References of "Riva, Laura"
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See detailHepatitis C Virus Life Cycle and Lipid Metabolism
Popescu, Costin-Ioan; Riva, Laura ULg; Vlaicu, Ovidiu et al

in Biology (2014), 3

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See detailDeletion of the ORF9p acidic cluster impairs the nuclear egress of Varicella-zoster virus capsids.
Riva, Laura ULg; Thiry, Marc ULg; Lebrun, Marielle ULg et al

in Journal of virology (2014)

The protein encoded by the ORF9 is essential for Varicella-zoster virus (VZV) replication. Previous studies documented its presence in the trans-Golgi network and its involvement in secondary envelopment ... [more ▼]

The protein encoded by the ORF9 is essential for Varicella-zoster virus (VZV) replication. Previous studies documented its presence in the trans-Golgi network and its involvement in secondary envelopment. In this work, we deleted the ORF9p acidic cluster, destroying its interaction with ORF47p and resulting in a nuclear accumulation of both proteins. This phenotype results to an accumulation of primary enveloped capsids in the perinuclear space, reflecting a capsid de-envelopment defect. [less ▲]

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See detailVaricella-zoster virus induces the formation of dynamic nuclear capsid aggregates.
Lebrun, Marielle ULg; Thelen, Nicolas ULg; Thiry, Marc ULg et al

in Virology (2014), 454-455

The first step of herpesviruses virion assembly occurs in the nucleus. However, the exact site where nucleocapsids are assembled, where the genome and the inner tegument are acquired, remains ... [more ▼]

The first step of herpesviruses virion assembly occurs in the nucleus. However, the exact site where nucleocapsids are assembled, where the genome and the inner tegument are acquired, remains controversial. We created a recombinant VZV expressing ORF23 (homologous to HSV-1 VP26) fused to the eGFP and dually fluorescent viruses with a tegument protein additionally fused to a red tag (ORF9, ORF21 and ORF22 corresponding to HSV-1 UL49, UL37 and UL36). We identified nuclear dense structures containing the major capsid protein, the scaffold protein and maturing protease, as well as ORF21 and ORF22. Correlative microscopy demonstrated that the structures correspond to capsid aggregates and time-lapse video imaging showed that they appear prior to the accumulation of cytoplasmic capsids, presumably undergoing the secondary egress, and are highly dynamic. Our observations suggest that these structures might represent a nuclear area important for capsid assembly and/or maturation before the budding at the inner nuclear membrane. [less ▲]

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See detailUnsaturated fatty acids prevent activation of NLRP3 inflammasome in human monocytes/macrophages
L'Homme, Laurent ULg; Esser, Nathalie ULg; Riva, Laura ULg et al

in Journal of Lipid Research (2013), 54

The NLRP3 inflammasome is involved in many obesity-associated diseases such as type 2 diabetes, atherosclerosis and gouty arthritis through its ability to induce IL-1β release. The molecular link between ... [more ▼]

The NLRP3 inflammasome is involved in many obesity-associated diseases such as type 2 diabetes, atherosclerosis and gouty arthritis through its ability to induce IL-1β release. The molecular link between obesity and inflammasome activation is still unclear but free fatty acids have been proposed as one triggering event. Here we reported opposite effects of saturated fatty acids (SFAs) compared to unsaturated fatty acids (UFAs) on NLRP3 inflammasome in human monocytes/macrophages. Palmitate and stearate, both SFAs, triggered IL-1β secretion in a caspase-1/ASC/NLRP3-dependent pathway. Unlike SFAs, the UFAs oleate and linoleate did not lead to IL-1β secretion. In addition, they totally prevented the IL-1β release induced by SFAs and, with less efficiency, by a broad range of NLRP3 inducers including nigericin, alum and MSU. UFAs did not affect the transcriptional effect of SFAs suggesting a specific effect on the NLRP3 activation. These results provide a new antiinflammatory mechanism of UFAs by preventing the activation of the NLRP3 inflammasome and therefore the IL-1β processing. By this way, UFAs might play a protective role in NLRP3-associated diseases. [less ▲]

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See detailORF9p: a new player in the Varicella-Zoster Virus egress
Riva, Laura ULg

Doctoral thesis (2013)

Le virus de la Varicelle et du Zona (VZV) appartient à la famille des herpesviridae, virus enveloppés de grande taille caractérisés par un génome à ADN. Tout comme les autres membres de sa famille, son ... [more ▼]

Le virus de la Varicelle et du Zona (VZV) appartient à la famille des herpesviridae, virus enveloppés de grande taille caractérisés par un génome à ADN. Tout comme les autres membres de sa famille, son cycle viral est complexe et beaucoup dʼétapes doivent encore être élucidées. Parmi les 72 ORFs, lʼORF9 est le plus fortement exprimé au cours de lʼinfection. La protéine codée par ce gène est essentielle pour la réplication du VZV. Elle est conservée parmi les alphaherpesvirus et appartient au tegument du virus. Cependant, jusquʼà présent aucune fonction nʼa été décrite pour lʼORF9p ou pour ses homologues. Le but principal de notre projet de recherche était de caractériser lʼORF9p avec une attention particulière sur la détermination de son rôle biologique dans lʼinfection. Grâce à une technique de recombinaison homologue en deux étapes, nous avons pu insérer différents mutants de lʼORF9 dans un BAC contenant le génome complet du VZV et analyser les phénotypes des virus correspondants ainsi produits. Nous avons montré que lʼORF9p est fortement phosphorylée au cours de lʼinfection, principalement par la kinase virale ORF47p qui reconnaît le site consensus 84SEDD87 dans la séquence de cette protéine. Nous avons par ailleurs montré lʼimportance du glutamate en position 85 pour la phosphorylation de lʼORF9p ainsi que pour lʼenveloppement secondaire et la production de particules virales libres complètes. De plus, la région acide 85EDDFEDIDE93 a été identifiée comme importante pour lʼinfectivité virale. Dans un contexte où cette région est délétée, un défaut dʼenveloppement est observé et la glycoprotéine gE, interactant de lʼORF9p, semble sʼaccumuler dans les membranes intracellulaires, suggérant une incapacité de cette glycoprotéine à rejoindre la membrane plasmique. Après un screening par double hybride en levure, nous avons mis en évidence plusieurs partenaires cellulaires de lʼORF9p. Parmi ceux- ci se trouve la protéine AP-1μ1, connue pour être responsable du transport vésiculaire dépendant de la clathrine entre le Trans-Golgi Network et les endosomes. Lʼinteraction avec cette protéine cellulaire a été confirmée dans un contexte infectieux. Ce travail met donc en évidence pour la première fois lʼimplication de lʼORF9p dans lʼassemblage et la sortie du VZV, en proposant deux modèles : 1) lʼORF9p serait responsable de lʼenvoi de gE à la surface cellulaire via son interaction avec cette glycoprotéine dʼune part et AP-1μ1 dʼautre part ; 2) lʼORF9p serait responsable du processus dʼenveloppement secondaire, nécessaire pour la production de particules virales libres. [less ▲]

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See detailORF9p phosphorylation by ORF47p is crucial for the formation and egress of the Varicella-zoster virus (VZV) viral particles.
Riva, Laura ULg; Thiry, Marc ULg; BONTEMS, Sébastien ULg et al

in Journal of Virology (2013), 87(5), 2868-2881

The role of the tegument during the herpesvirus lytic cycle is still not clearly established, particularly at the late phase of infection, when the newly produced viral particles need to be fully ... [more ▼]

The role of the tegument during the herpesvirus lytic cycle is still not clearly established, particularly at the late phase of infection, when the newly produced viral particles need to be fully assembled before being released from the infected cell. The Varicella-zoster virus (VZV) protein coded by ORF9 (ORF9p) is an essential tegument protein and, even though its mRNA is the most expressed during the productive infection, little is known about its functions. Using a GalK positive/negative selection technique, we modified a BAC containing the complete VZV genome creating viruses expressing mutant versions of ORF9p.We showed that ORF9p is hyper-phosphorylated during the infection, especially through its interaction with the viral Ser/Thr kinase ORF47p; we identified a consensus site within ORF9p recognized by ORF47p and demonstrated its importance for ORF9p phosphorylation. Strikingly, an ultra-structural analysis revealed that the mutation of this consensus site (Glutamate 85 to Arginine) strongly affects viral assembly and release, reproducing ORF47 kinase dead VZV phenotype. It also slightly diminishes the infectivity towards immature dendritic cells. Taken together, our results identify ORF9p as a new viral substrate of ORF47p and suggest a determinant role of this phosphorylation for viral infectivity, especially during the process of viral particle formation and egress. [less ▲]

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