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  • 11
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    Online Resource
    Differential pH-dependent cellular uptake pathways among foamy viruses elucidated using dual-colored fluorescent particles
    Springer Science and Business Media LLC ; 2012
    In:  Retrovirology Vol. 9, No. 1 ( 2012-12)
    Details
    In: Retrovirology, Springer Science and Business Media LLC, Vol. 9, No. 1 ( 2012-12)
    Abstract: It is thought that foamy viruses (FVs) enter host cells via endocytosis because all FV glycoproteins examined display pH-dependent fusion activities. Only the prototype FV (PFV) glycoprotein has also significant fusion activity at neutral pH, suggesting that its uptake mechanism may deviate from other FVs. To gain new insights into the uptake processes of FV in individual live host cells, we developed fluorescently labeled infectious FVs. Results N-terminal tagging of the FV envelope leader peptide domain with a fluorescent protein resulted in efficient incorporation of the fluorescently labeled glycoprotein into secreted virions without interfering with their infectivity. Double-tagged viruses consisting of an eGFP-tagged PFV capsid (Gag-eGFP) and mCherry-tagged Env (Ch-Env) from either PFV or macaque simian FV (SFVmac) were observed during early stages of the infection pathway. PFV Env, but not SFVmac Env, containing particles induced strong syncytia formation on target cells. Both virus types showed trafficking of double-tagged virions towards the cell center. Upon fusion and subsequent capsid release into the cytosol, accumulation of naked capsid proteins was observed within four hours in the perinuclear region, presumably representing the centrosomes. Interestingly, virions harboring fusion-defective glycoproteins still promoted virus attachment and uptake, but failed to show syncytia formation and perinuclear capsid accumulation. Biochemical and initial imaging analysis indicated that productive fusion events occur predominantly within 4–6 h after virus attachment. Non-fused or non-fusogenic viruses are rapidly cleared from the cells by putative lysosomal degradation. Quantitative monitoring of the fraction of individual viruses containing both Env and capsid signals as a function of time demonstrated that PFV virions fused within the first few minutes, whereas fusion of SFVmac virions was less pronounced and observed over the entire 90 minutes measured. Conclusions The characterized double-labeled FVs described here provide new mechanistic insights into FV early entry steps, demonstrating that productive viral fusion occurs early after target cell attachment and uptake. The analysis highlights apparent differences in the uptake pathways of individual FV species. Furthermore, the infectious double-labeled FVs promise to provide important tools for future detailed analyses on individual FV fusion events in real time using advanced imaging techniques.
    Type of Medium: Online Resource
    ISSN: 1742-4690
    URL: Article
    DOI: 10.1186/1742-4690-9-71
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2012
    detail.hit.zdb_id: 2142602-8
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  • 12
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    Restriction of diverse retroviruses by SAMHD1
    Springer Science and Business Media LLC ; 2013
    In:  Retrovirology Vol. 10, No. 1 ( 2013-12)
    Details
    In: Retrovirology, Springer Science and Business Media LLC, Vol. 10, No. 1 ( 2013-12)
    Type of Medium: Online Resource
    ISSN: 1742-4690
    URL: Article
    DOI: 10.1186/1742-4690-10-26
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2013
    detail.hit.zdb_id: 2142602-8
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  • 13
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    Prototype Foamy Virus Protease Activity Is Essential for Intraparticle Reverse Transcription Initiation but Not Absolutely Required for Uncoating upon Host Cell Entry
    American Society for Microbiology ; 2013
    In:  Journal of Virology Vol. 87, No. 6 ( 2013-03-15), p. 3163-3176
    Details
    In: Journal of Virology, American Society for Microbiology, Vol. 87, No. 6 ( 2013-03-15), p. 3163-3176
    Abstract: Foamy viruses (FVs) are unique among retroviruses in performing genome reverse transcription (RTr) late in replication, resulting in an infectious DNA genome, and also in their unusual Pol biosynthesis and encapsidation strategy. In addition, FVs display only very limited Gag and Pol processing by the viral protease (PR) during particle morphogenesis and disassembly, both thought to be crucial for viral infectivity. Here, we report the generation of functional prototype FV (PFV) particles from mature or partially processed viral capsid and enzymatic proteins with infectivity levels of up to 20% of the wild type. Analysis of protein and nucleic acid composition, as well as infectivity, of virions generated from different Gag and Pol combinations (including both expression-optimized and authentic PFV open reading frames [ORFs]) revealed that precursor processing of Gag, but not Pol, during particle assembly is essential for production of infectious virions. Surprisingly, when processed Gag (instead of Gag precursor) was provided together with PR-deficient Pol precursor during virus production, infectious, viral DNA-containing particles were obtained, even when different vector or proviral expression systems were used. Although virion infectivity was reduced to 0.5 to 2% relative to that of the respective parental constructs, this finding overturns the current dogma in the FV literature that viral PR activity is absolutely essential at some point during target cell entry. Furthermore, it demonstrates that viral PR-mediated Gag precursor processing during particle assembly initiates intraparticle RTr. Finally, it shows that reverse transcriptase (RT) and integrase are enzymatically active in the Pol precursor within the viral capsid, thus enabling productive host cell infection.
    Type of Medium: Online Resource
    ISSN: 0022-538X , 1098-5514
    URL: Article
    DOI: 10.1128/JVI.02323-12
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2013
    detail.hit.zdb_id: 1495529-5
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  • 14
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    Efficient Transient Genetic Manipulation In Vitro and In Vivo by Prototype Foamy Virus-mediated Nonviral RNA Transfer
    Elsevier BV ; 2014
    In:  Molecular Therapy Vol. 22, No. 8 ( 2014-08), p. 1460-1471
    Details
    In: Molecular Therapy, Elsevier BV, Vol. 22, No. 8 ( 2014-08), p. 1460-1471
    Type of Medium: Online Resource
    ISSN: 1525-0016
    URL: Article
    DOI: 10.1038/mt.2014.82
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2014
    detail.hit.zdb_id: 2001818-6
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  • 15
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    Cyclin A2 localises in the cytoplasm at the S/G2 transition to activate PLK1
    Life Science Alliance, LLC ; 2021
    In:  Life Science Alliance Vol. 4, No. 3 ( 2021-03), p. e202000980-
    Details
    In: Life Science Alliance, Life Science Alliance, LLC, Vol. 4, No. 3 ( 2021-03), p. e202000980-
    Abstract: Cyclin A2 is a key regulator of the cell cycle, implicated both in DNA replication and mitotic entry. Cyclin A2 participates in feedback loops that activate mitotic kinases in G2 phase, but why active Cyclin A2-CDK2 during the S phase does not trigger mitotic kinase activation remains unclear. Here, we describe a change in localisation of Cyclin A2 from being only nuclear to both nuclear and cytoplasmic at the S/G2 border. We find that Cyclin A2-CDK2 can activate the mitotic kinase PLK1 through phosphorylation of Bora, and that only cytoplasmic Cyclin A2 interacts with Bora and PLK1. Expression of predominately cytoplasmic Cyclin A2 or phospho-mimicking PLK1 T210D can partially rescue a G2 arrest caused by Cyclin A2 depletion. Cytoplasmic presence of Cyclin A2 is restricted by p21, in particular after DNA damage. Cyclin A2 chromatin association during DNA replication and additional mechanisms contribute to Cyclin A2 localisation change in the G2 phase. We find no evidence that such mechanisms involve G2 feedback loops and suggest that cytoplasmic appearance of Cyclin A2 at the S/G2 transition functions as a trigger for mitotic kinase activation.
    Type of Medium: Online Resource
    ISSN: 2575-1077
    URL: Article
    DOI: 10.26508/lsa.202000980
    Language: English
    Publisher: Life Science Alliance, LLC
    Publication Date: 2021
    detail.hit.zdb_id: 2948687-7
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  • 16
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    In vitro Assays and Imaging Methods for Drug Discovery for Cardiac Fibrosis
    Frontiers Media SA ; 2021
    In:  Frontiers in Physiology Vol. 12 ( 2021-7-8)
    Details
    In: Frontiers in Physiology, Frontiers Media SA, Vol. 12 ( 2021-7-8)
    Abstract: As a result of stress, injury, or aging, cardiac fibrosis is characterized by excessive deposition of extracellular matrix (ECM) components resulting in pathological remodeling, tissue stiffening, ventricular dilatation, and cardiac dysfunction that contribute to heart failure (HF) and eventually death. Currently, there are no effective therapies specifically targeting cardiac fibrosis, partially due to limited understanding of the pathological mechanisms and the lack of predictive in vitro models for high-throughput screening of antifibrotic compounds. The use of more relevant cell models, three-dimensional (3D) models, and coculture systems, together with high-content imaging (HCI) and machine learning (ML)-based image analysis, is expected to improve predictivity and throughput of in vitro models for cardiac fibrosis. In this review, we present an overview of available in vitro assays for cardiac fibrosis. We highlight the potential of more physiological 3D cardiac organoids and coculture systems and discuss HCI and automated artificial intelligence (AI)-based image analysis as key methods able to capture the complexity of cardiac fibrosis in vitro . As 3D and coculture models will soon be sufficiently mature for application in large-scale preclinical drug discovery, we expect the combination of more relevant models and high-content analysis to greatly increase translation from in vitro to in vivo models and facilitate the discovery of novel targets and drugs against cardiac fibrosis.
    Type of Medium: Online Resource
    ISSN: 1664-042X
    URL: Article
    DOI: 10.3389/fphys.2021.697270
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
    detail.hit.zdb_id: 2564217-0
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  • 17
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    Tracking Image Cross-Correlation for Elucidating the Fusion Process of Viruses
    Elsevier BV ; 2012
    In:  Biophysical Journal Vol. 102, No. 3 ( 2012-01), p. 618a-
    Details
    In: Biophysical Journal, Elsevier BV, Vol. 102, No. 3 ( 2012-01), p. 618a-
    Type of Medium: Online Resource
    ISSN: 0006-3495
    URL: Article
    DOI: 10.1016/j.bpj.2011.11.3369
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2012
    detail.hit.zdb_id: 1477214-0
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  • 18
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    The cooperative function of arginine residues in the Prototype Foamy Virus Gag C-terminus mediates viral and cellular RNA encapsidation
    Springer Science and Business Media LLC ; 2014
    In:  Retrovirology Vol. 11, No. 1 ( 2014-12)
    Details
    In: Retrovirology, Springer Science and Business Media LLC, Vol. 11, No. 1 ( 2014-12)
    Type of Medium: Online Resource
    ISSN: 1742-4690
    URL: Article
    DOI: 10.1186/s12977-014-0087-7
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2014
    detail.hit.zdb_id: 2142602-8
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  • 19
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    Analysis of Prototype Foamy Virus particle-host cell interaction with autofluorescent retroviral particles
    Springer Science and Business Media LLC ; 2010
    In:  Retrovirology Vol. 7, No. 1 ( 2010-12)
    Details
    In: Retrovirology, Springer Science and Business Media LLC, Vol. 7, No. 1 ( 2010-12)
    Abstract: The foamy virus (FV) replication cycle displays several unique features, which set them apart from orthoretroviruses. First, like other B/D type orthoretroviruses, FV capsids preassemble at the centrosome, but more similar to hepadnaviruses, FV budding is strictly dependent on cognate viral glycoprotein coexpression. Second, the unusually broad host range of FV is thought to be due to use of a very common entry receptor present on host cell plasma membranes, because all cell lines tested in vitro so far are permissive. Results In order to take advantage of modern fluorescent microscopy techniques to study FV replication, we have created FV Gag proteins bearing a variety of protein tags and evaluated these for their ability to support various steps of FV replication. Addition of even small N-terminal HA-tags to FV Gag severely impaired FV particle release. For example, release was completely abrogated by an N-terminal autofluorescent protein (AFP) fusion, despite apparently normal intracellular capsid assembly. In contrast, C-terminal Gag-tags had only minor effects on particle assembly, egress and particle morphogenesis. The infectivity of C-terminal capsid-tagged FV vector particles was reduced up to 100-fold in comparison to wild type; however, infectivity was rescued by coexpression of wild type Gag and assembly of mixed particles. Specific dose-dependent binding of fluorescent FV particles to target cells was demonstrated in an Env-dependent manner, but not binding to target cell-extracted- or synthetic- lipids. Screening of target cells of various origins resulted in the identification of two cell lines, a human erythroid precursor- and a zebrafish- cell line, resistant to FV Env-mediated FV- and HIV-vector transduction. Conclusions We have established functional, autofluorescent foamy viral particles as a valuable new tool to study FV - host cell interactions using modern fluorescent imaging techniques. Furthermore, we succeeded for the first time in identifying two cell lines resistant to Prototype Foamy Virus Env-mediated gene transfer. Interestingly, both cell lines still displayed FV Env-dependent attachment of fluorescent retroviral particles, implying a post-binding block potentially due to lack of putative FV entry cofactors. These cell lines might ultimately lead to the identification of the currently unknown ubiquitous cellular entry receptor(s) of FVs.
    Type of Medium: Online Resource
    ISSN: 1742-4690
    URL: Article
    DOI: 10.1186/1742-4690-7-45
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2010
    detail.hit.zdb_id: 2142602-8
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  • 20
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    The Foamy Virus Gag Proteins: What Makes Them Different?
    MDPI AG ; 2013
    In:  Viruses Vol. 5, No. 4 ( 2013-03-26), p. 1023-1041
    Details
    In: Viruses, MDPI AG, Vol. 5, No. 4 ( 2013-03-26), p. 1023-1041
    Type of Medium: Online Resource
    ISSN: 1999-4915
    URL: Article
    DOI: 10.3390/v5041023
    Language: English
    Publisher: MDPI AG
    Publication Date: 2013
    detail.hit.zdb_id: 2516098-9
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