Pattern of Coxsackie Adenovirus Receptor (CAR) Expression in Heart and Pituitary Autopsy Tissues

Coxsackie Adenovirus Receptor (CAR) was identified as a cell surface protein, which enables group B Coxsackie virus and Adenovirus of different groups to attach to the surface of the cells. CAR is a type 1 transmembrane protein belonging to a subgroup of immunoglobulin superfamily. The expression of CAR is developmentally regulated, and its tissue localisation is complex. In polarised epithelial cells, CAR is concentrated at the basolateral membrane of intercellular junctions where it acts as a component of tight junctional complex through its association with PDZ containing domains like zonula occludens-1 or MUPP-1. In the adult heart, CAR is localised at the cardiomyocyte sarcolemma and intercalated discs. In the nervous system of vertebrates, CAR is strongly expressed during embryogenesis, followed by a drastic reduction at the early postnatal stages. The absence of CAR in mice results in lethality at embryonic day 11 because of malformations of the heart. In the adult heart, ablation of CAR results in disturbed conduction of electrical activity from the atrium to the ventricles as indicated by the prolonged PR interval in electrocardiogram. Deletion of CAR also affects the localisation and expression of connexion ,45 at the atrioventricular node cell-cell junction, as well as localisation of (3- catenin and zonula occludens-1 at the ventricular intercalated discs. CAR homologs have been identified in a number of species including humans, mice, dogs, pigs and zebrafish and the proteins appeared to be highly conserved in evolution.