RESUMEN
Direct targeting of essential viral enzymes such as proteases, polymerases, and helicases has long been the major focus of antiviral drug design. Although successful for some viral enzymes, targeting viral helicases is notoriously difficult to achieve, demanding alternative strategies. Here, we show that the NS3 helicase of Zika virus (ZIKV) undergoes acetylation in its RNA-binding tunnel. Regulation of the acetylated state of K389 in ZIKV NS3 modulates RNA binding and unwinding and is required for efficient viral replication. NS3 acetylation is mediated by a specific isoform of the host acetyltransferase KAT5 (KAT5γ), which translocates from the nucleus to viral replication complexes upon infection. NS3 acetylation by KAT5γ and its proviral role are also conserved in West Nile virus (WNV), dengue virus (DENV), and yellow fever virus (YFV). Our study provides molecular insight into how a cellular acetyltransferase regulates viral helicase functions, unveiling a previously unknown target for antiviral drug development.
Asunto(s)
Flavivirus , Infección por el Virus Zika , Virus Zika , Humanos , Flavivirus/genética , Virus Zika/genética , Acetilación , ARN Helicasas/genética , Replicación Viral/fisiología , ADN Helicasas , Antivirales/farmacología , ARN , Proteínas no Estructurales Virales/metabolismoRESUMEN
The Zika virus (ZIKV) is a recently emerged mosquito-borne flavivirus that, while typically asymptomatic, can cause neurological symptoms in adults and birth defects in babies born to infected mothers. The interactions of ZIKV with many different pathways in the human host ultimately determine successful virus replication and ZIKV-induced pathogenesis; however, the molecular mechanisms of such host-ZIKV interactions have just begun to be elucidated. Here, we summarize the recent advances that defined the mechanisms by which ZIKV antagonizes antiviral innate immune signaling pathways, with a particular focus on evasion of the type I interferon response in the human host. Furthermore, we describe emerging evidence that indicated the contribution of several cell-intrinsic mechanisms to an effective restriction of ZIKV infection, such as nonsense-mediated mRNA decay, stress granule formation, and "reticulophagy", a type of selective autophagy. Finally, we summarize the recent work that identified strategies by which ZIKV modulated these intrinsic antiviral responses.
Asunto(s)
Interacciones Huésped-Patógeno/inmunología , Evasión Inmune , Inmunidad Innata , Infección por el Virus Zika/inmunología , Virus Zika/inmunología , Animales , Autofagia , Culicidae/virología , Humanos , Interferón Tipo I/inmunología , Estabilidad del ARN , Replicación Viral , Virus Zika/fisiologíaRESUMEN
14-3-3 protein family members facilitate the translocation of RIG-I-like receptors (RLRs) to organelles that mediate downstream RLR signaling, leading to interferon production. 14-3-3ϵ promotes the cytosolic-to-mitochondrial translocation of RIG-I, while 14-3-3η facilitates MDA5 translocation to mitochondria. We show that the NS3 protein of Zika virus (ZIKV) antagonizes antiviral gene induction by RIG-I and MDA5 by binding to and sequestering the scaffold proteins 14-3-3ϵ and 14-3-3η. 14-3-3-binding is mediated by a negatively charged RLDP motif in NS3 that is conserved in ZIKV strains of African and Asian lineages and is similar to the one found in dengue and West Nile viruses. ZIKV NS3 is sufficient to inhibit the RLR-14-3-3ϵ/η interaction and to suppress antiviral signaling. Mutational perturbation of 14-3-3ϵ/η binding in a recombinant ZIKV leads to enhanced innate immune responses and impaired growth kinetics. Our study provides molecular understanding of immune evasion functions of ZIKV, which may guide vaccine and anti-flaviviral therapy development.
Asunto(s)
Proteínas 14-3-3/metabolismo , Evasión Inmune/inmunología , Péptido Hidrolasas/metabolismo , Proteínas Virales/metabolismo , Infección por el Virus Zika/inmunología , Virus Zika/inmunología , Células A549 , Animales , Línea Celular , Chlorocebus aethiops , Proteína 58 DEAD Box/antagonistas & inhibidores , Células HEK293 , Células HeLa , Humanos , Inmunidad Innata/inmunología , Helicasa Inducida por Interferón IFIH1/antagonistas & inhibidores , Interferón beta/inmunología , Mitocondrias/metabolismo , Péptido Hidrolasas/genética , Interferencia de ARN , ARN Interferente Pequeño/genética , Receptores Inmunológicos , Serina Endopeptidasas , Células Vero , Proteínas Virales/genética , Virus Zika/genéticaRESUMEN
Aberrant expression of T cell-resident programmed cell death protein-1 (PD-1) is known to promote tumor progression. A recent study (Nature 2018;564:130-135) has now identified the E3 ubiquitin ligase FBXO38 as a crucial regulator of PD-1 protein turnover in T cells, providing a novel mechanism for potential use in cancer immunotherapy.
Asunto(s)
Neoplasias , Receptor de Muerte Celular Programada 1/genética , Humanos , Inmunoterapia , Linfocitos T , UbiquitinaciónRESUMEN
Heparan sulfate-modified proteoglycans (HSPGs) are important regulators of signaling and molecular recognition at the cell surface and in the extracellular space. Disruption of HSPG core proteins, HS-synthesis, or HS-degradation can have profound effects on growth, patterning, and cell survival. The Drosophila neuromuscular junction provides a tractable model for understanding the activities of HSPGs at a synapse that displays developmental and activity-dependent plasticity. Muscle cell-specific knockdown of HS biosynthesis disrupted the organization of a specialized postsynaptic membrane, the subsynaptic reticulum (SSR), and affected the number and morphology of mitochondria. We provide evidence that these changes result from a dysregulation of macroautophagy (hereafter referred to as autophagy). Cellular and molecular markers of autophagy are all consistent with an increase in the levels of autophagy in the absence of normal HS-chain biosynthesis and modification. HS production is also required for normal levels of autophagy in the fat body, the central energy storage and nutritional sensing organ in Drosophila. Genetic mosaic analysis indicates that HS-dependent regulation of autophagy occurs non-cell autonomously, consistent with HSPGs influencing this cellular process via signaling in the extracellular space. These findings demonstrate that HS biosynthesis has important regulatory effects on autophagy and that autophagy is critical for normal assembly of postsynaptic membrane specializations.