Role of Rab GTPases in HSV-1 infection: Molecular understanding of viral maturation and egress

Combating multidrug-resistant (MDR) Staphylococcus aureus infection using terpene and its derivative

Multidrug-resistant (MDR) Staphylococcus aureus represents a major global health issue resulting in a wide range of debilitating infections and fatalities. The slow progression of new antibiotics, limited choices for treatment, and scarcity of new drug approvals create immense obstacles in new drug line development. S. aureus poses a significant public health risk, due to the emergence of methicillin-resistant (MRSA) and vancomycin-resistant strains (VRSA), necessitating novel antibiotics for effective control management. Current studies are delving into the terpenes' potential as an antimicrobial agent, indicating positive prospects as promising substitutes or complementary to conventional antibiotics. Concurrent reactions of terpenes with conventional antibiotics create synergistic effects that significantly enhance antibiotic efficacy. Accumulated evidence has shown that while efflux pump (e.g., NorA, TetK, and MepA) is revealed as an essential defense of S. aureus against antibiotics, terpene and its derivative act as its potent inhibitor, suggesting the promising potential of terpenes in combating those infectious pathogens. Furthermore, pronounced cell membrane disruptive activity and antibiofilm properties by terpenes have been exerted, signifying their significance as promising prevention against microbial pathogenesis and antimicrobial resistance. This review provides an overview of the potential of terpenes and their derivatives in combating S. aureus infections, highlighting their potential mechanisms of action (MOA), synergistic effects with conventional antibiotics, and challenges in clinical translation. The unique properties of terpenes offer an opportunity for their use in developing an exceptional defense strategy against antibiotic-resistant S. aureus.

The Rab6 post-Golgi secretory pathway contributes to herpes simplex virus 1 (HSV-1) egress

Herpes simplex virus 1 (HSV-1) is an alpha herpesvirus that infects a majority of the world population. The mechanisms and cellular host factors involved in the intracellular transport and exocytosis of HSV-1 particles are not fully understood. To elucidate these late steps in the replication cycle, we developed a live-cell fluorescence microscopy assay of HSV-1 virion intracellular trafficking and exocytosis. This method allows us to track individual virus particles and identify the precise moment and location of particle exocytosis using a pH-sensitive reporter. We show that HSV-1 uses the host cell's post-Golgi secretory pathway during egress. The small GTPase, Rab6, binds to nascent secretory vesicles at the trans-Golgi network and plays important, but non-essential, roles in vesicle traffic and exocytosis at the plasma membrane, therefore making it a useful marker of the Golgi and post-Golgi secretory pathway. We show that HSV-1 particles colocalize with Rab6a in the region of the Golgi, cotraffic with Rab6a to the cell periphery, and undergo exocytosis from Rab6a vesicles. Consistent with previous reports, we find that HSV-1 particles accumulate at preferential egress sites in infected cells. The secretory pathway mediates this preferential/polarized egress, since Rab6a vesicles accumulate near the plasma membrane similarly in uninfected cells. These data suggest that, following particle envelopment, HSV-1 egress follows a pre-existing cellular secretory pathway to exit infected cells rather than novel, virus-induced mechanisms.

IMPORTANCE

Herpes simplex virus 1 (HSV-1) infects a majority of people. It establishes a life-long latent infection and occasionally reactivates, typically causing characteristic oral or genital lesions. Rarely in healthy natural hosts, but more commonly in zoonotic infections and in elderly, newborn, or immunocompromised patients, HSV-1 can cause severe herpes encephalitis. The precise cellular mechanisms used by HSV-1 remain an important area of research. In particular, the egress pathways that newly assembled virus particles use to exit from infected cells are unclear. In this study, we used fluorescence microscopy to visualize individual virus particles exiting from cells and found that HSV-1 particles use the pre-existing cellular secretory pathway.

Production Technologies for Recombinant Antibodies: Insights into Eukaryotic, Prokaryotic, and Transgenic Expression Systems

Recombinant antibodies, a prominent class of recombinant proteins, are witnessing substantial growth in research and diagnostics. Recombinant antibodies are being produced employing diverse hosts ranging from highly complex eukaryotes, for instance, mammalian cell lines (and insects, fungi, yeast, etc.) to unicellular prokaryotic models like gram-positive and gram-negative bacteria. This review delves into these production methods, highlighting approaches like antibody phage display that employs bacteriophages for gene library creation. Recent studies emphasize monoclonal antibody generation through hybridoma technology, utilizing hybridoma cells from myeloma and B-lymphocytes. Transgenic plants and animals have emerged as sources for polyclonal and monoclonal antibodies, with transgenic animals preferred due to their human-like post-translational modifications and reduced immunogenicity risk. Chloroplast expression offers environmental safety by preventing transgene contamination in pollen. Diverse production technologies, such as stable cell pools and clonal cell lines, are available, followed by purification via techniques like affinity chromatography. The burgeoning applications of recombinant antibodies in medicine have led to their large-scale industrial production.

Golgi apparatus targeted therapy in cancer: Are we there yet?

Membrane trafficking within the Golgi apparatus plays a pivotal role in the intracellular transportation of lipids and proteins. Dysregulation of this process can give rise to various pathological manifestations, including cancer. Exploiting Golgi defects, cancer cells capitalise on aberrant membrane trafficking to facilitate signal transduction, proliferation, invasion, immune modulation, angiogenesis, and metastasis. Despite the identification of several molecular signalling pathways associated with Golgi abnormalities, there remains a lack of approved drugs specifically targeting cancer cells through the manipulation of the Golgi apparatus. In the initial section of this comprehensive review, the focus is directed towards delineating the abnormal Golgi genes and proteins implicated in carcinogenesis. Subsequently, a thorough examination is conducted on the impact of these variations on Golgi function, encompassing aspects such as vesicular trafficking, glycosylation, autophagy, oxidative mechanisms, and pH alterations. Lastly, the review provides a current update on promising Golgi apparatus-targeted inhibitors undergoing preclinical and/or clinical trials, offering insights into their potential as therapeutic interventions. Significantly more effort is required to advance these potential inhibitors to benefit patients in clinical settings.

Insect-transmitted plant virus balances its vertical transmission through regulating Rab1-mediated receptor localization

Rice stripe virus (RSV) establishes infection in the ovaries of its vector insect, Laodelphax striatellus. We demonstrate that RSV infection delays ovarian maturation by inhibiting membrane localization of the vitellogenin receptor (VgR), thereby reducing the vitellogenin (Vg) accumulation essential for egg development. We identify the host protein L. striatellus Rab1 protein (LsRab1), which directly interacts with RSV nucleocapsid protein (NP) within nurse cells. LsRab1 is required for VgR surface localization and ovarian Vg accumulation. RSV inhibits LsRab1 function through two mechanisms: NP binding LsRab1 prevents GTP binding, and NP binding LsRab1-GTP complexes stimulates GTP hydrolysis, forming an inactive LsRab1 form. Through this dual inhibition, RSV infection prevents LsRab1 from facilitating VgR trafficking to the cell membrane, leading to inefficient Vg uptake. The Vg-VgR pathway is present in most oviparous animals, and the mechanisms detailed here provide insights into the vertical transmission of other insect-transmitted viruses of medical and agricultural importance.

Enterovirus-A71 exploits RAB11 to recruit chaperones for virus morphogenesis

BACKGROUND

Enterovirus 71 (EV-A71) causes Hand, Foot and Mouth Disease (HFMD) in children and has been associated with neurological complications. The molecular mechanisms involved in EV-A71 pathogenesis have remained elusive.

METHODS

A siRNA screen in EV-A71 infected-motor neurons was performed targeting 112 genes involved in intracellular membrane trafficking, followed by validation of the top four hits using deconvoluted siRNA. Downstream approaches including viral entry by-pass, intracellular viral genome quantification by qPCR, Western blot analyses, and Luciferase reporter assays allowed determine the stage of the infection cycle the top candidate, RAB11A was involved in. Proximity ligation assay, co-immunoprecipitation and multiplex confocal imaging were employed to study interactions between viral components and RAB11A. Dominant negative and constitutively active RAB11A constructs were used to determine the importance of the protein's GTPase activity during EV-A71 infection. Mass spectrometry and protein interaction analyses were employed for the identification of RAB11A's host interacting partners during infection.

RESULTS

Small GTPase RAB11A was identified as a novel pro-viral host factor during EV-A71 infection. RAB11A and RAB11B isoforms were interchangeably exploited by strains from major EV-A71 genogroups and by Coxsackievirus A16, another major causative agent of HFMD. We showed that RAB11A was not involved in viral entry, IRES-mediated protein translation, viral genome replication, and virus exit. RAB11A co-localized with replication organelles where it interacted with structural and non-structural viral components. Over-expression of dominant negative (S25N; GDP-bound) and constitutively active (Q70L; GTP-bound) RAB11A mutants had no effect on EV-A71 infection outcome, ruling out RAB11A's involvement in intracellular trafficking of viral or host components. Instead, decreased ratio of intracellular mature viral particles to viral RNA copies and increased VP0:VP2 ratio in siRAB11-treated cells supported a role in provirion maturation hallmarked by VP0 cleavage into VP2 and VP4. Finally, chaperones, not trafficking and transporter proteins, were found to be RAB11A's top interacting partners during EV-A71 infection. Among which, CCT8 subunit from the chaperone complex TRiC/CCT was further validated and shown to interact with viral structural proteins specifically, representing yet another novel pro-viral host factor during EV-A71 infection.

CONCLUSIONS

This study describes a novel, unconventional role for RAB11A during viral infection where it participates in the complex process of virus morphogenesis by recruiting essential chaperone proteins.

Pseudorabies virus hijacks the Rab6 protein to promote viral assembly and egress

Pseudorabies virus (PRV) is recognized as the aetiological agent responsible for Aujeszky's disease, or pseudorabies, in swine populations. Rab6, a member of the small GTPase family, is implicated in various membrane trafficking processes, particularly exocytosis regulation. Its involvement in PRV infection, however, has not been documented previously. In our study, we observed a significant increase in the Rab6 mRNA and protein levels in both PK-15 porcine kidney epithelial cells and porcine alveolar macrophages, as well as in the lungs and spleens of mice infected with PRV. The overexpression of wild-type Rab6 and its GTP-bound mutant facilitated PRV proliferation, whereas the GDP-bound mutant form of Rab6 had no effect on viral propagation. These findings indicated that the GTPase activity of Rab6 was crucial for the successful spread of PRV. Further investigations revealed that the reduction in Rab6 levels through knockdown significantly hampered PRV proliferation and disrupted virus assembly and egress. At the molecular level, Rab6 was found to interact with the PRV glycoproteins gB and gE, both of which are essential for viral assembly and egress. Our results collectively suggest that PRV exploits Rab6 to expedite its assembly and egress and identify Rab6 as a promising novel target for therapeutic treatment for PRV infection.

Herpes Simplex Virus 1 (HSV-1) Uses the Rab6 Post-Golgi Secretory Pathway For Viral Egress

Herpes Simplex Virus 1 (HSV-1) is an alpha herpesvirus that infects a majority of the world population. The mechanisms and cellular host factors involved in the intracellular transport and exocytosis of HSV-1 particles are not fully understood. To elucidate these late steps in the replication cycle, we developed a live-cell fluorescence microscopy assay of HSV-1 virion intracellular trafficking and exocytosis. This method allows us to track individual virus particles, and identify the precise moment and location of particle exocytosis using a pH-sensitive reporter. We show that HSV-1 uses the host Rab6 post-Golgi secretory pathway during egress. The small GTPase, Rab6, binds to nascent secretory vesicles at the trans-Golgi network and regulates vesicle trafficking and exocytosis at the plasma membrane. HSV-1 particles colocalize with Rab6a in the region of the Golgi, cotraffic with Rab6a to the cell periphery, and undergo exocytosis from Rab6a vesicles. Consistent with previous reports, we find that HSV-1 particles accumulate at preferential egress sites in infected cells. The Rab6a secretory pathway mediates this preferential/polarized egress, since Rab6a vesicles accumulate near the plasma membrane similarly in uninfected cells. These data suggest that, following particle envelopment, HSV-1 egress follows a pre-existing cellular secretory pathway to exit infected cells rather than novel, virus-induced mechanisms.

Advances in Recapitulating Alzheimer's Disease Phenotypes Using Human Induced Pluripotent Stem Cell-Based In Vitro Models

Alzheimer's disease (AD) is an incurable neurodegenerative disorder and the leading cause of death among older individuals. Available treatment strategies only temporarily mitigate symptoms without modifying disease progression. Recent studies revealed the multifaceted neurobiology of AD and shifted the target of drug development. Established animal models of AD are mostly tailored to yield a subset of disease phenotypes, which do not recapitulate the complexity of sporadic late-onset AD, the most common form of the disease. The use of human induced pluripotent stem cells (HiPSCs) offers unique opportunities to fill these gaps. Emerging technology allows the development of disease models that recapitulate a brain-like microenvironment using patient-derived cells. These models retain the individual's unraveled genetic background, yielding clinically relevant disease phenotypes and enabling cost-effective, high-throughput studies for drug discovery. Here, we review the development of various HiPSC-based models to study AD mechanisms and their application in drug discovery.

Effect of Shade on Agro-Morphological Parameters and Weed Flora of Saffron (Crocus sativus L.) Cultivation in the Semiarid Zone of Eastern Morocco

Saffron (Crocus sativus) has been an important medicinal plant since ancient times. This study aimed to seek the optimal light intensity for saffron growth by quantifying the effects of different shade levels on yield, vegetative growth, and weed development in the eastern region of Morocco. The plants were grown for 24 months in full sun (control) and 30%, 50%, and 70% shade. Overall, the results showed that shade positively affected the yield and vegetative growth parameters of saffron plants, with the highest yield (0.61 g/m²) and number of leaves (105 leaves/tuft) recorded when the plants were exposed to light shade (30%). The color of the leaves under the 70% shade levels was dark green. The results from the underground part showed that shade is positively correlated with the weight and diameter of daughter corms where the 70% shade recorded the highest values of weight (65 g) and percentage of large diameter corms (39%). As for weed density, this parameter was significantly affected by shade. The lowest weed density was recorded for the 70% shade treatment. In conclusion, 30% shade is suggested as optimal light irradiation for saffron cultivation.

Cepharanthine Suppresses Herpes Simplex Virus Type 1 Replication Through the Downregulation of the PI3K/Akt and p38 MAPK Signaling Pathways

Cepharanthine (CEP) is a naturally occurring isoquinoline alkaloid extracted from Stephania cepharantha Hayata. Although its underlying molecular mechanism is not fully understood, this compound is reported as a promising antiviral drug. In the present study, we explore the anti-HSV-1 effects and the underlying molecular mechanisms of CEP in vitro. Our results show that CEP could significantly inhibit the formation of plaque and the expression of viral proteins and exhibit a general suppression of replication-associated genes. Whereas HSV-1 infection increases the expressions of phosphoinositide 3-kinase (PI3K), protein kinase B (Akt), and p38 mitogen-activated protein kinase (p38 MAPK) in host cells, CEP was effective indirectly inhibiting phosphorylation levels of the targets in PI3K/Akt and p38 MAPK signaling pathways. Moreover, CEP markedly decreased G₀/G₁ phase and increased G₂/M phase cells and decreased the expression of cyclin-dependent kinase1 (CDK1) and cyclinB1 in a dose-dependent manner. Additionally, CEP increased apoptosis in infected cells, reduced B cell lymphoma-2 (Bcl-2) protein levels, and increased the protein levels of Bcl-associated X protein (Bax), cleaved-caspase3, and nuclear IκB kinaseα (IκBα). Collectively, CEP could arrest the cell cycle in the G₂/M phase and induce apoptosis in infected cells by inhibiting the PI3K/Akt and p38 MAPK signaling pathways, hence further reducing HSV-1 infection and subsequent reproduction.

Fuyuan Xingnao Decoction Promotes Angiogenesis Through the Rab1/AT1R Pathway in Diabetes Mellitus Complicated With Cerebral Infarction

Fuyuan Xingnao decoction (FYXN), a traditional Chinese formula comprised of seven herbs, has been utilized to treat diabetes mellitus complicated with cerebral infarction (DMCI) for years. Yet, its protective and regulatory mechanism is poorly understood. The aim of the study is to investigate the effects of FYXN on DMCI in vitro and in vivo, as well as its mechanism in angiogenesis. For in vivo experiments, FYXN was administered to DMCI rats with streptozotocin (STZ) injection-induced diabetes. Then middle cerebral artery occlusion (MCAO) was conducted and the cerebral cortex sections of the rats were obtained. The ultrastructure of cerebral microvessels and new vessel density of ischemic penumbra were evaluated by the transmission electron microscopy (TEM) assay and immunohistochemistry, respectively. Protein and mRNA expression levels of Rab1/AT1R in cortex were assayed by Western blotting and real-time fluorescence quantitative real-time polymerase chain reaction (RT-qPCR). In vitro, FYXN serum was produced in rats on the fourth day 2 h after the last FYXN administration. Green fluorescence was observed after transfection with lentivirus packaged Rab1-WT or siRNA for 24 h. The activity of brain microvascular endothelial cells (BMECs) treated with sera from these rats was tested by MTT assay and Transwell assays, respectively. The expression of AT1R on the cell membrane and endoplasmic reticulum of BMECs was evaluated by immunofluorescence staining. Protein expression levels of signaling molecules in the Rab1/AT1R pathways were also detected. Results showed that in vivo, FYXN treatment significantly intensified CD31 staining in the cortical areas and enhanced the mRNA and protein levels of AT1R, Ang II, Rab1a, Rab1b and VEGF expression in ischemic cerebral cortex tissues. In vitro, the expression levels of AT1R, Ang II, Rab1a, Rab1b and VEGF in the cerebral infarction model group were significantly higher than those in the control group, with further increases after administration of FYXN drug serum. FYXN promoted the proliferation and migration of BMECs by activating the Rab1/AT1R signaling pathway. In conclusion, FYXN exerts a protective effect against DMCI by promoting angiogenesis via the Rab1/AT1R pathway, which provides strong evidence for the therapeutic effect of FYXN on DMCI.

Host RAB11FIP5 protein inhibits the release of Kaposi's sarcoma-associated herpesvirus particles by promoting lysosomal degradation of ORF45

Open reading frame (ORF) 45 is an outer tegument protein of Kaposi's sarcoma-associated herpesvirus (KSHV). Genetic analysis of an ORF45-null mutant revealed that ORF45 plays a key role in the events leading to the release of KSHV particles. ORF45 associates with lipid rafts (LRs), which is responsible for the colocalization of viral particles with the trans-Golgi network and facilitates their release. In this study, we identified a host protein, RAB11 family interacting protein 5 (RAB11FIP5), that interacts with ORF45 in vitro and in vivo. RAB11FIP5 encodes a RAB11 effector protein that regulates endosomal trafficking. Overexpression of RAB11FIP5 in KSHV-infected cells decreased the expression level of ORF45 and inhibited the release of KSHV particles, as reflected by the significant reduction in the number of extracellular virions. In contrast, silencing endogenous RAB11FIP5 increased ORF45 expression and promoted the release of KSHV particles. We further showed that RAB11FIP5 mediates lysosomal degradation of ORF45, which impairs its ability to target LRs in the Golgi apparatus and inhibits ORF45-mediated colocalization of viral particles with the trans-Golgi network. Collectively, our results suggest that RAB11FIP5 enhances lysosome-dependent degradation of ORF45, which inhibits the release of KSHV particles, and have potential implications for virology and antiviral design.

Tour de Herpes: Cycling Through the Life and Biology of HSV-1

Herpes simplex virus type 1 (HSV-1) is a prevalent and important human pathogen that has been studied in a wide variety of contexts. This book provides protocols currently in use in leading laboratories in many fields of HSV-1 research. This introductory chapter gives a brief overview of HSV-1 biology and life cycle, covering basic aspects of virus structure, the prevalence of and diseases caused by the virus, replication in cultured cells, viral latency, antiviral defenses, and the mechanisms that the virus uses to counteract these defenses.

Proteomics Analysis Identifies IRSp53 and Fascin as Critical for PRV Egress and Direct Cell-Cell Transmission

Pseudorabies virus (PRV) has been widely used as a live trans-synaptic tracer for mapping neuronal circuits. Systematically identifying mature PRV virion proteomes and defining co-purified host proteins are necessary to fully understand the detailed mechanism underlying PRV transmission processes. Here, a PRV virion purification strategy based on sorting with flow cytometry is developed and the mature extracellular and intracellular PRV virion proteomes using LC coupled with MS/MS are characterized. In addition to viral proteins, a large number of host proteins are also identified, including proteins related to actin cytoskeletal dynamics and membrane protrusion. How many of these host proteins are true virion components are unknown and the majority of these may not be. Through functional analysis, it is found that IRSp53 and fascin are critical for the egress process and play a role in direct cell-cell transmission. Moreover, it is shown that CDC42 and Rac1 are also involved in the production of mature extracellular virions. The results suggest that the formation of the filopodia-like cytoskeleton and the rearrangement of the membrane, which are both associated with IRSp53 and fascin, may be important for the transmission of viruses used in neuronal tracing.

Herpes Simplex Virus, Alzheimer's Disease and a Possible Role for Rab GTPases

Herpes simplex virus (HSV) is a common pathogen, infecting 85% of adults in the United States. After reaching the nucleus of the long-lived neuron, HSV may enter latency to persist throughout the life span. Re-activation of latent herpesviruses is associated with progressive cognitive impairment and Alzheimer's disease (AD). As an enveloped DNA virus, HSV exploits cellular membrane systems for its life cycle, and thereby comes in contact with the Rab family of GTPases, master regulators of intracellular membrane dynamics. Knock-down and overexpression of specific Rabs reduce HSV production. Disheveled membrane compartments could lead to AD because membrane sorting and trafficking are crucial for synaptic vesicle formation, neuronal survival signaling and Abeta production. Amyloid precursor protein (APP), a transmembrane glycoprotein, is the parent of Abeta, the major component of senile plaques in AD. Up-regulation of APP expression due to HSV is significant since excess APP interferes with Rab5 endocytic trafficking in neurons. Here, we show that purified PC12-cell endosomes transport both anterograde and retrograde when injected into the squid giant axon at rates similar to isolated HSV. Intracellular HSV co-fractionates with these endosomes, contains APP, Rab5 and TrkA, and displays a second membrane. HSV infected PC12 cells up-regulate APP expression. Whether interference with Rabs has a specific effect on HSV or indirectly affects membrane compartment dynamics co-opted by virus needs further study. Ultimately Rabs, their effectors or their membrane-binding partners may serve as handles to reduce the impact of viral re-activation on cognitive function, or even as more general-purpose anti-microbial therapies.