomes isolated from effluent collected from human anterior segments in organ culture and aqueous humor obtained from human cadaveric eyes or from patients undergoing excisional surgery. Similar to results with cultured cells, myocilin associated predominately with exosomes in fresh samples, appeared mostly soluble at later times, and had biochemical properties (density of 1.13-1.19 g/ml in linear sucrose gradient) similar to those characteristics of exosomes. These data indicate that exosomes are present and may facilitate the transport of myocilin into the extracellular space of human ocular cells.
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Affiliation(s)
- KM Perkumas
- Departments of Ophthalmology and Vision Science
| | - EA Hoffman
- Departments of Ophthalmology and Vision Science
| | - BS McKay
- Departments of Ophthalmology and Vision Science
- Cell Biology and Anatomy, The University of Arizona
| | | | - WD Stamer
- Departments of Ophthalmology and Vision Science
- Pharmacology and
- Corresponding Author: W. Daniel Stamer, Ph.D., 655 North Alvernon Way, Suite 108, Tucson, AZ 85711, 520-626-7767,
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Lorusso A, Covino C, Priori G, Bachi A, Meldolesi J, Chieregatti E. Annexin2 coating the surface of enlargeosomes is needed for their regulated exocytosis. EMBO J 2006; 25:5443-56. [PMID: 17082761 PMCID: PMC1679766 DOI: 10.1038/sj.emboj.7601419] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2006] [Accepted: 10/10/2006] [Indexed: 01/07/2023] Open
Abstract
Enlargeosomes are small cytoplasmic vesicles that undergo rapid, Ca2+-dependent exo/endocytosis. The role of the cytoskeleton in these processes was unknown. In PC12-27 cells, microtubule disassembly had little effect on enlargeosomes, whereas microfilament disassembly increased markedly both their resting and stimulated exocytosis, and inhibited their endocytosis. Even at rest enlargeosomes are coated at their cytosolic surface by an actin-associated protein, annexin2, bound by a dual, Ca2+-dependent and Ca2+-independent mechanism. In contrast, the other enlargeosome marker, desmoyokin/Ahnak, is transported across the organelle membrane, apparently by an ABC transporter, and binds to its lumenal face. Annexin2-GFP expression revealed that, upon stimulation, the slow and random enlargeosome movement increases markedly and becomes oriented toward the plasma membrane. After annexin2 downregulation enlargeosome exocytosis induced by both [Ca2+]i rise and cytoskeleton disruption is inhibited, and the NGF-induced differentiation is blocked. Binding of annexin2 to the enlargeosome membrane, the most extensive ever reported (>50% annexin2 bound to approximately 3% of total membrane area), seems therefore to participate in the regulation of their exocytosis.
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Affiliation(s)
- Anna Lorusso
- Scientific Institute San Raffaele, ALEMBIC, Advanced Light and Electron Microscopy BioImaging Center, Milan, Italy
| | - Cesare Covino
- Scientific Institute San Raffaele, ALEMBIC, Advanced Light and Electron Microscopy BioImaging Center, Milan, Italy
| | - Giuseppina Priori
- Department of Neuroscience, Vita-Salute San Raffaele University, Center of Excellence in Cell Development, Milan, Italy
| | - Angela Bachi
- Scientific Institute San Raffaele, ALEMBIC, Advanced Light and Electron Microscopy BioImaging Center, Milan, Italy
| | - Jacopo Meldolesi
- Scientific Institute San Raffaele, ALEMBIC, Advanced Light and Electron Microscopy BioImaging Center, Milan, Italy
- Department of Neuroscience, Vita-Salute San Raffaele University, Center of Excellence in Cell Development, Milan, Italy
- IIT Research Unit of Molecular Neuroscience, Milan, Italy
| | - Evelina Chieregatti
- Department of Neuroscience, Vita-Salute San Raffaele University, Center of Excellence in Cell Development, Milan, Italy
- IIT Research Unit of Molecular Neuroscience, Milan, Italy
- Vita-Salute San Raffaele University, DIBIT, via Olgettina 58, 20132 Milan, Italy. Tel.: +39 022 643 4604; Fax: +39 022 643 4813; E-mail
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D'Agostino S, Salamone M, Di Liegro I, Vittorelli ML. Membrane vesicles shed by oligodendroglioma cells induce neuronal apoptosis. Int J Oncol 2006; 29:1075-85. [PMID: 17016637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023] Open
Abstract
In order to investigate the mechanism by which oligodendrogliomas cause neuronal damage, media conditioned by G26/24 oligodendroglioma cells, were fractionated into shed vesicles and vesicle-free supernatants, and added to primary cultures of rat fetal cortical neurons. After one night treatment with vesicles, a reproducible, dose-dependent, inhibitory effect on neurite outgrowth was already induced and, after 48-72 h of incubation, neuronal apoptosis was evident. Vesicle-free supernatants and vesicles shed by NIH-3T3 cells had no inhibitory effects on neurons. Western blot analyses showed that treated neurons expressed a decreased amount of neurofilament (NF), growth-associated protein (GAP-43) and microtubule-associated protein (MAP-2). Moreover procaspase-3 and -8 were activated while Bcl-2 expression was reduced. Vesicles were found positive for the proapoptotic molecule, Fas-ligand (Fas-L), and for the B isoform of Nogo protein, a myelin component with inhibitory effects on neurons. Nogo B involvement in the vesicle effects was analyzed both by testing the neutralizing capability of anti-Nogo antibodies and by removing the Nogo receptor from neurons by phospholipase C digestion. These treatments did not revert the vesicle effects. To test the role of Fas-L, vesicles were treated with functional anti-Fas-L monoclonals. Vesicle inhibitory and proapoptotic effects were reduced. Vesicles shed by ovarian carcinoma cells (OvCa), which are known to vehicle biologically active Fas-L, had similar effects on neurons to those of oligodendroglioma vesicles, and their inhibitory effects were also reduced by anti Fas-L antibodies. We therefore conclude that vesicles shed by G26/24 cells induce neuronal apoptosis at least partially by a Fas-L mediated mechanism.
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Affiliation(s)
- Stefania D'Agostino
- Dipartimento di Biologia Cellulare e dello Sviluppo, Università di Palermo, I-90128 Palermo, Italy
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Balcerzak M, Radisson J, Azzar G, Farlay D, Boivin G, Pikula S, Buchet R. A comparative analysis of strategies for isolation of matrix vesicles. Anal Biochem 2006; 361:176-82. [PMID: 17194438 DOI: 10.1016/j.ab.2006.10.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Accepted: 10/02/2006] [Indexed: 10/24/2022]
Abstract
Matrix vesicles (MVs) are extracellular organelles involved in the initial steps of mineralization. MVs are isolated by two methods. The first isolation method of MVs starts with collagenase digestion of osseous tissues, followed by two differential centrifugations. The second isolation method does not use proteases but rather starts with differential centrifugation, followed by a fractionation on a sucrose gradient. The first method results in a homogeneous population of MVs with higher cholesterol/lipid content, alkaline phosphatase activity, and mineral formation rate as compared with MVs isolated by the second method. The second method leads to higher protein diversity as compared with MVs isolated according to the first method. Due to their distinct protein composition, lipid-to-protein and cholesterol-to-phospholipid ratios, and differences in rates of mineral formation, both types of isolated MVs are crucial for proteomic analysis and for understanding the regulation of mineralization process at the molecular level.
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Affiliation(s)
- M Balcerzak
- Department of Cellular Biochemistry, Nencki Insitute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw, Poland
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Abstract
Exosomes are membrane vesicles that are released by cells upon fusion of multivesicular bodies with the plasma membrane. Their molecular composition reflects their origin in endosomes as intraluminal vesicles. In addition to a common set of membrane and cytosolic molecules, exosomes harbor unique subsets of proteins linked to cell type-associated functions. Exosome secretion participates in the eradication of obsolete proteins but several findings, essentially in the immune system, indicate that exosomes constitute a potential mode of intercellular communication. Release of exosomes by tumor cells and their implication in the propagation of unconventional pathogens such as prions suggests their participation in pathological situations. These findings open up new therapeutic and diagnostic strategies.
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Vermeer JEM, van Leeuwen W, Tobeña-Santamaria R, Laxalt AM, Jones DR, Divecha N, Gadella TWJ, Munnik T. Visualization of PtdIns3P dynamics in living plant cells. Plant J 2006; 47:687-700. [PMID: 16856980 DOI: 10.1111/j.1365-313x.2006.02830.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
To investigate PtdIns3P localization and function in plants, a fluorescent PtdIns3P-specific biosensor (YFP-2xFYVE) was created. On lipid dot blots it bound specifically and with high affinity to PtdIns3P. Transient expression in cowpea protoplasts labelled vacuolar membranes and highly motile structures undergoing fusion and fission. Stable expression in tobacco BY-2 cells labelled similar motile structures, but labelled vacuolar membranes hardly at all. YFP-2xFYVE fluorescence strongly co-localized with the pre-vacuolar marker AtRABF2b, partially co-localized with the endosomal tracer FM4-64, but showed no overlap with the Golgi marker STtmd-CFP. Treatment of cells with wortmannin, a PI3 kinase inhibitor, caused the YFP-2xFYVE fluorescence to redistribute into the cytosol and nucleus within 15 min. BY-2 cells expressing YFP-2xFYVE contained twice as much PtdIns3P as YFP-transformed cells, but this had no effect on cell-growth or stress-induced phospholipid signalling responses. Upon treatment with wortmannin, PtdIns3P levels were reduced by approximately 40% within 15 min in both cell lines. Stable expression of YFP-2xFYVE in Arabidopsis plants labelled different subcellular structures in root compared with shoot tissues. In addition labelling the motile structures common to all cells, YFP-2xFYVE strongly labelled the vacuolar membrane in leaf epidermal and guard cells, suggesting that cell differentiation alters the distribution of PtdIns3P. In dividing BY-2 cells, YFP-2xFYVE-labelled vesicles surrounded the newly formed cell plate, suggesting a role for PtdIns3P in cytokinesis. Together, these data show that YFP-2xFYVE may be used as a biosensor to specifically visualize PtdIns3P in living plant cells.
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Affiliation(s)
- Joop E M Vermeer
- Section of Molecular Cytology, Swammerdam Institute for Life Sciences, University of Amsterdam, Kruislaan 316, Amsterdam, The Netherlands
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Abstract
Tocopherol transfer protein (TTP) regulates vitamin E status by facilitating the secretion of tocopherol from liver to circulating lipoproteins. Heritable mutations in the ttpA gene, encoding for TTP, result in ataxia with vitamin E deficiency (AVED) syndrome, typified by low vitamin E levels and a plethora of neurological disorders. The molecular mechanisms by which TTP facilitates tocopherol secretion are presently unknown. We recently showed that vitamin E is taken up by hepatocytes through an endocytic process and that, shortly following uptake, the vitamin is found primarily in lysosomes. We showed further that TTP is localized to late endocytic vesicles and that it facilitates the intracellular trafficking of tocopherol from lysosomes to the plasma membrane. To gain insight into the molecular mechanisms that underlie TTP actions, we studied the physiological impact of three naturally occurring heritable mutations in the ttpA gene (the R59W, R221W, and A120T substitutions). We found that these mutations impair the ability of TTP to facilitate the secretion of vitamin E from cells. Furthermore, the degree of impairment corresponded to the severity of the AVED pathology associated with each mutation. In cells that express mutated TTP proteins, vitamin E did not traffic to the plasma membrane and remained "trapped" in lysosomes. In addition, we observed that substitution mutations that cause the AVED syndrome impart a marked instability on the TTP protein. These observations suggest that the physiological role of TTP is anchored in its ability to direct vitamin E trafficking from the endocytic compartment to transport vesicles that deliver the vitamin to the site of secretion at the plasma membrane.
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Affiliation(s)
- Jinghui Qian
- Division of Nutritional Sciences, Savage Hall, Cornell University, Ithaca, New York 14853, USA
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Solon J, Streicher P, Richter R, Brochard-Wyart F, Bassereau P. Vesicles surfing on a lipid bilayer: self-induced haptotactic motion. Proc Natl Acad Sci U S A 2006; 103:12382-7. [PMID: 16891411 PMCID: PMC1567888 DOI: 10.1073/pnas.0601400103] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Haptotaxis is a mechanism proposed at the end of the 1960s to explain cell motility. It describes cell movement induced by an adhesion gradient. In this work, we present evidence for self-induced haptotaxis using negatively charged giant vesicles interacting with positively charged supported lipid bilayers, which has not been previously described. Depending on the charge of the vesicle, we observed different behaviors. At low charge, no adhesion occurs. At high charge, the vesicle adheres but does not move. In a restricted range of intermediate charge densities, we found that the vesicle moves spontaneously with velocities of the order of a few micrometers per second over distances of >100 microm. We show that a local lipid transfer between the giant vesicle and the supported lipid bilayer takes place during the adhesion, breaking the symmetry and inducing a lateral charge gradient. This charge gradient polarizes the giant vesicle and induces its motion. To explain our observations, we propose a scaling model that relates the adhesion energy to the velocity of vesicle motion and to the characteristic lipid transfer time. Our measurements indicate that the effective adhesion energy is strongly reduced by counterions, which are dynamically trapped between the vesicle and the supported bilayer.
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Affiliation(s)
- Jéröme Solon
- *Institut Curie, Unité Mixte de Recherche 168, Centre National de la Recherche Scientifique, 26 Rue d’Ulm, 75248 Paris Cedex 05, France; and
| | - Pia Streicher
- *Institut Curie, Unité Mixte de Recherche 168, Centre National de la Recherche Scientifique, 26 Rue d’Ulm, 75248 Paris Cedex 05, France; and
| | - Ralf Richter
- Department of Biophysical Chemistry, University of Heidelberg, INF 253, 69120 Heidelberg, Germany
| | - Françoise Brochard-Wyart
- *Institut Curie, Unité Mixte de Recherche 168, Centre National de la Recherche Scientifique, 26 Rue d’Ulm, 75248 Paris Cedex 05, France; and
| | - Patricia Bassereau
- *Institut Curie, Unité Mixte de Recherche 168, Centre National de la Recherche Scientifique, 26 Rue d’Ulm, 75248 Paris Cedex 05, France; and
- To whom correspondence should be addressed. E-mail:
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