CTX, a Xenopus thymocyte receptor, defines a molecular family conserved throughout vertebrates

Junctional Adhesion Molecule (JAM)-C recruitment of Pard3 and drebrin to cell contacts initiates neuron-glia recognition and layer-specific cell sorting in developing cerebella

Sorting maturing neurons into distinct layers is critical for brain development, with disruptions leading to neurological disorders and pediatric cancers. Lamination coordinates where, when, and how cells interact, facilitating events that direct migrating neurons to their destined positions within emerging neural networks and control the wiring of connections in functional circuits. While the role of adhesion molecule expression and presentation in driving adhesive recognition during neuronal migration along glial fibers is recognized, the mechanisms by which the spatial arrangement of these molecules on the cell surface dictates adhesive specificity and translates contact-based external cues into intracellular responses like polarization and cytoskeletal organization remain largely unexplored. We used the cerebellar granule neuron (CGN) system to demonstrate that JAM-C receptor cis-binding on the same cell and trans-binding to neighboring cells controls the recruitment of the Pard3 polarity protein and drebrin microtubule-actin crosslinker at CGN to glial adhesion sites, complementing previous studies that showed Pard3 controls JAM-C exocytic surface presentation. Leveraging advanced imaging techniques, specific probes for cell recognition, and analytical methods to dissect adhesion dynamics, our findings reveal: 1) JAM-C cis or trans mutants result in reduced adhesion formation between CGNs and cerebellar glia, 2) these mutants exhibit delayed recruitment of Pard3 at the adhesion sites, and 3) CGNs with JAM-C mutations experience postponed sorting and entry into the cerebellar molecular layer (ML). By developing a conditional system to image adhesion components from two different cells simultaneously, we made it possible to investigate the dynamics of cell recognition on both sides of neuron-glial contacts and the subsequent recruitment of proteins required for CGN migration. This system and an approach that calculates local correlation based on convolution kernels at the cell adhesions site revealed that CGN to CGN JAM recognition preferentially recruits higher levels of Pard3 and drebrin than CGN to glia JAM recognition. The long latency time of CGNs in the inner external germinal layer (EGL) can be attributed to the combined strength of CGN-CGN contacts and the less efficient Pard3 recruitment by CGN-BG contacts, acting as gatekeepers to ML entry. As CGNs eventually transition to glia binding for radial migration, our research demonstrates that establishing permissive JAM-recognition sites on glia via cis and trans interactions of CGN JAM-C serves as a critical temporal checkpoint for sorting at the EGL to ML boundary. This mechanism integrates intrinsic and extrinsic cellular signals, facilitating heterotypic cell sorting into the ML and dictating the precise spatial organization within the cerebellar architecture.

Genomic view of the origins of cell-mediated immunity

NKp30 is an activating natural killer cell receptor (NKR) with a single-exon variable (VJ)-type immunoglobulin superfamily (IgSF) domain. Such VJ-IgSF domains predate the emergence of the antigen receptors (immunoglobulin and T cell receptor), which possess the same domain but undergo gene rearrangement. NCR3, the gene encoding NKp30, is present in jawed vertebrates from sharks to mammals; thus, unlike most NKR that are highly divergent among vertebrate taxa, NKp30 is uniquely conserved. We previously hypothesized that an ancestral NCR3 gene was encoded in the proto-major histocompatibility complex (MHC), the region where many immune-related genes have accumulated. Herein, we searched in silico databases to identify NCR3 paralogues and examined their genomic locations. We found a paralogue, NCR3H, in many vertebrates but was lost in mammals. Additionally, we identified a set of voltage-gated sodium channel beta (SCNB) genes as NCR3-distantly-related genes. Like NCR3, both NCR3H and SCNB proteins contain a single VJ-IgSF domain followed by a transmembrane region. These genes map to MHC paralogous regions, originally described in an invertebrate, along with genes encoding cell adhesion molecules involved in NK cell recognition networks. Other genes having no obvious relationship to immunity also map to these paralogous regions. These gene complexes were traced to several invertebrates, suggesting that the foundation of these cellular networks emerged before the genome-wide duplications in early gnathostome history. Here, we propose that this ancestral region was involved in cell-mediated immunity prior to the emergence of adaptive immunity and that NCR3 piggybacked onto this primordial complex, heralding the emergence of vertebrate NK cell/T cells.

VSIG2 promotes malignant progression of pancreatic ductal adenocarcinoma by enhancing LAMTOR2-mediated mTOR activation

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is one of the most intractable malignancies to overcome clinically due to its insidious onset as well as rapid progression. It is urgent to seek new diagnostic markers and therapeutic targets in order to furthest ameliorate the prognosis of patients with PDAC. V-set and immunoglobulin domain containing 2 (VSIG2) belongs to immunoglobulin superfamily (IgSF), which function as coinhibitory molecule to mediate immune evasion of tumors. Nevertheless, the role of VSIG2 in PDAC and related mechanism still keep unclear.

METHODS

Different expression of VSIG2 in PDAC tissues and cells were detected by bioinformatic analysis, immunohistochemistry, real-time quantitative PCR as well as western blotting. CCK-8, colony formation, Transwell assay, and scratch experiment were utilized to assess proliferation, invasion and migration properties of PDAC cells. The relationship of VSIG2 with late endosomal/lysosomal adaptor, MAPK and MTOR activator 2 (LAMTOR2) and mechanistic target of rapamycin (mTOR) was identified using mass spectrometry, co-immunoprecipitation and immunofluorescence. GO and KEGG enrichment analysis were performed for further pathway verification using western blotting. Additionally, subcutaneous xenograft tumor model and clinical samples analysis were implemented to further elucidate the oncogenic effect of VSIG2 on PDAC in vivo and clinically.

RESULTS

VSIG2 was highly expressed in PDAC tissues and cells. Overexpression of VSIG2 facilitated the proliferation, invasion and migration abilities of PDAC cells, while VSIG2-inhibition exerted opposite effects. Mechanistically, VSIG2 could simultaneously bind to LAMTOR2 and mTOR, thereby enhancing interaction between two molecules, which resulted in elevated phosphorylation-modificatory activation of mTOR and downstream key molecules. Clinically, up-regulation of VSIG2 was positively associated with advanced stage, overall survival and disease-free survival of PDAC patients.

CONCLUSIONS

Our study disclosed that VSIG2 was overexpressed in PDAC, which promoted the proliferation, invasion and metastasis. Mechanically, VSIG2 acted as a scaffold to recruit LAMTOR2 and mTOR simultaneously, stabilize the interaction between them, thus enhancing LAMTOR2-mediated mTOR phosphorylated activation. Collectively, VSIG2 could be exploited as a biomarker for diagnosis and prognosis monitor of PDAC in the future, meanwhile, targeting VSIG2 in PDAC management is expected to be a novel strategy. Video Abstract. Video Abstract.

The amphibian immune system

Amphibians are at the forefront of bridging the evolutionary gap between mammals and more ancient, jawed vertebrates. Currently, several diseases have targeted amphibians and understanding their immune system has importance beyond their use as a research model. The immune system of the African clawed frog, Xenopus laevis, and that of mammals is well conserved. We know that several features of the adaptive and innate immune system are very similar for both, including the existence of B cells, T cells and innate-like T cells. In particular, the study of the immune system at early stages of development is benefitted by studying X. laevis tadpoles. The tadpoles mainly rely on innate immune mechanisms including pre-set or innate-like T cells until after metamorphosis. In this review we lay out what is known about the innate and adaptive immune system of X. laevis including the lymphoid organs as well as how other amphibian immune systems are similar or different. Furthermore, we will describe how the amphibian immune system responds to some viral, bacterial and fungal insults. This article is part of the theme issue 'Amphibian immunity: stress, disease and ecoimmunology'.

The amphibian invitrome: Past, present, and future contributions to our understanding of amphibian immunity

Many amphibian populations are declining worldwide, and infectious diseases are a leading cause. Given the eminent threat infectious diseases pose to amphibian populations, there is a need to understand the host-pathogen-environment interactions that govern amphibian susceptibility to disease and mortality events. However, using animals in research raises an ethical dilemma, which is magnified by the alarming rates at which many amphibian populations are declining. Thus, in vitro study systems such as cell lines represent valuable tools for furthering our understanding of amphibian immune systems. In this review, we curate a list of the amphibian cell lines established to date (the amphibian invitrome), highlight how research using amphibian cell lines has advanced our understanding of the amphibian immune system, anti-ranaviral defence mechanisms, and Batrachochytrium dendrobatidis replication in host cells, and offer our perspective on how future use of amphibian cell lines can advance the field of amphibian immunology.

V-Set and immunoglobulin domain containing (VSIG) proteins as emerging immune checkpoint targets for cancer immunotherapy

The development of immune checkpoint inhibitors is becoming a promising approach to fight cancers. Antibodies targeting immune checkpoint proteins such as CTLA-4 and PD-1 can reinvigorate endogenous antitumor T-cell responses and bring durable advantages to several malignancies. However, only a small subset of patients benefit from these checkpoint inhibitors. Identification of new immune checkpoints with the aim of combination blockade of multiple immune inhibitory pathways is becoming necessary to improve efficiency. Recently, several B7 family-related proteins, TIGIT, VSIG4, and VSIG3, which belong to the VSIG family, have attracted substantial attention as coinhibitory receptors during T-cell activation. By interacting with their corresponding ligands, these VSIG proteins inhibit T-cell responses and maintain an immune suppressive microenvironment in tumors. These results indicated that VSIG family members are becoming putative immune checkpoints in cancer immunotherapy. In this review, we summarized the function of each VSIG protein in regulating immune responses and in tumor progression, thus providing an overview of our current understanding of VSIG family members.

Novel Diagnostic Biomarkers in Colorectal Cancer

Colorectal cancer (CRC) is still a leading cause of cancer death worldwide. Less than half of cases are diagnosed when the cancer is locally advanced. CRC is a heterogenous disease associated with a number of genetic or somatic mutations. Diagnostic markers are used for risk stratification and early detection, which might prolong overall survival. Nowadays, the widespread use of semi-invasive endoscopic methods and feacal blood tests characterised by suboptimal accuracy of diagnostic results has led to the detection of cases at later stages. New molecular noninvasive tests based on the detection of CRC alterations seem to be more sensitive and specific then the current methods. Therefore, research aiming at identifying molecular markers, such as DNA, RNA and proteins, would improve survival rates and contribute to the development of personalized medicine. The identification of “ideal” diagnostic biomarkers, having high sensitivity and specificity, being safe, cheap and easy to measure, remains a challenge. The purpose of this review is to discuss recent advances in novel diagnostic biomarkers for tumor tissue, blood and stool samples in CRC patients.

Identification of DNA methylation-driven genes and construction of a nomogram to predict overall survival in pancreatic cancer

Background

The incidence and mortality of pancreatic cancer (PC) has gradually increased. The aim of this study was to identify survival-related DNA methylation (DNAm)-driven genes and establish a nomogram to predict outcomes in patients with PC.

Methods

The gene expression, DNA methylation database, and PC clinical samples were downloaded from TCGA. DNAm-driven genes were identified by integrating analyses of gene expression and DNA methylation data. Survival-related DNAm-driven genes were screened via univariate, least absolute shrinkage and selection operator (LASSO), and multivariate Cox regression analyses to develop a risk score model for prognosis. Based on analyses of clinical parameters and risk score, a nomogram was built and validated. The independent cohort from GEO database were used for external validation.

Results

A total of 16 differentially expressed methylation-driven genes were identified. Based on LASSO Cox regression and multivariate Cox regression analysis, six genes (FERMT1, LIPH, LAMA3, PPP1R14D, NQO1, VSIG2) were chosen to develop the risk score model. In the Kaplan–Meier analysis, age, T stage, N stage, AJCC stage, radiation therapy history, tumor size, surgery type performed, pathological type, chemotherapy history, and risk score were potential prognostic factors in PC (P < 0.1). In the multivariate analysis, stage, chemotherapy, and risk score were significantly correlated to overall survival (P < 0.05). The nomogram was constructed with the three variables (stage, chemotherapy, and risk score) for predicting the 1-year, 2-year, and 3-year survival rates of PC patients. Nomogram performance was assessed by receiver operating characteristic (ROC) curves and calibration curves. 1-year, 2-year and 3-year AUC of nomogram model was 0.899, 0.765 and 0.776, respectively.

Conclusions

In our study, we successfully identified the six DNAm-driven genes (FERMT1, LIPH, LAMA3, PPP1R14D, NQO1, VSIG2) with a relationship to the outcomes of PC patients. The nomogram including stage, chemotherapy, and risk score could be used to predict survival in PC patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08097-w.

GPA33 is expressed on multiple human blood cell types and distinguishes CD4+ central memory T cells with and without effector function

The Ig superfamily protein glycoprotein A33 (GPA33) has been implicated in immune dysregulation, but little is known about its expression in the immune compartment. Here, we comprehensively determined GPA33 expression patterns on human blood leukocyte subsets, using mass and flow cytometry. We found that GPA33 was expressed on fractions of B, dendritic, natural killer and innate lymphoid cells. Most prominent expression was found in the CD4⁺ T cell compartment. Naïve and CXCR5⁺ regulatory T cells were GPA33^high, and naïve conventional CD4⁺ T cells expressed intermediate GPA33 levels. The expression pattern of GPA33 identified functional heterogeneity within the CD4⁺ central memory T cell (Tcm) population. GPA33⁺ CD4⁺ Tcm cells were fully undifferentiated, bona fide Tcm cells that lack immediate effector function, whereas GPA33^– Tcm cells exhibited rapid effector functions and may represent an early stage of differentiation into effector/effector memory T cells before loss of CD62L. Expression of GPA33 in conventional CD4⁺ T cells suggests a role in localization and/or preservation of an undifferentiated state. These results form a basis to study the function of GPA33 and show it to be a useful marker to discriminate between different cellular subsets, especially in the CD4⁺ T cell lineage.

Functional Interfaces, Biological Pathways, and Regulations of Interferon-Related DNA Damage Resistance Signature (IRDS) Genes

Interferon (IFN)-related DNA damage resistant signature (IRDS) genes are a subgroup of interferon-stimulated genes (ISGs) found upregulated in different cancer types, which promotes resistance to DNA damaging chemotherapy and radiotherapy. Along with briefly discussing IFNs and signalling in this review, we highlighted how different IRDS genes are affected by viruses. On the contrary, different strategies adopted to suppress a set of IRDS genes (STAT1, IRF7, OAS family, and BST2) to induce (chemo- and radiotherapy) sensitivity were deliberated. Significant biological pathways that comprise these genes were classified, along with their frequently associated genes (IFIT1/3, IFITM1, IRF7, ISG15, MX1/2 and OAS1/3/L). Major upstream regulators from the IRDS genes were identified, and different IFN types regulating these genes were outlined. Functional interfaces of IRDS proteins with DNA/RNA/ATP/GTP/NADP biomolecules featured a well-defined pharmacophore model for STAT1/IRF7-dsDNA and OAS1/OAS3/IFIH1-dsRNA complexes, as well as for the genes binding to GDP or NADP+. The Lys amino acid was found commonly interacting with the ATP phosphate group from OAS1/EIF2AK2/IFIH1 genes. Considering the premise that targeting IRDS genes mediated resistance offers an efficient strategy to resensitize tumour cells and enhances the outcome of anti-cancer treatment, this review can add some novel insights to the field.

V-Set and Immunoglobulin Domain-Containing 1 (VSIG1), Predominantly Expressed in Testicular Germ Cells, Is Dispensable for Spermatogenesis and Male Fertility in Mice

To elucidate the functional role of V-set and immunoglobulin domain-containing 1 (VSIG1) in spermatogenesis and fertilization, we knocked out (KO) VSIG1 in a mouse embryo using CRISPR/Cas9 (Clustered regularly interspaced short palindromic repeat/CRISPR-associated protein 9) -mediated genome editing. Reverse transcription PCR was performed using cDNA synthesized from VSIG1 KO testis RNA. Although Western blot analysis using a specific antibody to VSIG1 confirmed VSIG1 protein defects in the KO mice, hematoxylin-eosin staining analysis was similar in the KO and wild-type mice. Additionally, computer-assisted sperm analysis and in vitro fertilization experiments were conducted to confirm the activity and fertilization ability of sperm derived from the KO mouse. Mice lacking VSIG1 were viable and had no serious developmental defects. As they got older, the KO mice showed slightly higher weight loss, male mice lacking VSIG1 had functional testes, including normal sperm number and motility, and both male and female mice lacking VSIG1 were fertile. Our results from VSIG1 KO mice suggest that VSIG1 may not play essential roles in spermatogenesis and normal testis development, function, and maintenance. VSIG1 in sperm is dispensable for spermatogenesis and male fertility in mice. As several genes are known to possess slightly different functions depending on the species, the importance and molecular mechanism of VSIG1 in tissues of other species needs further investigation.

Viruses, cancer and non-self recognition

Virus-host interactions form an essential part of every aspect of life, and this review is aimed at looking at the balance between the host and persistent viruses with a focus on the immune system. The virus-host interaction is like a cat-and-mouse game and viruses have developed ingenious mechanisms to manipulate cellular pathways, most notably the major histocompatibility (MHC) class I pathway, to reside within infected cell while evading detection and destruction by the immune system. However, some of the signals sensing and responding to viral infection are derived from viruses and the fact that certain viruses can prevent the infection of others, highlights a more complex coexistence between the host and the viral microbiota. Viral immune evasion strategies also illustrate that processes whereby cells detect and present non-self genetic material to the immune system are interlinked with other cellular pathways. Immune evasion is a target also for cancer cells and a more detailed look at the interfaces between viral factors and components of the MHC class I peptide-loading complex indicates that these interfaces are also targets for cancer mutations. In terms of the immune checkpoint, however, viral and cancer strategies appear different.

Location of the Cell Adhesion Molecule "Coxsackievirus and Adenovirus Receptor" in the Adult Mouse Brain

The coxsackievirus and adenovirus receptor (CAR) is a single-pass transmembrane cell adhesion molecule (CAM). CAR is expressed in numerous mammalian tissues including the brain, heart, lung, and testes. In epithelial cells, CAR functions are typical of the quintessential roles of numerous CAMs. However, in the brain the multiple roles of CAR are poorly understood. To better understand the physiological role of CAR in the adult brain, characterizing its location is a primordial step to advance our knowledge of its functions. In addition, CAR is responsible for the attachment, internalization, and retrograde transport of canine adenovirus type 2 (CAV-2) vectors, which have found a niche in the mapping of neuronal circuits and gene transfer to treat and model neurodegenerative diseases. In this study, we used immunohistochemistry and immunofluorescence to document the global location of CAR in the healthy, young adult mouse brain. Globally, we found that CAR is expressed by maturing and mature neurons in the brain parenchyma and located on the soma and on projections. While CAR occasionally colocalizes with glial fibrillary acidic protein, this overlap was restricted to areas that are associated with adult neurogenesis.

Virus-Receptor Interactions: Structural Insights For Oncolytic Virus Development

Recent advancements in oncolytic virotherapy commend a special attention to developing new strategies for targeting cancer cells with oncolytic viruses (OVs). Modifications of the viral envelope or coat proteins serve as a logical mean of repurposing viruses for cancer treatment. In this review, we discuss how detailed structural knowledge of the interactions between OVs and their natural receptors provide valuable insights into tumor specificity of some viruses and re-targeting of alternate receptors for broad tumor tropism or improved tumor selectivity.

The Gut Microbiome on a Periodized Low-Protein Diet Is Associated With Improved Metabolic Health

A periodized (14 days on/14 days off) 5% low protein-high carbohydrate (pLPHC) diet protects against weight gain, improves glucose tolerance in mice and interacts with concurrent voluntary activity wheel training on several parameters including weight maintenance and liver FGF21 secretion. The gut microbiome (GM) responds to both diet and exercise and may influence host metabolism. This study compared the cecal GM after a 13.5-week intervention study in mice on a variety of dietary interventions ± concurrent voluntary exercise training in activity wheels. The diets included chronic chow diet, LPHC diet, 40 E% high protein-low carbohydrate (HPLC) diet, an obesigenic chronic high-fat diet (HFD) and the pLPHC diet. Our hypothesis was that the GM changes with pLPHC diet would generally reflect the improved metabolic health of the host and interact with concurrent exercise training. The GM analyses revealed greater abundance phylum Bacteroidetes and the genus Akkermansia on chronic and periodized LPHC and higher abundance of Oscillospira and Oscillibacter on HFD. The differences in diet-induced GM correlated strongly with the differences in a range of host metabolic health-measures. In contrast, no significant effect of concurrent exercise training was observed. In conclusion, pLPHC diet elicits substantial changes in the GM. In contrast, only subtle and non-significant effects of concurrent activity wheel exercise were observed. The pLPHC-associated microbiome may contribute to the healthier host phenotype observed in these mice.

Junctional Adhesion Molecules (JAMs): Cell Adhesion Receptors With Pleiotropic Functions in Cell Physiology and Development

Junctional adhesion molecules (JAM)-A, -B and -C are cell-cell adhesion molecules of the immunoglobulin superfamily which are expressed by a variety of tissues, both during development and in the adult organism. Through their extracellular domains, they interact with other adhesion receptors on opposing cells. Through their cytoplasmic domains, they interact with PDZ domain-containing scaffolding and signaling proteins. In combination, these two properties regulate the assembly of signaling complexes at specific sites of cell-cell adhesion. The multitude of molecular interactions has enabled JAMs to adopt distinct cellular functions such as the regulation of cell-cell contact formation, cell migration, or mitotic spindle orientation. Not surprisingly, JAMs regulate diverse processes such as epithelial and endothelial barrier formation, hemostasis, angiogenesis, hematopoiesis, germ cell development, and the development of the central and peripheral nervous system. This review summarizes the recent progress in the understanding of JAMs, including their characteristic structural features, their molecular interactions, their cellular functions, and their contribution to a multitude of processes during vertebrate development and homeostasis.

Membrane Dynamics and Signaling of the Coxsackievirus and Adenovirus Receptor

The coxsackievirus and adenovirus receptor (CAR) belongs to the immunoglobulin superfamily and acts as a receptor for some adenovirus types and group B coxsackieviruses. Its role is best described in epithelia where CAR participates to tight junction integrity and maintenance. Recently, several studies aimed to characterize its potential interaction with intracellular signaling pathways and highlighted several features linking CAR to gene expression. In addition, the molecular mechanisms leading to CAR-specific membrane targeting via the secretory pathway in polarized cells and its internalization are starting to be unraveled. This chapter discusses the interaction between membrane dynamics, intracellular trafficking, and signaling of CAR.

[Is there a risk of zoonotic disease due to adenoviruses?]

Every year brings another round of zoonotic viral infections. Usually they fall under the radar, but the occasional lethal epidemic brings another scare to the public and new urgency to the medical community. The types of these viruses (DNA vs. RNA genomes, enveloped vs. proteinaceous) as well as the preceding host(s) vary. Over the last 20 years, bats have been identified as an enigmatic carrier for several pathogens that have jumped the species barrier and infected humans. Factors that favour the emergence of zoonotic pathogens include the increasing overlap of the human and animal habitats, cultural activities, and the host reservoir. In this context, we asked whether bat and/or nonhuman primate adenoviruses are a risk for human health.

Glycoprotein A33 deficiency: a new mouse model of impaired intestinal epithelial barrier function and inflammatory disease

The cells of the intestinal epithelium provide a selectively permeable barrier between the external environment and internal tissues. The integrity of this barrier is maintained by tight junctions, specialised cell-cell contacts that permit the absorption of water and nutrients while excluding microbes, toxins and dietary antigens. Impairment of intestinal barrier function contributes to multiple gastrointestinal disorders, including food hypersensitivity, inflammatory bowel disease (IBD) and colitis-associated cancer (CAC). Glycoprotein A33 (GPA33) is an intestinal epithelium-specific cell surface marker and member of the CTX group of transmembrane proteins. Roles in cell-cell adhesion have been demonstrated for multiple CTX family members, suggesting a similar function for GPA33 within the gastrointestinal tract. To test a potential requirement for GPA33 in intestinal barrier function, we generated Gpa33^−/− mice and subjected them to experimental regimens designed to produce food hypersensitivity, colitis and CAC. Gpa33^−/− mice exhibited impaired intestinal barrier function. This was shown by elevated steady-state immunosurveillance in the colonic mucosa and leakiness to oral TRITC-labelled dextran after short-term exposure to dextran sodium sulphate (DSS) to injure the intestinal epithelium. Gpa33^−/− mice also exhibited rapid onset and reduced resolution of DSS-induced colitis, and a striking increase in the number of colitis-associated tumours produced by treatment with the colon-specific mutagen azoxymethane (AOM) followed by two cycles of DSS. In contrast, Gpa33^−/− mice treated with AOM alone showed no increase in sporadic tumour formation, indicating that their increased tumour susceptibility is dependent on inflammatory stimuli. Finally, Gpa33^−/− mice displayed hypersensitivity to food allergens, a common co-morbidity in humans with IBD. We propose that Gpa33^−/− mice provide a valuable model to study the mechanisms linking intestinal permeability and multiple inflammatory pathologies. Moreover, this model could facilitate preclinical studies aimed at identifying drugs that restore barrier function.

Highlighted Article: We show that GPA33, an intestine-specific cell surface protein, plays a role in the maintenance of intestinal barrier function and the prevention of intestinal pathologies such as food hypersensitivity, inflammatory bowel disease and colitis-associated cancer.

Mice depleted of the coxsackievirus and adenovirus receptor display normal spermatogenesis and an intact blood-testis barrier

The coxsackievirus and adenovirus receptor (CXADR (CAR)) is a cell adhesion molecule expressed mainly in epithelial cells. Numerous evidence indicate that CXADR has an important role in testis development and function of the blood-testis barrier (BTB) in vitro. The role of CXADR in testis physiology in vivo has, however, not been addressed. We therefore constructed a conditional CXADR knockout (cKO) mouse model in which CXADR can be depleted at any chosen timepoint by the administration of tamoxifen. We report for the first time that testicular depletion of CXADR in adult and pubertal mice does not alter BTB permeability or germ cell migration across the BTB during spermatogenesis. Adult cKO mice display normal junctional ultra-structure and localization of the junctional proteins claudin-3, occludin, junction-associated molecule-A (JAM-A), and ZO1. The BTB was intact with no leakage of biotin and lanthanum tracers into the tubular lumen. Adult CXADR cKO mice were fertile with normal sperm parameters and litter size. Breeding experiments and genotyping of the pups demonstrated that CXADR-negative sperm could fertilize WT eggs. In addition, knocking down CXADR from postnatal day 9 (P9) does not affect testicular development and BTB formation. These cKO mice were analyzed at P49 and P90 and display an intact barrier and uncompromised fertility. We conclude that CXADR possesses no direct role in testicular physiology in vivo.

Interferon alpha as a primary pathogenic factor in human lupus

Interferon alpha (IFN-α) is a critical mediator of human systemic lupus erythematosus (SLE). This review will summarize evidence supporting the role for IFN-α in the initiation of human SLE. IFN-α functions in viral immunity at the interface of innate and adaptive immunity, a position well suited to setting thresholds for autoimmunity. Some individuals treated with IFN-α for chronic viral infections develop de novo SLE, which frequently resolves when IFN-α is withdrawn, supporting the idea that IFN-α was causal. Abnormally high IFN-α levels are clustered within SLE families, suggesting that high serum IFN-α is a heritable risk factor for SLE. Additionally, SLE-risk genetic variants in the IFN-α pathway are gain of function in nature, resulting in either higher circulating IFN-α levels or greater sensitivity to IFN-α signaling in SLE patients. A recent genome-wide association study has identified additional novel genetic loci associated with high serum IFN-α in SLE patients. These data support the idea that genetically determined endogenous elevations in IFN-α predispose to human SLE. It is possible that some of these gain-of-function polymorphisms in the IFN-α pathway are useful in viral defense, and that risk of SLE is a burden we have taken on in the fight to defend ourselves against viral infection.

Pathobiology of junctional adhesion molecules

Junctional adhesion molecules are transmembrane proteins that belong to the immunoglobulin superfamily. In addition to their localization in close proximity to the tight junctions in endothelial and epithelial cells, junctional adhesion molecules are also expressed in circulating cells that do not form junctions, such as leukocytes and platelets. As a consequence, these proteins are associated not only with the permeability-regulating barrier function of the tight junctions, but also with other biologic processes, such as inflammatory reactions, responses to vascular injury, and tumor angiogenesis. Furthermore, because of their transmembrane topology, junctional adhesion molecules are poised both for receiving inputs from the cell interior (their expression, localization, and function being regulated in response to inflammatory cytokines and growth factors) and for translating extracellular adhesive events into functional responses. This review focuses on the different roles of junctional adhesion molecules in normal and pathologic conditions, with emphasis on inflammatory reactions and vascular responses to injury.

Trait-stratified genome-wide association study identifies novel and diverse genetic associations with serologic and cytokine phenotypes in systemic lupus erythematosus

Introduction

Systemic lupus erythematosus (SLE) is a highly heterogeneous disorder, characterized by differences in autoantibody profile, serum cytokines, and clinical manifestations. SLE-associated autoantibodies and high serum interferon alpha (IFN-α) are important heritable phenotypes in SLE which are correlated with each other, and play a role in disease pathogenesis. These two heritable risk factors are shared between ancestral backgrounds. The aim of the study was to detect genetic factors associated with autoantibody profiles and serum IFN-α in SLE.

Methods

We undertook a case-case genome-wide association study of SLE patients stratified by ancestry and extremes of phenotype in serology and serum IFN-α. Single nucleotide polymorphisms (SNPs) in seven loci were selected for follow-up in a large independent cohort of 538 SLE patients and 522 controls using a multi-step screening approach based on novel metrics and expert database review. The seven loci were: leucine-rich repeat containing 20 (LRRC20); protein phosphatase 1 H (PPM1H); lysophosphatidic acid receptor 1 (LPAR1); ankyrin repeat and sterile alpha motif domain 1A (ANKS1A); protein tyrosine phosphatase, receptor type M (PTPRM); ephrin A5 (EFNA5); and V-set and immunoglobulin domain containing 2 (VSIG2).

Results

SNPs in the LRRC20, PPM1H, LPAR1, ANKS1A, and VSIG2 loci each demonstrated strong association with a particular serologic profile (all odds ratios > 2.2 and P < 3.5 × 10^-4). Each of these serologic profiles was associated with increased serum IFN-α. SNPs in both PTPRM and LRRC20 were associated with increased serum IFN-α independent of serologic profile (P = 2.2 × 10^-6 and P = 2.6 × 10^-3 respectively). None of the SNPs were strongly associated with SLE in case-control analysis, suggesting that the major impact of these variants will be upon subphenotypes in SLE.

Conclusions

This study demonstrates the power of using serologic and cytokine subphenotypes to elucidate genetic factors involved in complex autoimmune disease. The distinct associations observed emphasize the heterogeneity of molecular pathogenesis in SLE, and the need for stratification by subphenotypes in genetic studies. We hypothesize that these genetic variants play a role in disease manifestations and severity in SLE.

Comparative and developmental study of the immune system in Xenopus

Xenopus laevis is the model of choice for evolutionary, comparative, and developmental studies of immunity, and invaluable research tools including MHC-defined clones, inbred strains, cell lines, and monoclonal antibodies are available for these studies. Recent efforts to use Silurana (Xenopus) tropicalis for genetic analyses have led to the sequencing of the whole genome. Ongoing genome mapping and mutagenesis studies will provide a new dimension to the study of immunity. Here we review what is known about the immune system of X. laevis integrated with available genomic information from S. tropicalis. This review provides compelling evidence for the high degree of similarity and evolutionary conservation between Xenopus and mammalian immune systems. We propose to build a powerful and innovative comparative biomedical model based on modern genetic technologies that takes take advantage of X. laevis and S. tropicalis, as well as the whole Xenopus genus. Developmental Dynamics 238:1249-1270, 2009. (c) 2009 Wiley-Liss, Inc.

Activation of the brain-specific neurogranin gene in murine T-cell lymphomas by proviral insertional mutagenesis

Neurogranin (Nrgn) is a highly expressed brain-specific protein, which sequesters calmodulin at low Ca(2+)-levels. We report here on retroviral activation of the Nrgn gene in tumors induced by the T-cell lymphomagenic SL3-3 murine leukemia virus. We have performed a systematic expression analysis of Nrgn in various mouse tissues and SL3-3 induced T-cell tumors. This demonstrated that insertional activation of Nrgn increased RNA and protein expression levels to that observed in brain. Furthermore, elevated Nrgn expression was also observed in some T-cell tumors with no detected provirus integrations into this genomic region. The presented data demonstrate that Nrgn can be produced at high levels outside the brain, and suggest a novel oncogenic role in T-cell lymphomas in mice.

Adenovirus receptors and their implications in gene delivery

Adenoviruses (Ads) have gained popularity as gene delivery vectors for therapeutic and prophylactic applications. Ad entry into host cells involves specific interactions between cell surface receptors and viral capsid proteins. Several cell surface molecules have been identified as receptors for Ad attachment and entry. Tissue tropism of Ad vectors is greatly influenced by their receptor usage. A variety of strategies have been investigated to modify Ad vector tropism by manipulating the receptor-interacting moieties. Many such strategies are aimed at targeting and/or detargeting of Ad vectors. In this review, we discuss the various cell surface molecules that are implicated as receptors for virus attachment and internalization. Special emphasis is given to Ad types that are utilized as gene delivery vectors. Various strategies to modify Ad tropism using the knowledge of Ad receptors are also discussed.

A33 antigen displays persistent surface expression

The A33 antigen is a cell surface glycoprotein of the small intestine and colonic epithelium with homology to tight junction-associated proteins of the immunoglobulin superfamily, including CAR and JAM. Its restricted tissue localization and high level of expression have led to its use as a target in colon cancer immunotherapy. Although the antigen is also present in normal intestine, radiolabeled antibodies against A33 are selectively retained by tumors in the gut as well as in metastatic lesions for as long as 6 weeks. Accordingly, we have studied the trafficking and kinetic properties of the antigen to determine its promise in two-step, pretargeted therapies. The localization, mobility, and persistence of the antigen were investigated, and this work has demonstrated that the antigen is both highly immobile and extremely persistent-retaining its surface localization for a turnover halflife of greater than 2 days. In order to explain these unusual properties, we explored the possibility that A33 is a component of the tight junction. The simple property of surface persistence, described here, may contribute to the prolonged retention of the clinically administered antibodies, and their uncommon ability to penetrate solid tumors.

DICAM, a novel dual immunoglobulin domain containing cell adhesion molecule interacts with alphavbeta3 integrin

Immunoglobulin (Ig) superfamily members are abundant with diverse functions including cell adhesion in various tissues. Here, we identified and characterized a novel adhesion molecule that belongs to the CTX protein family and named as DICAM (Dual Ig domain containing cell adhesion molecule). DICAM is a type I transmembrane protein with two V-type Ig domains in the extracellular region and a short cytoplasmic tail of 442 amino acids. DICAM is found to be expressed ubiquitously in various organs and cell lines. Subcellular localization of DICAM was observed in the cell-cell contact region and nucleus of cultured epithelial cells. Cell-cell contact region was colocalized with tight junction protein, ZO-1. The DICAM increased MDCK cell adhesion to 60% levels of fibronectin. DICAM mediated cell adhesion was specific for the alphavbeta3 integrin; other integrins, alpha2, alpha5, beta1, alpha2beta1, alpha5beta1, were not involved in cell adhesion. In identifying the interacting domain of DICAM with alphavbeta3, the Ig domain 2 showed higher cell adhesion activity than that of Ig domain 1. Although RGD motif in Ig domain 2 was engaged in cell adhesion, it was not participated in DICAM-alphavbeta3 mediated cell adhesion. Furthermore, differentially expressing DICAM stable cells showed well correlated cell to cell adhesion capability with integrin beta3-overexpressing cells. Collectively, these results indicate that DICAM, a novel dual Ig domain containing adhesion molecule, mediates cell adhesion via alphavbeta3 integrin.

B cell receptor accessory molecules in the channel catfish, Ictalurus punctatus

B cell receptor (BCR) accessory molecules CD79a and CD79b homologs were identified in the channel catfish, Ictalurus punctatus. Both are found as single copy genes that encode proteins containing a signal peptide, an extracellular immunoglobulin domain, a transmembrane region and a cytoplasmic tail containing an immune-receptor tyrosine-dased activation motif (ITAM). IpCD79a and IpCD79b transcripts correlate well with IgM message expression. They are highly expressed in peripheral blood leukocytes (PBL) enriched in membrane (m) IgM+ cells and catfish clonal B cell lines, but not in catfish clonal T cells, indicating that IpCD79a and IpCD79b expression is B cell restricted. Studies using catfish clonal B cells (3B11) transfected with constructs encoding epitope-tagged IpCD79a and IpCD79b revealed that IpCD79a was expressed as a 45 kDa protein and IpCD79b was expressed as a 32 kDa protein. Furthermore, co-immunoprecipitations of epitope-tagged CD79 proteins demonstrate that these molecules are non-covalently associated with mIgM. These data correlate with some of the previous immunoprecipitation data demonstrating that catfish mIgM associates with proteins of 45 and 32 kDa.

Reovirus preferentially infects the basolateral surface and is released from the apical surface of polarized human respiratory epithelial cells

Mammalian reoviruses infect respiratory and gastrointestinal epithelia and cause disease in neonates. Junctional adhesion molecule-A (JAM-A) is a serotype-independent receptor for reovirus. JAM-A localizes to tight junctions and contributes to paracellular permeability in polarized epithelia. To investigate the mechanisms of reovirus infection of polarized epithelial cells, we assessed reovirus replication, release, and spread after apical and basolateral adsorption to primary human airway epithelial cultures. Reovirus infection of human airway epithelia was more efficient after adsorption to the basolateral surface than after adsorption to the apical surface, and it was dependent on JAM-A. Reovirus binding to carbohydrate coreceptor sialic acid inhibited apical infection, which was partially ameliorated by treatment of the cultures with neuraminidase. Despite the preference for basolateral infection, reovirus was released from the apical surface of respiratory epithelia and did not disrupt tight junctions. These results establish the existence of an infectious circuit for reovirus in polarized human respiratory epithelial cells.

Coxsackievirus and adenovirus receptor is up-regulated in migratory germ cells during passage of the blood-testis barrier

The coxsackievirus and adenovirus receptor (CAR) is a cell adhesion molecule expressed in epithelial tight junctions and other cell-cell contacts. Using indirect immunofluorescence, quantitative RT-PCR, and Western blots, the expression and distribution of CAR in developing and adult testis are examined. CAR is highly expressed in both Sertoli and germ cells during perinatal and postnatal development, followed by a rapid down-regulation of both mRNA and protein levels. Interestingly, we find that CAR is a previously unknown downstream target for FSH because CAR mRNA levels were induced in primary cultures of FSH-stimulated Sertoli cells. In contrast to other epithelia, CAR is not a general component of tight junctions in the seminiferous epithelium, and Sertoli cells in the adult testis do not express CAR. Instead, CAR expression is stage dependent and specifically found in migratory germ cells. RT-PCR also demonstrated the presence of junctional adhesion molecule-like (JAML) in the testis. JAML was previously reported by others to form a functional complex with CAR regulating transepithelial migration of leukocytes. The expression of JAML in the testis suggests that a similar functional complex might be present during germ cell migration across the blood-testis barrier. Finally, an intermediate compartment occupied by CAR-positive, migrating germ cells and flanked by two occludin-containing junctions is identified. Together, these results implicate a function for CAR in testis morphogenesis and in migration of germ cells across the blood-testis barrier during spermatogenesis.

A seamless trespass: germ cell migration across the seminiferous epithelium during spermatogenesis

During spermatogenesis, preleptotene spermatocytes traverse the blood–testis barrier (BTB) in the seminiferous epithelium, which is reminiscent of viral pathogens breaking through the tight junctions of host epithelial cells. The process also closely resembles the migration of leukocytes across endothelial tight junctions to reach inflammation sites. Cell adhesion molecules of the immunoglobulin superfamily (e.g., JAM/CAR/nectin) participate in germ cell migration by conferring transient adhesion between Sertoli and germ cells through homophilic and heterophilic interactions. The same molecules also comprise the junctional complexes at the BTB. Interestingly, JAM/CAR/nectin molecules mediate virus uptake and leukocyte transmigration in strikingly similar manners. It is likely that the strategy used by viruses and leukocytes to break through junctional barriers is used by germ cells to open up the inter–Sertoli cell junctions. In associating these diverse cellular events, we highlight the “guiding” role of JAM/CAR/nectin molecules for germ cell passage. Knowledge on viral invasion and leukocyte transmigration has also shed insights into germ cell movement during spermatogenesis.

Junctional Adhesion Molecule-C Promotes Metastatic Potential of HT1080 Human Fibrosarcoma

The junctional adhesion molecule (JAM) family is a key molecule in a process called transendothelial migration or diapedesis. Here, we report implications of JAM-C in cancer metastasis. We first determined the mRNA expression of JAMs in 19 kinds of cancer cell lines. JAM-C was expressed in most of tumors having potent metastatic properties. Especially in murine K-1735 melanoma cell lines, the highly metastatic sublines (M2 and X21) strongly expressed JAM-C when compared with the poorly metastatic ones (C-10 and C23). Next, we investigated the role of JAM-C in cancer metastasis by using human JAM-C (hJAM-C) gene-transfected HT1080 fibrosarcoma cells. In comparison with mock-transfected HT1080 cells, these cells showed a significant increase in the adhesion to various extracellular substrates and the invasion across a Matrigel-coated membrane. The knockdown of hJAM-C using small interfering RNA resulted in the suppression of both the adhesion and the invasion of HT1080 cells, suggesting that endogenous hJAM-C might be involved in tumor metastasis. Finally, we studied the role of hJAM-C in an in vivo experimental metastatic model. The results showed that the overexpression of hJAM-C in HT1080 cells significantly decreased the life spans of the tumorbearing mice. In contrast, the knockdown of hJAM-C in HT1080 cells suppressed the weight gain of the lungs with metastatic colonies. We conclude that the expression of JAM-C promotes metastasis by enhancing both the adhesion of cancer cells to extracellular matrices and the subsequent invasion.

The Coxsackie and Adenovirus Receptor Binds Microtubules and Plays a Role in Cell Migration

The Coxsackie and adenovirus receptor (CAR), a cell adhesion molecule of the immunoglobulin superfamily, inhibits cell growth of a variety of tumors. The cytoplasmic domain of CAR has been implicated in decreased invasion and intracerebral growth of human U87 glioma cells. Using affinity binding, we identified tubulin as an interaction partner for the cytoplasmic domain of CAR. The interaction was specific; CAR and tubulin co-immunoprecipitated in cells expressing endogenous CAR and partially co-localized in situ. The binding of CAR to tubulin heterodimers and to microtubules was direct, with dissociation constants of approximately 1 mum for tubulin and approximately 32 nm for in vitro assembled microtubules. Whereas CAR-expressing U87 glioma cells had decreased migration in a chemotactic assay in Boyden chambers as compared with control cells, an effect that depended on the presence of the cytoplasmic domain of CAR, the difference was abrogated at low, non-cytotoxic doses of the taxane paclitaxel, a microtubule-stabilizing agent. These results indicate that CAR may affect cell migration through its interaction with microtubules.

The coxsackie- and adenovirus receptor (CAR) is an in vivo marker for epithelial tight junctions, with a potential role in regulating permeability and tissue homeostasis

The coxsackie- and adenovirus receptor (CAR) is a transmembrane protein belonging to the immunoglobulin superfamily. The function of CAR as a virus receptor has been extensively analyzed, while its physiological role and expression pattern in adult tissues have remained less clear. CAR associates with epithelial tight junctions in vitro and mediates cell-cell adhesion. Using a set of affinity-purified antibodies, we show that CAR is predominantly expressed in epithelial cells lining the body cavities in adult mice, where it specifically co-localizes with the tight junction components ZO-1 and occludin. Notably, CAR could not be detected in endothelial cells of the vasculature, including brain capillaries. CAR expression correlated positively with the maturity of tight junctions and inversely with permeability. With a few exceptions, the two known CAR isoforms were co-expressed in most epithelial cells analyzed. A CAR mutant lacking the intracellular tail over-expressed in transgenic mice was diffusely localized over the plasma membrane, showing the importance of this domain for correct subcellular localization in vivo. We conclude that CAR is localized to epithelial tight junctions in vivo where it may play a role in the regulation of epithelial permeability and tissue homeostasis.

Coxsackievirus and adenovirus receptor (CAR) is expressed in male germ cells and forms a complex with the differentiation factor JAM-C in mouse testis

The coxsackievirus and adenovirus receptor (CAR) is a transmembrane protein important for viral binding to target cells. Using RT-PCR, Western analysis, GST pull-down assay and indirect immunofluorescence, it was shown that CAR is expressed in male germ cells from mice, rats, and humans. CAR was detected in round spermatids in the testis as well as in purified, mature spermatozoa. The two membrane-bound isoforms of CAR occupied different subcellular sites in the acrosomal region of the spermatozoa. CAR was exposed on the surface of acrosome-reacted, but not acrosome-intact cells. Two CAR-binding proteins belonging to the ligand-of-numb protein-X (LNX) family also occupied distinct regions in spermatozoa. Finally, co-immunoprecipitation experiments demonstrated an interaction between CAR and JAM-C, a protein required for spermatid differentiation. Together, these findings imply a function for CAR in male fertility. The results also suggest that CAR in spermatozoa is inaccessible to adenovirus-based gene therapy vectors, and that the risk of germ line infection therefore is low.

Variable domains in hagfish: NICIR is a polymorphic multigene family expressed preferentially in leukocytes and is related to lamprey TCR-like

The jawless vertebrates, represented by hagfish and lampreys, are the most advanced animals that apparently lack T cell and B cell receptors. As such, they offer unique opportunities for understanding the evolution of antigen receptors and variable (V)-type immunoglobulin (Ig)-like domains. In the present study, we describe four hagfish Ig superfamily (IgSF) members carrying V-type domains. None of them appeared to have direct counterparts in jawed vertebrates, indicating that many IgSF molecules have either evolved independently in jawed and jawless vertebrates or diverged to the extent that clear homology is no longer recognizable. One of the members encoded a molecule closely related to the previously described membrane protein designated novel ITAM (immunoreceptor tyrosine-based activation motif)-containing IgSF receptors (NICIR). We show here that NICIR is a polymorphic multigene family with at least three members and is expressed predominantly in peripheral blood leukocytes. Phylogenetic analysis indicates that among known proteins, NICIR is most closely related to the lamprey molecule recently proposed to be a potential ancestor of T cell receptors.

Cell type- and region- dependent coxsackie adenovirus receptor expression in the central nervous system

Model systems have shown that adenoviral vector mediated transient gene expression can potentially be applied for the treatment of brain tumours, neurodegenerative diseases and brain injuries. Most studies utilized adenovirus serotype 5 (Ad5) based vectors, which as adhesion molecules require the coxsackie adenovirus receptor (CAR) as a critical determinant for cellular infection. In this report, we have systematically characterized CAR expression in the adult human central nervous system (CNS) by using immunohistochemistry. A total of 85 specimens from various CNS regions were investigated for CAR expression in a cell type-dependent context. The most marked staining positivity was found in the choroid plexus and the pituitary gland. The neocortex had scattered positive neurons, while the white matter was mainly negative. We need to consider the possible adverse effects and the possible damage caused by adenoviral gene therapy if the virus-vector also binds to normal brain cells.

Identification of adipocyte adhesion molecule (ACAM), a novel CTX gene family, implicated in adipocyte maturation and development of obesity

Few cell adhesion molecules have been reported to be expressed in mature adipocytes, and the significance of cell adhesion process in adipocyte biology is also unknown. In the present study, we identified ACAM (adipocyte adhesion molecule), a novel homologue of the CTX (cortical thymocyte marker in Xenopus) gene family. ACAM cDNA was isolated during PCR-based cDNA subtraction, and its mRNA was shown to be up-regulated in WATs (white adipose tissues) of OLETF (Otsuka Long-Evans Tokushima fatty) rats, an animal model for Type II diabetes and obesity. ACAM, 372 amino acids in total, has a signal peptide, V-type (variable) and C2-type (constant) Ig domains, a single transmembrane segment and a cytoplasmic tail. The amino acid sequence in rat is highly homologous to mouse (94%) and human (87%). ACAM mRNA was predominantly expressed in WATs in OLETF rats, and increased with the development of obesity until 30 weeks of age, which is when the peak of body mass is reached. Western blot analysis revealed that ACAM protein, approx. 45 kDa, was associated with plasma membrane fractions of mature adipocytes isolated from mesenteric and subdermal adipose deposits of OLETF rats. Up-regulation of ACAM mRNAs in obesity was also shown in WATs of genetically obese db/db mice, diet-induced obese ICR mice and human obese subjects. In primary cultured mouse and human adipocytes, ACAM mRNA expression was progressively up-regulated during differentiation. Several stably transfected Chinese-hamster ovary K1 cell lines were established, and the quantification of ACAM mRNA and cell aggregation assay revealed that the degree of homophilic aggregation correlated well with ACAM mRNA expression. In summary, ACAM may be the critical adhesion molecule in adipocyte differentiation and development of obesity.

Inhibition of coxsackie B virus infection by soluble forms of its receptors: binding affinities, altered particle formation, and competition with cellular receptors

We previously reported that soluble decay-accelerating factor (DAF) and coxsackievirus-adenovirus receptor (CAR) blocked coxsackievirus B3 (CVB3) myocarditis in mice, but only soluble CAR blocked CVB3-mediated pancreatitis. Here, we report that the in vitro mechanisms of viral inhibition by these soluble receptors also differ. Soluble DAF inhibited virus infection through the formation of reversible complexes with CVB3, while binding of soluble CAR to CVB induced the formation of altered (A) particles with a resultant irreversible loss of infectivity. A-particle formation was characterized by loss of VP4 from the virions and required incubation of CVB3-CAR complexes at 37 degrees C. Dimeric soluble DAF (DAF-Fc) was found to be 125-fold-more effective at inhibiting CVB3 than monomeric DAF, which corresponded to a 100-fold increase in binding affinity as determined by surface plasmon resonance analysis. Soluble CAR and soluble dimeric CAR (CAR-Fc) bound to CVB3 with 5,000- and 10,000-fold-higher affinities than the equivalent forms of DAF. While DAF-Fc was 125-fold-more effective at inhibiting virus than monomeric DAF, complement regulation by DAF-Fc was decreased 4 fold. Therefore, while the virus binding was a cooperative event, complement regulation was hindered by the molecular orientation of DAF-Fc, indicating that the regions responsible for complement regulation and virus binding do not completely overlap. Relative contributions of CVB binding affinity, receptor binding footprint on the virus capsid, and induction of capsid conformation alterations for the ability of cellular DAF and CAR to act as receptors are discussed.

Molecular and cellular insights into the coxsackie-adenovirus receptor: role in cellular interactions in the stem cell niche

In recent years, progress has been made in characterizing the molecular and cellular elements that are responsible for the regeneration in the damaged brain and highlighting the key role of the stromal-vascular 'environment' to orchestrate secondary neurogenesis and repair. Indeed, the ability of the stem cells to self-renew and differentiate is tightly regulated by stromal ependymal cells and endothelial cells expressing molecular cues that constitute the extracellular stem cell 'niche'. Several soluble growth factors such as EGF, TGFbeta, FGF2, SDF-1alpha and Noggin are important signals for the stem cell niche but little is known about the role of membrane-bound molecules in intercellular communications between the niche and the stem cells. In this mini-review, we highlight the emerging role of a family of adhesion molecules in the control of secondary neurogenesis. The coxsackie-adenovirus receptor (CAR) is a 46 kDa transmembrane protein and a member of the immunoglobulin super family. It is close structurally and evolutionary to other adhesion molecules involved in cell-cell interactions during embryogenesis, broadly expressed in the developing central nervous system but restricted to ependymal cells in the adult brain. This unique location and its newly established signalling properties further support the role of CAR in intercellular communications. Elucidating the other signalling molecules and manipulating the stromal-vascular niche for example by adenovirus gene therapy remain important goals for future clinical applications.

Susceptibility of B lymphocytes to adenovirus type 5 infection is dependent upon both coxsackie–adenovirus receptor and αvβ5 integrin expression

Human lymphocytes are resistant to genetic modification, particularly from recombinant adenoviruses, thus hampering the analysis of gene function using adenoviral vectors. This study engineered an Epstein–Barr virus-transformed B-lymphoblastoid cell line permissive to adenovirus infection and elucidated key roles for both the coxsackie–adenovirus receptor and αvβ5 integrin in mediating entry of adenoviruses into these cells. The work identified a strategy for engineering B cells to become susceptible to adenovirus infection and showed that such a strategy could be useful for the introduction of genes to alter lymphoblastoid-cell gene expression.

Genes "waiting" for recruitment by the adaptive immune system: the insights from amphioxus

In seeking evidence of the existence of adaptive immune system (AIS) in ancient chordate, cDNA clones of six libraries from a protochordate, the Chinese amphioxus, were sequenced. Although the key molecules such as TCR, MHC, Ig, and RAG in AIS have not been identified from our database, we demonstrated in this study the extensive molecular evidence for the presence of genes homologous to many genes that are involved in AIS directly or indirectly, including some of which may represent the putative precursors of vertebrate AIS-related genes. The comparative analyses of these genes in different model organisms revealed the different fates of these genes during evolution. Their gene expression pattern suggested that the primitive digestive system is the pivotal place of the origin and evolution of the AIS. Our studies support the general statement that AIS appears after the jawless/jawed vertebrate split. However our study further reveals the fact that AIS is in its twilight in amphioxus and the evolution of the molecules in amphioxus are waiting for recruitment by the emergence of AIS.

Protein aggregation during overexpression limited by peptide extensions with large net negative charge

Folding of the human coxsackie and adenovirus receptor immunoglobulin (Ig) variable-type domain (CAR D1) during overexpression in the Escherichia coli cytoplasm was shown previously to be partially rescued by fusion to a 22-residue C-terminal peptide. Here, peptide sequence features required for solubilization and folding of CAR D1 and similar Ig variable-type domains from two other human membrane proteins were investigated. Peptide extensions with net negative charge > -6 fully solubilized CAR D1, and approximately half of the peptide-solubilized protein was correctly folded. The Ig variable-type domains from human A33 antigen and myelin P-zero proteins were only partially solubilized by peptide extensions with net charge of -12, however, and only the solubilized P-zero domain appeared to fold correctly whereas the A33 domain formed soluble microaggregates of misfolded protein. Our results suggest a model where the large net charge of peptide extensions increases electrostatic repulsion between nascent polypeptides. The resulting decrease in aggregation rate can enable some polypeptides to fold spontaneously into their native protein conformations. Analysis of the solubility and folding status of sets of structurally homologous proteins, such as the Ig variable-type domains described here, during overexpression could provide insights into how amino acid and gene sequences influence the efficiency of spontaneous protein folding.

IMGT unique numbering for immunoglobulin and T cell receptor constant domains and Ig superfamily C-like domains

IMGT, the international ImMunoGeneTics information system (http://imgt.cines.fr) provides a common access to expertly annotated data on the genome, proteome, genetics and structure of immunoglobulins (IG), T cell receptors (TR), major histocompatibility complex (MHC), and related proteins of the immune system (RPI) of human and other vertebrates. The NUMEROTATION concept of IMGT-ONTOLOGY has allowed to define a unique numbering for the variable domains (V-DOMAINs) and for the V-LIKE-DOMAINs. In this paper, this standardized characterization is extended to the constant domains (C-DOMAINs), and to the C-LIKE-DOMAINs, leading, for the first time, to their standardized description of mutations, allelic polymorphisms, two-dimensional (2D) representations and tridimensional (3D) structures. The IMGT unique numbering is, therefore, highly valuable for the comparative, structural or evolutionary studies of the immunoglobulin superfamily (IgSF) domains, V-DOMAINs and C-DOMAINs of IG and TR in vertebrates, and V-LIKE-DOMAINs and C-LIKE-DOMAINs of proteins other than IG and TR, in any species.