CDC42 Use in Viral Cell Entry Processes by RNA Viruses

Integrated analysis of RNA-seq datasets reveals novel targets and regulators of COVID-19 severity

During the COVID-19 pandemic, RNA-seq datasets were produced to investigate the virus-host relationship. However, much of these data remains underexplored. To improve the search for molecular targets and biomarkers, we performed an integrated analysis of multiple RNA-seq datasets, expanding the cohort and including patients from different countries, encompassing severe and mild COVID-19 patients. Our analysis revealed that severe COVID-19 patients exhibit overexpression of genes coding for proteins of extracellular exosomes, endomembrane system, and neutrophil granules (e.g., S100A9, LY96, and RAB1B), which may play an essential role in the cellular response to infection. Concurrently, these patients exhibit down-regulation of genes encoding components of the T cell receptor complex and nucleolus, including TP53, IL2RB, and NCL Finally, SPI1 may emerge as a central transcriptional factor associated with the up-regulated genes, whereas TP53, MYC, and MAX were associated with the down-regulated genes during COVID-19. This study identified targets and transcriptional factors, lighting on the molecular pathophysiology of syndrome coronavirus 2 infection.

Identification of immune-responsive circular RNAs in shrimp (Litopenaeus vannamei) upon yellow head virus infection

Circular RNAs (circRNAs) are a subclass of non-coding RNAs (ncRNAs) formed through a process known as back-splicing. They play a crucial role in the genetic regulation of various biological processes. Currently, circRNAs have been identified as participants in the antiviral response within mammalian cells. However, circRNAs in shrimp infected with the yellow head virus (YHV) remain largely unexplored. Therefore, this study aims to identify circRNAs in the hemocytes of Litopenaeus vannamei during YHV infection. We discovered 358 differentially expressed circRNAs (DECs), with 177 of them being up-regulated and 181 down-regulated. Subsequently, eight DECs, including circ_alpha-1-inhibitor 3, circ_CDC42 small effector protein 2, circ_hemicentin 2, circ_integrin alpha V, circ_kazal-type proteinase inhibitor, circ_phenoloxidase 3, circ_related protein rab-8B, and circ_protein toll-like, were randomly selected for analysis of their expression patterns during YHV infection using qRT-PCR. Furthermore, the circRNAs' characteristics were confirmed through PCR, RNase R treatment, and Sanger sequencing, all of which were consistent with the features of circRNAs. These findings contribute to a better understanding of circRNAs' involvement in the antiviral response in shrimp.

The basis of complications in the context of SARS-CoV-2 infection: Pathological activation of ADAM17

The virulence of SARS-CoV-2 decreases with increasing infectivity, the primary approaches for antiviral treatments will be preventing or minimizing the complications resulting from virus infection. ADAM metallopeptidase domain 17 (ADAM17) activation by SARS-CoV-2 infection has a dual effect on the development of the disease: increased release of inflammatory cytokines and dysregulation of Angiotensin converting enzyme II (ACE2) on cell surfaces, inflammatory cytokine infiltration and loss of ACE2 protective function lead to a significant increase in the incidence of related complications. Importantly, pathologically activated ADAM17 showed superior features than S protein in regulating ACE2 expression and participating in the intra cellular replication of SARS-CoV-2. In short, SARS-CoV-2 elicits only a limited immune response when it promotes its own replication and pathogenicity through ADAM17. Therefore, the pathological activation of ADAM17 may also represent a diminished innate antiviral defense and an altered strategy of SARS-CoV-2 infection. In this review, we summarized recent advances in our understanding of the pathophysiology of ADAM17, with a focus on the new findings that SARS-CoV-2 affects ADAM17 expression through Furin protein converting enzyme and Mitogen-activated protein kinase (MAPK) pathway, and raises the hypothesis that SARS-CoV-2 may mediates the pathological activation of ADAM17 by hijacking the actin regulatory pathway, and discussed the underlying biological principles.

Potential role of PIM1 inhibition in the treatment of SARS-CoV-2 infection

BACKGROUND

SARS-CoV-2 infection involves disturbing multiple molecular pathways related to immunity and cellular functions. PIM1 is a serine/threonine-protein kinase found to be involved in the pathogenesis of several viral infections. One PIM1 substrate, Myc, was reported to interact with TMPRSS2, which is crucial for SARS-CoV-2 cell entry. PIM1 inhibitors were reported to have antiviral activity through multiple mechanisms related to immunity and proliferation. This study aimed to evaluate the antiviral activity of 2-pyridone PIM1 inhibitor against SARS-CoV-2 and its potential role in hindering the progression of COVID-19. It also aimed to assess PIM1 inhibitor's effect on the expression of several genes of Notch signaling and Wnt pathways. In vitro study was conducted on Vero-E6 cells infected by SARS-CoV-2 "NRC-03-nhCoV" virus. Protein-protein interaction of the study genes was assessed to evaluate their relation to cell proliferation and immunity. The effect of 2-pyridone PIM1 inhibitor treatment on viral load and mRNA expression of target genes was assessed at three time points.

RESULTS

Treatment with 2-pyridone PIM1 inhibitor showed potential antiviral activity against SARS-CoV-2 (IC50 of 37.255 µg/ml), significantly lowering the viral load. Functional enrichments of the studied genes include negative regulation of growth rate, several biological processes involved in cell proliferation, and Interleukin-4 production, with interleukin-6 as a predicted functional partner. These results suggest an interplay between study genes with relation to cell proliferation and immunity. Following in vitro SARS-CoV-2 infection, Notch pathway genes, CTNNB1, SUMO1, and TDG, were found to be overexpressed compared to uninfected cells. Treatment with 2-pyridone PIM1 inhibitor significantly lowers the expression levels of study genes, restoring Notch1 and BCL9 to the control level while decreasing Notch2 and CTNNB1 below control levels.

CONCLUSION

2-pyridone PIM1 inhibitor could hinder cellular entry of SARS-CoV-2 and modulate several pathways implicated in immunity, suggesting a potential benefit in the development of anti-SARS-CoV-2 therapeutic approach.

Role of Host Small GTPases in Apicomplexan Parasite Infection

The Apicomplexa are obligate intracellular parasites responsible for several important human diseases. These protozoan organisms have evolved several strategies to modify the host cell environment to create a favorable niche for their survival. The host cytoskeleton is widely manipulated during all phases of apicomplexan intracellular infection. Moreover, the localization and organization of host organelles are altered in order to scavenge nutrients from the host. Small GTPases are a class of proteins widely involved in intracellular pathways governing different processes, from cytoskeletal and organelle organization to gene transcription and intracellular trafficking. These proteins are already known to be involved in infection by several intracellular pathogens, including viruses, bacteria and protozoan parasites. In this review, we recapitulate the mechanisms by which apicomplexan parasites manipulate the host cell during infection, focusing on the role of host small GTPases. We also discuss the possibility of considering small GTPases as potential targets for the development of novel host-targeted therapies against apicomplexan infections.

Guanine nucleotide exchange factor DOCK11-binding peptide fused with a single chain antibody inhibits Hepatitis B Virus infection and replication

Hepatitis B virus (HBV) infection is a major global health problem with no established cure. Dedicator of cytokinesis 11 (DOCK11), known as a guanine nucleotide exchange factor (GEF) for Cdc42, is reported to be essential for the maintenance of HBV. However, potential therapeutic strategies targeting DOCK11 have not yet been explored. We have previously developed an in vitro virus method as a more efficient tool for the analysis of proteomics and evolutionary protein engineering. In this study, using the in vitro virus method, we screened and identified a novel antiasialoglycoprotein receptor (ASGR) antibody, ASGR3-10M, and a DOCK11-binding peptide, DCS8-42A, for potential use in HBV infection. We further constructed a fusion protein (10M-D42AN) consisting of ASGR3-10M, DCS8-42A, a fusogenic peptide, and a nuclear localization signal to deliver the peptide inside hepatocytes. We show using immunofluorescence staining that 10M-D42AN was endocytosed into early endosomes and released into the cytoplasm and nucleus. Since DCS8-42A shares homology with activated cdc42-associated kinase 1 (Ack1), which promotes EGFR endocytosis required for HBV infection, we also found that 10M-D42AN inhibited endocytosis of EGFR and Ack1. Furthermore, we show 10M-D42AN suppressed the function of DOCK11 in the host DNA repair system required for covalently closed circular DNA synthesis and suppressed HBV proliferation in mice. In conclusion, this study realizes a novel hepatocyte-specific drug delivery system using an anti-ASGR antibody, a fusogenic peptide, and DOCK11-binding peptide to provide a novel treatment for HBV.

The Process of Filopodia Induction during HPV Infection

Human Papillomavirus 16 (HPV16) infects mucosal and epithelial cells and has been identified as a high-risk HPV type that is an etiologic agent of human cancers. The initial infectious process, i.e., the binding of the virus particle and its entry into the host cell, has been studied extensively, although it is not fully understood. There is still a gap in understanding the steps by which the virus is able to cross the plasma membrane after receptor binding. In this study, we demonstrate that after HPV16 comes into contact with a plasma membrane receptor, there are cytoskeletal changes resulting in an increase of filopodia numbers. This increase in filopodia numbers was transient and was maintained during the first two hours after virus addition. Our data show that there is a statistically significant increase in infection when filopodia numbers are increased by the addition of drug and virus simultaneously, and a decrease in virus infection when filopodia formation is inhibited. We describe that HPV16 binding results in the activation of Cdc42 GTPase that in turn results in an increase in filopodia. siRNA directed at Cdc42 GTPase resulted in a statistically significant reduction of infection and a corresponding lack of filopodia induction.

Elevated Vulnerability of Chronic Leukemia Patients to COVID-19 Infection: A Systems Biology Approach

Background

Emerging evidence has shown that SARS-CoV-2 may affect the circulatory system in addition to the human respiratory system. However, no study has indicated whether patients with leukemia have a greater likelihood of SARS-CoV-2 infection or have poor treatment outcomes.

Objective

The study aimed to demonstrate the relationship between essential blood proteins and the major SARS-CoV-2 proteins by network pharmacology bioinformatics analysis.

Methods

Bioinformatics analysis was used to establish eight differentially expressed gene hubs in leukemia through differential gene screening, protein–protein interaction network analysis, and gene enrichment analysis. Molecular docking analysis was also conducted to dock the two up-regulated proteins with the spike glycoprotein in leukemia and the critical protease enzyme (Mpro) of SARS-CoV-2.

Results

We identified two up-regulated genes (PTPRC and BCL6) among the eight differentially expressed genes. The PTPRC and BCL6 also docked perfectly with the main SARS-CoV-2 structural proteins.

Conclusion and Recommendation

This study indicates that SARS-CoV-2 is likely to affect with the blood in patients with chronic leukemia. Therefore, patients with chronic leukemia require greater medical attention and precautions during the COVID-19 pandemic.

Interaction Network of Porcine Circovirus Type 3 and 4 Capsids with Host Proteins

An extensive understanding of the interactions between host cellular and viral proteins provides clues for studying novel antiviral strategies. Porcine circovirus type 3 (PCV3) and type 4 (PCV4) have recently been identified as viruses that can potentially damage the swine industry. Herein, 401 putative PCV3 Cap-binding and 484 putative PCV4 Cap-binding proteins were characterized using co-immunoprecipitation and liquid chromatography-mass spectrometry. Both PCV3 and PCV4 Caps shared 278 identical interacting proteins, but some putative interacting proteins (123 for PCV3 Cap and 206 for PCV4 Cap) differed. A protein-protein interaction network was constructed, and according to gene ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) database analyses, both PCV3 Cap- and PCV4 Cap-binding proteins participated mainly in ribosome biogenesis, nucleic acid binding, and ATP-dependent RNA helicase activities. Verification assays of eight putative interacting proteins indicated that nucleophosmin-1, nucleolin, DEAD-box RNA helicase 21, heterogeneous nuclear ribonucleoprotein A2/B1, YTH N6-methyladenosine RNA binding protein 1, and Y-box binding protein 1 bound directly to both PCV3 and PCV4 Caps, but ring finger protein 2 and signal transducer and activator of transcription 6 did not. Therefore, the interaction network provided helpful information to support further research into the underlying mechanisms of PCV3 and PCV4 infection.

Cortactin in Lung Cell Function and Disease

Cortactin (CTTN) is an actin-binding and cytoskeletal protein that is found in abundance in the cell cortex and other peripheral structures of most cell types. It was initially described as a target for Src-mediated phosphorylation at several tyrosine sites within CTTN, and post-translational modifications at these tyrosine sites are a primary regulator of its function. CTTN participates in multiple cellular functions that require cytoskeletal rearrangement, including lamellipodia formation, cell migration, invasion, and various other processes dependent upon the cell type involved. The role of CTTN in vascular endothelial cells is particularly important for promoting barrier integrity and inhibiting vascular permeability and tissue edema. To mediate its functional effects, CTTN undergoes multiple post-translational modifications and interacts with numerous other proteins to alter cytoskeletal structures and signaling mechanisms. In the present review, we briefly describe CTTN structure, post-translational modifications, and protein binding partners and then focus on its role in regulating cellular processes and well-established functional mechanisms, primarily in vascular endothelial cells and disease models. We then provide insights into how CTTN function affects the pathophysiology of multiple lung disorders, including acute lung injury syndromes, COPD, and asthma.

Virus interactions with the actin cytoskeleton-what we know and do not know about SARS-CoV-2

The actin cytoskeleton and actin-dependent molecular and cellular events are responsible for the organization of eukaryotic cells and their functions. Viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), depend on host cell organelles and molecular components for cell entry and propagation. Thus, it is not surprising that they also interact at many levels with the actin cytoskeleton of the host. There have been many studies on how different viruses reconfigure and manipulate the actin cytoskeleton of the host during successive steps of their life cycle. However, we know relatively little about the interactions of SARS-CoV-2 with the actin cytoskeleton. Here, we describe how the actin cytoskeleton is involved in the strategies used by different viruses for entry, assembly, and egress from the host cell. We emphasize what is known and unknown about SARS-CoV-2 in this regard. This review should encourage further investigation of the interactions of SARS-CoV-2 with cellular components, which will eventually be helpful for developing novel antiviral therapies for mitigating the severity of COVID-19.

Cell Division Control Protein 42 Interacts With Hepatitis E Virus Capsid Protein and Participates in Hepatitis E Virus Infection

Hepatitis E Virus (HEV) causes viral hepatitis in humans worldwide, while a subset of HEV species, avian HEV, causes hepatitis-splenomegaly syndrome in chickens. To date, there are few reports on the host proteins interacting with HEV and being involved in viral infection. Previous pull-down assay combining mass spectrometry indicated that cell division control protein 42 (CDC42), a member belonging to the Rho GTPase family, was pulled down by avian HEV capsid protein. We confirmed the direct interaction between CDC42 and avian and mammalian HEV capsid proteins. The interaction can increase the amount of active guanosine triphosphate binding CDC42 state (GTP-CDC42). Subsequently, we determined that the expression and activity of CDC42 were positively correlated with HEV infection in the host cells. Using the different inhibitors of CDC42 downstream signaling pathways, we found that CDC42-MRCK (a CDC42-binding kinase)-non-myosin IIA (NMIIA) pathway is involved in naked avian and mammalian HEV infection, CDC42-associated p21-activated kinase 1 (PAK1)-NMIIA/Cofilin pathway is involved in quasi-enveloped mammalian HEV infection and CDC42-neural Wiskott-Aldrich syndrome protein-actin-polymerizing protein Arp2/3 pathway (CDC42-(N-)WASP-Arp2/3) pathway participates in naked and quasi-enveloped mammalian HEV infection. Collectively, these results demonstrated for the first time that HEV capsid protein can directly bind to CDC42, and non- and quasi-enveloped HEV use different CDC42 downstream signaling pathways to participate in viral infection. The study provided some new insights to understand the life cycle of HEV in host cells and a new target of drug design for combating HEV infection.

SARS-CoV-2-host proteome interactions for antiviral drug discovery

Treatment options for COVID-19, caused by SARS-CoV-2, remain limited. Understanding viral pathogenesis at the molecular level is critical to develop effective therapy. Some recent studies have explored SARS-CoV-2-host interactomes and provided great resources for understanding viral replication. However, host proteins that functionally associate with SARS-CoV-2 are localized in the corresponding subnetwork within the comprehensive human interactome. Therefore, constructing a downstream network including all potential viral receptors, host cell proteases, and cofactors is necessary and should be used as an additional criterion for the validation of critical host machineries used for viral processing. This study applied both affinity purification mass spectrometry (AP-MS) and the complementary proximity-based labeling MS method (BioID-MS) on 29 viral ORFs and 18 host proteins with potential roles in viral replication to map the interactions relevant to viral processing. The analysis yields a list of 693 hub proteins sharing interactions with both viral baits and host baits and revealed their biological significance for SARS-CoV-2. Those hub proteins then served as a rational resource for drug repurposing via a virtual screening approach. The overall process resulted in the suggested repurposing of 59 compounds for 15 protein targets. Furthermore, antiviral effects of some candidate drugs were observed in vitro validation using image-based drug screen with infectious SARS-CoV-2. In addition, our results suggest that the antiviral activity of methotrexate could be associated with its inhibitory effect on specific protein-protein interactions.

A major quantitative trait locus affecting resistance to Tilapia lake virus in farmed Nile tilapia (Oreochromis niloticus)

Enhancing host resistance to infectious disease has received increasing attention in recent years as a major goal of farm animal breeding programs. Combining field data with genomic tools can provide opportunities to understand the genetic architecture of disease resistance, leading to new opportunities for disease control. In the current study, a genome-wide association study was performed to assess resistance to the Tilapia lake virus (TiLV), one of the biggest threats affecting Nile tilapia (Oreochromis niloticus); a key aquaculture species globally. A pond outbreak of TiLV in a pedigreed population of the GIFT strain was observed, with 950 fish classified as either survivor or mortality, and genotyped using a 65 K SNP array. A significant QTL of large effect was identified on chromosome Oni22. The average mortality rate of tilapia homozygous for the resistance allele at the most significant SNP (P value = 4.51E-10) was 11%, compared to 43% for tilapia homozygous for the susceptibility allele. Several candidate genes related to host response to viral infection were identified within this QTL, including lgals17, vps52, and trim29. These results provide a rare example of a major QTL affecting a trait of major importance to a farmed animal. Genetic markers from the QTL region have potential in marker-assisted selection to improve host resistance, providing a genetic solution to an infectious disease where few other control or mitigation options currently exist.

Reversal of SARS-CoV2-Induced Hypoxia by Nebulized Sodium Ibuprofenate in a Compassionate Use Program

INTRODUCTION

Sodium ibuprofenate in hypertonic saline (NaIHS) administered directly to the lungs by nebulization and inhalation has antibacterial and anti-inflammatory effects, with the potential to deliver these benefits to hypoxic patients. We describe a compassionate use program that offered this therapy to hospitalized COVID-19 patients.

METHODS

NaIHS (50 mg ibuprofen, tid) was provided in addition to standard of care (SOC) to hospitalized COVID-19 patients until oxygen saturation levels of > 94% were achieved on ambient air. Patients wore a containment hood to diminish aerosolization. Outcome data from participating patients treated at multiple hospitals in Argentina between April 4 and October 31, 2020, are summarized. Results were compared with a retrospective contemporaneous control (CC) group of hospitalized COVID-19 patients with SOC alone during the same time frame from a subset of participating hospitals from Córdoba and Buenos Aires.

RESULTS

The evolution of 383 patients treated with SOC + NaIHS [56 on mechanical ventilation (MV) at baseline] and 195 CC (21 on MV at baseline) are summarized. At baseline, NaIHS-treated patients had basal oxygen saturation of 90.7 ± 0.2% (74.3% were on supplemental oxygen at baseline) and a basal respiratory rate of 22.7 ± 0.3 breath/min. In the CC group, basal oxygen saturation was 92.6 ± 0.4% (52.1% were on oxygen supplementation at baseline) and respiratory rate was 19.3 ± 0.3 breath/min. Despite greater pulmonary compromise at baseline in the NaIHS-treated group, the length of treatment (LOT) was 9.1 ± 0.2 gs with an average length of stay (ALOS) of 11.5 ± 0.3 days, in comparison with an ALOS of 13.3 ± 0.9 days in the CC group. In patients on MV who received NaIHS, the ALOS was lower than in the CC group. In both NaIHS-treated groups, a rapid reversal of deterioration in oxygenation and NEWS2 scores was observed acutely after initiation of NaIHS therapy. No serious adverse events were considered related to ibuprofen therapy. Mortality was lower in both NaIHS groups compared with CC groups.

CONCLUSIONS

Treatment of COVID-19 pneumonitis with inhalational nebulized NaIHS was associated with rapid improvement in hypoxia and vital signs, with no serious adverse events attributed to therapy. Nebulized NaIHS s worthy of further study in randomized, placebo-controlled trials (ClinicalTrials.gov: NCT04382768).

DOCK11 and DENND2A play pivotal roles in the maintenance of hepatitis B virus in host cells

Human hepatitis B virus (HBV) infection remains a serious health problem worldwide. However, the mechanism for the maintenance of HBV in a latent state within host cells remains unclear. Here, using single-cell RNA sequencing analysis, we identified four genes linked to the maintenance of HBV in a liver cell line expressing HBV RNA at a low frequency. These genes included DOCK11 and DENND2A, which encode small GTPase regulators. In primary human hepatocytes infected with HBV, knockdown of these two genes decreased the amount of both HBV DNA and covalently closed circular DNA to below the limit of detection. Our findings reveal a role for DOCK11 and DENND2A in the maintenance of HBV.

Rho GTPases and the emerging role of tunneling nanotubes in physiology and disease

Tunneling nanotubes (TNTs) emerged as important specialized actin-rich membrane protrusions for cell-to-cell communication. These structures allow the intercellular exchange of material, such as ions, soluble proteins, receptors, vesicles and organelles, therefore exerting critical roles in normal cell function. Indeed, TNTs participate in a number of physiological processes, including embryogenesis, immune response, and osteoclastogenesis. TNTs have been also shown to contribute to the transmission of retroviruses (e.g., human immunodeficiency virus-1, HIV-1) and coronaviruses. As with other membrane protrusions, the involvement of Rho GTPases in the formation of these elongated structures is undisputable, although the mechanisms involved are not yet fully elucidated. The tight control of Rho GTPase function by guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) strongly suggests that localized control of these Rho regulators may contribute to TNT assembly and disassembly. Deciphering the intricacies of the complex signaling mechanisms leading to actin reorganization and TNT development would reveal important information about their involvement in normal cellular physiology as well as unveil potential targets for disease management.

Epigenetic Regulator miRNA Pattern Differences Among SARS-CoV, SARS-CoV-2, and SARS-CoV-2 World-Wide Isolates Delineated the Mystery Behind the Epic Pathogenicity and Distinct Clinical Characteristics of Pandemic COVID-19

A detailed understanding of the molecular mechanism of SARS-CoV-2 pathogenesis is still elusive, and there is a need to address its deadly nature and to design effective therapeutics. Here, we present a study that elucidates the interplay between the SARS-CoV and SARS-CoV-2 viruses' and host's miRNAs, an epigenetic regulator, as a mode of pathogenesis; and we explored how the SARS-CoV and SARS-CoV-2 infections differ in terms of their miRNA-mediated interactions with the host and the implications this has in terms of disease complexity. We have utilized computational approaches to predict potential host and viral miRNAs and their possible roles in different important functional pathways. We have identified several putative host antiviral miRNAs that can target the SARS viruses and also predicted SARS viruses-encoded miRNAs targeting host genes. In silico predicted targets were also integrated with SARS-infected human cell microarray and RNA-seq gene expression data. A comparison between the host miRNA binding profiles on 67 different SARS-CoV-2 genomes from 24 different countries with respective country's normalized death count surprisingly uncovered some miRNA clusters, which are associated with increased death rates. We have found that induced cellular miRNAs can be both a boon and a bane to the host immunity, as they have possible roles in neutralizing the viral threat; conversely, they can also function as proviral factors. On the other hand, from over representation analysis, our study revealed that although both SARS-CoV and SARS-CoV-2 viral miRNAs could target broad immune-signaling pathways; only some of the SARS-CoV-2 miRNAs are found to uniquely target some immune-signaling pathways, such as autophagy, IFN-I signaling, etc., which might suggest their immune-escape mechanisms for prolonged latency inside some hosts without any symptoms of COVID-19. Furthermore, SARS-CoV-2 can modulate several important cellular pathways that might lead to the increased anomalies in patients with comorbidities like cardiovascular diseases, diabetes, breathing complications, etc. This might suggest that miRNAs can be a key epigenetic modulator behind the overcomplications amongst the COVID-19 patients. Our results support that miRNAs of host and SARS-CoV-2 can indeed play a role in the pathogenesis which can be further concluded with more experiments. These results will also be useful in designing RNA therapeutics to alleviate the complications from COVID-19.

The actin cytoskeleton is important for rotavirus internalization and RNA genome replication

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Different stages of the rotavirus lifecycle depend on the dynamics of the actin cytoskeleton.

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Alpha-actinin, Diaph, and the GTPase Cdc42 are important for virus entry.

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The GTPAse Rac1 is required for maximal viral RNA synthesis.

Numerous host factors are required for the efficient replication of rotavirus, including the activation and inactivation of several cell signaling pathways. One of the cellular structures that are reorganized during rotavirus infection is the actin cytoskeleton. In this work, we report that the dynamics of the actin microfilaments are important at different stages of the virus life cycle, specifically, during virus internalization and viral RNA synthesis at 6 h post-infection. Our results show that the actin-binding proteins alpha-actinin 4 and Diaph, as well as the Rho-family small GTPase Cdc42 are necessary for an efficient virus entry, while GTPase Rac1 is required for maximal viral RNA synthesis.

Viral journeys on the intracellular highways

Viruses are obligate intracellular pathogens that are dependent on cellular machineries for their replication. Recent technological breakthroughs have facilitated reliable identification of host factors required for viral infections and better characterization of the virus-host interplay. While these studies have revealed cellular machineries that are uniquely required by individual viruses, accumulating data also indicate the presence of broadly required mechanisms. Among these overlapping cellular functions are components of intracellular membrane trafficking pathways. Here, we review recent discoveries focused on how viruses exploit intracellular membrane trafficking pathways to promote various stages of their life cycle, with an emphasis on cellular factors that are usurped by a broad range of viruses. We describe broadly required components of the endocytic and secretory pathways, the Endosomal Sorting Complexes Required for Transport pathway, and the autophagy pathway. Identification of such overlapping host functions offers new opportunities to develop broad-spectrum host-targeted antiviral strategies.

Cloning and differential expression analyses of Cdc42 from sheep

Introduction

Serological diagnosis of brucellosis is still a great challenge due to the infeasibility of discriminating infected animals from vaccinated ones, so it is necessary to search for diagnostic biomarkers for differential diagnosis of brucellosis.

Material and Methods

Cell division cycle 42 (Cdc42) from sheep (Ovis aries) (OaCdc42) was cloned by rapid amplification of cDNA ends (RACE), and then tissue distribution and differential expression levels of OaCdc42 mRNA between infected and vaccinated sheep were analysed by RT-qPCR.

Results

The full-length cDNA of OaCdc42 was 1,609 bp containing an open reading frame (ORF) of 576 bp. OaCdc42 mRNAs were detected in the heart, liver, spleen, lung, kidneys, rumen, small intestine, skeletal muscles, and buffy coat, and the highest expression was detected in the small intestine. Compared to the control, the levels of OaCdc42 mRNA from sheep infected with Brucella melitensis or sheep vaccinated with Brucella suis S2 was significantly different (P < 0.01) after 40 and 30 days post-inoculation, respectively. However, the expression of OaCdc42 mRNA was significantly different between vaccinated and infected sheep (P < 0.05 or P < 0.01) on days: 14, 30, and 60 post-inoculation, whereas no significant difference (P > 0.05) was noted 40 days post-inoculation. Moreover, the expression of OaCdc42 from both infected and vaccinated sheep showed irregularity.

Conclusion

OaCdc42 is not a good potential diagnostic biomarker for differential diagnosis of brucellosis in sheep.

Cloning and Differential Expression Analyses of Cdc42 from Sheep

INTRODUCTION

Serological diagnosis of brucellosis is still a great challenge due to the infeasibility of discriminating infected animals from vaccinated ones, so it is necessary to search for diagnostic biomarkers for differential diagnosis of brucellosis.

MATERIAL AND METHODS

Cell division cycle 42 (Cdc42) from sheep (Ovis aries) (OaCdc42) was cloned by rapid amplification of cDNA ends (RACE), and then tissue distribution and differential expression levels of OaCdc42 mRNA between infected and vaccinated sheep were analysed by RT-qPCR.

RESULTS

The full-length cDNA of OaCdc42 was 1,609 bp containing an open reading frame (ORF) of 576 bp. OaCdc42 mRNAs were detected in the heart, liver, spleen, lung, kidneys, rumen, small intestine, skeletal muscles, and buffy coat, and the highest expression was detected in the small intestine. Compared to the control, the levels of OaCdc42 mRNA from sheep infected with Brucella melitensis or sheep vaccinated with Brucella suis S2 was significantly different (P < 0.01) after 40 and 30 days post-inoculation, respectively. However, the expression of OaCdc42 mRNA was significantly different between vaccinated and infected sheep (P < 0.05 or P < 0.01) on days: 14, 30, and 60 post-inoculation, whereas no significant difference (P > 0.05) was noted 40 days post-inoculation. Moreover, the expression of OaCdc42 from both infected and vaccinated sheep showed irregularity.

CONCLUSION

OaCdc42 is not a good potential diagnostic biomarker for differential diagnosis of brucellosis in sheep.

All-Round Manipulation of the Actin Cytoskeleton by HIV

While significant progress has been made in terms of human immunodeficiency virus (HIV) therapy, treatment does not represent a cure and remains inaccessible to many people living with HIV. Continued mechanistic research into the viral life cycle and its intersection with many aspects of cellular biology are not only fundamental in the continued fight against HIV, but also provide many key observations of the workings of our immune system. Decades of HIV research have testified to the integral role of the actin cytoskeleton in both establishing and spreading the infection. Here, we review how the virus uses different strategies to manipulate cellular actin networks and increase the efficiency of various stages of its life cycle. While some HIV proteins seem able to bind to actin filaments directly, subversion of the cytoskeleton occurs indirectly by exploiting the power of actin regulatory proteins, which are corrupted at multiple levels. Furthermore, this manipulation is not restricted to a discrete class of proteins, but rather extends throughout all layers of the cytoskeleton. We discuss prominent examples of actin regulators that are exploited, neutralized or hijacked by the virus, and address how their coordinated deregulation can lead to changes in cellular behavior that promote viral spreading.

Interaction of the Small GTPase Cdc42 with Arginine Kinase Restricts White Spot Syndrome Virus in Shrimp

Many types of small GTPases are widely expressed in eukaryotes and have different functions. As a crucial member of the Rho GTPase family, Cdc42 serves a number of functions, such as regulating cell growth, migration, and cell movement. Several RNA viruses employ Cdc42-hijacking tactics in their target cell entry processes. However, the function of Cdc42 in shrimp antiviral immunity is not clear. In this study, we identified a Cdc42 protein in the kuruma shrimp (Marsupenaeus japonicus) and named it MjCdc42. MjCdc42 was upregulated in shrimp challenged by white spot syndrome virus (WSSV). The knockdown of MjCdc42 and injection of Cdc42 inhibitors increased the proliferation of WSSV. Further experiments determined that MjCdc42 interacted with an arginine kinase (MjAK). By analyzing the binding activity and enzyme activity of MjAK and its mutant, ΔMjAK, we found that MjAK could enhance the replication of WSSV in shrimp. MjAK interacted with the envelope protein VP26 of WSSV. An inhibitor of AK activity, quercetin, could impair the function of MjAK in WSSV replication. Further study demonstrated that the binding of MjCdc42 and MjAK depends on Cys²⁷¹ of MjAK and suppresses the WSSV replication-promoting effect of MjAK. By interacting with the active site of MjAK and suppressing its enzyme activity, MjCdc42 inhibits WSSV replication in shrimp. Our results demonstrate a new function of Cdc42 in the cellular defense against viral infection in addition to the regulation of actin and phagocytosis, which has been reported in previous studies. IMPORTANCE The interaction of Cdc42 with arginine kinase plays a crucial role in the host defense against WSSV infection. This study identifies a new mechanism of Cdc42 in innate immunity and enriches the knowledge of the antiviral innate immunity of invertebrates.