The coxsackievirus and adenovirus receptor is a transmembrane component of the tight junction

Abstract

The coxsackievirus and adenovirus receptor (CAR) mediates viral attachment and infection, but its physiologic functions have not been described. In nonpolarized cells, CAR localized to homotypic intercellular contacts, mediated homotypic cell aggregation, and recruited the tight junction protein ZO-1 to sites of cell-cell contact. In polarized epithelial cells, CAR and ZO-1 colocalized to tight junctions and could be coprecipitated from cell lysates. CAR expression led to reduced passage of macromolecules and ions across cell monolayers, and soluble CAR inhibited the formation of functional tight junctions. Virus entry into polarized epithelium required disruption of tight junctions. These results indicate that CAR is a component of the tight junction and of the functional barrier to paracellular solute movement. Sequestration of CAR in tight junctions may limit virus infection across epithelial surfaces.G roup B coxsackieviruses and a number of adenovirus serotypes initiate infection by binding to the coxsackievirus and adenovirus receptor (CAR) (1-3). CAR is a 46-kDa integral membrane protein with a typical transmembrane region, a long cytoplasmic domain, and an extracellular region composed of two Ig-like domains (1, 2). Both adenovirus (4) and coxsackievirus (5) interact with the N-terminal domain. Homologs of human CAR have been characterized in mice (2, 6), rats, pigs, dogs (7), and zebrafish (8). The murine and human proteins are very similar (91% amino acid identity within the extracellular domain, 77% within the transmembrane domain, and 95% identity within the cytoplasmic domain). Variant isoforms of CAR, which differ only at the C terminus and which most likely result from alternative splicing, have been identified in mice (6), humans, and rats (7). Despite evidence of its evolutionary conservation in mammals and nonmammalian vertebrates, the function of CAR is not known.Tight junctions are continuous circumferential intercellular contacts at the apical poles of lateral cell membranes, appearing in electron micrographs as a series of discrete contacts between the plasma membranes of adjacent cells (9). Tight junctions form a barrier that regulates the paracellular transit of water, solutes, and immune cells across an epithelium (10), and are essential for establishing cell polarity by separating the apical and basolateral domains of polarized epithelial cells (11). ZO-1, the first tight junction protein identified (12, 13), is an intracellular peripheral membrane scaffolding protein important for tight junction structure and assembly. In the present study, we found that in polarized epithelial cells CAR is expressed at the tight junction, where it associates with ZO-1 and functions in the barrier to the movement of macromolecules and ions. Materials and MethodsCell Culture. T-84, CALU-3, and 16HBE14o-cells were grown in 10% CO 2 in a 1:1 mixture of DMEM and Ham's F-12 medium with 10% FCS. To establish polarized monolayers, 5 ϫ 10 5 cells per well were plated on 12-mm diameter polyester filters with a ...

JAML mediates monocyte and CD8 T cell migration across the brain endothelium

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CAR is a cell–cell adhesion protein in human cancer cells and is expressionally modulated by dexamethasone, TNFα, and TGFβ

“…25 Previous immunofluorescence studies on lung epithelial tissue cells revealed restriction of CAR to basolateral membranes, with immunostaining most prominently at cell-cell adhesive structures 6 and tight junctions. 7 For human cancer cells, CAR has been shown to be homogeneously distributed throughout the cell membrane. 26,27 In these studies, cells were either stained as singular cells or under non-cell-cell contact-forming conditions.…”

“…In differentiated human or canine epithelial cells, CAR was found to be localized at basolateral cell-cell adhesions 6 and tight junctions. 7 Currently ongoing clinical trials with recombinant adenoviruses reveal that besides varying gene transfer efficiencies, one of the main problems in situ are severe immunological side reactions. 8,9 The synthetic glucocorticoid dexamethasone is an anti-inflammatory drug and is frequently applied in supportive cancer care including clinical trials with recombinant adenoviruses.…”

Gene therapy for barrett's esophagus: adenoviral gene transfer in different intestinal models

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