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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 356 (1992), S. 260-262 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] To monitor the folding process, we used a previously developed pulse-chase assay in influenza-infected cells3. At the end of each chase time, the cells were treated with a membrane permeant alkylatmg agent, N-ethyl maleimide (NEM), to trap folding intermediates4. The formation of disulphide bonds ...
    Type of Medium: Electronic Resource
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  • 2
    Keywords: CELLS ; HEART ; ACCUMULATION ; PHENOTYPE ; ORGANIZATION ; ARCHITECTURE ; laminopathies ; FILAMENTS ; OUTFLOW TRACT ; GILFORD-PROGERIA-SYNDROME
    Abstract: Mutations in the LMNA gene coding for the nuclear lamina proteins lamin A and its smaller splice form lamin C associate with a heterogeneous group of diseases collectively called laminopathies. Here, we describe a 2-year-old patient with a previously undescribed phenotype including right ventricular cardiomyopathy, progeroid features, and premature death. Sequencing of LMNA revealed a novel heterozygous de novo mutation p.L306R located in the alpha-helical rod domain of A-type lamins. Fibroblasts from the patient showed reduced proliferation and early premature replicative senescence, as characterized by progressive hyperlobulation of the nuclei, abnormally clustered centromeres, loss of lamin B1, and reorganization of promyelocytic leukemia nuclear bodies. Furthermore, the patient cells were more sensitive to double-strand DNA breaks. Similar structural and phenotypic defects were observed in normal fibroblasts transfected with FLAG-tagged p.L306R lamin A. Correspondingly, in vitro assembly studies revealed that the p.L306R generates a "hyper-assembly" mutant of lamin A that forms extensive fiber arrays under physiological conditions where wild-type lamin A is still largely soluble. In summary, we report a novel LMNA p.L306R mutation that leads to previously undescribed hyper-assembly of lamin A, heavy distortion of nuclear shape and that manifests as right ventricular cardiomyopathy and premature aging.
    Type of Publication: Journal article published
    PubMed ID: 25820511
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  • 3
    Keywords: RECEPTOR ; CELLS ; EXPRESSION ; INHIBITOR ; CELL ; MICROSCOPY ; PATHWAY ; PATHWAYS ; POPULATION ; RNA ; COMPLEX ; MECHANISM ; virus ; PLASMA ; MEMBRANE ; MAMMALIAN-CELLS ; PLASMA-MEMBRANE ; cholesterol ; LIPID RAFTS ; INHIBITORS ; LIGHT ; INFLUENZA-VIRUS ; SEMLIKI-FOREST-VIRUS ; USA ; LIGHT-MICROSCOPY ; ACTIN ; host ; TURNOVER ; CELLULAR RECEPTOR ; SIRNA ; LYMPHOCYTIC-CHORIOMENINGITIS-VIRUS ; CLATHRIN-MEDIATED ENDOCYTOSIS ; DIFFERENTIAL REQUIREMENTS ; ENDOSOMES ; ALPHA-DYSTROGLYCAN ; clathrin ; MEMBRANE DOMAINS ; virus entry endocytosis
    Abstract: The endocytic entry of lymphocytic choriomeningitis virus (LCMV) into host cells was compared to the entry of viruses known to exploit clathrin or caveolae/raft-dependent pathways. Pharmacological inhibitors, expression of pathway-specific dominant-negative constructs, and siRNA silencing of clathrin together with electron and light microscopy provided evidence that although a minority population followed a classical clathrin-mediated mechanism of entry, the majority of these enveloped RNA viruses used a novel endocytic route to late endosomes. The pathway was clathrin, dynamin-2, actin, Arf6, flotillin-1, caveolae, and lipid raft independent but required membrane cholesterol. Unaffected by perturbation of Rab5 or Rab7 and apparently without passing through Rab5/EEA1-positive early endosomes, the viruses reached late endosomes and underwent acid-induced penetration. This membrane trafficking route between the plasma membrane and late endosomes may function in the turnover of a select group of surface glycoproteins such as the dystroglycan complex, which serves as the receptor of LCMV. (c) 2008 Elsevier Inc. All rights reserved
    Type of Publication: Journal article published
    PubMed ID: 18554681
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  • 4
    Keywords: CELLS ; MODEL ; PATHWAY ; PROTEIN ; MOLECULES ; ACTIVATION ; INFECTION ; BINDING ; ASSOCIATION ; PLASMA ; LIPID RAFTS ; CHOLERA-TOXIN ; SIMIAN-VIRUS-40 ; INSECT CELLS ; glycosphingolipids ; SIMIAN VIRUS-40 ; INDEPENDENT ENDOCYTOSIS ; GANGLIOSIDE GM1 ; MURINE POLYOMA-VIRUS ; SHIGA TOXIN ; SV40 CAPSID PROTEINS
    Abstract: Incoming simian virus 40 (SV40) particles enter tight-fitting plasma membrane invaginations after binding to the carbohydrate moiety of GM1 gangliosides in the host cell plasma membrane through pentameric VP1 capsid proteins. This is followed by activation of cellular signalling pathways, endocytic internalization and transport of the virus via the endoplasmic reticulum to the nucleus. Here we show that the association of SV40 (as well as isolated pentameric VP1) with GM1 is itself sufficient to induce dramatic membrane curvature that leads to the formation of deep invaginations and tubules not only in the plasma membrane of cells, but also in giant unilamellar vesicles (GUVs). Unlike native GM1 molecules with long acyl chains, GM1 molecular species with short hydrocarbon chains failed to support such invagination, and endocytosis and infection did not occur. To conceptualize the experimental data, a physical model was derived based on energetic considerations. Taken together, our analysis indicates that SV40, other polyoma viruses and some bacterial toxins (Shiga and cholera) use glycosphingolipids and a common pentameric protein scaffold to induce plasma membrane curvature, thus directly promoting their endocytic uptake into cells
    Type of Publication: Journal article published
    PubMed ID: 20023649
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  • 5
    Keywords: imaging ; MAMMALIAN-CELLS ; ENDOPLASMIC-RETICULUM ; JC virus ; SIMIAN VIRUS-40 ; BREFELDIN-A ; MEMBRANE DOMAINS ; MURINE POLYOMA-VIRUS ; CAVEOLAR ENDOCYTOSIS ; GANGLIOSIDE GD1A ; VESICULAR-TRANSPORT
    Abstract: After binding to its cell surface receptor, ganglioside GM1, simian virus 40 (SV40) is endocytozed by lipid raft-mediated endocytosis and slowly transported to the endoplasmic reticulum where partial uncoating occurs. We analyzed the intracellular pathway taken by the virus in HeLa and CV-1 cells using a targeted siRNA silencing screen, electron microscopy and live-cell imaging as well as by testing a variety of cellular inhibitors and other perturbants. We found that the virus entered early endosomes, late endosomes, and probably endolysosomes before reaching the endoplasmic reticulum, and that this pathway was part of the infectious route. The virus was especially sensitive to a variety of perturbations that inhibited endosome acidification and maturation. Contrary to our previous models, which postulated passage of the virus through caveolin-rich organelles that we called caveosomes, we conclude that SV40 depends on the classical endocytic pathway for infectious entry.
    Type of Publication: Journal article published
    PubMed ID: 21345959
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  • 6
    Keywords: RECEPTOR ; CELLS ; KINASE ; PATHWAY ; TYROSINE KINASE ; fibroblasts ; TRANSPORT ; virus ; MOUSE ; PLASMA ; MEMBRANE ; LINE ; endocytosis ; PLASMA-MEMBRANE ; LIPID RAFTS ; ENDOPLASMIC-RETICULUM ; SIMIAN-VIRUS-40 ; plasma membrane ; SWITZERLAND ; INTERNALIZATION ; endoplasmic reticulum ; DYNAMIN ; GOLGI-COMPLEX ; GPI-ANCHORED PROTEINS ; SMOOTH ENDOPLASMIC-RETICULUM
    Abstract: Simian Virus 40 (SV40) has been shown to enter host cells by caveolar endocytosis followed by transport via caveosomes to the endoplasmic reticulum (ER). Using a caveolin-1 (cav-1)-deficient cell line (human hepatoma 7) and embryonic fibroblasts from a cav-1 knockout mouse, we found that in the absence of caveolae, but also in wild-type embryonic fibroblasts, the virus exploits an alternative, cav-1-independent pathway. Internalization was rapid (t(1/2)= 20 min) and cholesterol and tyrosine kinase dependent but independent of clathrin, dynamin II, and ARF6. The viruses were internalized in small, tight-fitting vesicles and transported to membrane-bounded, pH-neutral organelles similar to caveosomes but devoid of cav-1 and -2. The viruses were next transferred by microtubule-dependent vesicular transport to the ER, a step that was required for infectivity. Our results revealed the existence of a virus-activated endocytic pathway from the plasma membrane to the ER that involves neither clathrin nor caveolae and that can be activated also in the presence of cav-1
    Type of Publication: Journal article published
    PubMed ID: 15668298
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  • 7
    Keywords: CELLS ; CELL ; COMBINATION ; MICROSCOPY ; PROTEIN ; PROTEINS ; TIME ; ACTIVATION ; COMPLEX ; COMPLEXES ; INFECTION ; MECHANISM ; ACID ; PARTICLES ; virus ; PLASMA ; endocytosis ; ELECTRON ; KINETICS ; LIVING CELLS ; PROTEIN COMPLEXES ; ENDOPLASMIC-RETICULUM ; ELECTRON-MICROSCOPY ; DEPENDENCE ; HELA-CELLS ; SEMLIKI-FOREST-VIRUS ; INTERNALIZATION ; INDUCE ; USA ; animal ; microbiology ; host ; viral ; INTRACELLULAR TRAFFICKING ; viruses ; DEPENDENT ENDOCYTOSIS ; VIRUS ENTRY ; CLATHRIN-COATED PITS ; CLATHRIN-MEDIATED ENDOCYTOSIS ; COATED VESICLE FORMATION ; DIFFERENTIAL REQUIREMENTS ; ENDOSOMES ; INDEPENDENT ENDOCYTOSIS ; PSEUDOTYPED RETROVIRAL VECTORS
    Abstract: Vesicular stomatitis virus (VSV) is an animal virus that based on electron microscopy and its dependence on acidic cellular compartments for infection is thought to enter its host cells in a clathrin-dependent manner. The exact cellular mechanism, however, is largely unknown. In this study, we characterized the entry kinetics of VSV and elucidated viral requirements for host cell factors during infection in HeLa cells. We found that endocytosis of VSV was a fast process with a half time of 2.5 to 3 min and that acid activation occurred within 1 to 2 min after internalization in early endosomes. The majority of viral particles were endocytosed in a clathrin-based, dynamin-2-dependent manner. Although associated with some of the surface-bound viruses, the classical adaptor protein complex AP-2 was not required for infection. Time-lapse microscopy revealed that the virus either entered preformed clathrin-coated pits or induced de novo formation of pits. Dynamin-2 was recruited to plasma membrane-confined virus particles. Thus, VSV can induce productive internalization by exploiting a specific combination of the clathrin-associated proteins and cellular functions
    Type of Publication: Journal article published
    PubMed ID: 18971266
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  • 8
    Keywords: CELLS ; EXPRESSION ; MICROSCOPY ; MODEL ; SYSTEM ; PROTEIN ; PROTEINS ; MONOCLONAL-ANTIBODY ; PARTICLES ; virus ; MEMBRANE ; QUALITY-CONTROL ; MAMMALIAN-CELLS ; GOLGI-APPARATUS ; VACCINE ; VESICULAR STOMATITIS-VIRUS ; ENDOPLASMIC-RETICULUM ; electron microscopy ; ACIDIC PH ; ENVELOPE PROTEIN-E ; HEPATITIS-C VIRUS ; MEMBRANE- PROTEINS ; N-LINKED OLIGOSACCHARIDES
    Abstract: It is believed that flavivirus assembly occurs by intracellular budding of the nucleocapsid into the lumen of the endoplasmic reticulum (ER). Recombinant expression of tick-borne encephalitis (TBE) virus envelope proteins prM and E in mammalian cells leads to their incorporation into enveloped recombinant subviral particles (RSPs), which have been used as a model system for studying assembly and entry processes and are also promising vaccine candidates. In this study, we analyzed the formation and secretion of TBE virus RSPs and of a membrane anchor-free E homodimer in mammalian cells. Immunofluorescence microscopy showed that E was accumulated in the lumen of the ER. RSPs were observed by electron microscopy in the rough and smooth ER and in downstream compartments of the secretory pathway. About 75% of the particles appeared to be of the size expected for RSPs (about 30 nm in diameter), but a number of larger particles and tubular structures were also observed in these compartments. Secretion of membrane anchor- free E dimers was detected 30 min after synthesis of prM and E, and secretion of RSPs was detected 1 h after synthesis of prM and E. We also found that the presence of the single N-linked oligosaccharide side chain on the E protein and its trimming by glucosidases was necessary for secretion of RSPs and truncated E dimers. Our results suggest that incorporation of prM and E into RSPs occurs at the ER membrane without other viral elements being required, followed by rapid transport along the compartments of the secretory pathway and secretion. Moreover, the carbohydrate side chain of E is involved in at least one assembly or transport step
    Type of Publication: Journal article published
    PubMed ID: 12634393
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Trends in Biochemical Sciences 5 (1980), S. 104-106 
    ISSN: 0968-0004
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Trends in Biochemical Sciences 8 (1983), S. 245-250 
    ISSN: 0968-0004
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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