Ilaprazole and other novel prazole-based compounds that bind Tsg101 inhibit viral budding of HSV-1/2 and HIV from cells

Fetal brain response to maternal inflammation requires microglia

In utero infection and maternal inflammation can adversely impact fetal brain development. Maternal systemic illness, even in the absence of direct fetal brain infection, is associated with an increased risk of neuropsychiatric disorders in affected offspring. The cell types mediating the fetal brain response to maternal inflammation are largely unknown, hindering the development of novel treatment strategies. Here, we show that microglia, the resident phagocytes of the brain, highly express receptors for relevant pathogens and cytokines throughout embryonic development. Using a rodent maternal immune activation (MIA) model in which polyinosinic:polycytidylic acid is injected into pregnant mice, we demonstrate long-lasting transcriptional changes in fetal microglia that persist into postnatal life. We find that MIA induces widespread gene expression changes in neuronal and non-neuronal cells; importantly, these responses are abolished by selective genetic deletion of microglia, indicating that microglia are required for the transcriptional response of other cortical cell types to MIA. These findings demonstrate that microglia play a crucial durable role in the fetal response to maternal inflammation, and should be explored as potential therapeutic cell targets.

ESCRT machinery and virus infection

The endosomal sorting complex required for transport (ESCRT) machinery plays a significant role in the spread of human viruses. However, our understanding of how the host ESCRT machinery responds to viral infection remains limited. Emerging evidence suggests that the ESCRT machinery can be hijacked by viruses of different families to enhance their replication. Throughout their life cycle, these viruses can interfere with or exploit ESCRT-mediated physiological processes to increase their chances of infecting the host. In contrast, to counteract virus infection, the interferon-stimulated gene 15 (ISG15) or the E3 ISG15-protein ligase (HERC5) system within the infected cells is activated to degrade the ESCRT proteins. Many retroviral and RNA viral proteins have evolved "late (L) domain" motifs, which enable them to recruit host ESCRT subunit proteins to facilitate virus transport, replication, budding, mature, and even endocytosis, Therefore, the L domain motifs and ESCRT subunit proteins could serve as promising drug targets for antiviral therapy. This review investigated the composition and essential functions of the ESCRT, shedding light on the impact of ESCRT subunits and viral L domain motifs on the replication of viruses. Furthermore, the antiviral effects facilitated by the ESCRT machinery have been investigated, aiming to provide valuable insights to guide the development and utilization of antiviral drugs.

Sulfoxides in medicine

In the review, current status of sulfoxides on the pharmaceutical market is discussed. In the first part of the article, natural sulfoxides will be described with a special focus on sulforaphane and amanitin, a mushroom toxin which has been developed as payload in antibody drug conjugates in the possible cancer treatment. Controversies associated with the medical use of dimethylsulfoxide are briefly described in the next section. In the part devoted to PPIs, the benefits of using pure enantiomers (chiral switch) are discussed. An interesting approach, repositioning of drugs is exemplified by new possible applications of modafinil and sulindac. The review is concluded by presentation of cenicriviroc and adezmapimod, both with the status of promising drug candidates.

Backbone NMR resonance assignment of the apo human Tsg101-UEV domain

The Endosomal Sorting Complex Required for Transport (ESCRT) pathway, through inverse topology membrane remodeling, is involved in many biological functions, such as ubiquitinated membrane receptor trafficking and degradation, multivesicular bodies (MVB) formation and cytokinesis. Dysfunctions in ESCRT pathway have been associated to several human pathologies, such as cancers and neurodegenerative diseases. The ESCRT machinery is also hijacked by many enveloped viruses to bud away from the plasma membrane of infected cells. Human tumor susceptibility gene 101 (Tsg101) protein is an important ESCRT-I complex component. The structure of the N-terminal ubiquitin E2 variant (UEV) domain of Tsg101 (Tsg101-UEV) comprises an ubiquitin binding pocket next to a late domain [P(S/T)AP] binding groove. These two binding sites have been shown to be involved both in the physiological roles of ESCRT-I and in the release of the viral particles, and thus are attractive targets for antivirals. The structure of the Tsg101-UEV domain has been characterized, using X-ray crystallography or NMR spectroscopy, either in its apo-state or bound to ubiquitin or late domains. In this study, we report the backbone NMR resonance assignments, including the proline signals, of the apo human Tsg101-UEV domain, that so far was not publicly available. These data, that are in good agreement with the crystallographic structure of Tsg101-UEV domain, can therefore be used for further NMR studies, including protein-protein interaction studies and drug discovery.

Role of the Orphan Transporter SLC35E1 in the Nuclear Egress of Herpes Simplex Virus 1

This study developed a system consisting of two rounds of screening cellular proteins involved in the nuclear egress of herpes simplex virus 1 (HSV-1). Using this system, we first screened cellular proteins that interacted with the HSV-1 nuclear egress complex (NEC) consisting of UL34 and UL31 in HSV-1-infected cells, which are critical for the nuclear egress of HSV-1, by tandem affinity purification coupled with mass spectrometry-based proteomics technology. Next, we performed CRISPR/Cas9-based screening of live HSV-1-infected reporter cells under fluorescence microscopy using single guide RNAs targeting the cellular proteins identified in the first proteomic screening to detect the mislocalization of the lamin-associated protein emerin, which is a phenotype for defects in HSV-1 nuclear egress. This study focused on a cellular orphan transporter SLC35E1, one of the cellular proteins identified by the screening system. Knockout of SLC35E1 reduced HSV-1 replication and induced membranous invaginations containing perinuclear enveloped virions (PEVs) adjacent to the nuclear membrane (NM), aberrant accumulation of PEVs in the perinuclear space between the inner and outer NMs and the invagination structures, and mislocalization of the NEC. These effects were similar to those of previously reported mutation(s) in HSV-1 proteins and depletion of cellular proteins that are important for HSV-1 de-envelopment, one of the steps required for HSV-1 nuclear egress. Our newly established screening system enabled us to identify a novel cellular protein required for efficient HSV-1 de-envelopment. IMPORTANCE The identification of cellular protein(s) that interact with viral effector proteins and function in important viral procedures is necessary for enhancing our understanding of the mechanics of various viral processes. In this study, we established a new system consisting of interactome screening for the herpes simplex virus 1 (HSV-1) nuclear egress complex (NEC), followed by loss-of-function screening to target the identified putative NEC-interacting cellular proteins to detect a defect in HSV-1 nuclear egress. This newly established system identified SLC35E1, an orphan transporter, as a novel cellular protein required for efficient HSV-1 de-envelopment, providing an insight into the mechanisms involved in this viral procedure.

Aminomalononitrile inspired prebiotic chemistry as a novel multicomponent tool for the synthesis of imidazole and purine derivatives with anti-influenza A virus activity

Amino imidazole carbonitrile derivatives decorated with α-amino acid side-chains have been synthesized by a multicomponent microwave assisted reaction inspired by the prebiotic chemistry of aminomalononitrile as a tool for generating high chemical diversity. These compounds were used as annulation synthons for the preparation of 8,9-disubstituted-6,9-dihydro-1H-purin-6-ones by reaction with formic acid as a simple C-1 donor reagent. The novel heterocycles were characterized by significant activity against influenza A virus, amino imidazole carbonitrile derivatives showing the highest activity. Thus, the chemical complexity generated by prebiotic chemistry furnished a general tool for the identification of novel antiviral agents.

Amino imidazole carbonitrile derivatives decorated with α-amino acid side-chains have been synthesized by a multicomponent microwave assisted reaction inspired by the prebiotic chemistry of aminomalononitrile for generating high chemical diversity.

Importance of Viral Late Domains in Budding and Release of Enveloped RNA Viruses

Late assembly (L) domains are conserved sequences that are necessary for the late steps of viral replication, acting like cellular adaptors to engage the ESCRT membrane fission machinery that promote virion release. These short sequences, whose mutation or deletion produce the accumulation of immature virions at the plasma membrane, were firstly identified within retroviral Gag precursors, and in a further step, also in structural proteins of many other enveloped RNA viruses including arenaviruses, filoviruses, rhabdoviruses, reoviruses, and paramyxoviruses. Three classes of L domains have been identified thus far (PT/SAP, YPXnL/LXXLF, and PPxY), even if it has recently been suggested that other motifs could act as L domains. Here, we summarize the current state of knowledge of the different types of L domains and their cellular partners in the budding events of RNA viruses, with a particular focus on retroviruses.

Novel Tsg101 Binding Partners Regulate Viral L Domain Trafficking

Two decades ago, Tsg101, a component of the Endosomal Sorting Complexes Required for Transport (ESCRT) complex 1, was identified as a cellular factor recruited by the human immunodeficiency virus type 1 (HIV-1) to facilitate budding of viral particles assembled at the cell periphery. A highly conserved Pro-(Thr/Ser)-Ala-Pro [P(T/S)AP] motif in the HIV-1 structural polyprotein, Gag, engages a P(T/S)AP-binding pocket in the Tsg101 N-terminal domain. Since the same domain in Tsg101 that houses the pocket was found to bind mono-ubiquitin (Ub) non-covalently, Ub binding was speculated to enhance P(T/S)AP interaction. Within the past five years, we found that the Ub-binding site also accommodates di-Ub, with Lys63-linked di-Ub exhibiting the highest affinity. We also identified small molecules capable of disrupting Ub binding and inhibiting budding. The structural similarity of these molecules, prazoles, to nucleosides prompted testing for nucleic acid binding and led to identification of tRNA as a Tsg101 binding partner. Here, we discuss these recently identified interactions and their contribution to the viral assembly process. These new partners may provide additional insight into the control and function of Tsg101 as well as identify opportunities for anti-viral drug design.

Prazoles Targeting Tsg101 Inhibit Release of Epstein-Barr Virus following Reactivation from Latency

Epstein-Barr virus (EBV) is a ubiquitous herpesvirus responsible for several diseases, including cancers of lymphoid and epithelial cells. EBV cancers typically exhibit viral latency; however, the production and release of EBV through its lytic phase are essential for cancer development. Antiviral agents that specifically target EBV production do not currently exist. Previously, we reported that the proton pump inhibitor tenatoprazole, which blocks the interaction of ubiquitin with the ESCRT-1 factor Tsg101, inhibits production of several enveloped viruses, including EBV. Here, we show that three structurally distinct prazoles impair mature particle formation postreactivation and identify the impact on stages of replication. The prazoles did not impair expression of lytic genes representative of the different kinetic classes but interfered with capsid maturation in the nucleus as well as virion transport from the nucleus. Replacement of endogenous Tsg101 with a mutant Tsg101 refractory to prazole-mediated inhibition rescued EBV release. These findings directly implicate Tsg101 in EBV nuclear egress and identify prazoles as potential therapeutic candidates for conditions that rely on EBV replication, such as chronic active EBV infection and posttransplant lymphoproliferative disorders. IMPORTANCE Production of virions is necessary for the ubiquitous Epstein-Barr virus (EBV) to persist in humans and can set the stage for development of EBV cancers in at-risk individuals. In our attempts to identify inhibitors of the EBV lytic phase, we previously found that a prazole proton pump inhibitor, known to block the interaction of ubiquitin with the ESCRT-1 factor Tsg101, blocks production of EBV. We now find that three structurally distinct prazoles impair maturation of EBV capsids and virion transport from the nucleus and, by interfering with Tsg101, prevent EBV release from lytically active cells. Our findings not only implicate Tsg101 in EBV production but also identify widely used prazoles as candidates to prevent development of posttransplant EBV lymphomas.

Host and Viral Factors Involved in Nuclear Egress of Herpes Simplex Virus 1

Herpes simplex virus 1 (HSV-1) replicates its genome and packages it into capsids within the nucleus. HSV-1 has evolved a complex mechanism of nuclear egress whereby nascent capsids bud on the inner nuclear membrane to form perinuclear virions that subsequently fuse with the outer nuclear membrane, releasing capsids into the cytosol. The viral-encoded nuclear egress complex (NEC) plays a crucial role in this vesicle-mediated nucleocytoplasmic transport. Nevertheless, similar system mediates the movement of other cellular macromolecular complexes in normal cells. Therefore, HSV-1 may utilize viral proteins to hijack the cellular machinery in order to facilitate capsid transport. However, little is known about the molecular mechanisms underlying this phenomenon. This review summarizes our current understanding of the cellular and viral factors involved in the nuclear egress of HSV-1 capsids.

Why Cells and Viruses Cannot Survive without an ESCRT

Intracellular organelles enwrapped in membranes along with a complex network of vesicles trafficking in, out and inside the cellular environment are one of the main features of eukaryotic cells. Given their central role in cell life, compartmentalization and mechanisms allowing their maintenance despite continuous crosstalk among different organelles have been deeply investigated over the past years. Here, we review the multiple functions exerted by the endosomal sorting complex required for transport (ESCRT) machinery in driving membrane remodeling and fission, as well as in repairing physiological and pathological membrane damages. In this way, ESCRT machinery enables different fundamental cellular processes, such as cell cytokinesis, biogenesis of organelles and vesicles, maintenance of nuclear–cytoplasmic compartmentalization, endolysosomal activity. Furthermore, we discuss some examples of how viruses, as obligate intracellular parasites, have evolved to hijack the ESCRT machinery or part of it to execute/optimize their replication cycle/infection. A special emphasis is given to the herpes simplex virus type 1 (HSV-1) interaction with the ESCRT proteins, considering the peculiarities of this interplay and the need for HSV-1 to cross both the nuclear-cytoplasmic and the cytoplasmic-extracellular environment compartmentalization to egress from infected cells.