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Zhang JQ, Takahashi A, Gu JY, Zhang X, Kyumoto-Nakamura Y, Kukita A, Uehara N, Hiura H, Yamaza T, Kukita T. In vitro and in vivo detection of tunneling nanotubes in normal and pathological osteoclastogenesis involving osteoclast fusion. J Transl Med 2021; 101:1571-1584. [PMID: 34537825 DOI: 10.1038/s41374-021-00656-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [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: 03/04/2021] [Revised: 08/04/2021] [Accepted: 08/04/2021] [Indexed: 11/09/2022] Open
Abstract
Osteoclasts are multinucleated cells formed through specific recognition and fusion of mononuclear osteoclast precursors derived from hematopoietic stem cells. Detailed cellular events concerning cell fusion in osteoclast differentiation remain ambiguous. Tunneling nanotubes (TNTs), actin-based membrane structures, play an important role in intercellular communication between cells. We have previously reported the presence of TNTs in the fusion process of osteoclastogenesis. Here we analyzed morphological details of TNTs using scanning electron microscopy. The osteoclast precursor cell line RAW-D was stimulated to form osteoclast-like cells, and morphological details in the appearance of TNTs were extensively analyzed. Osteoclast-like cells could be classified into three types; early osteoclast precursors, late osteoclast precursors, and multinucleated osteoclast-like cells based on the morphological characteristics. TNTs were frequently observed among these three types of cells. TNTs could be classified into thin, medium, and thick TNTs based on the diameter and length. The shapes of TNTs were dynamically changed from thin to thick. Among them, medium TNTs were often observed between two remote cells, in which side branches attached to the culture substrates and beaded bulge-like structures were often observed. Cell-cell interaction through TNTs contributed to cell migration and rapid transport of information between cells. TNTs were shown to be involved in cell-cell fusion between osteoclast precursors and multinucleated osteoclast-like cells, in which movement of membrane vesicles and nuclei was observed. Formation of TNTs was also confirmed in primary cultures of osteoclasts. Furthermore, we have successfully detected TNTs formed between osteoclasts observed in the bone destruction sites of arthritic rats. Thus, formation of TNTs may be important for the differentiation of osteoclasts both in vitro and in vivo. TNTs could be one target cellular structure for the regulation of osteoclast differentiation and function in bone diseases.
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Affiliation(s)
- Jing-Qi Zhang
- Department of Molecular Cell Biology and Oral Anatomy, Division of Oral Biological Sciences, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Akira Takahashi
- Department of Fixed Prosthodontics, Division of Oral Rehabilitation, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Jiong-Yan Gu
- Department of Molecular Cell Biology and Oral Anatomy, Division of Oral Biological Sciences, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Xiaoxu Zhang
- Department of Implant and Rehabilitative Dentistry, Division of Oral Rehabilitation, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Yukari Kyumoto-Nakamura
- Department of Molecular Cell Biology and Oral Anatomy, Division of Oral Biological Sciences, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Akiko Kukita
- Department of Research Center of Arthroplasty, Faculty of Medicine, Saga University, Saga, Japan
| | - Norihisa Uehara
- Department of Molecular Cell Biology and Oral Anatomy, Division of Oral Biological Sciences, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Hidenobu Hiura
- Department of Molecular Cell Biology and Oral Anatomy, Division of Oral Biological Sciences, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
- Department of Orthodontics and Dentofacial Orthopedics, Division of Oral Health, Growth, and Development, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Takayoshi Yamaza
- Department of Molecular Cell Biology and Oral Anatomy, Division of Oral Biological Sciences, Faculty of Dental Science, Kyushu University, Fukuoka, Japan
| | - Toshio Kukita
- Department of Molecular Cell Biology and Oral Anatomy, Division of Oral Biological Sciences, Faculty of Dental Science, Kyushu University, Fukuoka, Japan.
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Jiao M, Wu D, Wei Q. Myosin II-interacting guanine nucleotide exchange factor promotes bleb retraction via stimulating cortex reassembly at the bleb membrane. Mol Biol Cell 2018; 29:643-656. [PMID: 29321250 PMCID: PMC6004584 DOI: 10.1091/mbc.e17-10-0579] [Citation(s) in RCA: 19] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 12/11/2017] [Accepted: 01/03/2018] [Indexed: 11/11/2022] Open
Abstract
Blebs are involved in various biological processes such as cell migration, cytokinesis, and apoptosis. While the expansion of blebs is largely an intracellular pressure-driven process, the retraction of blebs is believed to be driven by RhoA activation that leads to the reassembly of the actomyosin cortex at the bleb membrane. However, it is still poorly understood how RhoA is activated at the bleb membrane. Here, we provide evidence demonstrating that myosin II-interacting guanine nucleotide exchange factor (MYOGEF) is implicated in bleb retraction via stimulating RhoA activation and the reassembly of an actomyosin network at the bleb membrane during bleb retraction. Interaction of MYOGEF with ezrin, a well-known regulator of bleb retraction, is required for MYOGEF localization to retracting blebs. Notably, knockout of MYOGEF or ezrin not only disrupts RhoA activation at the bleb membrane, but also interferes with nonmuscle myosin II localization and activation, as well as actin polymerization in retracting blebs. Importantly, MYOGEF knockout slows down bleb retraction. We propose that ezrin interacts with MYOGEF and recruits it to retracting blebs, where MYOGEF activates RhoA and promotes the reassembly of the cortical actomyosin network at the bleb membrane, thus contributing to the regulation of bleb retraction.
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Affiliation(s)
- Meng Jiao
- Department of Biological Sciences, Fordham University, Bronx, NY 10458
| | - Di Wu
- Department of Biological Sciences, Fordham University, Bronx, NY 10458
| | - Qize Wei
- Department of Biological Sciences, Fordham University, Bronx, NY 10458
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3
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Abstract
Cup-shaped secretory portals at the cell plasma membrane called porosomes mediate the precision release of intravesicular material from cells. Membrane-bound secretory vesicles transiently dock and fuse at the base of porosomes facing the cytosol to expel pressurized intravesicular contents from the cell during secretion. The structure, isolation, composition, and functional reconstitution of the neuronal porosome complex have greatly progressed, providing a molecular understanding of its function in health and disease. Neuronal porosomes are 15 nm cup-shaped lipoprotein structures composed of nearly 40 proteins, compared to the 120 nm nuclear pore complex composed of >500 protein molecules. Membrane proteins compose the porosome complex, making it practically impossible to solve its atomic structure. However, atomic force microscopy and small-angle X-ray solution scattering studies have provided three-dimensional structural details of the native neuronal porosome at sub-nanometer resolution, providing insights into the molecular mechanism of its function. The participation of several porosome proteins previously implicated in neurotransmission and neurological disorders, further attest to the crosstalk between porosome proteins and their coordinated involvement in release of neurotransmitter at the synapse.
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Affiliation(s)
- Akshata R Naik
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Kenneth T Lewis
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Bhanu P Jena
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, USA
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4
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Li JR, Ross SS, Liu Y, Liu YX, Wang KH, Chen HY, Liu FT, Laurence TA, Liu GY. Engineered Nanostructures of Haptens Lead to Unexpected Formation of Membrane Nanotubes Connecting Rat Basophilic Leukemia Cells. ACS Nano 2015; 9:6738-6746. [PMID: 26057701 PMCID: PMC4758354 DOI: 10.1021/acsnano.5b02270] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A recent finding reports that co-stimulation of the high-affinity immunoglobulin E (IgE) receptor (FcεRI) and the chemokine receptor 1 (CCR1) triggered formation of membrane nanotubes among bone-marrow-derived mast cells. The co-stimulation was attained using corresponding ligands: IgE binding antigen and macrophage inflammatory protein 1α (MIP1 α), respectively. However, this approach failed to trigger formation of nanotubes among rat basophilic leukemia (RBL) cells due to the lack of CCR1 on the cell surface (Int. Immunol. 2010, 22 (2), 113-128). RBL cells are frequently used as a model for mast cells and are best known for antibody-mediated activation via FcεRI. This work reports the successful formation of membrane nanotubes among RBLs using only one stimulus, a hapten of 2,4-dinitrophenyl (DNP) molecules, which are presented as nanostructures with our designed spatial arrangements. This observation underlines the significance of the local presentation of ligands in the context of impacting the cellular signaling cascades. In the case of RBL, certain DNP nanostructures suppress antigen-induced degranulation and facilitate the rearrangement of the cytoskeleton to form nanotubes. These results demonstrate an important scientific concept; engineered nanostructures enable cellular signaling cascades, where current technologies encounter great difficulties. More importantly, nanotechnology offers a new platform to selectively activate and/or inhibit desired cellular signaling cascades.
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Affiliation(s)
- Jie-Ren Li
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Shailise S. Ross
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Yang Liu
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Ying X. Liu
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Kang-hsin Wang
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Huan-Yuan Chen
- Department of Dermatology, School of Medicine, University of California, Davis, Sacramento, California 95817, United States
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan, ROC
| | - Fu-Tong Liu
- Department of Dermatology, School of Medicine, University of California, Davis, Sacramento, California 95817, United States
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan, ROC
| | - Ted A. Laurence
- Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Gang-yu Liu
- Department of Chemistry, University of California, Davis, California 95616, United States
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5
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Chong K, Tan OLL, Almsherqi ZA, Lin Q, Kohlwein SD, Deng Y. Isolation of mitochondria with cubic membrane morphology reveals specific ionic requirements for the preservation of membrane structure. Protoplasma 2015; 252:689-696. [PMID: 25226828 DOI: 10.1007/s00709-014-0698-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2014] [Accepted: 09/01/2014] [Indexed: 06/03/2023]
Abstract
Biological membranes with cubic symmetry are a hallmark of virus-infected or diseased cells. The mechanisms of formation and specific cellular functions of cubic membranes, however, are unclear. The best-documented cubic membrane formation occurs in the free-living giant amoeba Chaos carolinense. In that system, mitochondrial inner membranes undergo a reversible structural change from tubular to cubic membrane organization upon starvation of the organism. As a prerequisite to further analyze the structural and functional features of cubic membranes, we adapted protocols for the isolation of mitochondria from starved amoeba and have identified buffer conditions that preserve cubic membrane morphology in vitro. The requirement for high concentration of ion-chelating agents in the isolation media supports the importance of a balanced ion milieu in establishing and maintaining cubic membranes in vivo.
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Affiliation(s)
- Ketpin Chong
- Cubic Membrane Laboratory, Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117597, Singapore
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Polevova S, Breygina M, Matveyeva N, Yermakov I. Periplasmic multilamellar membranous structures in Nicotiana tabacum L. pollen grains treated with Ni²⁺ or Cu²⁺. Protoplasma 2014; 251:1521-5. [PMID: 24802108 DOI: 10.1007/s00709-014-0651-y] [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] [Received: 01/23/2014] [Accepted: 04/18/2014] [Indexed: 06/03/2023]
Abstract
Essential trace elements Ni(2+) and Cu(2+) can block pollen germination without causing cell death. Mechanisms of this effect remain unclear. Using TEM, we studied the effects of Ni(2+) or Cu(2+) treatment on the ultrastructure of the aperture regions in tobacco pollen preparing to germinate in vitro, since in these zones, the main fluxes of water, ions, and metabolites cross the plasmalemma. Neither Ni(2+) nor Cu(2+) altered the cytoplasm ultrastructure, but both affected the reorganization of apertural periplasm during pollen activation. Numerous multilamellar membranous structures continuous with the plasma membrane could be seen in hydrated but not yet activated pollen. When the normal activation was completed, the structures disappeared and the plasmalemma became smooth. In the presence of 1 mM Ni(2+) or 100 μM Cu(2+), these structures preserved its original appearance. It is assumed to be the storage form for the membrane material, which is to provide an initial phase of the pollen tube growth. Ni(2+) and Cu(2+) affect the utilization of these membranes, thereby, blocking the pollen germination.
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Affiliation(s)
- Svetlana Polevova
- Higher Plants Department, Faculty of Biology, Lomonosov Moscow State University, Lenin Hills, Moscow, Russia, 119234,
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Avila-Calderón ED, Araiza-Villanueva MG, Cancino-Diaz JC, López-Villegas EO, Sriranganathan N, Boyle SM, Contreras-Rodríguez A. Roles of bacterial membrane vesicles. Arch Microbiol 2014; 197:1-10. [PMID: 25294190 DOI: 10.1007/s00203-014-1042-7] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 08/26/2014] [Accepted: 09/27/2014] [Indexed: 01/26/2023]
Abstract
Outer membrane vesicles (OMVs) are released from the outer membrane of Gram-negative bacteria. Moreover, Gram-positive bacteria also produce membrane-derived vesicles. As OMVs transport several bacterial components, especially from the cell envelope, their interaction with the host cell, with other bacteria or as immunogens, have been studied intensely. Several functions have been ascribed to OMVs, especially those related to the transport of virulence factors, antigenic protein composition, and development as acellular vaccines. In this work, we review some of the recent findings about OMVs produced by specific pathogenic bacterial species.
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Affiliation(s)
- Eric Daniel Avila-Calderón
- Departamento de Microbiología. Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Prol. Carpio y Plan de Ayala s/n, Col. Sto. Tomás, CP 11340, Mexico, D.F., Mexico
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8
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Pillet F, Lemonier S, Schiavone M, Formosa C, Martin-Yken H, Francois JM, Dague E. Uncovering by atomic force microscopy of an original circular structure at the yeast cell surface in response to heat shock. BMC Biol 2014; 12:6. [PMID: 24468076 PMCID: PMC3925996 DOI: 10.1186/1741-7007-12-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [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: 12/09/2013] [Accepted: 01/10/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Atomic Force Microscopy (AFM) is a polyvalent tool that allows biological and mechanical studies of full living microorganisms, and therefore the comprehension of molecular mechanisms at the nanoscale level. By combining AFM with genetical and biochemical methods, we explored the biophysical response of the yeast Saccharomyces cerevisiae to a temperature stress from 30°C to 42°C during 1 h. RESULTS We report for the first time the formation of an unprecedented circular structure at the cell surface that takes its origin at a single punctuate source and propagates in a concentric manner to reach a diameter of 2-3 μm at least, thus significantly greater than a bud scar. Concomitantly, the cell wall stiffness determined by the Young's Modulus of heat stressed cells increased two fold with a concurrent increase of chitin. This heat-induced circular structure was not found either in wsc1Δ or bck1Δ mutants that are defective in the CWI signaling pathway, nor in chs1Δ, chs3Δ and bni1Δ mutant cells, reported to be deficient in the proper budding process. It was also abolished in the presence of latrunculin A, a toxin known to destabilize actin cytoskeleton. CONCLUSIONS Our results suggest that this singular morphological event occurring at the cell surface is due to a dysfunction in the budding machinery caused by the heat shock and that this phenomenon is under the control of the CWI pathway.
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Affiliation(s)
- Flavien Pillet
- CNRS, LAAS, 7 avenue du colonel Roche, F-31077 Toulouse, France
- Université de Toulouse, UPS, INSA, INP, ISAE, LAAS, F-31077 Toulouse, France
| | - Stéphane Lemonier
- CNRS, LAAS, 7 avenue du colonel Roche, F-31077 Toulouse, France
- Université de Toulouse, UPS, INSA, INP, ISAE, LAAS, F-31077 Toulouse, France
- CNRS, ITAV-USR 3505, F31106 Toulouse, France
| | - Marion Schiavone
- CNRS, LAAS, 7 avenue du colonel Roche, F-31077 Toulouse, France
- Université de Toulouse, UPS, INSA, INP, ISAE, LAAS, F-31077 Toulouse, France
- Université de Toulouse, INSA, UPS, INP, 135 avenue de Rangueil, F-31077 Toulouse, France
- INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31077 Toulouse, France
- CNRS, UMR5504, F-31400 Toulouse, France
| | - Cécile Formosa
- CNRS, LAAS, 7 avenue du colonel Roche, F-31077 Toulouse, France
- Université de Toulouse, UPS, INSA, INP, ISAE, LAAS, F-31077 Toulouse, France
- CNRS, UMR 7565, SRSMC, Vandoeuvre-lès-Nancy, France
- Université de Lorraine, UMR 7565, Faculté de Pharmacie, Nancy, France
| | - Hélène Martin-Yken
- Université de Toulouse, INSA, UPS, INP, 135 avenue de Rangueil, F-31077 Toulouse, France
- INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31077 Toulouse, France
- CNRS, UMR5504, F-31400 Toulouse, France
| | - Jean Marie Francois
- Université de Toulouse, INSA, UPS, INP, 135 avenue de Rangueil, F-31077 Toulouse, France
- INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31077 Toulouse, France
- CNRS, UMR5504, F-31400 Toulouse, France
| | - Etienne Dague
- CNRS, LAAS, 7 avenue du colonel Roche, F-31077 Toulouse, France
- Université de Toulouse, UPS, INSA, INP, ISAE, LAAS, F-31077 Toulouse, France
- CNRS, ITAV-USR 3505, F31106 Toulouse, France
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9
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Adams PG, Cadby AJ, Robinson B, Tsukatani Y, Tank M, Wen J, Blankenship RE, Bryant DA, Hunter CN. Comparison of the physical characteristics of chlorosomes from three different phyla of green phototrophic bacteria. Biochim Biophys Acta 2013; 1827:1235-44. [PMID: 23867748 DOI: 10.1016/j.bbabio.2013.07.004] [Citation(s) in RCA: 22] [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] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 07/05/2013] [Accepted: 07/08/2013] [Indexed: 11/18/2022]
Abstract
Chlorosomes, the major antenna complexes in green sulphur bacteria, filamentous anoxygenic phototrophs, and phototrophic acidobacteria, are attached to the cytoplasmic side of the inner cell membrane and contain thousands of bacteriochlorophyll (BChl) molecules that harvest light and channel the energy to membrane-bound reaction centres. Chlorosomes from phototrophs representing three different phyla, Chloroflexus (Cfx.) aurantiacus, Chlorobaculum (Cba.) tepidum and the newly discovered "Candidatus (Ca.) Chloracidobacterium (Cab.) thermophilum" were analysed using PeakForce Tapping atomic force microscopy (PFT-AFM). Gentle PFT-AFM imaging in buffered solutions that maintained the chlorosomes in a near-native state revealed ellipsoids of variable size, with surface bumps and undulations that differ between individual chlorosomes. Cba. tepidum chlorosomes were the largest (133×57×36nm; 141,000nm(3) volume), compared with chlorosomes from Cfx. aurantiacus (120×44×30nm; 84,000nm(3)) and Ca. Cab. thermophilum (99×40×31nm; 65,000nm(3)). Reflecting the contributions of thousands of pigment-pigment stacking interactions to the stability of these supramolecular assemblies, analysis by nanomechanical mapping shows that chlorosomes are highly stable and that their integrity is disrupted only by very strong forces of 1000-2000pN. AFM topographs of Ca. Cab. thermophilum chlorosomes that had retained their attachment to the cytoplasmic membrane showed that this membrane dynamically changes shape and is composed of protrusions of up to 30nm wide and 6nm above the mica support, possibly representing different protein domains. Spectral imaging revealed significant heterogeneity in the fluorescence emission of individual chlorosomes, likely reflecting the variations in BChl c homolog composition and internal arrangements of the stacked BChls within each chlorosome.
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Affiliation(s)
- Peter G Adams
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
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10
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Svistounov D, Warren A, McNerney GP, Owen DM, Zencak D, Zykova SN, Crane H, Huser T, Quinn RJ, Smedsrød B, Le Couteur DG, Cogger VC. The Relationship between fenestrations, sieve plates and rafts in liver sinusoidal endothelial cells. PLoS One 2012; 7:e46134. [PMID: 23029409 PMCID: PMC3454341 DOI: 10.1371/journal.pone.0046134] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 08/28/2012] [Indexed: 01/22/2023] Open
Abstract
Fenestrations are transcellular pores in endothelial cells that facilitate transfer of substrates between blood and the extravascular compartment. In order to understand the regulation and formation of fenestrations, the relationship between membrane rafts and fenestrations was investigated in liver sinusoidal endothelial cells where fenestrations are grouped into sieve plates. Three dimensional structured illumination microscopy, scanning electron microscopy, internal reflectance fluorescence microscopy and two-photon fluorescence microscopy were used to study liver sinusoidal endothelial cells isolated from mice. There was an inverse distribution between sieve plates and membrane rafts visualized by structured illumination microscopy and the fluorescent raft stain, Bodipy FL C5 ganglioside GM1. 7-ketocholesterol and/or cytochalasin D increased both fenestrations and lipid-disordered membrane, while Triton X-100 decreased both fenestrations and lipid-disordered membrane. The effects of cytochalasin D on fenestrations were abrogated by co-administration of Triton X-100, suggesting that actin disruption increases fenestrations by its effects on membrane rafts. Vascular endothelial growth factor (VEGF) depleted lipid-ordered membrane and increased fenestrations. The results are consistent with a sieve-raft interaction, where fenestrations form in non-raft lipid-disordered regions of endothelial cells once the membrane-stabilizing effects of actin cytoskeleton and membrane rafts are diminished.
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Affiliation(s)
- Dmitri Svistounov
- Centre for Education and Research on Ageing and ANZAC Medical Research Institute, University of Sydney and Concord Hospital, Sydney, Australia
| | - Alessandra Warren
- Centre for Education and Research on Ageing and ANZAC Medical Research Institute, University of Sydney and Concord Hospital, Sydney, Australia
| | - Gregory P. McNerney
- NSF Center for Biophotonics Science and Technology, University of California Davis, Sacramento, California, United States of America
| | - Dylan M. Owen
- Centre for Vascular Research, University of New South Wales, Sydney, Australia
| | - Dusan Zencak
- Eskitis Institute, Griffith University, Brisbane, Australia
| | - Svetlana N. Zykova
- Centre for Education and Research on Ageing and ANZAC Medical Research Institute, University of Sydney and Concord Hospital, Sydney, Australia
| | - Harry Crane
- Centre for Education and Research on Ageing and ANZAC Medical Research Institute, University of Sydney and Concord Hospital, Sydney, Australia
| | - Thomas Huser
- NSF Center for Biophotonics Science and Technology, University of California Davis, Sacramento, California, United States of America
| | | | - Bård Smedsrød
- Department of Medical Biology, University of Tromso, Tromso, Norway
| | - David G. Le Couteur
- Centre for Education and Research on Ageing and ANZAC Medical Research Institute, University of Sydney and Concord Hospital, Sydney, Australia
- * E-mail:
| | - Victoria C. Cogger
- Centre for Education and Research on Ageing and ANZAC Medical Research Institute, University of Sydney and Concord Hospital, Sydney, Australia
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11
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Ben-Dov N, Korenstein R. Enhancement of cell membrane invaginations, vesiculation and uptake of macromolecules by protonation of the cell surface. PLoS One 2012; 7:e35204. [PMID: 22558127 PMCID: PMC3340387 DOI: 10.1371/journal.pone.0035204] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [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: 12/15/2011] [Accepted: 03/10/2012] [Indexed: 01/04/2023] Open
Abstract
The different pathways of endocytosis share an initial step involving local inward curvature of the cell’s lipid bilayer. It has been shown that to generate membrane curvature, proteins or lipids enforce transversal asymmetry of the plasma membrane. Thus it emerges as a general phenomenon that transversal membrane asymmetry is the common required element for the formation of membrane curvature. The present study demonstrates that elevating proton concentration at the cell surface stimulates the formation of membrane invaginations and vesiculation accompanied by efficient uptake of macromolecules (Dextran-FITC, 70 kD), relative to the constitutive one. The insensitivity of proton induced uptake to inhibiting treatments and agents of the known endocytic pathways suggests the entry of macromolecules to proceeds via a yet undefined route. This is in line with the fact that neither ATP depletion, nor the lowering of temperature, abolishes the uptake process. In addition, fusion mechanism such as associated with low pH uptake of toxins and viral proteins can be disregarded by employing the polysaccharide dextran as the uptake molecule. The proton induced uptake increases linearly in the extracellular pH range of 6.5 to 4.5, and possesses a steep increase at the range of 4> pH>3, reaching a plateau at pH≤3. The kinetics of the uptake implies that the induced vesicles release their content to the cytosol and undergo rapid recycling to the plasma membrane. We suggest that protonation of the cell’s surface induces local charge asymmetries across the cell membrane bilayer, inducing inward curvature of the cell membrane and consequent vesiculation and uptake.
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Affiliation(s)
- Nadav Ben-Dov
- Department of Physiology and Pharmacology, Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel
| | - Rafi Korenstein
- Department of Physiology and Pharmacology, Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel
- * E-mail:
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12
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Park SB, Jang HB, Nho SW, Cha IS, Hikima JI, Ohtani M, Aoki T, Jung TS. Outer membrane vesicles as a candidate vaccine against edwardsiellosis. PLoS One 2011; 6:e17629. [PMID: 21408115 PMCID: PMC3050902 DOI: 10.1371/journal.pone.0017629] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [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: 12/24/2010] [Accepted: 02/03/2011] [Indexed: 01/08/2023] Open
Abstract
Infection with Edwardsiella tarda, a gram-negative bacterium, causes high morbidity and mortality in both marine and freshwater fish. Outer membrane vesicles (OMVs) released from gram-negative bacteria are known to play important roles in bacterial pathogenesis and host immune responses, but no such roles for E. tarda OMVs have yet been described. In the present study, we investigated the proteomic composition of OMVs and the immunostimulatory effect of OMVs in a natural host, as well as the efficacy of OMVs when used as a vaccine against E. tarda infection. A total of 74 proteins, from diverse subcellular fractions, were identified in OMVs. These included a variety of important virulence factors, such as hemolysin, OmpA, porin, GAPDH, EseB, EseC, EseD, EvpC, EvpP, lipoprotein, flagellin, and fimbrial protein. When OMVs were administrated to olive flounder, significant induction of mRNAs encoding IL-1β, IL-6, TNFα, and IFNγ was observed, compared with the levels seen in fish injected with formalin-killed E. tarda. In a vaccine trial, olive flounder given OMVs were more effectively protected (p<0.0001) than were control fish. Investigation of OMVs may be useful not only for understanding the pathogenesis of E. tarda but also in development of an effective vaccine against edwardsiellosis.
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Affiliation(s)
- Seong Bin Park
- Aquatic Biotechnology Center, College of Veterinary Medicine, Gyeongsang National University, Jinju, South Korea
| | - Ho Bin Jang
- Aquatic Biotechnology Center, College of Veterinary Medicine, Gyeongsang National University, Jinju, South Korea
| | - Seong Won Nho
- Aquatic Biotechnology Center, College of Veterinary Medicine, Gyeongsang National University, Jinju, South Korea
| | - In Seok Cha
- Aquatic Biotechnology Center, College of Veterinary Medicine, Gyeongsang National University, Jinju, South Korea
| | - Jun-ichi Hikima
- Aquatic Biotechnology Center, College of Veterinary Medicine, Gyeongsang National University, Jinju, South Korea
| | - Maki Ohtani
- Aquatic Biotechnology Center, College of Veterinary Medicine, Gyeongsang National University, Jinju, South Korea
| | - Takashi Aoki
- Aquatic Biotechnology Center, College of Veterinary Medicine, Gyeongsang National University, Jinju, South Korea
- * E-mail: (TSJ); (TA)
| | - Tae Sung Jung
- Aquatic Biotechnology Center, College of Veterinary Medicine, Gyeongsang National University, Jinju, South Korea
- * E-mail: (TSJ); (TA)
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13
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Zheng W, Bergman B, Chen B, Zheng S, Xiang G, Rasmussen U. Cellular responses in the cyanobacterial symbiont during its vertical transfer between plant generations in the Azolla microphylla symbiosis. New Phytol 2009; 181:53-61. [PMID: 19076717 DOI: 10.1111/j.1469-8137.2008.02644.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The nitrogen-fixing symbiosis between cyanobacteria and the water fern Azolla microphylla is, in contrast to other cyanobacteria-plant symbioses, the only one of a perpetual nature. The cyanobacterium is vertically transmitted between the plant generations, via vegetative fragmentation of the host or sexually within megasporocarps. In the latter process, subsets of the cyanobacterial population living endophytically in the Azolla leaves function as inocula for the new plant generations. Using electron microscopy and immunogold-labeling, the fate of the cyanobacterium during colonization and development of the megasporocarp was revealed. On entering the indusium chamber of the megasporocarps as small-celled motile cyanobacterial filaments (hormogonia), these differentiated into large thick-walled akinetes (spores) in a synchronized manner. This process was accompanied by cytoplasmic reorganizations and the release of numerous membrane vesicles, most of which contained DNA, and the formation of a highly structured biofilm. Taken together the data revealed complex adaptations in the cyanobacterium during its transition between plant generations.
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Affiliation(s)
- Weiwen Zheng
- Key laboratory of Bio-Pesticide and Chemical Biology, Ministry of Education, Fujian Agriculture and Forestry University, China, 350002;Biotechnology Institute, Fujian Academy of Agricultural Sciences, Fuzhou, China, 350003;Department of Botany, Stockholm University, SE-10691 Stockholm, Sweden
| | - Birgitta Bergman
- Key laboratory of Bio-Pesticide and Chemical Biology, Ministry of Education, Fujian Agriculture and Forestry University, China, 350002;Biotechnology Institute, Fujian Academy of Agricultural Sciences, Fuzhou, China, 350003;Department of Botany, Stockholm University, SE-10691 Stockholm, Sweden
| | - Bin Chen
- Key laboratory of Bio-Pesticide and Chemical Biology, Ministry of Education, Fujian Agriculture and Forestry University, China, 350002;Biotechnology Institute, Fujian Academy of Agricultural Sciences, Fuzhou, China, 350003;Department of Botany, Stockholm University, SE-10691 Stockholm, Sweden
| | - Siping Zheng
- Key laboratory of Bio-Pesticide and Chemical Biology, Ministry of Education, Fujian Agriculture and Forestry University, China, 350002;Biotechnology Institute, Fujian Academy of Agricultural Sciences, Fuzhou, China, 350003;Department of Botany, Stockholm University, SE-10691 Stockholm, Sweden
| | - Guan Xiang
- Key laboratory of Bio-Pesticide and Chemical Biology, Ministry of Education, Fujian Agriculture and Forestry University, China, 350002;Biotechnology Institute, Fujian Academy of Agricultural Sciences, Fuzhou, China, 350003;Department of Botany, Stockholm University, SE-10691 Stockholm, Sweden
| | - Ulla Rasmussen
- Key laboratory of Bio-Pesticide and Chemical Biology, Ministry of Education, Fujian Agriculture and Forestry University, China, 350002;Biotechnology Institute, Fujian Academy of Agricultural Sciences, Fuzhou, China, 350003;Department of Botany, Stockholm University, SE-10691 Stockholm, Sweden
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14
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Abstract
Members of the Rho family of GTPases are key regulators of the actin cytoskeleton. In particular, activated Rac1 stimulates membrane dorsal ruffle formation in response to platelet-derived growth factor (PDGF). Abl-interactor (Abi)-1 and betaPIX, a guanine nucleotide exchange factor for Rac1, localise at these Rac1-induced actin structures and play important roles in the induction of membrane dorsal ruffling in response to PDGF in fibroblasts. Here, we demonstrate a novel interaction between Abi-1 and betaPIX using the yeast two-hybrid system, in vitro pull-down assays, and in vivo co-immunoprecipitation experiments. In vitro, the C-terminal fragment of betaPIX interacted with Abi-1, while in vivo the N-terminal fragment of betaPIX interacted with Abi-1. The biological function of this interaction was investigated in mouse fibroblasts in response to PDGF stimulation. Abi-1 and betaPIX co-localised in the cytoplasm and to membrane dorsal ruffles after PDGF treatment. We show that the co-expression of Abi-1 and truncated forms of betaPIX in mouse fibroblasts blocked PDGF-induced membrane dorsal ruffles. Together, these results show that the interaction between Abi-1 and betaPIX is involved in the formation of growth factor-induced membrane dorsal ruffles.
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Affiliation(s)
- Fanny Campa
- Max Planck Institute for Infection Biology, Department of Molecular Biology, Campus Charité Mitte, Berlin, Germany
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15
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Lee EY, Bang JY, Park GW, Choi DS, Kang JS, Kim HJ, Park KS, Lee JO, Kim YK, Kwon KH, Kim KP, Gho YS. Global proteomic profiling of native outer membrane vesicles derived from Escherichia coli. Proteomics 2007; 7:3143-53. [PMID: 17787032 DOI: 10.1002/pmic.200700196] [Citation(s) in RCA: 307] [Impact Index Per Article: 18.1] [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: 01/22/2023]
Abstract
Gram-negative bacteria constitutively secrete native outer membrane vesicles (OMVs) into the extracellular milieu. Although recent progress in this area has revealed that OMVs are essential for bacterial survival and pathogenesis, the mechanism of vesicle formation and the biological roles of OMVs have not been clearly defined. Using a proteomics approach, we identified 141 protein components of Escherichia coli-derived native OMVs with high confidence; two separate analyses yielded identifications of 104 and 117 proteins, respectively, with 80 proteins overlapping between the two trials. In the group of identified proteins, the outer membrane proteins were highly enriched, whereas inner membrane proteins were lacking, suggesting that a specific sorting mechanism for vesicular proteins exists. We also identified proteins involved in vesicle formation, the removal of toxic compounds and attacking phage, and the elimination of competing organisms, as well as those involved in facilitating the transfer of genetic material and protein to other bacteria, targeting host cells, and modulating host immune responses. This study provides a global view of native bacterial OMVs. This information will help us not only to elucidate the biogenesis and functions of OMV from nonpathogenic and pathogenic bacteria but also to develop vaccines and antibiotics effective against pathogenic strains.
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Affiliation(s)
- Eun-Young Lee
- Department of Life Science and Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Republic of Korea
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16
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Goh T, Uchida W, Arakawa S, Ito E, Dainobu T, Ebine K, Takeuchi M, Sato K, Ueda T, Nakano A. VPS9a, the common activator for two distinct types of Rab5 GTPases, is essential for the development of Arabidopsis thaliana. Plant Cell 2007; 19:3504-15. [PMID: 18055610 PMCID: PMC2174884 DOI: 10.1105/tpc.107.053876] [Citation(s) in RCA: 80] [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] [Received: 07/02/2007] [Revised: 09/09/2007] [Accepted: 10/12/2007] [Indexed: 05/18/2023]
Abstract
Rab5, a subfamily of Rab GTPases, regulates a variety of endosomal functions as a molecular switch. Arabidopsis thaliana has two different types of Rab5-member GTPases: conventional type, ARA7 and RHA1, and a plant-specific type, ARA6. We found that only one guanine nucleotide exchange factor (GEF), named VPS9a, can activate all Rab5 members to GTP-bound forms in vitro in spite of their diverged structures. In the vps9a-1 mutant, whose GEF activity is completely lost, embryogenesis was arrested at the torpedo stage. Green fluorescent protein (GFP)-ARA7 and ARA6-GFP were diffused in cytosol like GDP-fixed mutants of Rab5 in vps9a-1, indicating that both types of GTPase are regulated by VPS9a. In the leaky vps9a-2 mutant, elongation of the primary root was severely affected. Overexpression of the GTP-fixed form of ARA7 suppressed the vps9a-2 mutation, but overexpression of ARA6 had no apparent effects. These results indicate that the two types of plant Rab5 members are functionally differentiated, even though they are regulated by the same activator, VPS9a.
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Affiliation(s)
- Tatsuaki Goh
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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17
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Abstract
OBJECTIVE To assess pinopode formation in Lif null and Hoxa10 null mice with infertility secondary to failed implantation. DESIGN Controlled animal experiment. SETTING Animal research and laboratory facility. ANIMAL(S) Lif null, Hoxa10 null, and ICR mice and Sprague-Dawley rats. INTERVENTION(S) Endometrial tissue was collected during the peri-implantation period and after ovariectomy. MAIN OUTCOME MEASURE(S) Endometrial epithelial tissue was examined under scanning-electron microscopy and assigned a score depending on the number of pinopodes present. RESULT(S) Pinopode scores in ICR, Lif null, and Hoxa10 null mice were comparable throughout the peri-implantation period, rising on day 3.5 of pregnancy and remaining elevated through to day 7.5, suggesting that pinopodes are not a good indicator of receptivity in mice. In contrast, pinopode scores in rats clearly demarcated the window of receptivity, appearing on day 4 of pregnancy and declining sharply on day 6. Pinopode scores were low in E(2)-treated ovariectomized mice, but unexpectedly, pinopode scores in vehicle-injected ovariectomized ICR mice were markedly elevated. CONCLUSION(S) Lif null and Hoxa10 null mice, in which implantation is impaired, have a similar number of pinopodes to fertile ICR mice. Pinopodes do not define a window of implantation in mice.
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Affiliation(s)
- Claire E Quinn
- Division of Reproductive Sciences, Samuel Lunenfeld Research Institute, and the Fran and Lawrence Bloomberg Department of Obstetrics and Gynecology, Mount Sinai Hospital, University of Toronto, Institute of Medical Sciences, Toronto, Ontario, Canada
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18
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Schmutz C, Stevens J, Spang A. Functions of the novel RhoGAP proteins RGA-3 and RGA-4 in the germ line and in the early embryo of C. elegans. Development 2007; 134:3495-505. [PMID: 17728351 DOI: 10.1242/dev.000802] [Citation(s) in RCA: 49] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
We have identified two redundant GTPase activating proteins (GAPs) - RGA-3 and RGA-4 - that regulate Rho GTPase function at the plasma membrane in early Caenorhabditis elegans embryos. Knockdown of both RhoGAPs resulted in extensive membrane ruffling, furrowing and pronounced pseudo-cleavages. In addition, the non-muscle myosin NMY-2 and RHO-1 accumulated on the cortex at sites of ruffling. RGA-3 and RGA-4 are GAPs for RHO-1, but most probably not for CDC-42, because only RHO-1 was epistatic to the two GAPs, and the GAPs had no obvious influence on CDC-42 function. Furthermore, knockdown of either the RHO-1 effector, LET-502, or the exchange factor for RHO-1, ECT-2, alleviated the membrane-ruffling phenotype caused by simultaneous knockdown of both RGA-3 and RGA-4 [rga-3/4 (RNAi)]. GFP::PAR-6 and GFP::PAR-2 were localized at the anterior and posterior part of the early C. elegans embryo, respectively showing that rga-3/4 (RNAi) did not interfere with polarity establishment. Most importantly, upon simultaneous knockdown of RGA-3, RGA-4 and the third RhoGAP present in the early embryo, CYK-4, NMY-2 spread over the entire cortex and GFP::PAR-2 localization at the posterior cortex was greatly diminished. These results indicate that the functions of CYK-4 are temporally and spatially distinct from RGA-3 and RGA-4 (RGA-3/4). RGA-3/4 and CYK-4 also play different roles in controlling LET-502 activation in the germ line, because rga-3/4 (RNAi), but not cyk-4 (RNAi), aggravated the let-502(sb106) phenotype. We propose that RGA-3/4 and CYK-4 control with which effector molecules RHO-1 interacts at particular sites at the cortex in the zygote and in the germ line.
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Affiliation(s)
- Cornelia Schmutz
- Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
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19
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Abstract
Exocytosis is a key biological process that controls the neurotransmission and release of hormones from cells. In endocrine cells, hormones are packed into secretory vesicles and released into the extracellular environment via openings in the plasma membrane, a few hundred nanometers wide, which form as a result of fusion of the membranes of the granule and cell. The complex processes and dynamics that result in the formation of the fusion pore, as well as its structure, remain scantly understood. A number of different exocytosis mechanisms have been postulated. Furthermore, the possibility exists that several mechanisms occur simultaneously. We present here an investigation of the cell membrane dynamics during exocytosis in anterior pituitary cells, especially gonadotropes, which secrete LH, a hormone central to ovulation. Gonadotrope enrichment was achieved using immunolabeled magnetic nanobeads. Three complementary imaging techniques were used to realize a fine structure study of the dynamics of the exocytosis-like sites occurring during secretion. Living pituitary and gonadotrope-enriched cells were imaged with atomic force microscopy, as well as cells that had been fixed to obtain better resolution. Atomic force microscopy, along with scanning and transmission electron microscopy, studies of these cells revealed that there are at least two different site configurations: simple single fusion pores and a complex association of pores consisting of a simple primary site combined with secondary attachments.
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Affiliation(s)
- Pascale Savigny
- MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand
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20
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Shimada A, Niwa H, Tsujita K, Suetsugu S, Nitta K, Hanawa-Suetsugu K, Akasaka R, Nishino Y, Toyama M, Chen L, Liu ZJ, Wang BC, Yamamoto M, Terada T, Miyazawa A, Tanaka A, Sugano S, Shirouzu M, Nagayama K, Takenawa T, Yokoyama S. Curved EFC/F-BAR-domain dimers are joined end to end into a filament for membrane invagination in endocytosis. Cell 2007; 129:761-72. [PMID: 17512409 DOI: 10.1016/j.cell.2007.03.040] [Citation(s) in RCA: 316] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2006] [Revised: 01/18/2007] [Accepted: 03/02/2007] [Indexed: 11/17/2022]
Abstract
Pombe Cdc15 homology (PCH) proteins play an important role in a variety of actin-based processes, including clathrin-mediated endocytosis (CME). The defining feature of the PCH proteins is an evolutionarily conserved EFC/F-BAR domain for membrane association and tubulation. In the present study, we solved the crystal structures of the EFC domains of human FBP17 and CIP4. The structures revealed a gently curved helical-bundle dimer of approximately 220 A in length, which forms filaments through end-to-end interactions in the crystals. The curved EFC dimer fits a tubular membrane with an approximately 600 A diameter. We subsequently proposed a model in which the curved EFC filament drives tubulation. In fact, striation of tubular membranes was observed by phase-contrast cryo-transmission electron microscopy, and mutations that impaired filament formation also impaired membrane tubulation and cell membrane invagination. Furthermore, FBP17 is recruited to clathrin-coated pits in the late stage of CME, indicating its physiological role.
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Affiliation(s)
- Atsushi Shimada
- RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
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21
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Tan TT, Morgelin M, Forsgren A, Riesbeck K. Haemophilus influenzaeSurvival during Complement‐Mediated Attacks Is Promoted byMoraxella catarrhalisOuter Membrane Vesicles. J Infect Dis 2007; 195:1661-70. [PMID: 17471436 DOI: 10.1086/517611] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2006] [Accepted: 12/29/2006] [Indexed: 11/03/2022] Open
Abstract
Moraxella catarrhalis causes respiratory tract infections in children and in adults with chronic obstructive pulmonary disease. It is often isolated as a copathogen with Haemophilus influenzae. The underlying mechanism for this cohabitation is unclear. Here, in clinical specimens from a patient with M. catarrhalis infection, we document that outer membrane vesicles (OMVs) carrying ubiquitous surface protein (Usp) A1 and UspA2 (hereafter, UspA1/A2) were secreted. Further analyses revealed that OMVs isolated in vitro also contained UspA1/A2, which mediate interactions with, among other proteins, the third component of the complement system (C3). OMVs from M. catarrhalis wild-type clinical strains bound to C3 and counteracted the complement cascade to a larger extent than did OMVs without UspA1/A2. In contrast, UspA1/A2-deficient OMVs were significantly weaker inhibitors of complement-dependent killing of H. influenzae. Thus, our results suggest that a novel strategy exists in which pathogens collaborate to conquer innate immunity and that the M. catarrhalis vaccine candidates UspA1/A2 play a major role in this interaction.
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Affiliation(s)
- Thuan Tong Tan
- Medical Microbiology, Department of Laboratory Medicine, Malmo University Hospital, Lund University, Malmo, Malmo, Sweden
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22
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Quinn C, Ryan E, Claessens EA, Greenblatt E, Hawrylyshyn P, Cruickshank B, Hannam T, Dunk C, Casper RF. The presence of pinopodes in the human endometrium does not delineate the implantation window. Fertil Steril 2007; 87:1015-21. [PMID: 17224147 DOI: 10.1016/j.fertnstert.2006.08.101] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [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: 04/08/2006] [Revised: 08/09/2006] [Accepted: 08/09/2006] [Indexed: 10/23/2022]
Abstract
OBJECTIVE To assess pinopode formation in human endometrium during the luteal phase of the menstrual cycle and in the first trimester of pregnancy. DESIGN Prospective clinical study. SETTING Outpatient infertility clinics and outpatient family planning clinic. PATIENT(S) Thirty-two regularly cycling infertile women, 15 regularly cycling fertile women, 9 women receiving elective termination of pregnancy, and 1 woman receiving GnRH agonist and hormone therapy addback. INTERVENTION(S) Endometrial tissue was collected by suction pipelle and examined by scanning electron microscopy for pinopode formation. MAIN OUTCOME MEASURE(S) Endometrial tissue was scored (0, 1, 2, 3, or 4) depending on the percentage of the surface covered in pinopodes (from 0% to >20% of 100 fields). RESULT(S) Pinopodes were present throughout the luteal phase of the menstrual cycle, up to the 11th week of pregnancy, and in the endometrium of the woman on GnRH agonist and hormone therapy. CONCLUSION(S) Pinopodes can be detected in the progesterone-exposed endometrium for an extended period of time, in contradistinction to the perception that they are markers for the implantation window in the human endometrium.
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Affiliation(s)
- Claire Quinn
- Division of Reproductive Sciences, Samuel Lunenfeld Research Institute, and the Fran and Lawrence Bloomberg Department of Obstetrics and Gynecology, Mount Sinai Hospital, Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada
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23
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Ivaska J, Pallari HM, Nevo J, Eriksson JE. Novel functions of vimentin in cell adhesion, migration, and signaling. Exp Cell Res 2007; 313:2050-62. [PMID: 17512929 DOI: 10.1016/j.yexcr.2007.03.040] [Citation(s) in RCA: 544] [Impact Index Per Article: 32.0] [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: 01/25/2007] [Revised: 03/20/2007] [Accepted: 03/26/2007] [Indexed: 02/07/2023]
Abstract
Vimentin is the major intermediate filament (IF) protein of mesenchymal cells. It shows dynamically altered expression patterns during different developmental stages and high sequence homology throughout all vertebrates, suggesting that the protein is physiologically important. Still, until recently, the real tasks of vimentin have been elusive, primarily because the vimentin-deficient mice were originally characterized as having a very mild phenotype. Recent studies have revealed several key functions for vimentin that were not obvious at first sight. Vimentin emerges as an organizer of a number of critical proteins involved in attachment, migration, and cell signaling. The highly dynamic and complex phosphorylation of vimentin seems to be a likely regulator mechanism for these functions. The implicated novel vimentin functions have broad ramifications into many different aspects of cell physiology, cellular interactions, and organ homeostasis.
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Affiliation(s)
- Johanna Ivaska
- VTT Medical Biotechnology, Itäinen Pitkäkatu 4C, FI-20520 Turku, Finland
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24
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Sallé L, Brette F. T-tubules: a key structure of cardiac function and dysfunction. Arch Mal Coeur Vaiss 2007; 100:225-30. [PMID: 17536428] [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] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The sarcolemmal membrane of mammalian ventricular cardiomyocytes are characterised by the presence of invaginations called transverse tubules (T-tubules) which constitute a network, the transverse tubule system. T-tubules occur at the Z line as transverse elements with also longitudinal extensions. While the existence of T-tubules has been known since a long time, recent studies have suggested their structure and function can be more complex than previously believed. Many of the proteins involved in excitation-contraction coupling process are concentrated within the T-tubular network, suggesting T-tubules are a highly specialized membrane system. Thus, T-tubules are a key determinant of cardiac cell function. The fundamental role of T-tubules is emphasized by changes in their structure and protein expression occurring during pathologies such as cardiac hypertrophy and heart failure. This review summarizes recent studies which highlight the key-role of the T-tubules in the regulation of cardiac function. Changes observed in pathological conditions are also discussed.
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Affiliation(s)
- L Sallé
- EA3212 Laboratoire de physiologie cellulaire, Université de Caen, 14032 Caen, France
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25
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Ma Y, Cai S, Lv Q, Jiang Q, Zhang Q, Sodmergen, Zhai Z, Zhang C. Lamin B receptor plays a role in stimulating nuclear envelope production and targeting membrane vesicles to chromatin during nuclear envelope assembly through direct interaction with importin beta. J Cell Sci 2007; 120:520-30. [PMID: 17251381 DOI: 10.1242/jcs.03355] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [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
Lamin B receptor (LBR), a chromatin and lamin binding protein in the inner nuclear membrane, has been proposed to play a vital role in nuclear envelope (NE) assembly. But the specific role for LBR in NE assembly remains unknown. In the present study, we show that overexpression of LBR causes membrane overproduction, inducing NE invagination and membrane stack formation, and that these processes require the transmembrane domain of LBR. Biochemical analysis shows that the N-terminal domain of LBR directly interacts with importin beta in a Ran sensitive and importin alpha independent manner. Using an in vitro NE assembly assay, we also demonstrate that blocking full length LBR binding sites on importin beta, by the addition of the LBR N-terminal domain inhibits the recruitment of LBR-containing vesicles to importin beta- or Ran-coated beads to form NE structure. Our results suggest that LBR is recruited to chromatin through direct interaction with importin beta to contribute to the fusion of membrane vesicles and formation of the NE.
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Affiliation(s)
- Yan Ma
- The Key Laboratory of Cell Proliferation and Differentiation of Ministry of Education, The National Key Laboratory of Bio-membrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing 100871, China
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26
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Nevot M, Deroncelé V, Messner P, Guinea J, Mercadé E. Characterization of outer membrane vesicles released by the psychrotolerant bacterium Pseudoalteromonas antarctica NF3. Environ Microbiol 2007; 8:1523-33. [PMID: 16913913 PMCID: PMC4379500 DOI: 10.1111/j.1462-2920.2006.01043.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [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] [Indexed: 11/30/2022]
Abstract
Pseudoalteromonas antarctica NF3 is an Antarctic psychrotolerant Gram-negative bacterium that accumulates large amounts of an extracellular polymeric substance (EPS) with high protein content. Transmission electron microscopy analysis after high-pressure freezing and freeze substitution (HPF-FS) shows that the EPS is composed of a capsular polymer and large numbers of outer membrane vesicles (OMVs). These vesicles are bilayered structures and predominantly spherical in shape, with an average diameter of 25-70 nm, which is similar to what has been observed in OMVs from other Gram-negative bacteria. Analyses of lipopolysaccharide (LPS), phospholipids and protein profiles of OMVs are consistent with the bacterial outer membrane origin of these vesicles. In an initial attempt to elucidate the functions of OMVs proteins, we conducted a proteomic analysis on 1D SDS-PAGE bands. Those proteins putatively identified match with outer membrane proteins and proteins related to nutrient processing and transport in Gram-negative bacteria. This approach suggests that OMVs present in the EPS from P. antarctica NF3, might function to deliver proteins to the external media, and therefore play an important role in the survival of the bacterium in the extreme Antarctic environment.
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Affiliation(s)
- Maria Nevot
- Laboratorio de Microbiología, Facultad de Farmacia, Universidad de Barcelona, Spain
| | - Víctor Deroncelé
- Laboratorio de Microbiología, Facultad de Farmacia, Universidad de Barcelona, Spain
| | - Paul Messner
- Zentrum für NanoBiotechnologie, Universität für Bodenkultur Wien, Vienna, Austria
| | - Jesús Guinea
- Laboratorio de Microbiología, Facultad de Farmacia, Universidad de Barcelona, Spain
| | - Elena Mercadé
- Laboratorio de Microbiología, Facultad de Farmacia, Universidad de Barcelona, Spain
- For correspondence. ; Tel. (+34) 93 402 4496; Fax (+34) 93 402 4498
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Onfelt B, Nedvetzki S, Benninger RKP, Purbhoo MA, Sowinski S, Hume AN, Seabra MC, Neil MAA, French PMW, Davis DM. Structurally distinct membrane nanotubes between human macrophages support long-distance vesicular traffic or surfing of bacteria. J Immunol 2007; 177:8476-83. [PMID: 17142745 DOI: 10.4049/jimmunol.177.12.8476] [Citation(s) in RCA: 333] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We report that two classes of membrane nanotubes between human monocyte-derived macrophages can be distinguished by their cytoskeletal structure and their functional properties. Thin membrane nanotubes contained only F-actin, whereas thicker nanotubes, i.e., those > approximately 0.7 microm in diameter, contained both F-actin and microtubules. Bacteria could be trapped and surf along thin, but not thick, membrane nanotubes toward connected macrophage cell bodies. Once at the cell body, bacteria could then be phagocytosed. The movement of bacteria is aided by a constitutive flow of the nanotube surface because streptavidin-coated beads were similarly able to traffic along nanotubes between surface-biotinylated macrophages. Mitochondria and intracellular vesicles, including late endosomes and lysosomes, could be detected within thick, but not thin, membrane nanotubes. Analysis from kymographs demonstrated that vesicles moved in a stepwise, bidirectional manner at approximately 1 microm/s, consistent with their traffic being mediated by the microtubules found only in thick nanotubes. Vesicular traffic in thick nanotubes and surfing of beads along thin nanotubes were both stopped upon the addition of azide, demonstrating that both processes require ATP. However, microtubule destabilizing agents colchicine or nocodazole abrogated vesicular transport but not the flow of the nanotube surface, confirming that distinct cytoskeletal structures of nanotubes give rise to different functional properties. Thus, membrane nanotubes between macrophages are more complex than unvarying ubiquitous membrane tethers and facilitate several means for distal interactions between immune cells.
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Affiliation(s)
- Björn Onfelt
- Division of Cell and Molecular Biology, National Heart and Lung Institute, Imperial College London, South Kensington Campus, London, UK
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Abstract
Euglenids comprise a group of single-celled eukaryotes with diverse modes of nutrition, including phagotrophy and photosynthesis. The level of morphological diversity present in this group provides an excellent system for demonstrating evolutionary transformations in morphological characters. This diversity also provides compelling evidence for major events in eukaryote evolution, such as the punctuated effects of secondary endosymbiosis and mutations in underlying developmental mechanisms. In this essay, we synthesize evidence for the origin, adaptive significance and diversification of the euglenid cytoskeleton, especially pellicle ultrastructure, pellicle surface patterns, pellicle strip number and the feeding apparatus. We also highlight holes in our knowledge that must be filled before we are able to confidently describe euglenid cell biology and infer the earliest stages in euglenid evolution. Nonetheless, by possessing combinations of characters resulting from adaptive change and morphostasis, euglenids have retained key pieces of evidence necessary for reconstructing the early evolution and diversification of eukaryotic life.
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Affiliation(s)
- Brian S Leander
- Canadian Institute for Advanced Research, Program in Integrated Microbial Biodiversity, Departments of Botany and Zoology, University of British Columbia, Vancouver, Canada.
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Carneiro SM, Fernandes W, Sant'Anna SS, Yamanouye N. Microvesicles in the venom of Crotalus durissus terrificus (Serpentes, Viperidae). Toxicon 2007; 49:106-10. [PMID: 17084429 DOI: 10.1016/j.toxicon.2006.04.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2005] [Revised: 03/17/2006] [Accepted: 04/07/2006] [Indexed: 11/25/2022]
Abstract
Microvesicles with electron-dense content are consistently observed by transmission electron microscopy on the luminal face of secretory cells of venom glands of viperid snakes. In this work, we evaluated their presence in Crotalus durissus terrificus venom glands and also in freshly collected venom. Microvesicles were found in the venom glands mainly in regions of exocytosis. They ranged from 40 to 80 nm in diameter. Freeze-fracture replicas of the glands revealed particles on the cytoplasmic leaflet (P-face) of these vesicles, suggesting that they carry transmembrane proteins. Vesicles separated by ultracentrifugation from cell-free venom were similar in size and structure to the microvesicles observed in the glands. A fine fuzzy coat surrounded each microvesicle. The function of these venom vesicles is still unknown, but they may contribute to inactivation of stored venom components, or their activation after the venom is released.
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Affiliation(s)
- Sylvia Mendes Carneiro
- Laboratório de Biologia Celular, Instituto Butantan, Av. Vital Brasil, 1500, São Paulo, SP 05503-900, Brasil.
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Abstract
It is becoming increasingly clear that herpesviruses can exploit the endocytic pathway to infect cells, yet several important features of this process remain poorly defined. Using herpes simplex virus-1 (HSV-1) as a model, we demonstrate that endocytosis of the virions mimic many features of phagocytosis. During entry, HSV-1 virions associated with plasma membrane protrusions followed by a phagocytosis-like uptake involving rearrangement of actin cytoskeleton and trafficking of the virions in large phagosome-like vesicles. RhoA GTPase was activated during this process and the mode of entry was cell type-specific. Clathrin-coated vesicles had no detectable role in virion trafficking as Eps15 dominant-negative mutants failed to affect HSV-1 uptake. Binding and fusion of the virion envelope with the phagosomal membrane is likely facilitated by clustering of nectin-1 (or HVEM) in phagosomes, which was observed in infected cells. Collectively, our data suggests a novel mode of uptake by which the virus can infect both professional and nonprofessional phagocytes.
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Affiliation(s)
- Christian Clement
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, College of Medicine, Chicago, IL 60612, USA
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31
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Nankoe SR, Sever S. Dynasore puts a new spin on dynamin: a surprising dual role during vesicle formation. Trends Cell Biol 2006; 16:607-9. [PMID: 17064900 DOI: 10.1016/j.tcb.2006.10.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [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: 08/09/2006] [Revised: 09/27/2006] [Accepted: 10/12/2006] [Indexed: 11/21/2022]
Abstract
During clathrin-mediated endocytosis, dynamin promotes the formation of clathrin-coated vesicles, but its mode of action is unresolved. In a recent study, Macia and colleagues made use of dynasore, a dynamin-specific inhibitor, to show that dynamin plays a dual role in endocytosis: they confirmed that dynamin is involved in detaching fully formed coated pits from the membrane, and also propose a new role for dynamin earlier in the process at the point of invagination.
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Affiliation(s)
- Sharif R Nankoe
- Nephrology Division, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02129, USA
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Baldassarre M, Ayala I, Beznoussenko G, Giacchetti G, Machesky LM, Luini A, Buccione R. Actin dynamics at sites of extracellular matrix degradation. Eur J Cell Biol 2006; 85:1217-31. [PMID: 17010475 DOI: 10.1016/j.ejcb.2006.08.003] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [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: 07/20/2006] [Revised: 08/10/2006] [Accepted: 08/10/2006] [Indexed: 10/24/2022] Open
Abstract
The degradation of extracellular matrix (ECM) by proteases is crucial in physiological and pathological cell invasion alike. In vitro, degradation occurs at specific sites where invasive cells make contact with the ECM via specialized plasma membrane protrusions termed invadopodia. Here we present an extensive morpho-functional analysis of invadopodia actively engaged in ECM degradation and show that they are actin comet-based structures, not unlike the well-known bacteria-propelling actin tails. The relative mapping of the basic molecular components of invadopodia to actin tails is also provided. Finally, a live-imaging analysis of invadopodia highlights the intrinsic long-term stability of the structures coupled to a highly dynamic actin turnover. The results offer new insight into the tight coordination between signalling, actin remodelling and trafficking activities occurring at sites of focalized ECM degradation by invadopodia. In conclusion, invadopodia-associated actin comets are a striking example of consistently arising, spontaneous expression of actin-driven propulsion events that also represent a valuable experimental paradigm.
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Affiliation(s)
- Massimiliano Baldassarre
- Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Via Nazionale 8A, I-66030 S. Maria Imbaro, Chieti, Italy
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Hnasko R, Carter JM, Medina F, Frank PG, Lisanti MP. PV-1 labels trans-cellular openings in mouse endothelial cells and is negatively regulated by VEGF. Cell Cycle 2006; 5:2021-8. [PMID: 16969078 DOI: 10.4161/cc.5.17.3217] [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] [Indexed: 11/19/2022] Open
Abstract
The PV-1 protein is endogenously expressed from a single mRNA in the mouse pancreatic MS-1 endothelial cell line as a 60-kDa N-glycosylated and 50-kDa non-glycosylated protein that form DTT sensitive oligomers. In the absence of cell permeabilization, PV-1 antibodies label transcellular openings of variable size, many that penetrate through the cytosol with circular openings on the free and attached surface of the plasma membrane. Intracellular PV-1 is localized in perinuclear aggregates that can extend as a fibrous network through the cytosol and often surround the nuclear compartment. In some cells, PV-1 is organized as a large unipolar spindle-like structure that is often associated with severe deformation of the nucleus. The VEGF-R2 inhibitor SU5614 increased the PV-1 protein levels in a dose-dependent manner and inhibited MS-1 cell growth, without inducing apoptosis. This report provides compelling evidence for a functional role of PV-1 in the formation of large transendothelial channels and modulation of nuclear shape. Moreover, these data suggest the PV-1 protein is negatively regulated by VEGF.
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Affiliation(s)
- Robert Hnasko
- United States Department of Agriculture, Agricultural Research Service-Pacific West Area, Western Region Research Center, Foodborne Contaminants Research Unit, Albany, California, USA
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Abstract
Cubic membranes represent highly curved, three-dimensional nanoperiodic structures that correspond to mathematically well defined triply periodic minimal surfaces. Although they have been observed in numerous cell types and under different conditions, particularly in stressed, diseased, or virally infected cells, knowledge about the formation and function of nonlamellar, cubic structures in biological systems is scarce, and research so far is restricted to the descriptive level. We show that the “organized smooth endoplasmic reticulum” (OSER; Snapp, E.L., R.S. Hegde, M. Francolini, F. Lombardo, S. Colombo, E. Pedrazzini, N. Borgese, and J. Lippincott-Schwartz. 2003. J. Cell Biol. 163:257–269), which is formed in response to elevated levels of specific membrane-resident proteins, is actually the two-dimensional representation of two subtypes of cubic membrane morphology. Controlled OSER induction may thus provide, for the first time, a valuable tool to study cubic membrane formation and function at the molecular level.
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Affiliation(s)
- Zakaria A Almsherqi
- Cubic Membrane Laboratory, Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597
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Abstract
Electron microscope tomography produces three-dimensional reconstructions and has been used to image organelles both isolated and in situ, providing new insight into their structure and function. It is analogous to the various tomographies used in medical imaging. Compared with light microscopy, electron tomography offers an improvement in resolution of 30- to 80-fold and currently ranges from 3 to 8 nm, thus filling the gap between high-resolution structure determinations of isolated macromolecules and larger-scale studies on cells and tissues by light microscopy. Here, we provide an introduction to electron tomography and applications of the method in characterizing organelle architecture that also show its power for suggesting functional significance. Further improvements in labeling modalities, imaging tools, specimen preparation, and reconstruction algorithms promise to increase the quality and breadth of reconstructions by electron tomography and eventually to allow the mapping of the cellular proteomes onto detailed three-dimensional models of cellular structure.
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Affiliation(s)
- Terrence G Frey
- Department of Biology, San Diego State University, San Diego, California 92182-4614, USA.
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Treanor B, Lanigan PMP, Kumar S, Dunsby C, Munro I, Auksorius E, Culley FJ, Purbhoo MA, Phillips D, Neil MAA, Burshtyn DN, French PMW, Davis DM. Microclusters of inhibitory killer immunoglobulin-like receptor signaling at natural killer cell immunological synapses. ACTA ACUST UNITED AC 2006; 174:153-61. [PMID: 16801390 PMCID: PMC2064172 DOI: 10.1083/jcb.200601108] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We report the supramolecular organization of killer Ig–like receptor (KIR) phosphorylation using a technique applicable to imaging phosphorylation of any green fluorescent protein–tagged receptor at an intercellular contact or immune synapse. Specifically, we use fluorescence lifetime imaging (FLIM) to report Förster resonance energy transfer (FRET) between GFP-tagged KIR2DL1 and a Cy3-tagged generic anti-phosphotyrosine monoclonal antibody. Visualization of KIR phosphorylation in natural killer (NK) cells contacting target cells expressing cognate major histocompatibility complex class I proteins revealed that inhibitory signaling is spatially restricted to the immune synapse. This explains how NK cells respond appropriately when simultaneously surveying susceptible and resistant target cells. More surprising, phosphorylated KIR was confined to microclusters within the aggregate of KIR, contrary to an expected homogeneous distribution of KIR signaling across the immune synapse. Also, yellow fluorescent protein–tagged Lck, a kinase important for KIR phosphorylation, accumulated in a multifocal distribution at inhibitory synapses. Spatial confinement of receptor phosphorylation within the immune synapse may be critical to how activating and inhibitory signals are integrated in NK cells.
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Affiliation(s)
- Bebhinn Treanor
- Division of Cell and Molecular Biology, Imperial College London, London SW7 2AZ, England, UK
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Abstract
A primary goal of cell biology is to uncover the mechanisms of cellular processes. A detailed structural understanding of the organelles and subcellular structures involved in these processes has often formed the foundation for the elucidation of their function. Electron tomography is a powerful technique for characterizing subcellular architecture and structural details in three dimensions. Electron tomography of cryofixed, freeze-substituted, and plastic-embedded samples allows three-dimensional visualization and display of dynamic, pleiomorphic structures at a resolution of approximately 7 nm in cell volumes up to approximately 25 microm(3). In this review, we describe the electron tomography protocols that we have employed to determine the 3D architecture of complex cellular structures, thereby gaining insights into their functional organization. We stress the need for studying specimens preserved by cryofixation methods to obtain accurate information on the geometry and size of cellular structures. We also discuss some of the challenges associated with the staining of certain types of membranes. Finally, we provide examples of how tomographic data can be analyzed, dissected, and displayed using the tools built into the IMOD software package.
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Affiliation(s)
- Bryon S Donohoe
- University of Colorado at Boulder, MCD Biology, Boulder, CO 80309, USA
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Abstract
The replication of many viruses is associated with specific intracellular compartments called virus factories or virioplasm. These are thought to provide a physical scaffold to concentrate viral components and thereby increase the efficiency of replication. The formation of virus replication sites often results in rearrangement of cellular membranes and reorganization of the cytoskeleton. Similar rearrangements are seen in cells in response to protein aggregation, where aggresomes and autophagosomes are produced to facilitate protein degradation. Here I review the evidence that some viruses induce aggresomes and autophagosomes to generate sites of replication.
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Affiliation(s)
- Thomas Wileman
- School of Medicine, Health Policy and Practice, University of East Anglia, Norwich NR4 7TJ, UK.
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Cabezas P, Risco C. Studying cellular architecture in three dimensions with improved resolution: Ta replicas revisited. Cell Biol Int 2006; 30:747-54. [PMID: 16798024 DOI: 10.1016/j.cellbi.2006.05.006] [Citation(s) in RCA: 4] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2006] [Revised: 04/04/2006] [Accepted: 05/11/2006] [Indexed: 11/17/2022]
Abstract
Metal replicas have been used for surface analysis of biological structures with a variety of spatial resolutions. Platinum (Pt) has been the metal of choice because it provides very stable replicas and images of high contrast. Some other metals, such as tantalum (Ta) have been reported to provide better resolution on isolated macromolecular complexes and cellular structures. Our goal is to study the gain in detail with Ta and to evaluate if it provides enough detail and resolution to assist in the study of complex volumes of intact cellular structures obtained by methods that reach molecular resolution. To this purpose Pt and Ta replicas of cellular structures and viruses have been studied by transmission electron microscopy (TEM). Replicas of Ta show new details on the surface of two types of isolated viral particles such as 100 nm bunyaviruses and large, > 300 nm, vaccinia virus (VV). Inside cells, the structural pieces that build VV immature particles are visualized only in Ta replicas. Looking for smaller intracellular complexes, new details are also seen in nuclear pores from Ta replicas. Additional masses, most likely representing the cargo during transport, are distinguished in some of the pores. Visualization of proteins in plasma membranes strongly suggests that detail and resolution of Ta replicas are similar to those estimated for 3D maps currently obtained by electron tomography of viruses and cells.
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Affiliation(s)
- Pilar Cabezas
- Department of Structure of Macromolecules, Centro Nacional de Biotecnología, CSIC, Campus Universidad Autónoma, Darwin 3, Cantoblanco, 28049 Madrid, Spain
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40
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Abstract
OBJECTIVES To compare the morphological changes and quantitative distribution of lamellar bodies (Lb) (membrane coating granules) in the hamster cheek pouch epithelium with smokeless tobacco (ST). MATERIALS AND METHODS Archives of experimental material from previously published studies [S. Ashrafi, A. Das, R. Worawongvasu, B. Mehdinejad and J. Waterhouse (1992) Scanning Microscopy6: 183] were utilized. Animals in experimental group received most ST (snuff) in their right pouch, 5 days weekly, for 24 months, while no snuff was given to control group. After 24 months, the epithelial tissues were processed for electron microscopic study. Volume densities of Lb were assessed by morphometry. MAIN OUTCOME MEASURES Densities of Lb in the two groups, experimental vs control. RESULTS In the control, Lb extruded their contents into the intercellular spaces of upper granular layers and in between the last granular cell layers and keratin layers to form a permeability barrier. Conversely, in the smokeless tobacco-treated epithelium, the majority of the Lb that were formed remained inside and accumulated within the granular cells, without extruding their contents into the intercellular spaces to form a lipid compound permeability barrier. CONCLUSIONS Commercial alkaline ST may have contributed to the abnormal accumulation of Lb in the granular cell layer and affected the extrusion process of Lb to form an incomplete permeability barrier in the oral epithelium.
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Affiliation(s)
- M D Colvard
- Department of Oral Medicine and Diagnostic Sciences, College of Dentistry, University of Illinois at Chicago, Chicago, IL 60612-7227, USA.
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41
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Kopp P, Lammers R, Aepfelbacher M, Woehlke G, Rudel T, Machuy N, Steffen W, Linder S. The kinesin KIF1C and microtubule plus ends regulate podosome dynamics in macrophages. Mol Biol Cell 2006; 17:2811-23. [PMID: 16554367 PMCID: PMC1474789 DOI: 10.1091/mbc.e05-11-1010] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [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: 01/02/2023] Open
Abstract
Microtubules are important for the turnover of podosomes, dynamic, actin-rich adhesions implicated in migration and invasion of monocytic cells. The molecular basis for this functional dependency, however, remained unclear. Here, we show that contact by microtubule plus ends critically influences the cellular fate of podosomes in primary human macrophages. In particular, we identify the kinesin KIF1C, a member of the Kinesin-3 family, as a plus-end-enriched motor that targets regions of podosome turnover. Expression of mutation constructs or small interfering RNA-/short hairpin RNA-based depletion of KIF1C resulted in decreased podosome dynamics and ultimately in podosome deficiency. Importantly, protein interaction studies showed that KIF1C binds to nonmuscle myosin IIA via its PTPD-binding domain, thus providing an interface between the actin and tubulin cytoskeletons, which may facilitate the subcellular targeting of podosomes by microtubules. This is the first report to implicate a kinesin in podosome regulation and also the first to describe a function for KIF1C in human cells.
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Affiliation(s)
- Petra Kopp
- *Institut für Prophylaxe und Epidemiologie der Kreislaufkrankheiten, Ludwig-Maximilians-Universität, 80336 Munich, Germany
| | - Reiner Lammers
- Medizinische Klinik IV, Universität Tübingen, 72076 Tübingen, Germany
| | - Martin Aepfelbacher
- Institut für Infektionsmedizin, Universitätsklinikum Hamburg Epppendorf, 20246 Hamburg, Germany
| | - Günther Woehlke
- Institut für Zellbiologie, Ludwig-Maximilians-Universität, 80336 Munich, Germany
| | - Thomas Rudel
- Max-Planck-Institut für Infektionsbiologie, 10117 Berlin, Germany; and
| | - Nikolaus Machuy
- Max-Planck-Institut für Infektionsbiologie, 10117 Berlin, Germany; and
| | - Walter Steffen
- Institut für Molekular- und Zellphysiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany
| | - Stefan Linder
- *Institut für Prophylaxe und Epidemiologie der Kreislaufkrankheiten, Ludwig-Maximilians-Universität, 80336 Munich, Germany
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Abstract
Magnetosomes are membranous bacterial organelles sharing many features of eukaryotic organelles. Using electron cryotomography, we found that magnetosomes are invaginations of the cell membrane flanked by a network of cytoskeletal filaments. The filaments appeared to be composed of MamK, a homolog of the bacterial actin-like protein MreB, which formed filaments in vivo. In a mamK deletion strain, the magnetosome-associated cytoskeleton was absent and individual magnetosomes were no longer organized into chains. Thus, it seems that prokaryotes can use cytoskeletal filaments to position organelles within the cell.
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Affiliation(s)
- Arash Komeili
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
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43
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Elsegood CL, Mamo JCL. An investigation by electron microscopy of chylomicron remnant uptake by human monocyte-derived macrophages. Atherosclerosis 2005; 188:251-9. [PMID: 16310792 DOI: 10.1016/j.atherosclerosis.2005.10.043] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2005] [Revised: 09/01/2005] [Accepted: 10/27/2005] [Indexed: 11/19/2022]
Abstract
Human monocyte-derived macrophages (HMM) internalise proatherogenic chylomicron remnants via several high affinity receptor pathways. However, the endocytic ultrastructures responsible for the uptake of chylomicron remnants by macrophages have not previously been described. In this study, we have utilised transmission electron microscopy together with colloidal gold-labelling of chylomicron remnants to investigate the pathways involved in macrophage uptake of chylomicron remnants. We found that macrophages internalise chylomicron remnants via surface-connected compartments of up to 600 nm as well as non-clathrin coated pits. Chylomicron remnants were found to be distributed internally in a number of endocytic vesicles including early cysternal endosomes, spherical late endosomes and tubular vesicular compartments. Uptake of chylomicron remnants by HMM via phagocytosis or macropinocytosis was excluded based on the observations that lipoproteins were not found in phagolysosomes nor modified by inhibitors of these two processes, respectively. The latter observation contrasts with previous reports of chylomicron remnant internalisation by macrophages of other species.
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Affiliation(s)
- Caryn L Elsegood
- ATN Centre for Metabolic Fitness, School of Public Health, Curtin University of Technology, Australia
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Li YC, Li YN, Cheng CX, Sakamoto H, Kawate T, Shimada O, Atsumi S. Subsurface cisterna-lined axonal invaginations and double-walled vesicles at the axonal–myelin sheath interface. Neurosci Res 2005; 53:298-303. [PMID: 16129504 DOI: 10.1016/j.neures.2005.07.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2005] [Revised: 07/12/2005] [Accepted: 07/28/2005] [Indexed: 11/16/2022]
Abstract
The axonal-myelin sheath interface of vertebrate myelinated axons possesses special structural complexities, and there may be an intercellular macromolecular traffic transversing the periaxonal cleft that spans the internodal axon. By conventional electron microscopy and serial sectioning, we observed a category of double-walled vesicles at the axonal-myelin sheath interface, which often contained ribosome-like particles or endoplasmic reticulum. Some of them were demonstrated to continue with the subjacent axon with a thin stalk. In addition, we described a special category of axonal invaginations, probably mediated by subsurface cisternae. The functional implications of these specialized structures were discussed.
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Affiliation(s)
- Yan-Chao Li
- Department of Anatomy, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 1110 Shimokato Tamaho-Cho, Yamanashi 409-3898, Japan.
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45
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Abstract
Adult NMRI mice were superovulated using human menopausal chorionic gonadotropic hormones (hMG and hCG), and then some of them were daily injected with progesterone (1 mg/mouse). At 3.5 and 4.5 days after hCG injection scanning electron micrographs revealed that the hyperstimulated and progesterone-injected group had well-developed pinopodes while most of the hyperstimulated group without progesterone injection had no pinopodes 3.5 days after stimulation. The results suggest that the lifespan of pinopodes is short and changeable during hyperstimulation and that progesterone causes premature formation of the pinopodes and that implantation after ovarian stimulation might depend upon the timing of the pinopode expression.
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Affiliation(s)
- Mojdeh Salehnia
- Department of Anatomy, School of Medical Science, Tarbiat Modarres Univ., Tehran, Iran
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46
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Abstract
The polarized architecture of epithelial cells is a fundamental determinant of cell structures and functions. Both formation and orientation of proper epithelial polarity are needed for cell-cell or cell-matrix adhesion, signal transduction and cytoskeletal interactions of multimolecular complexes at apical, lateral and basal cell membranes. These cell membrane domains are usually segregated by some junctional complexes. Recent molecular genetic studies on the anchor structure between myelin sheaths and axons have indicated the specific molecular organization for polarization of axolemma and the myelin sheaths at paranodes, termed 'septate-like junctions'. It was also speculated that other mammalian organs may use a similar junctional system. The protein 4.1 B was originally found to be localized in paranodes and juxtaparanodes of myelinated nerve fibers. Our recent immunohistochemical studies on protein 4.1B have indicated its significance for the cell-cell and/or cell-matrix adhesion in various rodent organs. The protein 4.1 family of proteins have been supposed to possess variable molecular domains relating to cell adhesion, ion balance, receptor responses and signal transduction. Therefore, more precise studies on the molecular structure and the functional domains of protein 4.1B, as well as on its changes under physiological and pathological conditions, may provide a clue for organogenesis in various mammalian organs.
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Affiliation(s)
- Nobuo Terada
- Department of Anatomy, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Tamaho, Japan.
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Massol RH, Larsen JE, Kirchhausen T. Possible role of deep tubular invaginations of the plasma membrane in MHC-I trafficking. Exp Cell Res 2005; 306:142-9. [PMID: 15878340 DOI: 10.1016/j.yexcr.2005.01.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [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: 12/02/2004] [Revised: 01/18/2005] [Accepted: 01/26/2005] [Indexed: 11/29/2022]
Abstract
Tubules and vesicles are membrane carriers involved in traffic along the endocytic and secretory routes. The small GTPase Arf6 regulates a recycling branch of short dynamic tubular intermediates used by major histocompatibility class I (MHC-I) molecules to traffic through vesicles between endosomes and the plasma membrane. We observed that Arf6 also affects a second network of very long and stable tubules containing MHC-I, many of which correspond to deep invaginations of the plasma membrane. Treatment with wortmannin, an inhibitor of phosphatidylinositol-3-phosphate kinase, prevents formation of the short dynamic tubules while increasing the number of the long and very stable ones. Expression of NefAAAA, a mutant form of HIV Nef, increases the number of cells containing the stable tubules, and is used here as a tool to facilitate their study. Photoactivation of NefAAAA-PA-GFP demonstrates that this molecule traffics from endosomes to the tubules. Finally, live-cell imaging also shows internalization of MHC-I molecules into these tubules, suggesting that this is an additional route for MHC-I traffic.
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Affiliation(s)
- Ramiro H Massol
- Department of Cell Biology and The CBR Institute for Biomedical Research, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA
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Borm B, Requardt RP, Herzog V, Kirfel G. Membrane ruffles in cell migration: indicators of inefficient lamellipodia adhesion and compartments of actin filament reorganization. Exp Cell Res 2005; 302:83-95. [PMID: 15541728 DOI: 10.1016/j.yexcr.2004.08.034] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.7] [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: 06/14/2004] [Revised: 08/25/2004] [Indexed: 01/06/2023]
Abstract
During epithelial cell migration, membrane ruffles can be visualized by phase contrast microscopy as dark waves arising at the leading edge of lamellipodia that move centripetally toward the main cell body. Despite the common use of the term membrane ruffles, their structure, molecular composition, and the mechanisms leading to their formation remained largely unknown. We show here that membrane ruffles differ from the underlying cell lamella by more densely packed bundles of actin filaments that are enriched in the actin cross-linkers filamin and ezrin, pointing to a specific bundling process based on these cross-linkers. The accumulation of phosphorylated, that is, inactivated, cofilin in membrane ruffles suggests that they are compartments of inhibited actin filament turnover. High Rac1 and low RhoA activities were found under conditions of suboptimal integrin-ligand interaction correlating with low lamellipodia persistence, inefficient migration, and high ruffling rates. Based on these findings, we define membrane ruffles as distinct compartments of specific composition that form as a consequence of inefficient lamellipodia adhesion.
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Affiliation(s)
- Bodo Borm
- Institute for Cell Biology, University of Bonn, 53121 Bonn, Germany
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Abstract
BACKGROUND Invadopodia are membrane protrusions into the extracellular matrix by aggressive tumour cells. These structures are associated with sites of matrix degradation and invasiveness of malignant tumour cells in an in vitro fibronectin degradation/invasion assay. The Rho family small G proteins, consisting of the Rho, Rac and Cdc42 subfamilies, are implicated in various cell functions, such as cell shape change, adhesion, and motility, through reorganization of the actin cytoskeleton. We studied the roles of the Rho family small G proteins in invadopodia formation. RESULTS We first demonstrated that invadopodia of RPMI7951 human melanoma cells extended into the matrix substratum on a vertical view using a laser scanning confocal microscope system. We confirmed that invadopodia were rich in actin filaments (F-actin) and visualized clearly with F-actin staining on a vertical view as well as on a horizontal view. We then studied the roles of Rho, Rac, and Cdc42 in invasiveness of the same cell line. In the in vitro fibronectin degradation/invasion assay, a dominant active mutant of Cdc42 enhanced dot-like degradation, whereas a dominant active mutant of Rac enhanced diffuse-type degradation. Furthermore, frabin, a GDP/GTP exchange protein for Cdc42 with F-actin-binding activity, enhanced both dot-like and diffuse-type degradation. However, a dominant active mutant of Rho did not affect the fibronectin degradation. Moreover, inhibition of phosphatidylinositol-3 kinase (PI3K) disrupted the Rac and Cdc42-dependent actin structures and blocked the fibronectin degradation. CONCLUSION These results suggest that Cdc42 and Rac play important roles in fibronectin degradation and invasiveness in a coordinate manner through the frabin-Cdc42/Rac-PI3K signalling pathway.
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Affiliation(s)
- Hirokazu Nakahara
- The First Department of Oral & Maxillofacial Surgery, Osaka University Graduate School of Dentistry, Suita 565-0871, Japan.
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Abstract
Micrometer-size patterned lipid bilayers containing liganded lipids are used to control the location and size of receptor clusters and enable direct visualization of structural reorganization of cellular components. Subsequent to concentration of Fcepsilon receptor I, the mast cell receptor for IgE, and colocalized tyrosine phosphorylation activity, Lyn kinase and other proteins anchored to the inner leaflet of the plasma membrane redistribute selectively with the receptor clusters in a process that depends on actin polymerization. Surprisingly, outer leaflet components characteristically associated with lipid rafts do not detectably coredistribute with these inner leaflet components. Cell activation using patterned surfaces provides unique insights into cell membrane structural organization, revealing dynamic, large-scale uncoupling of inner and outer leaflet components of lipid rafts.
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Affiliation(s)
- Min Wu
- Department of Chemistry and Chemical Biology and School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
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