1,720,962 research outputs found
Interaction of Human Cytomegalovirus Tegument Proteins ppUL35 and ppUL35A with Sorting Nexin 5 Regulates Glycoprotein B (gpUL55) Localization
No full textABSTRACT
Human cytomegalovirus (HCMV) is a widespread human pathogen that causes asymptomatic infection in healthy individuals but poses a serious threat to immunocompromised patients. During the late phase of HCMV infection, the viral capsid is transported to the cytoplasmic viral assembly center (cVAC), where it is enclosed by the tegument protein layer and the viral envelope. The cVAC consists of circularly arranged vesicles from the
trans
-Golgi and endosomal networks. The HCMV gene UL35 encodes ppUL35 and its shorter form, ppUL35A. We have previously shown that the UL35 gene is involved in HCMV assembly, but it is unknown how UL35 proteins regulate viral assembly. Here we show that sorting nexin 5 (SNX5), a component of the retromer and part of the retrograde transport pathway, interacts with UL35 proteins. Expression of wild-type proteins but not mutants defective in SNX5 binding resulted in the cellular redistribution of the cation-independent mannose-6-phosphate receptor (CI-M6PR), indicating that UL35 proteins bind and negatively regulate SNX5 to modulate cellular transport pathways. Furthermore, binding of UL35 proteins to SNX5 was required for efficient viral replication and for transport of the most abundant HCMV glycoprotein B (gB; gpUL55) to the cVAC. These results indicate that ppUL35 and ppUL35A control the localization of the essential gB through the regulation of a retrograde transport pathway. Thus, this work is the first to define a molecular interaction between a tegument protein and a vesicular transport factor to regulate glycoprotein localization.
IMPORTANCE
Human cytomegalovirus is ubiquitously present in the healthy population, but reactivation or reinfection can cause serious, life-threatening infections in immunocompromised patients. For completion of its lytic cycle, human cytomegalovirus induces formation of an assembly center where mature virus particles are formed from multiple viral proteins. Viral glycoproteins use separate vesicular pathways for transport to the assembly center, which are incompletely understood. Our research identified a viral structural protein which affects the localization of one of the major glycoproteins. We could link this change in glycoprotein localization to an interaction of the structural protein with a cellular protein involved in regulation of vesicle transport. This increases our understanding of how the virus intersects into cellular regulatory pathways to enhance its own replication.
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Untersuchung der Protein-Protein-Interaktion der Proteine ppUL35 und ppUL35A des humanen Cytomegalievirus mit dem zellulären Protein Sorting Nexin 5
Full text linkEine Infektion oder Reaktivierung des Humanen Cytomegalievirus (HCMV) in immunsupprimierten Patienten (HIV-Patienten, Organtransplantatempfänger) kann zu schweren Erkrankungen sowie Organschädigungen oder Organabstoßung führen. Die Aufklärung molekularer Prozesse während der Infektion ist entscheidend für das Verständnis viraler Replikation sowie die Entwicklung antiviraler Interventionen. Während der späten Phase der Infektion wird das Kapsid aus dem Zellkern zum viralen Assembly Center transportiert. Dort werden die vollständigen Viruspartikel aus Kapsiden, Tegumentproteinen und viralen Hüllproteinen gebildet. Das Assembly Center besteht aus ringförmig angeordneten Vesikel, die aus dem Trans Golgi-Netzwerk und dem endosomalen Transportweg stammen. Das HCMV-Gen UL35 kodiert für zwei Proteine, ppUL35 und seine kurze Form ppUL35A, die neben einer transaktivierenden Funktion in der initialen Phase wichtige Funktionen in der späten Phase bei der Bildung der Partikel erfüllen. In einem Yeast-Two-Hybrid-Screen konnten mehrere zelluläre Interaktionspartner von ppUL35 identifiziert werden. Ziel dieser Arbeit war die Validierung und funktionelle Analyse einzelner dieser Protein-Interaktionen, um daraus Erkenntnisse äber die Rolle von ppUL35 bzw. ppUL35A abzuleiten. Sorting Nexin 5 (SNX5), ein Bestandteil des Retromers und Teil des retrograden Transportweges, konnte als Interaktor beider UL35-Proteine identifiziert werden. Die transiente Expression von ppUL35 oder ppUL35A zeigte einen Einfluss auf den endosomalen Weg, erkennbar an der Umverteilung des kationen-unabhängigen Mannose-6-Phosphatrezeptors (CI-M6PR). Eine vergleichbare Umverteilung war für die Depletion von endogenem SNX5 beschrieben worden, so dass eine hemmende Funktion der UL35-Proteine angenommen wurde. Entsprechend führte die transiente Expression von SNX5 in infizierten Zellen zu einem verringerten Virustiter. Mittels Pentapeptid-Scanning-Mutagenese wurde eine SNX5-bindungsdefizente UL35-Mutante identifiziert, die nach Transfektion keine CI-M6PR-Umverteilung bewirkte. Somit ist die Interaktion der UL35-Proteine mit SNX5 ursächlich für die Störung der zellulären Transportprozesse. Die Deletion bzw. Mutation von UL35 bzw. UL35A im HCMV-Genom führte zu einem verringerten Virustiter und einer veränderten Lokalisation des Glykoproteins gpUL55(gB). Dessen Reifungsprozess erfolgt, abweichend von anderen viralen Glykoproteinen, entlang des sekretorischen und endsomalen Weges. Durch siRNA-vermittelte Depletion von SNX5 konnten die Virusreplikation der UL35-Mutanten teilweise auf Wildtyp-Niveau angehoben und die Lokalisation von gpUL55(gB) wiederhergestellt werden. Diese Arbeit zeigt, dass ppUL35 und ppUL35A die Lokalisation des essentiellen gpUL55(gB) maßgeblich durch die Regulation eines retrograden Transportweges bestimmen.An infection or reactivation of Human Cytomegalovirus (HCMV) in immunocompromised individuals (HIV patients, organ transplant recipients) can lead to severe complications, organ damage or transplant rejection. The elucidation of molecular processes during infection is indispensable for our understanding of viral replication and the development of antiviral intervention strategies. During the late phase of infection, the viral capsid is transported out of the nucleus and is completed in the viral assembly center (AC) with tegument proteins and envelope proteins. The assembly center consists of circular rearranged vesicles from the trans golgi network and the endosomal pathway. The HCMV gene UL35 encodes for two proteins, ppUL35 and its shorter form ppUL35A. In addition to transactivation activity during the immediate early phase, UL35 fullfills an important role during the maturation of the virus particle. Several cellular proteins were identified as interaction partners of ppUL35 in a yeast two hybrid screen. The aim of this thesis was the validation and functional analysis of some of these protein interactions to gain insights into the role of ppUL35 and ppUL35A. Sorting Nexin 5 (SNX5), a component of the retromer and part of the retrograde transport pathway, was identified as an interaction partner of both UL35-proteins. Transient expression of ppUL35 and ppUL35A affected the endosomal pathway, as evidenced by a redistribution of the cation independent mannose-6-phosphate receptor (CI-M6PR). A comparable redistribution of CI-M6PR described after depletion of SNX5 led to the assumption of an inhibitory role for the UL35 proteins. Accordingly, the transient expression of SNX5 in infected cells resulted in a reduced virus titer. Pentapeptide scanning mutagenesis generated a SNX5 binding deficient ppUL35 mutant, whose transfection did not induce a redistribution of CI-M6PR. Therefore, the interaction of the UL35 proteins with SNX5 is the reason for the interference of the cellular transport pathways. Deletion or mutation of UL35 or UL35A in the HCMV genome led to a reduced virus titer and an altered localization of glycoprotein gpUL55(gB). The maturation process of gpUL55(gB), which differs from other viral glycoproteins, occurs along the secretory and endosomal transport pathways. RNAi induced depletion of SNX5 was able to increase virus replication of UL35 mutants almost to wildtype levels and to restore gpUL55(gB) localization. This thesis demonstrates that ppUL35 and ppUL35A control the localization of the essential gpUL55 (gB) through the regulation of a retrograde transport pathway
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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