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 potential of a combination of pungent spices as a novel supplement in gilthead seabream (Sparus aurata) diets to aid in the strategic use of fish oil in aquafeeds: a holistic perspective

This work studied the potential of a combination of pungent spices (capsicum, black pepper, ginger, and cinnamaldehyde) to be used as a supplement in diets of gilthead seabream (Sparus aurata; 44.1 ± 4.2 g). During 90 days, fish were fed three experimental diets with low inclusion of fish oil and containing poultry fat as the main source of lipids, supplemented with graded levels of the tested supplement: 0 (control), 0.1 (SPICY0.1%), and 0.15% (SPICY0.15%). As a result, the pungent spices enhanced the growth performance, the activity of the bile-salt-activated lipase in the intestine, and decreased fat deposit levels within enterocytes. The SPICY0.1% diet reduced the feed conversion ratio and the perivisceral fat index and lipid deposits in the liver. Moreover, the ratio of docosahexaenoic acid/eicosapentaenoic acid in fillet increased in fish fed the SPICY0.1% diet, while the hepatic levels of docosahexaenoic acid and total n-3 polyunsaturated fatty acids increased in fish fed the SPICY0.15% diet. Furthermore, there was an effect on the expression of some biomarkers related to lipid metabolism in 2-h postprandial fish (fasn, elovl6, scd1b, cyp7a1, lpl, and pparβ), and in 48 h fasted-fish fed with the SPICY0.1% diet, a regulation of the intestinal immune response was indicated. However, no significant differences were found in lipid apparent digestibility and proximate macronutrient composition. The spices did not affect biomarkers of hepatic or oxidative stress. No differences in microbial diversity were found, except for an increase in Simpson's Index in the posterior intestine of fish fed the SPICY0.1% diet, reflected in the increased relative abundance of the phylum Chloroflexi and lower relative abundances of the genera Campylobacter, Corynebacterium, and Peptoniphilus. In conclusion, the supplementation of gilthead seabream diets with pungent spices at an inclusion of 0.1% was beneficial to enhance growth performance and feed utilization; reduce fat accumulation in the visceral cavity, liver, and intestine; and improve the fish health status and condition. Results suggest that the tested supplement can be used as part of a nutritional strategy to promote a more judicious use of fish oil in fish diets due to its decreasing availability and rising costs.

ZO-1 expression in normal human macula densa: Immunohistochemical and immunofluorescence investigations

The macula densa (MD) is an anatomical structure having a plaque shape, placed in the distal end of thick ascending limb of each nephron and belonging to juxtaglomerular apparatus (JGA). The aim of the present investigation is to investigate the presence of ZO-1, a specific marker of tight juncions (TJs), in MD cells. Six samples of normal human renal tissue were embedded in paraffin for ZO-1 expression analysis by immunohistochemical and immunofluorescence techniques. We detected ZO-1 expression in the apical part of cell membrane in MD cells by immunohistochemistry. In addition, ZO-1 and nNOS expressions (a specific marker of MD) were colocalized in MD cells providing clear evidence of TJs presence in normal human MD. Since ZO-1 is responsible for diffusion barrier formation, its presence in the MD supports the existence of a tubulomesangial barrier that ensures a regulated exchange between MD and JGA effectors in renal and glomerular haemodynamic homeostasis.

Exosomes mediate Coxsackievirus B3 transmission and expand the viral tropism

Specific virus-receptor interactions are important determinants in viral host range, tropism and pathogenesis, influencing the location and initiation of primary infection as well as viral spread to other target organs/tissues in the postviremic phase. Coxsackieviruses of Group B (CVB) and its six serotypes (CVB1-6) specifically interact with two receptor proteins, coxsackievirus-adenovirus receptor (CAR) and decay-accelerating factor (DAF), and cause various lesions in most permissive tissues. However, our previous data and other studies revealed that virus receptor-negative cells or tissues can be infected with CVB type 3 (CVB3), which can also effectively replicate. To study this interesting finding, we explored the possibility that exosomes are involved in CVB3 tropism and that exosomes functionally enhance CVB3 transmission. We found that exosomes carried and delivered CVB3 virions, resulting in efficient infection in receptor-negative host cells. We also found that delivery of CVB3 virions attached to exosomes depended on the virus receptor CAR. Importantly, exosomes carrying CVB3 virions exhibited greater infection efficiency than free virions because they accessed various entry routes, overcoming restrictions to viral tropism. In vivo experiments demonstrated that inhibition of exosome coupling with virions attenuated CVB3-induced immunological system dysfunction and reduced mortality. Our study describes a new mechanism in which exosomes contribute to viral tropism, spread, and pathogenesis.

CXADR: From an Essential Structural Component to a Vital Signaling Mediator in Spermatogenesis

Canonical coxsackievirus and adenovirus receptor (CXADR) is a transmembrane component of cell junctions that is crucial for cardiac and testicular functions via its homophilic and heterophilic interaction. CXADR is expressed in both Sertoli cells and germ cells and is localized mainly at the interface between Sertoli-Sertoli cells and Sertoli-germ cells. Knockout of CXADR in mouse Sertoli cells specifically impairs male reproductive functions, including a compromised blood-testis barrier, apoptosis of germ cells, and premature loss of spermatids. Apart from serving as an important component for cell junctions, recent progress has showed the potential roles of CXADR as a signaling mediator in spermatogenesis. This review summarizes current research progress related to the regulation and role of CXADR in spermatogenesis as well as in pathological conditions. We hope this review provides some future directions and a blueprint to promote the further study on the roles of CXADR.

Modulation of gut microbiota and intestinal immune response in gilthead seabream (Sparus aurata) by dietary bile salt supplementation

Given their role in lipid digestion, feed supplementation with bile salts could be an economic and sustainable solution to alterations in adiposity and intestinal inflammation generated by some strategies currently used in aquaculture. An important part of the metabolism of bile salts takes place in the intestine, where the microbiota transforms them into more toxic forms. Consequently, we aimed to evaluate the gut immune response and microbial populations in gilthead seabream (Sparus aurata) fed a diet supplemented with a blend of bile salts with proven background as a regulator of lipid metabolism and fat content. After the 90-day feeding trial, a differential modulation of the microbiota between the anterior and posterior intestine was observed. While in the anterior intestine the relative abundance of Desulfobacterota doubled, in the posterior intestine, the levels of Firmicutes increased and Proteobacteria, Actinobacteriota, and Campylobacterota were reduced when supplementing the diet with bile salts. Even so, only in the anterior intestine, there was a decrease in estimated richness (Chao1 and ACE indices) in presence of dietary bile salts. No significant differences were displayed in alpha (Shannon and Simpson indices) nor beta-diversity, showing that bile sales did not have a great impact on the intestinal microbiota. Regarding the gene expression profile in 2 h postprandial-fish, several changes were observed in the analyzed biomarkers of epithelial integrity, nutrient transport, mucus production, interleukins, cell markers, immunoglobulin production and pathogen recognition receptors. These results may indicate the development of an intestinal immune-protective status to tackle future threats. This work also suggests that this immune response is not only regulated by the presence of the dietary bile salts in the intestine, but also by the microbial populations that are in turn modulated by bile salts. After a fasting period of 2 days, the overall gene expression profile was stabilized with respect to fish fed the unsupplemented diet, indicating that the effect of bile salts was transient after short periods of fasting. On the balance, bile salts can be used as a dietary supplement to enhance S. aurata farming and production without compromising their intestinal health.

The IgCAM CAR Regulates Gap Junction-Mediated Coupling on Embryonic Cardiomyocytes and Affects Their Beating Frequency

The IgCAM coxsackie-adenovirus receptor (CAR) is essential for embryonic heart development and electrical conduction in the mature heart. However, it is not well-understood how CAR exerts these effects at the cellular level. To address this question, we analyzed the spontaneous beating of cultured embryonic hearts and cardiomyocytes from wild type and CAR knockout (KO) embryos. Surprisingly, in the absence of the CAR, cultured cardiomyocytes showed increased frequencies of beating and calcium cycling. Increased beatings of heart organ cultures were also induced by the application of reagents that bind to the extracellular region of the CAR, such as the adenovirus fiber knob. However, the calcium cycling machinery, including calcium extrusion via SERCA2 and NCX, was not disrupted in CAR KO cells. In contrast, CAR KO cardiomyocytes displayed size increases but decreased in the total numbers of membrane-localized Cx43 clusters. This was accompanied by improved cell-cell coupling between CAR KO cells, as demonstrated by increased intercellular dye diffusion. Our data indicate that the CAR may modulate the localization and oligomerization of Cx43 at the plasma membrane, which could in turn influence electrical propagation between cardiomyocytes via gap junctions.

Characterization of junctional structures in the gingival epithelium as barriers against bacterial invasion

BACKGROUND AND OBJECTIVE

Adherens junctions (AJs) and tight junctions (TJs) are known to play a crucial role in maintaining the physical barrier function of the epithelium. Here, we aimed to characterize the distribution of AJs and TJs throughout the gingival epithelium and to obtain insights into the physiological importance of these junctional structures.

METHODS

Sections of mouse gingival tissue were examined using transmission electron microscopy (TEM) and bio-high voltage electron microscopy tomography. The gingival sections were stained for E-cadherin and JAM-A as markers of AJs and TJs, respectively, and examined using confocal microscopy and lattice structured illumination microscopy. Bacteria within the gingival epithelium were examined using in situ hybridization.

RESULTS

Junctional structures, including desmosomes, AJs, and TJs, were observed throughout the gingival epithelium. The expression levels of E-cadherin were particularly low in the granular/keratinized layers of the oral epithelium (OE), while extremely low JAM-A levels were detected in the granular/keratinized layers of the sulcular epithelium (SE). The three-dimensional rendering of the junctional structures revealed that both AJs and TJs in the gingival epithelium formed discontinuous short bands or patches. Interestingly, strong bacterial signals were observed at the granular/keratinized layers of both SE and OE, but a few bacteria were detected within the junctional epithelium (JE) and the basal/spinous layers of the SE and OE.

CONCLUSIONS

AJs and TJs form a discontinuous barrier throughout paracellular passage in the gingival epithelium; nevertheless, they seem to play an important role in defending against invading bacteria.

The Revolving Door of Adenovirus Cell Entry: Not All Pathways Are Equal

Adenoviruses represent exceptional candidates for wide-ranging therapeutic applications, from vectors for gene therapy to oncolytics for cancer treatments. The first ever commercial gene therapy medicine was based on a recombinant adenovirus vector, while most recently, adenoviral vectors have proven critical as vaccine platforms in effectively controlling the global coronavirus pandemic. Here, we discuss factors involved in adenovirus cell binding, entry, and trafficking; how they influence efficiency of adenovirus-based vectors; and how they can be manipulated to enhance efficacy of genetically modified adenoviral variants. We focus particularly on endocytosis and how different adenovirus serotypes employ different endocytic pathways to gain cell entry, and thus, have different intracellular trafficking pathways that subsequently trigger different host antiviral responses. In the context of gene therapy, the final goal of the adenovirus vector is to efficiently deliver therapeutic transgenes into the target cell nucleus, thus allowing its functional expression. Aberrant or inefficient endocytosis can impede this goal, therefore, it should be considered when designing and constructing adenovirus-based vectors.

Coxsackievirus and Adenovirus Receptor (CXADR): Recent Findings and Its Role and Regulation in Spermatogenesis

Coxsackievirus and adenovirus receptor (CXADR) belongs to immunoglobulin superfamily of cell adhesion molecules. It expresses in most tissues, but displays unique and indispensable functions in some tissues such as heart and testis. CXADR is a multifunctional protein that can serve as a viral receptor, a junction structural protein and a signalling molecule. Thus, it exerts a wide range of functions such as facilitating leukocyte transmigration, regulating barrier function and cell adhesion, promoting EMT transition, and mediating spermatogenesis. This review aims to provide an overview and highlights some recent findings on CXADR in the field with emphasis on studies in the testis, upon which future studies can be designed to delineate the roles and regulation of CXADR in spermatogenesis.

Induction of the Coxsackievirus and Adenovirus Receptor in Macrophages During the Formation of Atherosclerotic Plaques

Multiple viruses are implicated in atherosclerosis, but the mechanisms by which they infect cells and contribute to plaque formation in arterial walls are not well understood. Based on reports showing the presence of enterovirus in atherosclerotic plaques we hypothesized that the coxsackievirus and adenovirus receptor (CXADR/CAR), although absent in normal arteries, could be induced during plaque formation. Large-scale microarray and mass spectrometric analyses revealed significant up-regulation of CXADR messenger RNA and protein levels in plaque-invested carotid arteries compared with control arteries. Macrophages were identified as a previously unknown cellular source of CXADR in human plaques and plaques from Ldr-/-Apob100/100 mice. CXADR was specifically associated with M1-polarized macrophages and foam cells and was experimentally induced during macrophage differentiation. Furthermore, it was significantly correlated with receptors for other viruses linked to atherosclerosis. The results show that CXADR is induced in macrophages during plaque formation, suggesting a mechanism by which enterovirus infect cells in atherosclerotic plaques.

Colorectal Cancer Stem Cell States Uncovered by Simultaneous Single-Cell Analysis of Transcriptome and Telomeres

Cancer stem cells (CSCs) presumably contribute to tumor progression and drug resistance, yet their definitive features have remained elusive. Here, simultaneous measurement of telomere length and transcriptome in the same cells enables systematic assessment of CSCs in primary colorectal cancer (CRC). The in-depth transcriptome profiled by SMART-seq2 is independently validated by high-throughput scRNA-seq using 10 × Genomics. It is found that rare CSCs exist in dormant state and display plasticity toward cancer epithelial cells (EPCs) that essentially are presumptive tumor-initiating cells (TICs), while both retaining the prominent signaling pathways including WNT, TGF-β, and HIPPO/YAP. Moreover, CSCs exhibit chromosome copy number variation (CNV) pattern resembling cancer EPCs but distinct from normal stem cells, suggesting the phylogenetic relationship between CSCs and cancer EPCs. Notably, CSCs maintain shorter telomeres and possess minimal telomerase activity consistent with their nonproliferative nature, unlike cancer EPCs. Additionally, the specific signature of CSCs particularly NOTUM, SMOC2, BAMBI, PHLDA1, and TNFRSF19 correlates with the prognosis of CRC. These findings characterize the heterogeneity of CSCs and their linkage to cancer EPCs/TICs, some of which are conventionally regarded as CSCs.

Airway tight junctions as targets of viral infections

The apical junctional complexes (AJCs) of airway epithelial cells are a key component of the innate immune system by creating barriers to pathogens, inhaled allergens, and environmental particles. AJCs form between adjacent cells and consist of tight junctions (TJs) and adherens junctions (AJs). Respiratory viruses have been shown to target various components of the AJCs, leading to airway epithelial barrier dysfunction by different mechanisms. Virus-induced epithelial permeability may allow for allergens and bacterial pathogens to subsequently invade. In this review, we discuss the pathophysiologic mechanisms leading to disruption of AJCs and the potential ensuing ramifications. We focus on the following viruses that affect the pulmonary system: respiratory syncytial virus, rhinovirus, influenza viruses, immunodeficiency virus, and other viruses such as coxsackievirus, adenovirus, coronaviruses, measles, parainfluenza virus, bocavirus, and vaccinia virus. Understanding the mechanisms by which viruses target the AJC and impair barrier function may help design therapeutic innovations to treat these infections.

Genetic Delivery and Gene Therapy in Pulmonary Hypertension

Pulmonary hypertension (PH) is a progressive complex fatal disease of multiple etiologies. Hyperproliferation and resistance to apoptosis of vascular cells of intimal, medial, and adventitial layers of pulmonary vessels trigger excessive pulmonary vascular remodeling and vasoconstriction in the course of pulmonary arterial hypertension (PAH), a subgroup of PH. Multiple gene mutation/s or dysregulated gene expression contribute to the pathogenesis of PAH by endorsing the proliferation and promoting the resistance to apoptosis of pulmonary vascular cells. Given the vital role of these cells in PAH progression, the development of safe and efficient-gene therapeutic approaches that lead to restoration or down-regulation of gene expression, generally involved in the etiology of the disease is the need of the hour. Currently, none of the FDA-approved drugs provides a cure against PH, hence innovative tools may offer a novel treatment paradigm for this progressive and lethal disorder by silencing pathological genes, expressing therapeutic proteins, or through gene-editing applications. Here, we review the effectiveness and limitations of the presently available gene therapy approaches for PH. We provide a brief survey of commonly existing and currently applicable gene transfer methods for pulmonary vascular cells in vitro and describe some more recent developments for gene delivery existing in the field of PH in vivo.

Role of coxsackie-adenovirus receptor in cardiac development and pathogenesis of congenital heart disease

The coxsackie-adenovirus receptor (CAR) is a cell surface transmembrane protein originally recognized for its role as a binding site for coxsackie- and adeno-viruses. As such, it is believed to play an important role in pathogenesis of myocarditis. Other studies have suggested that CAR also plays an important role in embryonic development, which is not surprising given the strong expression of the receptor in heart, brain, liver, pancreas, kidney, small intestine, and various epithelia during development. A number of studies have looked at downregulation and upregulation of CAR and have confirmed the central role of CAR during critical periods of development. These studies all demonstrated embryonic lethality with variable phenotypes: electrophysiological abnormalities, cardiac structural deformations, and extracardiac abnormalities, such as lymphatic malformations. The purpose of this review is to summarize the existing literature about CAR and formulate some questions for future studies, with an emphasis on the role of CAR during embryonic heart development.

Naturally occurring variants in the transmembrane and cytoplasmic domains of the human Coxsackie- and adenovirus receptor have no impact on virus internalisation

The Coxsackie- and adenovirus receptor (CAR) mediates homophilic cell-cell contacts and susceptibility to both human pathogenic viruses through its membrane-distal immunoglobulin domain. In the present study, we screened five missense variants of the human CAR gene for their influence on adenovector or Coxsackievirus entry into Chinese hamster ovary cells. The CAR variants facilitated virus internalisation to a similar extent as wild type CAR. This underlines CAR's presumed invariance and essential physiological role in embryogenesis.

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.

The coxsackievirus and adenovirus receptor: virological and biological beauty

The coxsackievirus and adenovirus receptor (CAR) is an essential multifunctional cellular protein that is only beginning to be understood. CAR serves as a receptor for many adenoviruses, human group B coxsackieviruses, swine vesicular disease virus, and possibly other viruses. While named for its function as a viral receptor, CAR is also involved in cell adhesion, immune cell activation, synaptic transmission, and signaling. Knockout mouse models were first to identify some of these biological functions; however, tissue-specific model systems have shed light on the complexity of different CAR isoforms and their specific activities. Many of these functions are mediated by the large number of interacting proteins described so far, and several new putative interactions have recently been discovered. As antiviral and gene therapy strategies that target CAR continue to emerge, future work poised to understand the biological implications of manipulating CAR in vivo is critical.

Upregulation of HLA Class I and Antiviral Tissue Responses in Hashimoto's Thyroiditis

Background: Hashimoto's thyroiditis (HT) is a common autoimmune disease of unknown origin. However, viral infections have been implicated as triggers for autoimmunity. Human leukocyte antigen (HLA) class I presents antigens to circulating immune cells and plays a crucial role in the defense against viral infections. This study aimed to investigate the presence of enterovirus and HLA class I expression in one of the largest HT thyroid tissue cohorts to date. In addition, viral receptors and viral immune response proteins were examined. Methods: Thyroid tissue samples from 46 HT patients were obtained using core needle biopsy. Thyroid tissue collected during neck surgery for other reasons than thyroid autoimmunity served as controls. Standard immunohistochemistry on formalin-fixed, paraffin-embedded tissue samples were used to detect HLA class I, enteroviral capsid protein 1 (VP1), and coxsackie and adenovirus receptor (CAR) in thyroid cells. A subset of the samples was examined with combined immunofluorescence staining for signal transducer and activator of transcription 1 (STAT1) and protein kinase R (PKR). Results: Significantly more HLA class I-positive samples were found in the HT group (31 out of 46 [67.4%]) than in the control group (5 out of 24 [20.8%]) (p < 0.001). Moreover, the semiquantitative score assessing the grade of HLA class I expression was significantly higher in the HT group (3.9 ± 3.1) than in the control group (0.5 ± 0.9) (p < 0.001). In addition, STAT1 was colocalized with HLA class I, and PKR and VP1 were also found and were colocalized together. VP1 was detected in both controls and the HT samples, with slightly more VP1⁺ thyroid cells in the HT samples (20.1% ± 16.4%) than in controls (14.9% ± 10.5%). Finally, the presence of CAR in thyroid cells was confirmed. Conclusion: The current study confirmed that HLA class I hyperexpression is a defining feature of HT. Thyroid cells express CAR, thus making them susceptible to enterovirus infection. The colocalization of HLA class I with STAT1 and VP1 with PKR indicates an intracellular, antiviral host response. These findings support the concept of a firm link between viral infection and autoimmune thyroid diseases.

The Healing Power of Neutrophils

Neutrophils promptly accumulate in large numbers at sites of tissue injury. Injuries to the skin or mucosae disrupt barriers against the external environment, and the bactericidal actions of neutrophils are important in preventing microbial invasion. Neutrophils have also been associated with exacerbated inflammation, for example in non-healing wounds or in conditions such as inflammatory bowel disease (IBD). However, additional neutrophil functions important for angiogenesis and tissue restoration have been uncovered in models of sterile and ischemic injury, as well as in tumors. These functions are also relevant in healing skin and mucosal wounds, and can be impaired in conditions associated with non-healing wounds, such as diabetes. Here, we discuss our current understanding of neutrophil contributions to healing, and how the latter can be compromised in disease.

Data on localization of coxsackievirus and adenovirus receptor (CAR) in prenatal and adult rat olfactory, intestine, pancreas, liver, ovary, and testis

The data in the present article are related to the previous article entitled “Coxsackievirus and adenovirus receptor-positive cells compose the putative stem/progenitor cell niches in the marginal cell layer and parenchyma of the rat anterior pituitary” (M. Chen et al. 2013). The data describe the characteristic localization in the immature cells of the prenatal and adult tissues beyond the germ layer. Germ cells and the reproductive tissues of both sexes showed distinct intracellular polarities of CAR: apical, basolateral, and pericellular in the immature cells of the embryo and adult tissues. In addition, the data describe on localization of CAR in the methimazole-induced damage of olfactory epithelium tissue. The data show that the CAR-_immuno-positive cells at the apical side of the olfactory epithelium disappeared following methimazole treatment and reappeared in the regenerating stem/progenitor cells (positive for KI67 and E-cadherin) of the basal layer with basolateral expression.

Blood-Bile Barrier: Morphology, Regulation, and Pathophysiology

The term blood-bile barrier (BBlB) refers to the physical structure within a hepatic lobule that compartmentalizes and hence segregates sinusoidal blood from canalicular bile. Thus, this barrier provides physiological protection in the liver, shielding the hepatocytes from bile toxicity and restricting the mixing of blood and bile. BBlB is primarily composed of tight junctions; however, adherens junction, desmosomes, gap junctions, and hepatocyte bile transporters also contribute to the barrier function of the BBlB. Recent findings also suggest that disruption of BBlB is associated with major hepatic diseases characterized by cholestasis and aberrations in BBlB thus may be a hallmark of many chronic liver diseases. Several molecular signaling pathways have now been shown to play a role in regulating the structure and function and eventually contribute to regulation of the BBlB function within the liver. In this review, we will discuss the structure and function of the BBlB, summarize the methods to assess the integrity and function of BBlB, discuss the role of BBlB in liver pathophysiology, and finally, discuss the mechanisms of BBlB regulation. Collectively, this review will demonstrate the significance of the BBlB in both liver homeostasis and hepatic dysfunction.

Data on localization of coxsackievirus and adenovirus receptor (CAR) in the embryonic rat brain

The data in the present article are related to the previous article entitled "Coxsackievirus and adenovirus receptor-positive cells compose the putative stem/progenitor cell niches in the marginal cell layer and parenchyma of the rat anterior pituitary" (Chen et al., 2013). The data describe the characteristic localization of coxsackievirus and adenovirus receptor (CAR), a junctional adhesion molecule involved in the regulation of cell-cell interactions, migration, proliferation, and growth (Coyne and Bergelson, 2005, Matthaus et al., 2017, Raschperger et al., 2006, Schiestl and Gietz, 1989) and in the stem/progenitor cell niche in the embryonic rat pituitary gland (Chen et al., 2013, Yoshida et al., 2016). Immunohistochemical analyses of CAR showed frequent colocalization with SOX2 in the embryonic rat brain, except for choroid plexus cells. CAR showed distinct apical and basolateral polarity. These data contribute to our understanding of prenatal brain development.

Cisplatin Synergistically Enhances Antitumor Potency of Conditionally Replicating Adenovirus via p53 Dependent or Independent Pathways in Human Lung Carcinoma

Cisplatin is ranked as one of the most powerful and commonly prescribed anti-tumor chemotherapeutic agents which improve survival in many solid tumors including non-small cell lung cancer. However, the treatment of advanced lung cancer is restricted due to chemotherapy resistance. Here, we developed and investigated survivin promoter regulating conditionally replicating adenovirus (CRAd) for its anti-tumor potential alone or in combination with cisplatin in two lung cancer cells, H23, H2126, and their resistant cells, H23/CPR, H2126/CPR. To measure the expression of genes which regulate resistance, adenoviral transduction, metastasis, and apoptosis in cancer cells, RT-PCR and Western blotting were performed. The anti-tumor efficacy of the treatments was evaluated through flow cytometry, MTT and transwell assays. This study demonstrated that co-treatment with cisplatin and CRAd exerts synergistic anti-tumor effects on chemotherapy sensitive lung cancer cells and monotherapy of CRAd could be a practical approach to deal with chemotherapy resistance. Combined treatment induced stronger apoptosis by suppressing the anti-apoptotic molecule Bcl-2, and reversed epithelial to mesenchymal transition. In conclusion, cisplatin synergistically increased the tumor-killing of CRAd by (1) increasing CRAd transduction via enhanced CAR expression and (2) increasing p53 dependent or independent apoptosis of lung cancer cell lines. Also, CRAd alone proved to be a very efficient anti-tumor agent in cancer cells resistant to cisplatin owing to upregulated CAR levels. In an exciting outcome, we have revealed novel therapeutic opportunities to exploit intrinsic and acquired resistance to enhance the therapeutic index of anti-tumor treatment in lung cancer.

Unexpected subcellular distribution of a specific isoform of the Coxsackie and adenovirus receptor, CAR-SIV, in human pancreatic beta cells

AIMS/HYPOTHESIS

The Coxsackie and adenovirus receptor (CAR) is a transmembrane cell-adhesion protein that serves as an entry receptor for enteroviruses and may be essential for their ability to infect cells. Since enteroviral infection of beta cells has been implicated as a factor that could contribute to the development of type 1 diabetes, it is often assumed that CAR is displayed on the surface of human beta cells. However, CAR exists as multiple isoforms and it is not known whether all isoforms subserve similar physiological functions. In the present study, we have determined the profile of CAR isoforms present in human beta cells and monitored the subcellular localisation of the principal isoform within the cells.

METHODS

Formalin-fixed, paraffin-embedded pancreatic sections from non-diabetic individuals and those with type 1 diabetes were studied. Immunohistochemistry, confocal immunofluorescence, electron microscopy and western blotting with isoform-specific antisera were employed to examine the expression and cellular localisation of the five known CAR isoforms. Isoform-specific qRT-PCR and RNA sequencing (RNAseq) were performed on RNA extracted from isolated human islets.

RESULTS

An isoform of CAR with a terminal SIV motif and a unique PDZ-binding domain was expressed at high levels in human beta cells at the protein level. A second isoform, CAR-TVV, was also present. Both forms were readily detected by qRT-PCR and RNAseq analysis in isolated human islets. Immunocytochemical studies indicated that CAR-SIV was the principal isoform in islets and was localised mainly within the cytoplasm of beta cells, rather than at the plasma membrane. Within the cells it displayed a punctate pattern of immunolabelling, consistent with its retention within a specific membrane-bound compartment. Co-immunofluorescence analysis revealed significant co-localisation of CAR-SIV with zinc transporter protein 8 (ZnT8), prohormone convertase 1/3 (PC1/3) and insulin, but not proinsulin. This suggests that CAR-SIV may be resident mainly in the membranes of insulin secretory granules. Immunogold labelling and electron microscopic analysis confirmed that CAR-SIV was localised to dense-core (insulin) secretory granules in human islets, whereas no immunolabelling of the protein was detected on the secretory granules of adjacent exocrine cells. Importantly, CAR-SIV was also found to co-localise with protein interacting with C-kinase 1 (PICK1), a protein recently demonstrated to play a role in insulin granule maturation and trafficking.

CONCLUSIONS/INTERPRETATION

The SIV isoform of CAR is abundant in human beta cells and is localised mainly to insulin secretory granules, implying that it may be involved in granule trafficking and maturation. We propose that this subcellular localisation of CAR-SIV contributes to the unique sensitivity of human beta cells to enteroviral infection.

CXADR-Mediated Formation of an AKT Inhibitory Signalosome at Tight Junctions Controls Epithelial-Mesenchymal Plasticity in Breast Cancer

Tight junctions (TJ) act as hubs for intracellular signaling pathways controlling epithelial cell fate and function. Deregulation of TJ is a hallmark of epithelial-mesenchymal transition (EMT), which contributes to carcinoma progression and metastasis. However, the signaling mechanisms linking TJ to the induction of EMT are not understood. Here, we identify a TJ-based signalosome, which controls AKT signaling and EMT in breast cancer. The coxsackie and adenovirus receptor (CXADR), a TJ protein with an essential yet uncharacterized role in organogenesis and tissue homeostasis, was identified as a key component of the signalosome. CXADR regulated the stability and function of the phosphatases and AKT inhibitors PTEN and PHLPP2. Loss of CXADR led to hyperactivation of AKT and sensitized cells to TGFβ1-induced EMT. Conversely, restoration of CXADR stabilized PHLPP2 and PTEN, inhibited AKT, and promoted epithelial differentiation. Loss of CXADR in luminal A breast cancer correlated with loss of PHLPP2 and PTEN and poor prognosis. These results show that CXADR promotes the formation of an AKT-inhibitory signalosome at TJ and regulates epithelial-mesenchymal plasticity in breast cancer cells. Moreover, loss of CXADR might be used as a prognostic marker in luminal breast cancer. SIGNIFICANCE: The tight junction protein CXADR controls epithelial-mesenchymal plasticity in breast cancer by stabilizing the AKT regulators PTEN and PHLPP2.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/1/47/F1.large.jpg.

Protective Role of Coxsackie-Adenovirus Receptor in the Pathogenesis of Inflammatory Bowel Diseases

AIM

To investigate the role of Coxsackie-adenovirus receptor (CAR) in inflammatory bowel disease (IBD).

BACKGROUND

CAR, a type I transmembrane protein with functions in virus attachment, has been shown to be associated with epithelial tight junctions (TJs) and mediates cell adhesion, implying its potential roles in the pathogenesis of IBD.

METHODS AND MATERIALS

To determine the effect of CAR in IBD using QPCR and Western blotting to determine the expression of CAD in TNF-α induced NCM460 and SW480 cells and IBD tissues compared to control groups. Furthermore, TJs dysregulation, FITC-Dextran permeability assay, qRT-PCR, Western blot, and IF assessed the permeability in CAR overexpressed cells treated with TNF-α. HE, qRT-PCR, Western blot, and IHC assay were used to assess the CAR overexpressed cells whether they have the effect to cure DSS induced ulcerative colitis rat model in vivo.

RESULT

We found CAR levels in human colon cell lines are significantly downregulated under the treatment of tumor necrosis factor-alpha (TNF-α). Furthermore, overexpression of CAR markedly prevented TNF-α induced inflammatory response, TJs dysregulation, and permeability disruption (FITC-Dextran permeability assay) in cells. Consistent with these findings in vitro, we found that CAR overexpression could suppress gut inflammation, attenuate the downregulation of TJ protein ZO-1 and Occludin, and limit the induction of barrier permeability in a DSS induced ulcerative colitis rat model in vivo. Together, our findings strongly suggest that CAR could protect tight junctions and has an anti-inflammatory effect during the pathogenesis of IBD. Thus CAR may serve as a therapeutic target for the diagnosis and treatment of IBD.

Genome-wide binding of transcription factor ZEB1 in triple-negative breast cancer cells

Zinc finger E-box binding homeobox 1 (ZEB1) is a transcriptional regulator involved in embryonic development and cancer progression. ZEB1 induces epithelial-mesenchymal transition (EMT). Triple-negative human breast cancers express high ZEB1 mRNA levels and exhibit features of EMT. In the human triple-negative breast cancer cell model Hs578T, ZEB1 associates with almost 2,000 genes, representing many cellular functions, including cell polarity regulation (DLG2 and FAT3). By introducing a CRISPR-Cas9-mediated 30 bp deletion into the ZEB1 second exon, we observed reduced migratory and anchorage-independent growth capacity of these tumor cells. Transcriptomic analysis of control and ZEB1 knockout cells, revealed 1,372 differentially expressed genes. The TIMP metallopeptidase inhibitor 3 and the teneurin transmembrane protein 2 genes showed increased expression upon loss of ZEB1, possibly mediating pro-tumorigenic actions of ZEB1. This work provides a resource for regulators of cancer progression that function under the transcriptional control of ZEB1. The data confirm that removing a single EMT transcription factor, such as ZEB1, is not sufficient for reverting the triple-negative mesenchymal breast cancer cells into more differentiated, epithelial-like clones, but can reduce tumorigenic potential, suggesting that not all pro-tumorigenic actions of ZEB1 are linked to the EMT.

Evaluation of adenovirus 19a as a novel vector for mucosal vaccination against influenza A viruses

Since preexisting immunity and enhanced infection rates in a clinical trial of an HIV vaccine have raised some concerns on adenovirus (Ad) serotype 5-based vaccines, we evaluated the subgroup D adenovirus serotype Ad19a for its suitability as novel viral vector vaccine against mucosal infections. In BALB/c mice, we compared the immunogenicity and efficacy of E1/E3-deleted Ad19a vectors encoding the influenza A virus (IAV)-derived antigens hemagglutinin (HA) and nucleoprotein (NP) to the most commonly used Ad5 vectors. The adenoviral vectors were applied intranasally and induced detectable antigen-specific T cell responses in the lung and in the spleen as well as robust antibody responses. A prior DNA immunization significantly improved the immunogenicity of both vectors and resulted in full protection against a lethal infection with a heterologous H3N2 virus. Nevertheless, the Ad5-based vectors were slightly superior in reducing viral replication in the lung which corresponded to higher NP-specific T cell responses measured in the lungs.

KIF22 coordinates CAR and EGFR dynamics to promote cancer cell proliferation

The coxsackievirus and adenovirus receptor (CAR) is a transmembrane receptor that plays a key role in cell-cell adhesion. CAR is found in normal epithelial cells and is increased in abundance in various human tumors, including lung carcinomas. We investigated the potential mechanisms by which CAR contributes to cancer cell growth and found that depletion of CAR in human lung cancer cells reduced anchorage-independent growth, epidermal growth factor (EGF)-dependent proliferation, and tumor growth in vivo. EGF induced the phosphorylation of CAR and its subsequent relocalization to cell junctions through the activation of the kinase PKCδ. EGF promoted the binding of CAR to the chromokinesin KIF22. KIF22-dependent regulation of microtubule dynamics led to delayed EGFR internalization, enhanced EGFR signaling, and coordination of CAR dynamics at cell-cell junctions. These data suggest a role for KIF22 in the coordination of membrane receptors and provide potential new therapeutic strategies to combat lung tumor growth.

Defenders and Challengers of Endothelial Barrier Function

Regulated vascular permeability is an essential feature of normal physiology and its dysfunction is associated with major human diseases ranging from cancer to inflammation and ischemic heart diseases. Integrity of endothelial cells also play a prominent role in the outcome of surgical procedures and organ transplant. Endothelial barrier function and integrity are regulated by a plethora of highly specialized transmembrane receptors, including claudin family proteins, occludin, junctional adhesion molecules (JAMs), vascular endothelial (VE)-cadherin, and the newly identified immunoglobulin (Ig) and proline-rich receptor-1 (IGPR-1) through various distinct mechanisms and signaling. On the other hand, vascular endothelial growth factor (VEGF) and its tyrosine kinase receptor, VEGF receptor-2, play a central role in the destabilization of endothelial barrier function. While claudins and occludin regulate cell-cell junction via recruitment of zonula occludens (ZO), cadherins via catenin proteins, and JAMs via ZO and afadin, IGPR-1 recruits bullous pemphigoid antigen 1 [also called dystonin (DST) and SH3 protein interacting with Nck90/WISH (SH3 protein interacting with Nck)]. Endothelial barrier function is moderated by the function of transmembrane receptors and signaling events that act to defend or destabilize it. Here, I highlight recent advances that have provided new insights into endothelial barrier function and mechanisms involved. Further investigation of these mechanisms could lead to the discovery of novel therapeutic targets for human diseases associated with endothelial dysfunction.

Anti-coxsackievirus B4 (CV-B4) enhancing activity of serum associated with increased viral load and pathology in mice reinfected with CV-B4

In previous studies it was shown that inoculation of Swiss albino mice with CV-B4 E2 resulted in the production of serum IgG capable of enhancing the CV-B4 E2 infection of murine spleen cells cultures. To investigate whether such an enhancing activity of serum can play a role in vivo, we decided to study the CV-B4 E2 infection in mice exposed to successive inoculations of virus. In Swiss albino mice infected with CV-B4 E2 at the age of 21 days, anti-CV-B4 E2 neutralizing and enhancing activities of their serum peaked after 55 d. In contrast, mice inoculated at the age of 55 d expressed much lower activities. Despite the neutralizing activity of serum, CV-B4 E2 inoculated a second time to 55 day-old animals spread into the host. At the age of 72 and 89 d the levels of viral RNA and infectious particles were higher in organs of animals exposed to 2 successive infections compared with animals infected once at the age of 21 d or 55 d. In animals with 2 successive inoculations of CV-B4 E2 there was a relationship between the anti-CV-B4 E2 enhancing activity of serum and the level of viral RNA in organs and an enhancement of pathology was observed as displayed by histological analysis of pancreas and hyperglycaemia. Altogether our data strongly suggest that an anti-CV-B4 E2 enhancing activity in the host can play a role in the outcome of a secondary infection with this virus.

[Enterovirus infection during pregnancy: Underestimated cause of fetal and neonatal complications?]

Enteroviruses are responsible for about one billion infections every year in the world. The clinical expression is in the vast majority asymptomatic cases (90%). Its consequences during pregnancy are rarely described. From the Medline database, we selected and analyzed 34 articles ranging from 1965 to 2015, to analyse the current knowledge of enterovirus infection consequences during pregnancy. We found that enterovirus infections may be the cause of fetal loss. The enterovirus infections during the 2nd and 3rd trimester may also lead to in utero fetal anomalies and death, but also to severe neonatal infections. PCR enterovirus detection should be performed during pregnancy and the peripartum in case of unexplained fever, specific fetal anomalies or unexplained fetal demise.

Adenovirus transduction: More complicated than receptor expression

The abundance and accessibility of a primary virus receptor are critical factors that impact the susceptibility of a host cell to virus infection. The Coxsackievirus and adenovirus receptor (CAR) has two transmembrane isoforms that occur due to alternative splicing and differ in localization and function in polarized epithelia. To determine the relevance of isoform-specific expression across cell types, the abundance and localization of both isoforms were determined in ten common cell lines, and correlated with susceptibility to adenovirus transduction relative to polarized primary human airway epithelia. Data show that the gene and protein expression for each isoform of CAR varies significantly between cell lines and polarization, as indicated by high transepithelial resistance, is inversely related to adenovirus transduction. In summary, the variability of polarity and isoform-specific expression among model cells are critical parameters that must be considered when evaluating the clinical relevance of potential adenovirus-mediated gene therapy and anti-adenovirus strategies.

Cell-cell communication mediated by the CAR subgroup of immunoglobulin cell adhesion molecules in health and disease

The immunoglobulin superfamily represents a diverse set of cell-cell contact proteins and includes well-studied members such as NCAM1, DSCAM, L1 or the contactins which are strongly expressed in the nervous system. In this review we put our focus on the biological function of a less understood subgroup of Ig-like proteins composed of CAR (coxsackievirus and adenovirus receptor), CLMP (CAR-like membrane protein) and BT-IgSF (brain and testis specific immunoglobulin superfamily). The CAR-related proteins are type I transmembrane proteins containing an N-terminal variable (V-type) and a membrane proximal constant (C2-type) Ig domain in their extracellular region which are implicated in homotypic adhesion. They are highly expressed during embryonic development in a variety of tissues including the nervous system whereby in adult stages the protein level of CAR and CLMP decreases, only BT-IgSF expression increases within age. CAR-related proteins are concentrated at specialized cell-cell communication sites such as gap or tight junctions and are present at the plasma membrane in larger protein complexes. Considerable progress has been made on the molecular structure and interactions of CAR while research on CLMP and BT-IgSF is at an early stage. Studies on mouse mutants revealed biological functions of CAR in the heart and for CLMP in the gastrointestinal and urogenital systems. Furthermore, CAR and BT-IgSF appear to regulate synaptic function in the hippocampus.

CXCL12 retargeting of an adenovirus vector to cancer cells using a bispecific adapter

Ad vectors are promising delivery vehicles for cancer therapeutic interventions. However, their application is limited by promiscuous tissue tropism and hepatotoxicity. This limitation can be avoided by altering the native tropism of Ads so that they can be redirected to the target cells through alternate cellular receptors. The CXCR4 chemokine receptor belongs to a large superfamily of G-protein-coupled receptors and is known to be upregulated in a wide variety of cancers, including breast cancer and melanoma. These receptors have been associated with cancer cell survival, progression, and metastasis. In the current study, an Ad to cancer cells overexpressing CXCR4 by using a bispecific adapter, sCAR-CXCL12, was retargeted. The sCAR-CXCL12 adapter contained the soluble ectodomain form of the native Ad5 receptor (sCAR), which was fused to a mature human chemokine ligand, CXCL12, through a short peptide linker. A dramatic increase in the infectivity of cancer cells using a targeted Ad vector compared with an untargeted vector was observed. Furthermore, sCAR-CXCL12 attenuated Ad infection of liver ex vivo and in vivo and enhanced Ad vector infection of xenograft tumors implanted in immunodeficient SCID-bg mice. Thus, the sCAR-CXCL12 adapter could be used to retarget Ad vectors to chemokine receptor-positive tumors.

Regulation of the Coxsackie and adenovirus receptor expression is dependent on cystic fibrosis transmembrane regulator in airway epithelial cells

The coxsackievirus and adenovirus receptor (CAR), in addition to serving as viral receptor, is a component of tight junctions and plays an important role in tissue homeostasis. Defects in the cystic fibrosis transmembrane regulator (CFTR) in lung epithelial cells are linked to inflammation and susceptibility for respiratory tract infections. Here, we demonstrate that CAR expression and infectivity with adenovirus (Ad) are increased in cystic fibrosis airway epithelial cells. Inhibition of CFTR or histone deacetylase (HDAC) enhanced CAR expression while CFTR overexpression or restoration of the diminished HDAC activity in cystic fibrosis cells reduced CAR expression. This connects the CFTR to CAR expression and infectivity with adenovirus through HDAC.

TNFα promotes CAR-dependent migration of leukocytes across epithelial monolayers

Trans-epithelial migration (TEpM) of leukocytes during inflammation requires engagement with receptors expressed on the basolateral surface of the epithelium. One such receptor is Coxsackie and Adenovirus Receptor (CAR) that binds to Junctional Adhesion Molecule-like (JAM-L) expressed on leukocytes. Here we provide the first evidence that efficient TEpM of monocyte-derived THP-1 cells requires and is controlled by phosphorylation of CAR. We show that TNFα acts in a paracrine manner on epithelial cells via a TNFR1-PI3K-PKCδ pathway leading to CAR phosphorylation and subsequent transmigration across cell junctions. Moreover, we show that CAR is hyper-phosphorylated in vivo in acute and chronic lung inflammation models and this response is required to facilitate immune cell recruitment. This represents a novel mechanism of feedback between leukocytes and epithelial cells during TEpM and may be important in controlling responses to pro-inflammatory cytokines in pathological settings.

CXADR is required for AJ and TJ assembly during porcine blastocyst formation

Coxsackie virus and adenovirus receptor (CXADR) is a member of the immunoglobulin superfamily as well as a member of the junctional adhesion molecule family of adhesion receptor. In human pre-implantation embryos, CXADR was detected and co-localized with tight junction (TJ) proteins on the membrane of the trophectoderm. However, its physiological roles were not elucidated in terms of blastocyst formation. Here, we reported expression patterns and biological functions of CXADR in porcine pre-implantation embryos. The transcripts of CXADR were detected at all stages of pre-implantation. Particularly, its expression dramatically increased and preferentially localized at the edge of cell–cell contacts, rather than in the nucleus from the eight-cell stage onwards. CXADR expression was knocked down (KD) by microinjecting double-stranded RNA into one-cell parthenotes. The vast majority of CXADR KD embryos failed to develop to the blastocyst stage, and a few developed KD blastocysts did not expand fully. Analysis of adherens junction (AJ)- and TJ-associated genes/proteins using qRT-PCR, immunocytochemistry and assessment of TJ permeability using FITC-dextran uptake assay revealed that the developmental failure and relatively small cavities are attributed to the defects of TJ assembly. In summary, CXADR is necessary for the AJ and TJ assembly/biogenesis during pre-implantation development.

Connections matter--how viruses use cell–cell adhesion components

The epithelium is a highly organized type of animal tissue. Except for blood and lymph vessels, epithelial cells cover the body, line its cavities in single or stratified layers and support exchange between compartments. In addition, epithelia offer to the body a barrier to pathogen invasion. To transit through or to replicate in epithelia, viruses have to face several obstacles, starting from cilia and glycocalyx where they can be neutralized by secreted immunoglobulins. Tight junctions and adherens junctions also prevent viruses to cross the epithelial barrier. However, viruses have developed multiple strategies to blaze their path through the epithelium by utilizing components of cell–cell adhesion structures as receptors. In this Commentary, we discuss how viruses take advantage of the apical junction complex to spread. Whereas some viruses quickly disrupt epithelium integrity, others carefully preserve it and use cell adhesion proteins and their cytoskeletal connections to rapidly spread laterally. This is exemplified by the hidden transmission of enveloped viruses that use nectins as receptors. Finally, several viruses that replicate preferentially in cancer cells are currently used as experimental cancer therapeutics. Remarkably, these viruses use cell adhesion molecules as receptors, probably because--to reach tumors and metastases--ncolytic viruses must efficiently traverse or break epithelia.

Targeted Adenoviral Vectors I

Human adenovirus (Ad) has been used extensively to develop gene transfer vectors for vaccine and gene therapy applications. A major factor limiting the efficacy of the current generation of Ad vectors is their inability to accomplish specific gene delivery to the cells of interest. Transductional targeting strategies seek to redirect virus binding to the appropriate cellular receptor to increase infection efficiency in selected cell types to achieve therapeutic intervention. These efforts mainly focused on incorporating targeting ligands by means of chemical conjugation or genetic modification of Ad capsid proteins and using bispecific adapter molecules to mediate virus recognition of target cells. This review summarizes current progress in Ad tropism modification maneuvers that embody genetic capsid modification and adapter-based approaches that have encouraging implications for further development of advanced vectors suitable for clinical translation.

Coxsackie-adenovirus receptor expression is enhanced in pancreas from patients with type 1 diabetes

OBJECTIVES

One of the theories connecting enterovirus (EV) infection of human islets with type 1 diabetes (T1D) is the development of a fertile field in the islets. This implies induction of appropriate proteins for the viral replication such as the coxsackie-adenovirus receptor (CAR). The aim of this study was to investigate to what extent CAR is expressed in human islets of Langerhans, and what conditions that would change the expression.

DESIGN

Immunohistochemistry for CAR was performed on paraffin-embedded pancreatic tissue from patients with T1D (n=9 recent onset T1D, n=4 long-standing T1D), islet autoantibody-positive individuals (n=14) and non-diabetic controls (n=24) individuals. The expression of CAR was also examined by reverse transcription PCR on microdissected islets (n=5), exocrine tissue (n=5) and on explanted islets infected with EV or exposed to chemokines produced by EV-infected islet cells.

RESULTS

An increased frequency of patients with T1D and autoantibody-positive individuals expressed CAR in the pancreas (p<0.039). CAR staining was detected more frequently in pancreatic islets from patients with T1D and autoantibody-positive subjects (15/27) compared with (6/24) non-diabetic controls (p<0.033). Also in explanted islets cultured in UV-treated culture medium from coxsackievirus B (CBV)-1-infected islets, the expression of the CAR gene was increased compared with controls. Laser microdissection of pancreatic tissue revealed that CAR expression was 10-fold higher in endocrine compared with exocrine cells of the pancreas. CAR was also expressed in explanted islets and the expression level decreased with time in culture. CBV-1 infection of explanted islets clearly decreased the expression of CAR (p<0.05). In contrast, infection with echovirus 6 did not affect the expression of CAR.

CONCLUSIONS

CAR is expressed in pancreatic islets of patients with T1D and the expression level of CAR is increased in explanted islets exposed to proinflammatory cytokines/chemokines produced by infected islets. T1D is associated with increased levels of certain chemokines/cytokines in the islets and this might be the mechanism behind the increased expression of CAR in TID islets.

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.

The Mammalian Blood-Testis Barrier: Its Biology and Regulation

Spermatogenesis is the cellular process by which spermatogonia develop into mature spermatids within seminiferous tubules, the functional unit of the mammalian testis, under the structural and nutritional support of Sertoli cells and the precise regulation of endocrine factors. As germ cells develop, they traverse the seminiferous epithelium, a process that involves restructuring of Sertoli-germ cell junctions, as well as Sertoli-Sertoli cell junctions at the blood-testis barrier. The blood-testis barrier, one of the tightest tissue barriers in the mammalian body, divides the seminiferous epithelium into 2 compartments, basal and adluminal. The blood-testis barrier is different from most other tissue barriers in that it is not only comprised of tight junctions. Instead, tight junctions coexist and cofunction with ectoplasmic specializations, desmosomes, and gap junctions to create a unique microenvironment for the completion of meiosis and the subsequent development of spermatids into spermatozoa via spermiogenesis. Studies from the past decade or so have identified the key structural, scaffolding, and signaling proteins of the blood-testis barrier. More recent studies have defined the regulatory mechanisms that underlie blood-testis barrier function. We review here the biology and regulation of the mammalian blood-testis barrier and highlight research areas that should be expanded in future studies.

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.

Epithelial adhesion molecules and the regulation of intestinal homeostasis during neutrophil transepithelial migration

Epithelial adhesion molecules play essential roles in regulating cellular function and maintaining mucosal tissue homeostasis. Some form epithelial junctional complexes to provide structural support for epithelial monolayers and act as a selectively permeable barrier separating luminal contents from the surrounding tissue. Others serve as docking structures for invading viruses and bacteria, while also regulating the immune response. They can either obstruct or serve as footholds for the immune cells recruited to mucosal surfaces. Currently, it is well appreciated that adhesion molecules collectively serve as environmental cue sensors and trigger signaling events to regulate epithelial function through their association with the cell cytoskeleton and various intracellular adapter proteins. Immune cells, particularly neutrophils (PMN) during transepithelial migration (TEM), can modulate adhesion molecule expression, conformation, and distribution, significantly impacting epithelial function and tissue homeostasis. This review discusses the roles of key intestinal epithelial adhesion molecules in regulating PMN trafficking and outlines the potential consequences on epithelial function.

Two types of functionally distinct fiber containing structural protein complexes are produced during infection of adenovirus serotype 5

Adenoviruses are common pathogens. The localization of their receptors coxsackievirus and adenovirus receptor, and desmoglein-2 in cell-cell junction complexes between polarized epithelial cells represents a major challenge for adenovirus infection from the apical surface. Structural proteins including hexon, penton base and fiber are excessively produced in serotype 5 adenovirus (Ad5)-infected cells. We have characterized the composition of structural protein complexes released from Ad5 infected cells and their capacity in remodeling cell-cell junction complexes. Using T84 cells as a model for polarized epithelium, we have studied the effect of Ad5 structural protein complexes in remodeling cell-cell junctions in polarized epithelium. The initial Ad5 infection in T84 cell culture was inefficient. However, progressive distortion of cell-cell junction in association with fiber release was evident during progression of Ad5 infection. Incubation of T84 cell cultures with virion-free supernatant from Ad5 infected culture resulted in distortion of cell-cell junctions and decreased infectivity of Ad5-GFP vector. We used gel filtration chromatography to fractionate fiber containing virion–free supernatant from Ad5 infected culture supernatant. Fiber containing fractions were further characterized for their capacity to inhibit the infection of Ad5-GFP vector, their composition in adenovirus structural proteins using western blot and LC-MS/MS and their capacity in remolding cell-cell junctions. Fiber molecules in complexes containing penton base and hexon, or mainly hexon were identified. Only the fiber complexes with relatively high content of penton base, but not the fiber-hexon complexes with low penton base, were able to penetrate into T84 cells and cause distortion of cell-cell junctions. Our findings suggest that these two types of fiber complexes may play different roles in adenoviral infection.

Expression of human decay-accelerating factor on intestinal epithelium of transgenic mice does not facilitate infection by the enteral route

In vitro, infection of polarized human intestinal epithelial cells by coxsackievirus B3 (CVB3) depends on virus interaction with decay-accelerating factor (DAF), a receptor expressed on the apical cell surface. Although mice are highly susceptible to CVB3 infection when virus is delivered by intraperitoneal injection, infection by the enteral route is very inefficient. Murine DAF, unlike human DAF, does not bind virus, and we hypothesized that the absence of an accessible receptor on the intestinal surface is an important barrier to infection by the oral route. We generated transgenic mice that express human DAF specifically on intestinal epithelium and measured their susceptibility to infection by a DAF-binding CVB3 isolate. Human DAF permitted CVB3 to bind to the intestinal surface ex vivo and to infect polarized monolayers of small-intestinal epithelial cells derived from DAF transgenic mice. However, expression of human DAF did not facilitate infection by the enteral route either in immunocompetent animals or in animals deficient in the interferon alpha/beta receptor. These results indicate that the absence of an apical receptor on intestinal epithelium is not the major barrier to infection of mice by the oral route.

IMPORTANCE

CVB3 infection of human intestinal epithelial cells depends on DAF at the apical cell surface, and expression of human DAF on murine intestinal epithelial cells permits their infection in vitro. However, expression of human DAF on the intestinal surface of transgenic mice did not facilitate infection by the oral route. Although the role of intestinal DAF in human infection has not been directly examined, these results suggest that DAF is not the critical factor in mice.

miR-466 is putative negative regulator of Coxsackie virus and Adenovirus Receptor

This study aimed at elucidating how Coxsackie B virus (CVB) perturbs the host's microRNA (miRNA) regulatory pathways that lead to antiviral events. The results of miRNA profiling in rat pancreatic cells infection models revealed that rat rno-miR-466d was up-regulated in CVB infection. Furthermore, in silico studies showed that Coxsackie virus and Adenovirus Receptor (CAR), a cellular receptor, was one of the rno-miR-466d targets involved in viral entry. Subsequent experiments also proved that both the rno-miR-466d and the human hsa-miR-466, which are orthologs of the miR-467 gene family, could effectively down-regulate the levels of rat and human CAR protein expression, respectively.