A putative receptor for Venezuelan equine encephalitis virus from mosquito cells

Channeling the Natural Properties of Sindbis Alphavirus for Targeted Tumor Therapy

Sindbis alphavirus vectors offer a promising platform for cancer therapy, serving as valuable models for alphavirus-based treatment. This review emphasizes key studies that support the targeted delivery of Sindbis vectors to tumor cells, highlighting their effectiveness in expressing tumor-associated antigens and immunomodulating proteins. Among the various alphavirus vectors developed for cancer therapy, Sindbis-vector-based imaging studies have been particularly extensive. Imaging modalities that enable the in vivo localization of Sindbis vectors within lymph nodes and tumors are discussed. The correlation between laminin receptor expression, tumorigenesis, and Sindbis virus infection is examined. Additionally, we present alternative entry receptors for Sindbis and related alphaviruses, such as Semliki Forest virus and Venezuelan equine encephalitis virus. The review also discusses cancer treatments that are based on the alphavirus vector expression of anti-tumor agents, including tumor-associated antigens, cytokines, checkpoint inhibitors, and costimulatory immune molecules.

Attachment, Entry, and Intracellular Trafficking of Classical Swine Fever Virus

Classical swine fever virus (CSFV), which is a positive-sense, single-stranded RNA virus with an envelope, is a member of the Pestivirus genus in the Flaviviridae family. CSFV causes a severe and highly contagious disease in pigs and is prevalent worldwide, threatening the pig farming industry. The detailed mechanisms of the CSFV life cycle have been reported, but are still limited. Some receptors and attachment factors of CSFV, including heparan sulfate (HS), laminin receptor (LamR), complement regulatory protein (CD46), MER tyrosine kinase (MERTK), disintegrin, and metalloproteinase domain-containing protein 17 (ADAM17), were identified. After attachment, CSFV internalizes via clathrin-mediated endocytosis (CME) and/or caveolae/raft-dependent endocytosis (CavME). After internalization, CSFV moves to early and late endosomes before uncoating. During this period, intracellular trafficking of CSFV relies on components of the endosomal sorting complex required for transport (ESCRT) and Rab proteins in the endosome dynamics, with a dependence on the cytoskeleton network. This review summarizes the data on the mechanisms of CSFV attachment, internalization pathways, and intracellular trafficking, and provides a general view of the early events in the CSFV life cycle.

Entry receptor LDLRAD3 is required for Venezuelan equine encephalitis virus peripheral infection and neurotropism leading to pathogenesis in mice

Venezuelan equine encephalitis virus (VEEV) is an encephalitic alphavirus responsible for epidemics of neurological disease across the Americas. Low-density lipoprotein receptor class A domain-containing 3 (LDLRAD3) is a recently reported entry receptor for VEEV. Here, using wild-type and Ldlrad3-deficient mice, we define a critical role for LDLRAD3 in controlling steps in VEEV infection, pathogenesis, and neurotropism. Our analysis shows that LDLRAD3 is required for efficient VEEV infection and pathogenesis prior to and after central nervous system invasion. Ldlrad3-deficient mice survive intranasal and intracranial VEEV inoculation and show reduced infection of neurons in different brain regions. As LDLRAD3 is a determinant of pathogenesis and an entry receptor required for VEEV infection of neurons of the brain, receptor-targeted therapies may hold promise as countermeasures.

A molecular understanding of alphavirus entry and antibody protection

Alphaviruses are arthropod-transmitted RNA viruses that cause epidemics of human infection and disease on a global scale. These viruses are classified as either arthritogenic or encephalitic based on their genetic relatedness and the clinical syndromes they cause. Although there are currently no approved therapeutics or vaccines against alphaviruses, passive transfer of monoclonal antibodies confers protection in animal models. This Review highlights recent advances in our understanding of the host factors required for alphavirus entry, the mechanisms of action by which protective antibodies inhibit different steps in the alphavirus infection cycle and candidate alphavirus vaccines currently under clinical evaluation that focus on humoral immunity. A comprehensive understanding of alphavirus entry and antibody-mediated protection may inform the development of new classes of countermeasures for these emerging viruses.

Glycosaminoglycan binding by arboviruses: a cautionary tale

Arboviruses are medically important arthropod-borne viruses that cause a range of diseases in humans from febrile illness to arthritis, encephalitis and hemorrhagic fever. Given their transmission cycles, these viruses face the challenge of replicating in evolutionarily divergent organisms that can include ticks, flies, mosquitoes, birds, rodents, reptiles and primates. Furthermore, their cell attachment receptor utilization may be affected by the opposing needs for generating high and sustained serum viremia in vertebrates such that virus particles are efficiently collected during a hematophagous arthropod blood meal but they must also bind sufficiently to cellular structures on divergent organisms such that productive infection can be initiated and viremia generated. Sulfated polysaccharides of the glycosaminoglycan (GAG) groups, primarily heparan sulfate (HS), have been identified as cell attachment moieties for many arboviruses. Original identification of GAG binding as a phenotype of arboviruses appeared to involve this attribute arising solely as a consequence of adaptation of virus isolates to growth in cell culture. However, more recently, naturally circulating strains of at least one arbovirus, eastern equine encephalitis, have been shown to bind HS efficiently and the GAG binding phenotype continues to be associated with arbovirus infection in published studies. If GAGs are attachment receptors for many naturally circulating arboviruses, this could lead to development of broad-spectrum antiviral therapies through blocking of the virus-GAG interaction. This review summarizes the available data for GAG/HS binding as a phenotype of naturally circulating arbovirus strains emphasizing the importance of avoiding tissue culture amplification and artifactual phenotypes during their isolation.

LAMR1 restricts Zika virus infection by attenuating the envelope protein ubiquitination

Zika virus (ZIKV) infection can cause severe neurological disorders, including Guillain–Barre syndrome and meningoencephalitis in adults and microcephaly in fetuses. Here, we reveal that laminin receptor 1 (LAMR1) is a novel host resistance factor against ZIKV infection. Mechanistically, we found that LAMR1 binds to ZIKV envelope (E) protein via its intracellular region and attenuates E protein ubiquitination through recruiting the deubiquitinase eukaryotic translation initiation factor 3 subunit 5 (EIF3S5). We further found that the conserved G282 residue of E protein is essential for its interaction with LAMR1. Moreover, a G282A substitution abolished the binding of E protein to LAMR1 and inhibited LAMR1-mediated E protein deubiquitination. Together, our results indicated that LAMR1 represses ZIKV infection through binding to E protein and attenuating its ubiquitination.

LDLRAD3 is a receptor for Venezuelan equine encephalitis virus

Venezuelan equine encephalitis virus (VEEV) is a neurotropic alphavirus transmitted by mosquitoes that causes encephalitis and death in humans¹. VEEV is a biodefence concern because of its potential for aerosol spread and the current lack of sufficient countermeasures. The host factors that are required for VEEV entry and infection remain poorly characterized. Here, using a genome-wide CRISPR-Cas9-based screen, we identify low-density lipoprotein receptor class A domain-containing 3 (LDLRAD3)-a highly conserved yet poorly characterized member of the scavenger receptor superfamily-as a receptor for VEEV. Gene editing of mouse Ldlrad3 or human LDLRAD3 results in markedly reduced viral infection of neuronal cells, which is restored upon complementation with LDLRAD3. LDLRAD3 binds directly to VEEV particles and enhances virus attachment and internalization into host cells. Genetic studies indicate that domain 1 of LDLRAD3 (LDLRAD3(D1)) is necessary and sufficient to support infection by VEEV, and both anti-LDLRAD3 antibodies and an LDLRAD3(D1)-Fc fusion protein block VEEV infection in cell culture. The pathogenesis of VEEV infection is abrogated in mice with deletions in Ldlrad3, and administration of LDLRAD3(D1)-Fc abolishes disease caused by several subtypes of VEEV, including highly virulent strains. The development of a decoy-receptor fusion protein suggests a strategy for the prevention of severe VEEV infection and associated disease in humans.

RPSA distribution and expression in tissues and immune cells of pathogen-infected mice

AIMS

40S ribosomal protein SA (RPSA), a component of the small ribosomal subunit, is a high-affinity receptor of laminin that is widely expressed in cells and involves in many biological processes. However, it hasn't been reported which tissues and cells may be targeted by RPSA-mediated pathogen regulation. Therefore, in this study, a gram-positive bacterium Streptococcus suis Type 2 (SS2), gram-negative bacterium Actinobacillus pleuropneumoniae (A.pleuropneumoniae), and porcine circovirus Type 2 (PCV2) were used to infect ICR mice.

METHODS AND RESULTS

The effects of infection with the three pathogens on expression levels of RPSA in mouse tissues and peripheral blood immune cells were analysed by immunohistochemistry and flow cytometry. The results suggested that the pathological changes in mice infected with SS2 were mainly manifested as congestion and inflammatory infiltration in the meninges, lungs, hearts and livers. The mice infected with A.pleuropneumoniae or PCV2 showed lung lesions and mild hepatocyte degeneration, respectively. In uninfected mice, RPSA protein was expressed to various degrees in all tissues except the spleen. After SS2 infection for 3 d, the expression of RPSA in the liver and brain increased, while decreased significantly in the heart and duodenum. These results were corroborated on examining the correlation between RPSA expression and the process of SS2 infection, except that there was no significant difference between the expression levels in the heart at 1 d and 3 d. After A.pleuropneumoniae and PCV2 infection for 3 d, the expression of RPSA decreased in the heart, and brain, respectively. Additionally, under physiological conditions, RPSA expression in CD4⁺ T cells, CD8⁺ T cells, neutrophils, and macrophages in the peripheral blood of mice was higher than that in B cells and NK cells. After SS2 infection for 3 d, RPSA expression increased significantly in CD4⁺ T cells and CD8⁺ T cells but decreased significantly in macrophages. The expression of RPSA after A.pleuropneumoniae and PCV2 infection were similar, and RPSA expression decreased only in macrophages.

CONCLUSIONS

The results revealed that RPSA showed different expression levels in tissues and immune cells due to different pathogens causing disease courses, suggesting different target tissues and target cells in RPSA-mediated pathogenesis after infection, which supports the systematic study of the pathogenesis of RPSA in infectious diseases.

Host Factors and Pathways Involved in the Entry of Mosquito-Borne Alphaviruses

Chikungunya virus (CHIKV) is an arthropod-borne virus that has re-emerged recently and has spread to previously unaffected regions, resulting in millions of infections worldwide. The genus Alphavirus, in the family Togaviridae, contains several members with a similar potential for epidemic emergence. In order for CHIKV to replicate in targeted cell types it is essential for the virus to enter these cells. In this review, we summarize our current understanding of the versatile and promiscuous steps in CHIKV binding and entry into human and mosquito host cells. We describe the different entry pathways, receptors, and attachment factors so far described for CHIKV and other mosquito-borne alphaviruses and discuss them in the context of tissue tropism and potential therapeutic targeting.

Bacterial genome-wide association study of hyper-virulent pneumococcal serotype 1 identifies genetic variation associated with neurotropism

Hyper-virulent Streptococcus pneumoniae serotype 1 strains are endemic in Sub-Saharan Africa and frequently cause lethal meningitis outbreaks. It remains unknown whether genetic variation in serotype 1 strains modulates tropism into cerebrospinal fluid to cause central nervous system (CNS) infections, particularly meningitis. Here, we address this question through a large-scale linear mixed model genome-wide association study of 909 African pneumococcal serotype 1 isolates collected from CNS and non-CNS human samples. By controlling for host age, geography, and strain population structure, we identify genome-wide statistically significant genotype-phenotype associations in surface-exposed choline-binding (P = 5.00 × 10-08) and helicase proteins (P = 1.32 × 10-06) important for invasion, immune evasion and pneumococcal tropism to CNS. The small effect sizes and negligible heritability indicated that causation of CNS infection requires multiple genetic and other factors reflecting a complex and polygenic aetiology. Our findings suggest that certain pathogen genetic variation modulate pneumococcal survival and tropism to CNS tissue, and therefore, virulence for meningitis.

Identification of the Neuroinvasive Pathogen Host Target, LamR, as an Endothelial Receptor for the Treponema pallidum Adhesin Tp0751

Treponema pallidum subsp. pallidum is the causative agent of syphilis, a human-specific sexually transmitted infection that causes a multistage disease with diverse clinical manifestations. Treponema pallidum undergoes rapid vascular dissemination to penetrate tissue, placental, and blood-brain barriers and gain access to distant tissue sites. The rapidity and extent of T. pallidum dissemination are well documented, but the molecular mechanisms have yet to be fully elucidated. One protein that has been shown to play a role in treponemal dissemination is Tp0751, a T. pallidum adhesin that interacts with host components found within the vasculature and mediates bacterial adherence to endothelial cells under shear flow conditions. In this study, we further explore the molecular interactions of Tp0751-mediated adhesion to the vascular endothelium. We demonstrate that recombinant Tp0751 adheres to human endothelial cells of macrovascular and microvascular origin, including a cerebral brain microvascular endothelial cell line. Adhesion assays using recombinant Tp0751 N-terminal truncations reveal that endothelial binding is localized to the lipocalin fold-containing domain of the protein. We also confirm this interaction using live T. pallidum and show that spirochete attachment to endothelial monolayers is disrupted by Tp0751-specific antiserum. Further, we identify the 67-kDa laminin receptor (LamR) as an endothelial receptor for Tp0751 using affinity chromatography, coimmunoprecipitation, and plate-based binding methodologies. Notably, LamR has been identified as a receptor for adhesion of other neurotropic invasive bacterial pathogens to brain endothelial cells, including Neisseria meningitidis, Haemophilus influenzae, and Streptococcus pneumoniae, suggesting the existence of a common mechanism for extravasation of invasive extracellular bacterial pathogens.IMPORTANCE Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subsp. pallidum. The continued incidence of syphilis demonstrates that screening and treatment strategies are not sufficient to curb this infectious disease, and there is currently no vaccine available. Herein we demonstrate that the T. pallidum adhesin Tp0751 interacts with endothelial cells that line the lumen of human blood vessels through the 67-kDa laminin receptor (LamR). Importantly, LamR is also a receptor for meningitis-causing neuroinvasive bacterial pathogens such as Neisseria meningitidis, Haemophilus influenzae, and Streptococcus pneumoniae Our findings enhance understanding of the Tp0751 adhesin and present the intriguing possibility that the molecular events of Tp0751-mediated treponemal dissemination may mimic the endothelial interaction strategies of other invasive pathogens.

Investigating Bacterial Penetration of the Blood-Brain Barrier for the Pathogenesis, Prevention, and Therapy of Bacterial Meningitis

The most distressing aspect of bacterial meningitis is limited improvement in the mortality and morbidity despite attributable advances in antimicrobial chemotherapy and supportive care. A major contributing factor to such mortality and morbidity is our incomplete understanding of the pathogenesis of this disease. Microbial penetration of the blood-brain barrier, a prerequisite for the development of bacterial meningitis, exploits specific host and bacterial factors as well as host cell signaling molecules. Determination and characterization of such host and bacterial factors have been instrumental for developing our current knowledge on the pathogenesis of bacterial meningitis. In addition, counteracting such host and microbial factors has been shown to be efficacious in the prevention of bacterial meningitis. Antimicrobial therapy alone has limited efficacy in improving the outcome of bacterial meningitis. Recent studies suggest that counteracting targets contributing to bacterial penetration of the blood-brain barrier are a beneficial therapeutic adjunct to antimicrobial therapy in improving the outcome of bacterial meningitis. Taken together, these findings indicate that the elucidation of host and bacterial factors contributing to microbial penetration of the blood-brain barrier provides a novel strategy for investigating the pathogenesis, prevention, and therapy of bacterial meningitis.

Patented therapeutic approaches targeting LRP/LR for cancer treatment

Introduction: The ubiquitously expressed 37 kDa/67 kDa high-affinity laminin receptor (laminin receptor precursor/laminin receptor, LRP/LR) is a protein found to play several roles within cells. The receptor is located in the nucleus, cytosol and the cell surface. LRP/LR mediates cell proliferation, cell adhesion and cell differentiation. As a result, it is seen to enhance tumor angiogenesis as well as invasion and adhesion, key steps in the metastatic cascade of cancer. Recent findings have shown that LRP/LR is involved in the maintenance of cell viability through apoptotic evasion, allowing for tumor progression. Thus, several patented therapeutic approaches targeting the receptor for the prevention and treatment of cancer have emerged.Areas covered: The several roles that LRP/LR plays in cancer progression as well as an overview of the current therapeutic patented strategies targeting LRP/LR and cancer to date.Expert opinion: Small molecule inhibitors, monoclonal antibodies and small interfering RNAs might act used as powerful tools in preventing tumor angiogenesis and metastasis through the induction of apoptosis and telomere erosion in several cancers. This review offers an overview of the roles played by LRP/LR in cancer progression, while providing novel patented approaches targeting the receptor as potential therapeutic routes for the treatment of cancer as well as various other diseases.

Current Understanding of the Molecular Basis of Venezuelan Equine Encephalitis Virus Pathogenesis and Vaccine Development

Dedication

This review is dedicated in the memory of Dr Radha K. Maheshwari, a great mentor and colleague, whose passion for research and student training has left a lasting effect on this manuscript and many other works.

Abstract

Venezuelan equine encephalitis virus (VEEV) is an alphavirus in the family Togaviridae. VEEV is highly infectious in aerosol form and a known bio-warfare agent that can cause severe encephalitis in humans. Periodic outbreaks of VEEV occur predominantly in Central and South America. Increased interest in VEEV has resulted in a more thorough understanding of the pathogenesis of this disease. Inflammation plays a paradoxical role of antiviral response as well as development of lethal encephalitis through an interplay between the host and viral factors that dictate virus replication. VEEV has efficient replication machinery that adapts to overcome deleterious mutations in the viral genome or improve interactions with host factors. In the last few decades there has been ongoing development of various VEEV vaccine candidates addressing the shortcomings of the current investigational new drugs or approved vaccines. We review the current understanding of the molecular basis of VEEV pathogenesis and discuss various types of vaccine candidates.

Invasion of midgut epithelial cells by a persistently transmitted virus is mediated by sugar transporter 6 in its insect vector

Insect transmission is obligatory for persistently transmitted viruses because the vector insect is the only means of virus spread in nature. The insect midgut is the first major barrier limiting virus acquisition, but the mechanisms by which viruses are able to cross the cell membrane and then infect the midgut epithelial cells of the insect have not been elucidated completely. Here, we found that the outer capsid or nucleocapsid protein (NP) of three viruses can interact and colocalize with sugar transporter 6 that is highly expressed in the midgut of Laodelphax striatellus (LsST6). In contrast, LsST6 did not interact with the NP of rice grassy stunt virus, which cannot be transmitted by the same planthopper. LsST6 not only altered the cellular location of viral proteins and then colocalized with them in the cell membrane, but also mediated the entry of rice stripe virus (RSV) particles into Spodoptera frugiperda 9 (Sf9) cells that expressed the heterologous gene LsST6. We further showed that RSV particles initially bound to the cell membrane of midgut epithelial cells where it colocalized with LsST6, and then invaded the cytoplasm. When LsST6 expression was knocked down, viral titre, acquisition percentage and transmission efficiency of the treated insect decreased significantly, but virus replication was not affected. This work thus uncovered a strategy by which LsST6 mediates viral entry into midgut epithelial cells and leads to successful transmission by the insect vector.

The Transition of the 37-Kda Laminin Receptor (Rpsa) to Higher Molecular Weight Species: Sumoylation or Artifact?

The 37-kDa laminin receptor (37LRP or RPSA) is a remarkable, multifaceted protein that functions in processes ranging from matrix adhesion to ribosome biogenesis. Its ability to engage extracellular laminin is further thought to contribute to cellular migration and invasion. Most commonly associated with metastatic cancer, RPSA is also increasingly found to be important in other pathologies, including microbial infection, neurodegenerative disease and developmental malformations. Importantly, it is thought to have higher molecular weight forms, including a 67-kDa species (67LR), the expression of which is linked to strong laminin binding and metastatic behavior. The composition of these larger forms has remained elusive and controversial. Homo- and heterodimerization have been proposed as events capable of building the larger species from the monomeric 37-kDa precursor, but solid evidence is lacking. Here, we present data suggesting that higher molecular weight species require SUMOylation to form. We also comment on the difficulty of isolating larger RPSA species for unambiguous identification and demonstrate that cell lines stably expressing tagged RPSA for long periods of time fail to produce tagged higher molecular weight RPSA. It is possible that higher molecular weight species like 67LR are not derived from RPSA.

Viral receptors of the gut: vector-borne viruses of medical importance

Arthropods transmit several medically important arboviruses that cause diseases in humans. Therapeutic strategies to treat or prevent diseases transmitted by the arthropods are limiting. Understanding the role of arthropod gut receptors in the interactions with various arboviruses would provide important means for the development of a strong anti-vector vaccine. In this review, we summarize some of the potential findings in the field of arthropod gut receptors for tick-borne or mosquito-borne viruses and discuss their relevance in the development of a broad-spectrum transmission-blocking vaccine to treat or control various diseases caused by arboviruses.

Laminin receptor is an interacting partner for viral outer capsid protein VP5 in grass carp reovirus infection

Grass carp reovirus (GCRV) is responsible for viral hemorrhagic disease in cultured grass carp Ctenopharyngon idellus. Through yeast two-hybrid screen, laminin receptor (LamR) was identified as a potential interacting partner for the outer capsid protein VP5 of GCRV. We cloned and sequenced the gene encoding grass carp LamR. Viral attachment assay demonstrated the involvement of membrane-associated LamR in GCRV infection. Solid-phase overlay assays demonstrated that GCRV interacted with GST-tagged LamR in vitro. In contrast to VP7, GST-tagged VP5 was shown to associate with LamR in both pull-down and solid-phase blot overlay assays. With the reduction of LamR expression in CIK cells achieved by RNAi, remarkably reduced infection efficiency of GCRV was observed. CIK cells pretreated with polyclonal antibody against LamR resulted in dose-dependent inhibition of GCRV infection. These results collectively indicated that grass carp LamR was involved in GCRV infection by interacting with viral outer capsid protein VP5.

Identification of (-)-epigallocatechin-3-gallate as a potential agent for blocking infection by grass carp reovirus

Grass carp reovirus (GCRV), the representative strain of the species Aquareovirus C, serves as a model for studying the pathogenesis of aquareoviruses. Previously, epigallocatechin gallate (EGCG) was shown to inhibit orthoreovirus infection. The aim of this study was to test its potential in blocking infection by GCRV. We show that adhesion to the CIK (Ctenopharyngodon idellus kidney) cell surface by GCRV particles is inhibited in a dose-dependent manner by EGCG, as well as by a crude extract of green tea. We also evaluated the safety of EGCG and green tea extract using CIK cells, and the results suggest that EGCG is a promising compound that may be developed as a plant-derived small molecular therapeutic agent against grass carp hemorrhagic disease caused by GCRV infection. As the ligand for the 37/67-kDa laminin receptor (LamR), EGCG's blocking effect on GCRV attachment was associated with the binding potential of GCRV particles to LamR, which was inferred from a VOPBA assay.

Deciphering the complex three-way interaction between the non-integrin laminin receptor, galectin-3 and Neisseria meningitidis

The non-integrin laminin receptor (LAMR1/RPSA) and galectin-3 (Gal-3) are multi-functional host molecules with roles in diverse pathological processes, particularly of infectious or oncogenic origins. Using bimolecular fluorescence complementation and confocal imaging, we demonstrate that the two proteins homo- and heterodimerize, and that each isotype forms a distinct cell surface population. We present evidence that the 37 kDa form of LAMR1 (37LRP) is the precursor of the previously described 67 kDa laminin receptor (67LR), whereas the heterodimer represents an entity that is distinct from this molecule. Site-directed mutagenesis confirmed that the single cysteine (C(173)) of Gal-3 or lysine (K(166)) of LAMR1 are critical for heterodimerization. Recombinant Gal-3, expressed in normally Gal-3-deficient N2a cells, dimerized with endogenous LAMR1 and led to a significantly increased number of internalized bacteria (Neisseria meningitidis), confirming the role of Gal-3 in bacterial invasion. Contact-dependent cross-linking determined that, in common with LAMR1, Gal-3 binds the meningococcal secretin PilQ, in addition to the major pilin PilE. This study adds significant new mechanistic insights into the bacterial-host cell interaction by clarifying the nature, role and bacterial ligands of LAMR1 and Gal-3 isotypes during colonization.

In vitro adaptation of SAV3 in cell culture correlates with reduced in vivo replication capacity and virulence to Atlantic salmon (Salmo salar L.) parr

Salmonid alphavirus (SAV) is the causative agent of pancreas disease affecting Atlantic salmon and rainbow trout and causes a major burden to the aquaculture industry. This study describes a Norwegian subtype SAV3 virus isolate (SAV3-H10) subjected to serial passages in Chinook salmon embryo cells (CHSE-214) followed by Asian Grouper skin cells (AGK). Two passages from CHSE and one after transfer to AGK cells were chosen for further investigation, based on variation in degree and development of cytopathic effect (CPE). After plaque purification, several in vitro studies were performed. Cell viability after infection, viral replication and ability to cause morphological changes in CHSE and AGK cells was studied for the three isolates. The AGK-transferred isolate was identified with the strongest abilities to reduce cell viability, replicate more and cause more CPE in cell culture when compared with the early and late CHSE-grown isolates. Subsequently, the isolates were tested in an experimental fish challenge, showing higher viral load and higher pathological score for the least cell-cultured isolate. Full-length sequencing of the viral genome of the three isolates revealed divergence in four amino acid positions and the AGK-grown isolate also had a 3 nt deletion in the 3'UTR. In conclusion, we show that cell culture of SAV3-H10 selects for strains inducing earlier CPE in vitro with increased viral replication. In vivo, the effect is reversed, with lower replication levels and lower pathology scores in target organs. This study outlines a path to identify potential virulence motifs of SAV3.

Tissue Barriers to Arbovirus Infection in Mosquitoes

Arthropod-borne viruses (arboviruses) circulate in nature between arthropod vectors and vertebrate hosts. Arboviruses often cause devastating diseases in vertebrate hosts, but they typically do not cause significant pathology in their arthropod vectors. Following oral acquisition of a viremic bloodmeal from a vertebrate host, the arbovirus disease cycle requires replication in the cellular environment of the arthropod vector. Once the vector has become systemically and persistently infected, the vector is able to transmit the virus to an uninfected vertebrate host. In order to systemically infect the vector, the virus must cope with innate immune responses and overcome several tissue barriers associated with the midgut and the salivary glands. In this review we describe, in detail, the typical arbovirus infection route in competent mosquito vectors. Based on what is known from the literature, we explain the nature of the tissue barriers that arboviruses are confronted with in a mosquito vector and how arboviruses might surmount these barriers. We also point out controversial findings to highlight particular areas that are not well understood and require further research efforts.

Force-induced globule-coil transition in laminin binding protein and its role for viral-cell membrane fusion

The specific interactions of the pairs laminin binding protein (LBP)-purified tick-borne encephalitis viral surface protein E and certain recombinant fragments of this protein, as well as West Nile viral surface protein E and certain recombinant fragments of that protein, are studied by combined methods of single-molecule dynamic force spectroscopy (SMDFS), enzyme immunoassay and optical surface waves-based biosensor measurements. The experiments were performed at neutral pH (7.4) and acid pH (5.3) conditions. The data obtained confirm the role of LBP as a cell receptor for two typical viral species of the Flavivirus genus. A comparison of these data with similar data obtained for another cell receptor of this family, namely human αVβ3 integrin, reveals that both these receptors are very important. Studying the specific interaction between the cell receptors in question and specially prepared monoclonal antibodies against them, we could show that both interaction sites involved in the process of virus-cell interaction remain intact at pH 5.3. At the same time, for these acid conditions characteristic for an endosome during flavivirus-cell membrane fusion, SMDFS data reveal the existence of a force-induced (effective already for forces as small as 30-70 pN) sharp globule-coil transition for LBP and LBP-fragments of protein E complexes. We argue that this conformational transformation, being an analog of abrupt first-order phase transition and having similarity with the famous Rayleigh hydrodynamic instability, might be indispensable for the flavivirus-cell membrane fusion process.

Mutational Analysis of Measles Virus Suggests Constraints on Antigenic Variation of the Glycoproteins

Measles virus undergoes error-prone replication like other RNA viruses, but over time, it has remained antigenically monotypic. The constraints on the virus that prevent the emergence of antigenic variants are unclear. As a first step in understanding this question, we subjected the measles virus genome to unbiased insertional mutagenesis, and viruses that could tolerate insertions were rescued. Only insertions in the nucleoprotein, phosphoprotein, matrix protein, as well as intergenic regions were easily recoverable. Insertions in the glycoproteins of measles virus were severely under-represented in our screen. Host immunity depends on developing neutralizing antibodies to the hemagglutinin and fusion glycoproteins; our analysis suggests that these proteins occupy very little evolutionary space and therefore have difficulty changing in the face of selective pressures. We propose that the inelasticity of these proteins prevents the sequence variation required to escape antibody neutralization in the host, allowing for long-lived immunity after infection with the virus.

The laminin receptor is a cellular attachment receptor for classical Swine Fever virus

Classical swine fever virus (CSFV) is the causative agent of classical swine fever (CSF), a highly contagious, economically important viral disease in many countries. The E(rns) and E2 envelope glycoproteins are responsible for the binding to and entry into the host cell by CSFV. To date, only one cellular receptor, heparan sulfate (HS), has been identified as being involved in CSFV attachment. HS is also present on the surface of various cells that are nonpermissive to CSFV. Hence, there must be another receptor(s) that has been unidentified to date. In this study, we used a set of small interfering RNAs (siRNAs) against a number of porcine cell membrane protein genes to screen cellular proteins involved in CSFV infection. This approach resulted in the identification of several proteins, and of these, the laminin receptor (LamR) has been demonstrated to be a cellular receptor for several viruses. Confocal analysis showed that LamR is colocalized with CSFV virions on the membrane, and a coimmunoprecipitation assay indicated that LamR interacts with the CSFV E(rns) protein. In inhibition assays, anti-LamR antibodies, soluble laminin, or LamR protein significantly inhibited CSFV infection in a dose-dependent manner. Transduction of PK-15 cells with a recombinant lentivirus expressing LamR yielded higher viral titers. Moreover, an attachment assay demonstrated that LamR functions during virus attachment. We also demonstrate that LamR acts as an alternative attachment receptor, especially in SK6 cells. These results indicate that LamR is a cellular attachment receptor for CSFV.

IMPORTANCE

Classical swine fever virus (CSFV) is the causative agent of classical swine fever (CSF), an economically important viral disease affecting the pig industry in many countries. To date, only heparan sulfate (HS) has been identified to be an attachment receptor for CSFV. Here, using RNA interference screening with small interfering RNAs (siRNAs) against a number of porcine membrane protein genes, we identified the laminin receptor (LamR) to be another attachment receptor. We demonstrate the involvement of LamR together with HS in virus attachment, and we elucidate the relationship between LamR and HS. LamR also serves as an attachment receptor for many viral pathogens, including dengue virus, a fatal human flavivirus. The study will help to enhance our understanding of the life cycle of flaviviruses and the development of antiviral strategies for flaviviruses.

Looking into laminin receptor: critical discussion regarding the non-integrin 37/67-kDa laminin receptor/RPSA protein

The 37/67-kDa laminin receptor (LAMR/RPSA) was originally identified as a 67-kDa binding protein for laminin, an extracellular matrix glycoprotein that provides cellular adhesion to the basement membrane. LAMR has evolutionary origins, however, as a 37-kDa RPS2 family ribosomal component. Expressed in all domains of life, RPS2 proteins have been shown to have remarkably diverse physiological roles that vary across species. Contributing to laminin binding, ribosome biogenesis, cytoskeletal organization, and nuclear functions, this protein governs critical cellular processes including growth, survival, migration, protein synthesis, development, and differentiation. Unsurprisingly given its purview, LAMR has been associated with metastatic cancer, neurodegenerative disease and developmental abnormalities. Functioning in a receptor capacity, this protein also confers susceptibility to bacterial and viral infection. LAMR is clearly a molecule of consequence in human disease, directly mediating pathological events that make it a prime target for therapeutic interventions. Despite decades of research, there are still a large number of open questions regarding the cellular biology of LAMR, the nature of its ability to bind laminin, the function of its intrinsically disordered C-terminal region and its conversion from 37 to 67 kDa. This review attempts to convey an in-depth description of the complexity surrounding this multifaceted protein across functional, structural and pathological aspects.

Small molecule-sensing strategy and techniques for understanding the functionality of green tea

Various low-molecular-weight phytochemicals in green tea (Camellia sinensis L.), especially (-)-epigallocatechin-3-O-gallate (EGCG), are known to be involved in health promotion and disease risk reduction. However, the underlying mechanism has remained elusive because of the absence of an analytical technique that can easily detect the precise behavior of such a small molecule. Recently, we have identified a cell-surface EGCG-sensing receptor and the related signaling molecules that control the physiological functions of EGCG. We also developed a novel in situ label-free imaging technique for visualizing spatially resolved biotransformations based on simultaneous mapping of EGCG and its phase II metabolites. Furthermore, we established a chemometric method capable of evaluating the functionality of multicomponent green tea extracts by focusing on their compositional balances. This review highlights our proposed small molecule-sensing techniques for detecting the complex behavior of green tea components and linking such information to an enhanced understanding of green tea functionality.

Fusion-related host proteins are actively regulated by NA during influenza infection as revealed by quantitative proteomics analysis

Three recombinant influenza A viruses with different neuraminidases (NAs) in the background of A/PR/8/34 (PR8), named rPR8-H5N1NA, rPR8-H9N2NA, and rPR8-H1N1NA, derived from H5N1, H9N2, H1N1 (swine) viruses, respectively, were constructed. We performed a quantitative proteomics analysis to investigate differential protein expression in Madin-Darby canine kidney (MDCK) cells infected with recombinant and wild-type influenza viruses to determine whether NA replacement would alter host cell gene expression. Using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-TOF MS) and two-dimensional gel electrophoresis (2-DE), we identified 12 up-regulated and 49 down-regulated protein spots, including cytoskeletal proteins, molecular biosynthesis proteins, ubiquitin-proteasome pathway proteins, and heat shock proteins. The most significant changes in infected cells were observed for molecular biosynthesis proteins. We found more differentially expressed protein spots in cells infected with rPR8-H5N1NA or rPR8-H9N2NA viruses than cells infected with wild-type virus. Many of those proteins are postulated to be involved in cell-cell fusion, but the full mechanism remains to be explored. Meanwhile, our data demonstrate that the wild-type virus has evolutionary advantages over recombinant viruses.

The 37kDa/67kDa laminin receptor acts as a receptor for Aβ42 internalization

Neuronal loss is a major neuropathological hallmark of Alzheimer's disease (AD). The associations between soluble Aβ oligomers and cellular components cause this neurotoxicity. The 37 kDa/67 kDa laminin receptor (LRP/LR) has recently been implicated in Aβ pathogenesis. In this study the mechanism underlying the pathological role of LRP/LR was elucidated. Försters Resonance Energy Transfer (FRET) revealed that LRP/LR and Aβ form a biologically relevant interaction. The ability of LRP/LR to form stable associations with endogenously shed Aβ was confirmed by pull down assays and Aβ-ELISAs. Antibody blockade of this association significantly lowered Aβ₄₂ induced apoptosis. Furthermore, antibody blockade and shRNA mediated downregulation of LRP/LR significantly hampered Aβ₄₂ internalization. These results suggest that LRP/LR is a receptor for Aβ₄₂ internalization, mediating its endocytosis and contributing to the cytotoxicity of the neuropeptide by facilitating intra-cellular Aβ₄₂ accumulation. These findings recommend anti-LRP/LR specific antibodies and shRNAs as potential therapeutic tools for AD treatment.

Interaction of human laminin receptor with Sup35, the [PSI⁺] prion-forming protein from S. cerevisiae: a yeast model for studies of LamR interactions with amyloidogenic proteins

The laminin receptor (LamR) is a cell surface receptor for extracellular matrix laminin, whereas the same protein within the cell interacts with ribosomes, nuclear proteins and cytoskeletal fibers. LamR has been shown to be a receptor for several bacteria and viruses. Furthermore, LamR interacts with both cellular and infectious forms of the prion protein, PrP(C) and PrP(Sc). Indeed, LamR is a receptor for PrP(C). Whether LamR interacts with PrP(Sc) exclusively in a capacity of the PrP receptor, or LamR specifically recognizes prion determinants of PrP(Sc), is unclear. In order to explore whether LamR has a propensity to interact with prions and amyloids, we examined LamR interaction with the yeast prion-forming protein, Sup35. Sup35 is a translation termination factor with no homology or functional relationship to PrP. Plasmids expressing LamR or LamR fused with the green fluorescent protein (GFP) were transformed into yeast strain variants differing by the presence or absence of the prion conformation of Sup35, respectively [PSI⁺] and [psi⁻]. Analyses by immunoprecipitation, centrifugal fractionation and fluorescent microscopy reveal interaction between LamR and Sup35 in [PSI⁺] strains. The presence of [PSI⁺] promotes LamR co-precipitation with Sup35 as well as LamR aggregation. In [PSI⁺] cells, LamR tagged with GFP or mCherry forms bright fluorescent aggregates that co-localize with visible [PSI⁺] foci. The yeast prion model will facilitate studying the interaction of LamR with amyloidogenic prions in a safe and easily manipulated system that may lead to a better understanding and treatment of amyloid diseases.

Effect of larval density and Sindbis virus infection on immune responses in Aedes aegypti

Stressful environmental conditions during mosquito larval development may enhance susceptibility of adult mosquitoes to viral pathogens. Although anti-viral defense system in mosquitoes remains uncertain, stress-related enhancement of mosquito susceptibility to viral pathogens may be due to alteration of signaling pathways such as the Toll and immune deficiency (IMD) pathways. To test the influence of larval density and Sindbis virus (SINV) infection on mosquito Toll/Imd pathways, 100 or 200 Aedes aegypti larvae were reared in 2L of live oak (Quercus virginiana) leaf infusion and the adults were fed on SINV-infected (treatments) or non-infected (controls) bovine blood. SINV infection status and expression of genes encoding three antimicrobial peptides (cecropin, defensin, diptericin), an iron-binding protein (transferrin), and four regulators of Toll/Imd pathways (caspar, cactus, Rel1A, Rel2) were quantified by RT-qPCR at 7 and 14days post blood meals. Irrespective of larval density, females incubated for 14days after an infectious blood meal had significantly higher SINV titers compared to females from low density treatments that were incubated for 7days. For both larval densities and time intervals, there was significant down-regulation of the Toll/Imd regulator genes in SINV-infected mosquitoes compared to controls. At day 7 post-infection, there was significant down-regulation of cecropin, defensin, diptericin and transferrin in SINV-infected mosquitoes at low larval density but this effect was only observed for diptericin at high larval density. These genes remained suppressed on day 14, except cecropin which was significantly up-regulated at both larval densities, and transferrin which was similar to controls at low larval density. We conclude that SINV infection suppresses Toll/Imd pathways, but high larval density enables SINV to attain maximum titers in Ae. aegypti much earlier compared to low density treatments despite the up-regulation of cecropin.

Nature, nurture and evolution of intra-species variation in mosquito arbovirus transmission competence

Mosquitoes vary in their competence or ability to transmit arthropod-borne viruses (arboviruses). Many arboviruses cause disease in humans and animals. Identifying the environmental and genetic causes of variation in mosquito competence for arboviruses is one of the great challenges in public health. Progress identifying genetic (nature) and environmental (nurture) factors influencing mosquito competence for arboviruses is reviewed. There is great complexity in the various traits that comprise mosquito competence. The complex interactions between environmental and genetic factors controlling these traits and the factors shaping variation in Nature are largely unknown. The norms of reaction of specific genes influencing competence, their distributions in natural populations and the effects of genetic polymorphism on phenotypic variation need to be determined. Mechanisms influencing competence are not likely due to natural selection because of the direct effects of the arbovirus on mosquito fitness. More likely the traits for mosquito competence for arboviruses are the effects of adaptations for other functions of these competence mechanisms. Determining these other functions is essential to understand the evolution and distributions of competence for arboviruses. This information is needed to assess risk from mosquito-borne disease, predict new mosquito-arbovirus systems, and provide novel strategies to mitigate mosquito-borne arbovirus transmission.

Venezuelan equine encephalitis virus glycoprotein pseudotyping confers neurotropism to lentiviral vectors

We have produced high-titre HIV-1 green fluorescent protein-expressing lentiviral (LV) vectors pseudotyped with strain 3908 Venezuelan equine encephalitis virus glycoprotein (VEEV-G) and used them to study transduction of: (1) rat embryonic motor neuron (MN) and striatal neuron primary cultures, (2) differentiated MN cell line NSC-34 and (3) adult rat striatum. In primary neuronal cultures, transduction with VEEV-G-pseudotyped LV was more efficient and more neuronal than with vesicular stomatitis virus glycoprotein (VSV-G)-pseudotyped LV. In NSC-34 cells clear retrograde transport of VEEV-G vector particles was observed. In the striatum at the injection site, transduction with the VEEV-G vectors driven by cytomegalovirus or phosphoglycerate kinase promoters exhibited a distinct neuronal tropism with no microglial and only a minor astroglial component, superior to that obtained with VSV-G-pseudotyped LV, irrespective of the promoter used. Neuronal transduction efficiency increased over time. Distal to the injection site transduction of mitral cells in the olfactory bulb, thalamic neurons and dopaminergic neurons in the substantia nigra pars compacta was detected. This, together with observations of retrograde axonal trafficking in vitro indicates that these vectors also possess low level of retrograde neuronal transduction capability in vivo. In this study, we demonstrate both strong neurotropism as well as sustainability of expression and minimal host immune response in vivo, making the VEEV-G-pseudotyped LV vectors potentially useful for gene therapy of neurodegenerative diseases.

Comprehensive proteomic analysis of nonintegrin laminin receptor interacting proteins

Human nonintegrin laminin receptor is a multifunctional protein acting as an integral component of the ribosome and a cell surface receptor for laminin-1. The laminin receptor is overexpressed in several human cancers and is also the cell surface receptor for several viruses and pathogenic prion proteins, making it a pathologically significant protein. This study focused on the proteomic characterization of laminin receptor interacting proteins from Mus musculus. The use of affinity chromatography with immobilized recombinant laminin receptor coupled with mass spectrometry analysis identified 45 proteins with high confidence. Following validation through coimmunoprecipitation, the proteins were classified based on predicted function into ribosomal, RNA processing, signal transduction/metabolism, protein processing, cytoskeleton/cell anchorage, DNA/chromatin, and unknown functions. A significant portion of the identified proteins is related to functions or localizations previously described for laminin receptor. This work represents a comprehensive proteomic approach to studying laminin receptor and provides an essential stepping stone to a better mechanistic understanding of this protein's diverse functions.

Mapping the laminin receptor binding domains of Neisseria meningitidis PorA and Haemophilus influenzae OmpP2

Neisseria meningitidis, Haemophilus influenzae and Streptococcus pneumoniae are major bacterial agents of meningitis. They each bind the 37/67-kDa laminin receptor (LamR) via the surface protein adhesins: meningococcal PilQ and PorA, H. influenzae OmpP2 and pneumococcal CbpA. We have previously reported that a surface-exposed loop of the R2 domain of CbpA mediates LamR-binding. Here we have identified the LamR-binding regions of PorA and OmpP2. Using truncated recombinant proteins we show that binding is dependent on amino acids 171-240 and 91-99 of PorA and OmpP2, respectively, which are predicted to localize to the fourth and second surface-exposed loops, respectively, of these proteins. Synthetic peptides corresponding to the loops bound LamR and could block LamR-binding to bacterial ligands in a dose dependant manner. Meningococci expressing PorA lacking the apex of loop 4 and H. influenzae expressing OmpP2 lacking the apex of loop 2 showed significantly reduced LamR binding. Since both loops are hyper-variable, our data may suggest a molecular basis for the range of LamR-binding capabilities previously reported among different meningococcal and H. influenzae strains.

Green tea polyphenol EGCG sensing motif on the 67-kDa laminin receptor

Background

We previously identified the 67-kDa laminin receptor (67LR) as the cell-surface receptor conferring the major green tea polyphenol (–)-epigallocatechin-3-O-gallate (EGCG) responsiveness to cancer cells. However, the underlying mechanism for interaction between EGCG and 67LR remains unclear. In this study, we investigated the possible role of EGCG-67LR interaction responsible for its bioactivities.

Methodology/Principal Findings

We synthesized various peptides deduced from the extracellular domain corresponding to the 102-295 region of human 67LR encoding a 295-amino acid. The neutralizing activity of these peptides toward EGCG cell-surface binding and inhibition of cancer cell growth were assayed. Both activities were inhibited by a peptide containing the 10-amino acid residues, IPCNNKGAHS, corresponding to residues 161-170. Furthermore, mass spectrometric analysis revealed the formation of a EGCG-LR161-170 peptide complex. A study of the amino acid deletion/replacement of the peptide LR161-170 indicated that the 10-amino acid length and two basic amino acids, K¹⁶⁶ and H¹⁶⁹, have a critical role in neutralizing EGCG’s activities. Moreover, neutralizing activity against the anti-proliferation action of EGCG was observed in a recombinant protein of the extracellular domain of 67LR, and this effect was abrogated by a deletion of residues 161-170. These findings support that the 10 amino-acid sequence, IPCNNKGAHS, might be the functional domain responsible for the anti-cancer activity of EGCG.

Conclusions/Significance

Overall, our results highlight the nature of the EGCG-67LR interaction and provide novel structural insights into the understanding of 67LR-mediated functions of EGCG, and could aid in the development of potential anti-cancer compounds for chemopreventive or therapeutic uses that can mimic EGCG-67LR interactions.

An update on mosquito cell expressed dengue virus receptor proteins

Dengue is the most important mosquito transmitted viral disease of humans worldwide. Despite intensive study over several decades, many of the fine details of the dengue virus (DENV) replication cycle remain unknown, although generally more is known about the phase of the replication cycle in mammalian cells as compared to the phase in mosquito cells. This results from a combination of less research emphasis on the mosquito stage, as well as fewer tools such as specific antibodies against mosquito proteins and insect informatics databases. The binding of a virus to a host cell is a first and critical stage in the infectious process and the mechanism and identity of cellular proteins involved in this process remains largely unknown. This short review aims to provide an update on our current understanding of the proteins expressed by mosquito cells that mediate DENV binding as a prerequisite to DENV entry and replication.

Receptor mimicry as novel therapeutic treatment for biothreat agents

The specter of intentional release of pathogenic microbes and their toxins is a real threat. This article reviews the literature on adhesins of biothreat agents, their interactions with oligosaccharides and the potential for anti-adhesion compounds as an alternative to conventional therapeutics. The minimal binding structure of ricin has been well characterised and offers the best candidate for successful anti-adhesion therapy based on the Galβ1-4GlcNAc structure. The botulinum toxin serotypes A-F bind to a low number of gangliosides (GT1b, GQ1b, GD1a and GD1b) hence it should be possible to determine the minimal structure for binding. The minimal disaccharide sequence of GalNAcβ1-4Gal found in the gangliosides asialo-GM1 and asialo-GM2 is required for adhesion for many respiratory pathogens. Although a number of adhesins have been identified in bacterial biothreat agents such as Yersinia pestis, Bacillus anthracis, Francisella tularensis, Brucella species and Burkholderia pseudomallei, specific information regarding their in vivo expression during pneumonic infection is lacking. Limited oligosaccharide inhibition studies indicate the potential of GalNAcβ1-4Gal, GalNAcβ-3Gal and the hydrophobic compound, para-nitrophenol as starting points for the rational design of generic anti-adhesion compounds. A cocktail of multivalent oligosaccharides based on the minimal binding structures of identified adhesins would offer the best candidates for anti-adhesion therapy.

Extraribosomal functions associated with the C terminus of the 37/67 kDa laminin receptor are required for maintaining cell viability

The 37/67 kDa laminin receptor (LAMR) is a multifunctional protein, acting as an extracellular receptor, localizing to the nucleus, and playing roles in rRNA processing and ribosome assembly. LAMR is important for cell viability; however, it is unclear which of its functions are essential. We developed a silent mutant LAMR construct, resistant to siRNA, to rescue the phenotypic effects of knocking down endogenous LAMR, which include inhibition of protein synthesis, cell cycle arrest, and apoptosis. In addition, we generated a C-terminal-truncated silent mutant LAMR construct structurally homologous to the Archaeoglobus fulgidus S2 ribosomal protein and missing the C-terminal 75 residues of LAMR, which displays more sequence divergence. We found that HT1080 cells stably expressing either silent mutant LAMR construct still undergo arrest in the G₁ phase of the cell cycle when treated with siRNA. However, the expression of full-length silent mutant LAMR rescues cell viability, whereas the expression of the C-terminal-truncated LAMR does not. Interestingly, we also found that both silent mutant constructs restore protein translation and localize to the nucleus. Our findings indicate that the ability of LAMR to regulate viability is associated with its C-terminal 75 residues. Furthermore, this function is distinct from its role in cell proliferation, independent of its ribosomal functions, and may be regulated by a nonnuclear localization.

Interactions between laminin receptor and the cytoskeleton during translation and cell motility

Human laminin receptor acts as both a component of the 40S ribosomal subunit to mediate cellular translation and as a cell surface receptor that interacts with components of the extracellular matrix. Due to its role as the cell surface receptor for several viruses and its overexpression in several types of cancer, laminin receptor is a pathologically significant protein. Previous studies have determined that ribosomes are associated with components of the cytoskeleton, however the specific ribosomal component(s) responsible has not been determined. Our studies show that laminin receptor binds directly to tubulin. Through the use of siRNA and cytoskeletal inhibitors we demonstrate that laminin receptor acts as a tethering protein, holding the ribosome to tubulin, which is integral to cellular translation. Our studies also show that laminin receptor is capable of binding directly to actin. Through the use of siRNA and cytoskeletal inhibitors we have shown that this laminin receptor-actin interaction is critical for cell migration. These data indicate that interactions between laminin receptor and the cytoskeleton are vital in mediating two processes that are intimately linked to cancer, cellular translation and migration.

Green tea polyphenol sensing

Green tea polyphenols have emerged over the past two decades as an important dietary factor for health promotion. There is considerable evidence that tea polyphenols, in particular (-)-epigallocatechin-3-gallate (EGCG) inhibit carcinogenesis. However, the mechanisms for the cancer-preventive activity of EGCG are not completely characterized and many features remain to be elucidated. Recently we have identified a cell-surface EGCG receptor and the relating molecules that confer EGCG responsiveness to many cancer cells at physiological concentrations. Here, we review some of the reported mechanisms for the cancer chemopreventive action of EGCG and provide an overview of several molecules that sense and manage the physiological functions of EGCG.

Structure-guided identification of a laminin binding site on the laminin receptor precursor

The 37/ 67-kDa human laminin receptor (LamR) is a cell surface receptor for laminin, prion protein, and a variety of viruses. Because of its wide range of ligands, LamR plays a role in numerous pathologies. LamR overexpression correlates with a highly invasive cell phenotype and increased metastatic ability, mediated by interactions between LamR and laminin. In addition, the specific targeting of LamR with small interfering RNAs, blocking antibodies, and Sindbis viral vectors confers anti-tumor effects. We adopted a structure-based approach to map a laminin binding site on human LamR by comparing the sequences and crystal structures of LamR and Archaeoglobus fulgidus S2p, a non-laminin-binding ortholog. Here, we identify a laminin binding site on LamR, comprising residues Phe32, Glu35, and Arg155, which are conserved among mammalian species. Mutation of these residues results in a significant loss of laminin binding. Further, recombinant wild-type LamR is able to act as a soluble decoy to inhibit cellular migration towards laminin. Mutation of this laminin binding site results in loss of migration inhibition, which demonstrates the physiological role of Phe32, Glu35, and Arg155 for laminin binding activity. Mapping of the LamR binding site should contribute to the development of therapeutics that inhibit LamR interactions with laminin and may aid in the prevention of tumor growth and metastasis.

Acute bacterial meningitis in infants and children

Bacterial meningitis continues to be an important cause of mortality and morbidity in neonates and children throughout the world. The introduction of the protein conjugate vaccines against Haemophilus influenzae type b, Streptococcus pneumoniae, and Neisseria meningitidis has changed the epidemiology of bacterial meningitis. Suspected bacterial meningitis is a medical emergency and needs empirical antimicrobial treatment without delay, but recognition of pathogens with increasing resistance to antimicrobial drugs is an important factor in the selection of empirical antimicrobial regimens. At present, strategies to prevent and treat bacterial meningitis are compromised by incomplete understanding of the pathogenesis. Further research on meningitis pathogenesis is thus needed. This Review summarises information on the epidemiology, pathogenesis, new diagnostic methods, empirical antimicrobial regimens, and adjunctive treatment of acute bacterial meningitis in infants and children.

Evolving role of laminin receptors in microbial pathogenesis and therapeutics of CNS infection

Evaluation of: Orihuela CJ, Mahdavi J, Thornton J et al.: Laminin receptor initiates bacterial contact with the blood brain barrier in experimental meningitis models. J. Clin. Invest. 119(6), 1638-1646 (2009). Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae are the common pathogens causing bacterial meningitis in childhood. Using in vitro and in vivo models of the blood-brain barrier, affinity chromatography, coimmunoprecipitation, retagging and in vivo imaging approaches, Orihuela et al. have demonstrated that the 37/67-kDa laminin receptor (LR) is a common receptor for all three bacteria on the surface of rodent and human brain microvascular endothelial cells. Pneumococcal choline-binding protein A, meningococcal pilus biogenesis protein Q and class 1 porin, and outer membrane protein P2 of H. influenzae have been identified by mutagenesis as the corresponding bacterial LR-binding adhesins. Their studies further suggest that the bacterial adhesins bind to a common adhesion-recognition site, which is present in the carboxyl terminus of LR. Since these bacterial adhesins and other microbial virulence factors bind to the same host receptor at the blood-brain barrier, LR may provide a broad-spectrum therapeutic target for the prevention and treatment of the CNS infection.

A structural and functional perspective of alphavirus replication and assembly

Alphaviruses are small, spherical, enveloped, positive-sense ssRNA viruses responsible for a considerable number of human and animal diseases. Alphavirus members include Chikungunya virus, Sindbis virus, Semliki Forest virus, the western, eastern and Venezuelan equine encephalitis viruses, and the Ross River virus. Alphaviruses can cause arthritic diseases and encephalitis in humans and animals and continue to be a worldwide threat. The viruses are transmitted by blood-sucking arthropods, and replicate in both arthropod and vertebrate hosts. Alphaviruses form spherical particles (65-70 nm in diameter) with icosahedral symmetry and a triangulation number of four. The icosahedral structures of alphaviruses have been defined to very high resolutions by cryo-electron microscopy and crystallographic studies. In this review, we summarize the major events in alphavirus infection: entry, replication, assembly and budding. We focus on data acquired from structural and functional studies of the alphaviruses. These structural and functional data provide a broader perspective of the virus lifecycle and structure, and allow additional insight into these important viruses.

Multiple functions of the 37/67-kd laminin receptor make it a suitable target for novel cancer gene therapy

The 37/67-kd laminin receptor, LAMR, is a multifunctional protein that associates with the 40S ribosomal subunit and also localizes to the cell membrane to interact with the extracellular matrix. LAMR is overexpressed in many types of cancer, playing important roles in tumor-cell migration and invasion. Here, we show that LAMR is also vital for tumor-cell proliferation, survival, and protein translation. Small-interfering RNA (siRNA)-mediated reduction in expression of LAMR leads to G1 phase cell-cycle arrest in vitro by altering cyclins A2/B1, cyclin-dependent kinases (CDKs) 1/2, Survivin, and p21 expression levels. In vivo, reduction in LAMR expression results in inhibition of HT1080 cells to develop tumors. We also found that LAMR's ribosomal functions are critical for translation as reduction in LAMR expression leads to a dramatic decrease in newly synthesized proteins. Further, cells with lower expression of LAMR have fewer 40S subunits and 80S monosomes, causing an increase in free 60S ribosomal subunits. These results indicate that LAMR is able to regulate tumor development in many ways; further enhancing its potential as a target for gene therapy. To test this, we developed a novel Sindbis/Lenti pseudotype vector carrying short-hairpin RNA (shRNA) designed against lamr. This pseudotype vector effectively reduces LAMR expression and specifically targets tumors in vivo. Treatment of tumor-bearing severe combine immunodeficient (SCID) mice with this pseudotype vector significantly inhibits tumor growth. Thus, we show that LAMR can be used as a target in novel therapy for tumor reduction and elimination.