Small Hydrophobic Protein Research Articles

Epithelial membrane protein 1 in human cancer: a potential diagnostic biomarker and therapeutic target.

Epithelial membrane protein 1 (EMP1) is a member of the small hydrophobic membrane protein subfamily. EMP1 is aberrantly expressed in various tumor tissues and governs multiple cellular behaviors (e.g., proliferation, differentiation, and migration). The resultant regulation of the cancer pathway is responsible for the metastasis of cancer cells and determines the risk of malignant tumor progression. This review provides an updated overview of EMP1 as either an oncogene or a tumor suppressor contingent on the cancer type and summarizes its upstream regulators and downstream target genes. This systematic review summarizes our current understanding of the role of EMP1 in malignant tumor development, including critical functional mechanisms and implications for its potential use as the biomarker and therapeutic target.

Human metapneumovirus SH protein promotes JAK1 degradation to impair host IL-6 signaling.

Human metapneumovirus (HMPV) is a leading cause of respiratory infections in children, older adults, and those with underlying conditions (K. M. Edwards et al., N Engl J Med 368:633-643, 2013, https://doi.org/10.1056/NEJMoa1204630; A. R. Falsey et al., J Infect Dis 187:785-790, 2003, https://doi.org/10.1086/367901; J. S. Kahn, Clin Microbiol Rev 19:546-557, 2006, https://doi.org/10.1128/CMR.00014-06; N. Shafagati and J. Williams, F1000Res 7:135, 2018, https://doi.org/10.12688/f1000research.12625.1). HMPV must evade immune defenses to replicate successfully; however, the viral proteins used to accomplish this are poorly characterized. The HMPV small hydrophobic (SH) protein has been reported to inhibit signaling through type I and type II interferon (IFN) receptors in vitro in part by preventing STAT1 phosphorylation (A. K. Hastings et al., Virology (Auckl) 494:248-256, 2016, https://doi.org/10.1016/j.virol.2016.04.022). HMPV infection also inhibits IL-6 signaling. However, the mechanisms by which SH inhibits signaling and its involvement in IL-6 signaling inhibition are unknown. Here, we used transfection of SH expression plasmids and SH-deleted virus (ΔSH) to show that SH is the viral factor responsible for the inhibition of IL-6 signaling during HMPV infection. Transfection of SH-expression vectors or infection with wild-type, but not ΔSH virus, blocked IL-6-mediated STAT3 activation. Furthermore, JAK1 protein (but not RNA) was significantly reduced in cells infected with wild-type, but not ΔSH virus. The SH-mediated reduction of JAK1 was partially restored by the addition of proteasome inhibitors, suggesting proteasomal degradation of JAK1. Confocal microscopy indicated that infection relocalized JAK1 to viral replication factories. Co-immunoprecipitation showed that SH interacts with JAK1 and ubiquitin, further linking SH to proteasomal degradation machinery. These data indicate that SH inhibits IL-6 and IFN signaling in infected cells in part by promoting proteasomal degradation of JAK1 and that SH is necessary for IL-6 and IFN signaling inhibition in infection. These findings enhance our understanding of the immune evasion mechanisms of an important respiratory pathogen.IMPORTANCEHuman metapneumovirus (HMPV) is a common cause of severe respiratory illness, especially in children and older adults, in whom it is a leading cause of hospitalization. Prior research suggests that severe HMPV infection is driven by a strong immune response to the virus, especially by inflammatory immune signals like interferons (IFN). HMPV produces a small hydrophobic (SH) protein that is known to block IFN signaling, but the mechanism by which it functions and its ability to inhibit other important immune signals remains unexplored. This paper demonstrates that SH can inhibit another related immune signal, IL-6, and that SH depletes JAKs, which are critical proteins involved in both IL-6 and IFN signaling. A robust understanding of how HMPV and related viruses interfere with immune signals important for disease could pave the way for future treatments aimed at mitigating severe infections.

Small hydrophobic (SH) proteins of Pneumoviridae and Paramyxoviridae: small but mighty.

Small hydrophobic (SH) proteins are a class of viral accessory proteins expressed by many members of the negative-stranded RNA viral families Paramyxoviridae and Pneumoviridae. Identified SH proteins are type I or II transmembrane (TM) proteins with a single-pass TM domain. Little is known about the functions of SH proteins; however, several possess viroporin activity, enhancing membrane permeability of infected cells or those expressing SH protein. Moreover, several SH proteins inhibit apoptosis and immune signaling pathways within infected cells, including TNF and interferon signaling, or activate inflammasomes. SH proteins are generally nonessential for viral replication in vitro, but loss of SH is often associated with reduced replication in vivo, suggesting a role in enhancing viral replication or evading host immunity. Analogous proteins are expressed by a variety of pathogens of public health importance; thus, understanding the functional importance and mechanisms of SH proteins provides insight into the pathogenesis and replication of negative-sense RNA viruses.

Evolution and ecology of Jeilongvirus among wild rodents and shrews in Singapore

BackgroundJeilongvirus was proposed as a new genus within the Paramyxoviridae in 2018. The advancement in metagenomic approaches has encouraged multiple reports of Jeilongvirus detection following the initial species discovery, enriching species diversity and host range within the genus. However, Jeilongvirus remains understudied in Singapore, where interfaces between humans and small mammals are plentiful.MethodsHere, we utilized metagenomic sequencing for the exploration of viral diversity in small mammal tissues. Upon discovery of Jeilongvirus, molecular screening and full genome sequencing was conducted, with the data used to conduct statistical modelling and phylogenetic analysis.ResultsWe report the presence of Jeilongvirus in four species of Singapore wild small mammals, detected in their spleen and kidney. We show that full genomes of three Singapore Jeilongvirus encode for eight ORFs including the small hydrophobic and transmembrane proteins. All generated genomes cluster phylogenetically within the small mammal subclade, but share low genetic similarity with representative Jeilongvirus species. Statistical modelling showed no spatial or temporal patterns and differences among species, life history traits and habitat types.ConclusionsThis study serves as a basis for understanding dynamics between Jeilongvirus and small mammal hosts in Singapore by displaying the virus generalist nature. In addition, the initial detection can help to invoke improved routine surveillance and detection of circulating pathogens in synanthropic hosts.

Cationic-nanogel nasal vaccine containing the ectodomain of RSV-small hydrophobic protein induces protective immunity in rodents.

Respiratory syncytial virus (RSV) is a leading cause of upper and lower respiratory tract infection, especially in children and the elderly. Various vaccines containing the major transmembrane surface proteins of RSV (proteins F and G) have been tested; however, they have either afforded inadequate protection or are associated with the risk of vaccine-enhanced disease (VED). Recently, F protein-based maternal immunization and vaccines for elderly patients have shown promising results in phase III clinical trials, however, these vaccines have been administered by injection. Here, we examined the potential of using the ectodomain of small hydrophobic protein (SHe), also an RSV transmembrane surface protein, as a nasal vaccine antigen. A vaccine was formulated using our previously developed cationic cholesteryl-group-bearing pullulan nanogel as the delivery system, and SHe was linked in triplicate to pneumococcal surface protein A as a carrier protein. Nasal immunization of mice and cotton rats induced both SHe-specific serum IgG and mucosal IgA antibodies, preventing viral invasion in both the upper and lower respiratory tracts without inducing VED. Moreover, nasal immunization induced greater protective immunity against RSV in the upper respiratory tract than did systemic immunization, suggesting a critical role for mucosal RSV-specific IgA responses in viral elimination at the airway epithelium. Thus, our nasal vaccine induced effective protection against RSV infection in the airway mucosa and is therefore a promising vaccine candidate for further development.

Mumps resurgence in a highly vaccinated population: Insights gained from surveillance in Canada, 2002–2020

Although mumps vaccination has been routine in Canada for decades, mumps cases and outbreaks continue to occur periodically. Mumps surveillance, including monitoring of the mumps virus genotype associated with disease activity, is important to document baseline activity and to advance further research into vaccine effectiveness. Here we describe a detailed analysis of mumps cases that have been detected in Canada from 2002 to 2020, with a focus on the mumps molecular epidemiology. In total, 7395 cases of mumps were reported to the surveillance system, with outbreaks occurring in the years 2007, 2010 and 2016 to 2018. Adolescents and young adults aged 15 to 29 years had the highest risk of being a case (rate ratios ranging from 1.50 to 2.29), compared to adults aged 30 to 39. Genotypes of mumps viruses were determined in 3225 specimens. Genotype G was predominantly detected (96% of genotyped specimens) and was first reported in 2005. Other genotypes were more likely to be detected in cases that also reported travel (or were linked to imported cases) than the cases with genotype G detected (p < 0.0001). The genotype G viruses had little sequence diversity in the 316 nucleotide window used for genotyping (the small hydrophobic protein gene) and mainly belonged to a single phylogenetic lineage that included the MuVi/Sheffield.GBR/1.05 reference sequence. The analysis of over ten years of data has demonstrated that mumps genotype G, specifically belonging to a single lineage, the Sheffield lineage, is the endemically circulating virus in Canada. This lineage is seen also in other countries using the genotype A vaccine. Mumps remains endemic despite high MMR vaccination coverage which has been sufficient to eliminate circulation of measles and rubella in Canada, raising the hypothesis of the evolution towards a vaccine escape mumps virus.

A vibrational spectroscopic approach to elucidate the molecular mechanism behind the channel activity of viroporins.

The prevalence of diseases caused by pathogenic viruses and the scarcity of treatment and vaccination options call for extensive research of the molecular mechanisms underlying the function of these viruses. Small hydrophobic viral proteins with ion channel activity, so-called viroporins, are involved in the virus particle entry into and release from the host cell. One of these viroporins, the Influenza A M2 channel, has shown to be the target for anti-viral drugs motivating spectroscopic investigations of other viroporins to understand their relevance as potential anti-viral treatment targets. We used the Influenza A M2 viroporin as a model system to establish a vibrational spectroscopic approach to examine the gating mechanism and proton conductance of this pH-activated proton channel. In this work, we immobilized reconstituted M2 on a self-assembled monolayer bound to a nanostructured gold film that can be used for surface-enhanced infrared absorption (SEIRA) spectroscopy. Employing pH-induced SEIRA difference spectroscopy we monitor protonation events and changes in the α-helix amide I absorption due to a pH-dependent channel opening that leads to proton conductivity. Furthermore, the surface selection rule of SEIRA enabled us to observe the reorientation of the α-helical structures associated with the channel opening in-situ. Combining the spectroscopic data with computational vibrational spectroscopic calculations we model the large-scale reorganization of M2's α-helices, and by this quantify the opening angle of the channel transitioning from closed to the activated state. We aim to utilize this approach to enable a combined structural and functional analysis of viroporins of current relevance.

Diagnosis of avian metapneumovirus infection using multiplex PCR

Avian metapneumovirus infection causes significant economic damage to poultry farming, which consists of losses from a decrease in safety and productivity, as well as the cost of health and preventive measures.The causative agent of the disease is avian metapneumovirus family Paramyxoviridae subfamily Pneumovirinae genus Metapneumovirus. The viral genome consists of 8 genes encoding 9 proteins: N-nucleoprotein, P-phosphoprotein, Mmatrix protein, F-fusion protein, M2 (M2-1,M2-2) - elongation/transcription factor, SH-(small) hydrophobic protein, Gglycoprotein, L-(large) polymerase. The virus lacks non-structural NS1 and NS2 proteins that counteract interferon.Based on the nucleotide seguence of the variable glycoprotein G gene, avian metapneumovirus was classified into four 4 subtypes of MPV are officially known, although recent publications have reported of two new pneumoviruses, GuMPV and AMPV PAR-05 isolated from the seagull and parrot in North America.The diversity of pathogen subtypes and differences in virulence properties of metapneumovirus create difficulties both in the prevention of this disease and in its diagnosis.The complexity of isolating the metapneumovirus from the test material is due to the short period of persistence of the virus in the organs of birds. It is possible to isolate the RNA of the causative agent of MPVI by the molecular biological method within 17-19 days after infection. The aim of our work was development and testing of primers and probes for the simultaneous detection and differentiation of avian metapneumovirus subtypes A and B by PCR with real-time fluorescence detection, with high specificity.Using vaccine strains 8544 and VC-03, the conditions for PCR were selected according to the composition of the PCR mixture and the annealing temperature of primers and probes. During PCR, we recorded the fluorescence signal through the FAM channel for cDNA obtained from the 8544 vaccine strain, and through the HEX channel for the VC-03 vaccine strain. The specificity of the developed primers and probes was also tested in studies with heterogeneous viruses such as Newcastle disease, classical and variant strains of chicken infectious bronchitis virus, and with bird DNA.The studies conducted to determine the specificity of the primers selected by us for multiplex PCR diagnostics make it possible to simultaneously specifically detect subtypes A and B of the causative agent of MPVI in birds in real time using different fluorescence channels, while other non-target respiratory pathogens were not observed.

Analysis of Subcellular Localization and Pathogenicity of Plum Bark Necrosis Stem-Pitting Associated Virus Protein P6

Infection of <i>plum bark necrosis stem pitting associated virus</i> (PBNSPaV) has been reported in many <i>Prunus</i> species in several countries, causing significant economic losses. The very small proteins encoded by plant viruses are often overlooked due to their short sequences and uncertain significance. However, numerous studies have indicated that they might play important roles in the pathogenesis of virus infection. The role of small hydrophobic protein P6, encoded by the open reading frame 2 of PBNSPaV, has not been well explored. In this study, we amplified the P6 fragment from a PBNSPaV isolate by RT-PCR using specific primers and found that it is 174 bp long and encodes a protein of approximately 6.3 kD with a transmembrane domain. Subcellular localization analysis of P6 proteins in tobacco leaves showed that P6 localizes to the cytomembrane and nuclear membrane. To further clarify the pathogenicity of P6 proteins, we constructed a PVX-P6 expression vector by inserting the p6 fragment into a <i>potato virus X</i> (PVX)-based vector and transformed it into <i>Agrobacterium tumefaciens GV3101</i>. Infiltration of <i>Nicotiana benthamiana</i> (<i>N. benthamiana)</i> with the PVX vector-transformed <i>A. tumefaciens</i> led to slight mosaic symptoms at 14 days of post-inoculation. Meanwhile, infiltration with the PVX-P6 vector-transformed <i>A. tumefaciens</i> resulted in no significant symptoms. These results demonstrated that heterologous expression of P6 in <i>N. benthamiana</i> could not enhance the pathogenicity of PVX. Our study indicates that P6 may not be a potential pathogenic factor associate with the causing of symptoms, and the mode of action of PBNSPaV-P6 protein remains to be further studied.

Interaction between Movement Proteins of Hibiscus green spot virus.

Movement proteins (MPs) of plant viruses enable the translocation of viral genomes from infected to healthy cells through plasmodesmata (PD). The MPs functions involve the increase of the PD permeability and routing of viral genome both to the PD entrance and through the modified PD. Hibiscus green spot virus encodes two MPs, termed BMB1 and BMB2, which act in concert to accomplish virus cell-to-cell transport. BMB1, representing an NTPase/helicase domain-containing RNA-binding protein, localizes to the cytoplasm and the nucleoplasm. BMB2 is a small hydrophobic protein that interacts with the endoplasmic reticulum (ER) membranes and induces local constrictions of the ER tubules. In plant cells, BMB2 localizes to PD-associated membrane bodies (PAMBs) consisting of modified ER tubules and directs BMB1 to PAMBs. Here, we demonstrate that BMB1 and BMB2 interact in vitro and in vivo, and that their specific interaction is essential for BMB2-directed targeting of BMB1 to PAMBs. Using mutagenesis, we show that the interaction involves the C-terminal BMB1 region and the N-terminal region of BMB2.

Dynamic study of small toxic hydrophobic proteins PepA1 and PepG1 of Staphylococcus aureus

Toxin-antitoxin (TA) systems are small genetic elements which encode toxin proteins that interfere with vital cellular functions. PepA1 and PepG1 toxin proteins, known also as SprA1 and SprG1, are type I TA. In Staphylococcus aureus (S. aureus), their expression without the antitoxin counterparts (SprA1AS and SprF1), is lethal to the pathogen. Molecular Dynamics (MD) simulation was performed for PepA1 and PepG1 to understand their dynamic state, conformational changes, and their toxicity. The protein structures were constructed and used for MD simulation and the conformational changes, stability, flexibility, fluctuations, hydrophobicity, and role of their dynamic state on function prediction were studied extensively by GROMACS MD simulation analysis tools. In silico study indicated that the PepA1 and PepG1 proteins change their structural conformation from an open to closed state where PepA1 conformational changes were faster (10 ns) than PepG1 (20 ns) while PepG1 exerted more stability and flexibility than PepA1. According to SASA values, PepG1 is more hydrophobic than the PepA1 and forms fewer hydrogen bonds than PepA1. The in vivo study with PepA1 and PepG1 proteins provided evidence that both the conformation changes between the open and closed states and the amino acid sequence are crucial for peptide toxicity.

Peracetic Acid-Based Oxidation for Ultrafiltration during Natural Water Treatment: Significant Performance Enhancement and Novel Prediction Based on PARAFAC-EEMs Coupling Hydrophilicity Characteristic

In this study, peracetic acid (PAA) preoxidation based on Fe(II) and UV activation was proposed to mitigate the membrane fouling caused by natural organic matters (NOM) in surface water. Owing to the dual effect of oxidation and coagulation, Fe(II)/UV/PAA preoxidation was an efficient alternative strategy prior to the ultrafiltration (UF) process, with a significantly improved membrane flux by 2.35 times and a remarkably lessened reversible fouling and irreversible fouling resistance by 95.6% and 95.7%, respectively. The degradation effect of naproxen (NAP) exhibited that the oxidation capacities followed the sequence of Fe(II)/UV/PAA > UV/PAA > Fe(II)/PAA > Fe(II)/UV. Among them, the UV/PAA system with stronger oxidative capacity exerted superior removal of organics and irreversible fouling than the Fe(II)/PAA system. For the first time, the PARAFAC-EEMs method was employed to monitor the degradation effect of oxidation on hydrophilic/hydrophobic (HPI/HPO) parts in NOM components and their influence on membrane fouling. It was found that R–C• produced by the UV/PAA process preferentially degraded C1HPI, C2HPI, and C3N-HPO components, and the recalcitrant foulants that caused irreversible fouling in the Fe(II)/UV/PAA system were small hydrophobic proteins. Moreover, the novel prediction of membrane fouling revealed that C1HPI had a higher correlation with irreversible membrane fouling than C1N-HPO. There was a certain correlation between the irreversible fouling resistance and tyrosine-like proteins and a poor correlation with humics. Hence, the PARAFAC-EEMs method has a great potential for rapid detection and prediction of membrane fouling caused by the HPI/HPO parts of different fluorescent NOM components.

Role of a bacterial glycolipid in Sec-independent membrane protein insertion

Non-proteinaceous components in membranes regulate membrane protein insertion cooperatively with proteinaceous translocons. An endogenous glycolipid in the Escherichia coli membrane called membrane protein integrase (MPIase) is one such component. Here, we focused on the Sec translocon-independent pathway and examined the mechanisms of MPIase-facilitated protein insertion using physicochemical techniques. We determined the membrane insertion efficiency of a small hydrophobic protein using solid-state nuclear magnetic resonance, which showed good agreement with that determined by the insertion assay using an in vitro translation system. The observed insertion efficiency was strongly correlated with membrane physicochemical properties measured using fluorescence techniques. Diacylglycerol, a trace component of E. coli membrane, reduced the acyl chain mobility in the core region and inhibited the insertion, whereas MPIase restored them. We observed the electrostatic intermolecular interactions between MPIase and the side chain of basic amino acids in the protein, suggesting that the negatively charged pyrophosphate of MPIase attracts the positively charged residues of a protein near the membrane surface, which triggers the insertion. Thus, this study demonstrated the ingenious approach of MPIase to support membrane insertion of proteins by using its unique molecular structure in various ways.

Branched PCL-Based Thermogelling Copolymers: Controlling Polymer Architecture to Tune Drug Release Profiles

Temperature-responsive hydrogels, or thermogels, are a unique class of biomaterials that show facile and spontaneous transition from solution to gel when warmed. Their high biocompatibility, and ease of formulation with both small molecule drugs and biologics have made these materials prime candidates as injectable gel depots for sustained local drug delivery. At present, controlling the kinetics and profile of drug release from thermogels is achieved mainly by varying the ratio of hydrophobic: hydrophilic composition and the polymer molecular weight. Herein, we introduce polymer branching as a hitherto-overlooked polymer design parameter that exhibits profound influences on the rate and profile of drug release. Through a family of amphiphilic thermogelling polymers with systematic variations in degree of branching, we demonstrate that more highly-branched polymers are able to pack less efficiently with each other during thermogel formation, with implications on their physical properties and stability towards gel erosion. This in turn resulted in faster rates of release for both encapsulated small molecule hydrophobic drug and protein. Our results demonstrate the possibility of exploiting polymer branching as a hitherto-overlooked design parameter for tailoring the kinetics and profile of drug release in injectable thermogel depots.

Small RNA and Transcriptome Sequencing of a Symptomatic Peony Plant Reveals Mixed Infections with Novel Viruses.

To identify the viruses in tree peony plants associated with the symptoms of yellowing, leaf rolling, stunted growth, and decline, high-throughput sequencing of small RNA and mRNA was conducted from a single symptomatic plant. Bioinformatic analyses and reconstruction of viral genomes indicated mixed viral infections involving cycas necrotic stunt virus, apple stem grooving virus, lychnis mottle virus, grapevine line pattern virus, and three new viruses designated as peony yellowing-associated citrivirus (PYaCV, Citrivirus in Betaflexiviridae), peony betaflexivirus 1 (PeV1, unclassified in Betaflexiviridae), and peony leafroll-associated virus (PLRaV, Ampelovirus in Closteroviridae). PYaCV was 8,666 nucleotides (nt) in length, comprising three open reading frames (ORFs), and shared 63.8 to 75.9% nt sequence identity with citrus leaf blotch virus (CLBV) isolates. However, the ORF encoding the replication-associated protein (REP) shared 57 and 52% sequence identities at the nt and amino acid (aa) level, respectively, with other reported CLBV isolates, which were below the criterion for species classification within the family Betaflexiviridae. Recombination analysis identified putative recombination sites in PYaCV, which originated from CLBV. PeV1, only identified from the transcriptome data, was 8,124 nt in length, with five ORFs encoding the REP (ORF1), triple gene block (ORF2 to 4) and coat protein (CP, ORF5). Phylogenetic analysis and sequence comparison showed that PeV1 clustered with an unassigned member, the garlic yellow mosaic-associated virus within the Betaflexiviridae family, into a separate clade. Partial genome sequence analysis of PLRaV (12,545 nt) showed it contained seven ORFs encoding the partial polyprotein 1a, the RNA-dependent RNA polymerase (RdRp), two small hydrophobic proteins p11 and p6, HSP70h, p55, and a CP duplicate, which shared low aa sequence identity with Closteroviridae family members. Phylogenetic analysis based on the aa sequences of RdRp or HSP70h indicated that PLRaV clustered with grapevine leafroll-associated virus 1 (GLRaV-1) and GLRaV-13 in the Ampelovirus genus. Field investigation confirmed the wide distribution of these viruses, causing mixed infections of peony plants in Beijing.

Role of metapneumoviral glycoproteins in the evasion of the host cell innate immune response.

Human metapneumovirus (HMPV), an unsegmented negative-strand RNA virus, is the second most detected respiratory pathogen and one of the leading causes of respiratory illness in infants and immunodeficient individuals. HMPV infection of permissive cells in culture triggers a transient IFN response, which is efficiently suppressed later in infection. We report that two structural glycoproteins of the virus - namely G (Glycoprotein) and SH (Small Hydrophobic) - suppress the type I interferon (IFN) response in cell culture. This is manifested by inhibition of diverse steps of IFN induction and response, such as phosphorylation and nuclear translocation of IFN regulatory factor-3 and -7 (IRF3, IRF7), major transcription factors of the IFN gene. Furthermore, HMPV suppresses the cellular response to IFN by inhibiting the phosphorylation of STAT1 (Signal Transducer and Activator of Transcription 1), required for the induction of IFN-stimulated genes that act as antivirals. Site-directed mutagenesis revealed an important role of critical cysteine (Cys) residues in the Cys-rich carboxy terminal region of the SH protein in IFN suppression, whereas for G, the ectodomain plays a role. These results shed light on the mechanism of IFN suppression by HMPV, and may also offer avenues for new antiviral approaches in the future.

Unravelling the Immunomodulatory Effects of Viral Ion Channels, towards the Treatment of Disease.

The current COVID-19 pandemic has highlighted the need for the research community to develop a better understanding of viruses, in particular their modes of infection and replicative lifecycles, to aid in the development of novel vaccines and much needed anti-viral therapeutics. Several viruses express proteins capable of forming pores in host cellular membranes, termed “Viroporins”. They are a family of small hydrophobic proteins, with at least one amphipathic domain, which characteristically form oligomeric structures with central hydrophilic domains. Consequently, they can facilitate the transport of ions through the hydrophilic core. Viroporins localise to host membranes such as the endoplasmic reticulum and regulate ion homeostasis creating a favourable environment for viral infection. Viroporins also contribute to viral immune evasion via several mechanisms. Given that viroporins are often essential for virion assembly and egress, and as their structural features tend to be evolutionarily conserved, they are attractive targets for anti-viral therapeutics. This review discusses the current knowledge of several viroporins, namely Influenza A virus (IAV) M2, Human Immunodeficiency Virus (HIV)-1 Viral protein U (Vpu), Hepatitis C Virus (HCV) p7, Human Papillomavirus (HPV)-16 E5, Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) Open Reading Frame (ORF)3a and Polyomavirus agnoprotein. We highlight the intricate but broad immunomodulatory effects of these viroporins and discuss the current antiviral therapies that target them; continually highlighting the need for future investigations to focus on novel therapeutics in the treatment of existing and future emergent viruses.

Activation of the PDGF β Receptor by a Persistent Artificial Signal Peptide

Most eukaryotic transmembrane and secreted proteins contain N-terminal signal peptides that mediate insertion of the nascent translation products into the membrane of the endoplasmic reticulum. After membrane insertion, signal peptides typically are cleaved from the mature protein and degraded. Here, we tested whether a small hydrophobic protein selected for growth promoting activity in mammalian cells retained transforming activity while also acting as a signal peptide. We replaced the signal peptide of the PDGF β receptor (PDGFβR) with a previously described 29-residue artificial transmembrane protein named 9C3 that can activate the PDGFβR in trans. We showed that a modified version of 9C3 at the N-terminus of the PDGFβR can function as a signal peptide, as assessed by its ability to support high level expression, glycosylation, and cell surface localization of the PDGFβR. The 9C3 signal peptide retains its ability to interact with the transmembrane domain of the PDGFβR and cause receptor activation and cell proliferation. Cleavage of the 9C3 signal peptide from the mature receptor is not required for these activities. However, signal peptide cleavage does occur in some molecules, and the cleaved signal peptide can persist in cells and activate a co-expressed PDGFβR in trans. Our finding that a hydrophobic sequence can display signal peptide and transforming activity suggest that some naturally occurring signal peptides may also display additional biological activities by interacting with the transmembrane domains of target proteins.

A viroporin-like 2B protein of duck hepatitis A virus 1 that induces incomplete autophagy in DEF cells

Duck hepatitis A virus 1 (DHAV-1) can cause high morbidity and fatal acute infectious hepatitis in ducklings, which seriously endangers animal husbandry. Viroporin is a small molecular weight hydrophobic transmembrane protein encoded by the virus, that has been suggested to induce autophagy in host cells by increasing the membrane permeability through disturbing the ion balance. In this study, we aimed to investigate whether the DHAV-1 2B protein can induce autophagy in DEF cells with a viroporin-like function. Bioinformatics analysis has indicated that the 2B protein is characterized by a viroporin domain, which is consistent with the type IA viroporin transmembrane protein. We experimentally confirmed that the 2B protein disturbed the Ca2+ balance of infected cells by elevating the intracellular Ca2+ concentration. Eukaryotic expression of the 2B protein upregulates the expression of microtubule-associated protein 1 light chain 3 II (LC3-II) and the number of autophagosomes in the cell. Interestingly, the Western Blot (WB) results showed that 2B protein expression induced less protein degradation of the autophagic substrate sequestosome 1 (SQSTM1/p62) than the positive control, while microscopy observations showed that the autophagosomes did not colocalize with the lysosomes. In summary, 2B protein expression induced autophagy in host cells, but the autophagic flow was incomplete. The results of this experiment are expected to provide reference scientific data for elucidating the infective and pathogenic mechanism of DHAV-1.

Designing of Potential Polyvalent Vaccine Model for Respiratory Syncytial Virus by System Level Immunoinformatics Approaches.

Background Respiratory syncytial virus (RSV) infection is a public health epidemic, leading to around 3 million hospitalization and about 66,000 deaths each year. It is a life-threatening condition exclusive to children with no effective treatment. Methods In this study, we used system-level and vaccinomics approaches to design a polyvalent vaccine for RSV, which could stimulate the immune components of the host to manage this infection. Our framework involves data accession, antigenicity and subcellular localization analysis, T cell epitope prediction, proteasomal and conservancy evaluation, host-pathogen-protein interactions, pathway studies, and in silico binding affinity analysis. Results We found glycoprotein (G), fusion protein (F), and small hydrophobic protein (SH) of RSV as potential vaccine candidates. Of these proteins (G, F, and SH), we found 9 epitopes for multiple alleles of MHC classes I and II bear significant binding affinity. These potential epitopes were linked to form a polyvalent construct using AAY, GPGPG linkers, and cholera toxin B adjuvant at N-terminal with a 23.9 kDa molecular weight of 224 amino acid residues. The final construct was a stable, immunogenic, and nonallergenic protein containing cleavage sites, TAP transport efficiency, posttranslation shifts, and CTL epitopes. The molecular docking indicated the optimum binding affinity of RSV polyvalent construct with MHC molecules (-12.49 and -10.48 kcal/mol for MHC classes I and II, respectively). This interaction showed that a polyvalent construct could manage and control this disease. Conclusion Our vaccinomics and system-level investigation could be appropriate to trigger the host immune system to prevent RSV infection.