CAR: A virus receptor within the tight junction

https://doi.org/10.1016/j.addr.2005.01.007Get rights and content

Abstract

The coxsackievirus and adenovirus receptor (CAR) mediates cell attachment and infection by coxsackie B viruses and by a number of adenoviruses. CAR also mediates homotypic intercellular interactions. In polarized epithelial cells, CAR is closely associated with the tight junction, where it contributes to the barrier to paracellular flow of solutes and macromolecules. CAR's biological roles are not well defined, but emerging evidence suggests that it may function during embryonic development and in regulating cell proliferation.

Introduction

Viruses initiate infection by attaching to receptors on the surface of a susceptible cell. Expression of specific receptors is often an important determinant of a cell's susceptibility to infection and of virus tropism for particular tissues. The coxsackievirus and adenovirus receptor (CAR) was first identified as a cellular protein involved in attachment and infection by group B coxsackieviruses (CVB) and later found to be an adenovirus (Ad) receptor as well [1], [2], [3], [4]. Because of widespread interest in adenoviruses as vectors for therapeutic gene delivery, considerable attention has been paid to CAR's role in virus tropism, and to the structural features important for virus attachment. However, CAR's natural biological functions remain uncertain.

CAR belongs to a growing subfamily of immunoglobulin-like surface molecules, many of which have been localized to sites of cell–cell contact and appear to function in cell adhesion or intercellular recognition. CAR mediates homotypic cell–cell interactions and functions as a transmembrane component of the epithelial cell tight junction [5]. This review will discuss CAR's function as a virus receptor and as a tight junction protein, and describe evidence regarding its broad biological functions.

Section snippets

Protein structure

CAR cDNA encodes a 36O- amino acid protein; cleavage of a 19-residue signal peptide results in a mature protein of 346 amino acids. CAR's predicted molecular weight is approximately 38,000, but it migrates at 46,000 on SDS polyacrylamide gels, most likely due to glycosylation. CAR contains a single membrane-spanning domain that separates an extracellular domain of 216 residues from a 107-residue intracellular domain (Fig. 1A). The cytoplasmic domain contains a site for palmitylation [6],

Evolutionary conservation

CAR has been identified in a variety of mammalian species [3], [24], [30], [31], as well as in non-mammalian vertebrates such as the fish and frog [32], but we have found no obvious CAR homologue in Drosophila or nematodes. Zebrafish and human CAR are 44% identical overall. More extensive conservation within the cytoplasmic domain (66% identity) may suggest that the this portion of the molecule participates in intracellular interactions that are also conserved.

CAR belongs to a family of

Function and association with TJ components

Tight junctions between epithelial cells regulate the flow of ions and macromolecules across the intact epithelium, and serve to divide the apical and basolateral membrane compartments. A variety of evidence indicates that CAR is a component of the tight junction [5]. In polarized epithelial cell lines, and in primary human airway epithelial cells, CAR can be seen–both by confocal microscopy and thin-section electron microscopy–at the apical pole of the lateral membrane, where it colocalizes

CAR tissue distribution

Initial RNA blot analysis suggested that in adults, human CAR is most highly expressed in the heart, brain, and pancreas, with significant levels in the testis and prostate [3], [24]. This RNA expression pattern is consistent with the tropism of coxsackievirus B3, which infects by way of the GI tract, and which causes myocarditis, meningoencephalitis, and pancreatitis. CAR-binding adenoviruses primarily infect the respiratory tract, although these adenoviruses, like CVB, are a major cause of

Development

CAR expression levels change dramatically during development. In the mouse embryo, CAR expression is prominent in the brain, but expression levels drop significantly within the first month of life [11], [94], [95]. High levels of CAR expression in the newborn brain may account for the unique susceptibility of newborn, but not adult, mice to encephalitis caused by CVB [96], [97]. Expression on fetal and regenerating myocytes may account for the susceptibility of these cells, but not adult

Concluding remarks

Since it was isolated in 1997, CAR has been of interest to virologists, gene therapists, and cell biologists. Although it was first identified as a receptor permitting virus attachment, it is now clear that CAR serves an important function in cell–cell interaction. Increasing evidence suggests that CAR functions in the regulation of cell proliferation, and our own recent data indicate that it is essential for normal embryonic development. The mechanisms by which CAR-mediated signals lead to

Acknowledgments

We thank Susan Pichla for help in preparing figures. Our work is supported by grants from the NIH and the American Heart Association.

References (109)

  • M. Aurrand-Lions et al.

    JAM-2, a novel immunoglobulin superfamily molecule, expressed by endothelial and lymphatic cells

    J. Biol. Chem.

    (2001)
  • K. Hirata et al.

    Cloning of an immunoglobulin family adhesion molecule selectively expressed by endothelial cells

    J. Biol. Chem.

    (2001)
  • T. Ishida et al.

    Targeted disruption of endothelial cell-selective adhesion molecule inhibits angiogenic processes in vitro and in vivo

    J. Biol. Chem.

    (2003)
  • E. Raschperger et al.

    CLMP, a novel member of the CTX family and a new component of epithelial tight junctions

    J. Biol. Chem.

    (2004)
  • S. Suzu et al.

    Molecular cloning of a novel immunoglobulin superfamily gene preferentially expressed by brain and testis

    Biochem. Biophys. Res. Commun.

    (2002)
  • T. Toyofuku et al.

    Direct association of the gap junction protein connexin-43 with ZO-1 in cardiac myocytes

    J. Biol. Chem.

    (1998)
  • L. Gonzalez-Mariscal et al.

    MAGUK proteins: structure and role in the tight junction

    Semin. Cell Dev. Biol.

    (2000)
  • A.S. Fanning et al.

    The tight junction protein ZO-1 establishes a link between the transmembrane protein occludin and the actin cytoskeleton

    J. Biol. Chem.

    (1998)
  • G. Bazzoni et al.

    Interaction of junctional adhesion molecule with the tight junction components ZO-1, cingulin, and occludin

    J. Biol. Chem.

    (2000)
  • K. Ebnet et al.

    Junctional adhesion molecule interacts with the PDZ domain-containing proteins AF-6 and ZO-1

    J. Biol. Chem.

    (2000)
  • C.B. Coyne et al.

    The coxsackievirus and adenovirus receptor interacts with the multi-PDZ domain protein-1 (MUPP-1) within the tight junction

    J. Biol. Chem.

    (2004)
  • Y. Hamazaki et al.

    Multi-PDZ domain protein 1 (MUPP1) is concentrated at tight junctions through its possible interaction with claudin-1 and junctional adhesion molecule

    J. Biol. Chem.

    (2002)
  • I.Y. Dobrosotskaya et al.

    MAGI-1 interacts with beta-catenin and is associated with cell–cell adhesion structures

    Biochem. Biophys. Res. Commun.

    (2000)
  • K.M. Patrie et al.

    Interaction of two actin-binding proteins, synaptopodin and alpha-actinin-4, with the tight junction protein MAGI-1

    J. Biol. Chem.

    (2002)
  • K. Sollerbrant et al.

    The Coxsackievirus and adenovirus receptor (CAR) forms a complex with the PDZ domain-containing protein ligand-of-numb protein-X (LNX)

    J. Biol. Chem.

    (2003)
  • S.E. Dho et al.

    The mammalian numb phosphotyrosine-binding domain. Characterization of binding specificity and identification of a novel PDZ domain-containing numb binding protein, LNX

    J. Biol. Chem.

    (1998)
  • E.S. Barton et al.

    Junction adhesion molecule is a receptor for reovirus

    Cell

    (2001)
  • M.A. Clark et al.

    Intestinal M cells and their role in bacterial infection

    Int. J. Med. Microbiol.

    (2003)
  • N.E. Bowles et al.

    Detection of viruses in myocardial tissues by polymerase chain reaction. evidence of adenovirus as a common cause of myocarditis in children and adults

    J. Am. Coll. Cardiol.

    (2003)
  • R.P. Tomko et al.

    Expression of the adenovirus receptor and its interaction with the fiber knob

    Exp. Cell Res.

    (2000)
  • S.A. Ross et al.

    Efficient adenovirus transduction of 3T3-L1 adipocytes stably expressing coxsackie–adenovirus receptor

    Biochem. Biophys. Res. Commun.

    (2003)
  • J.S. Kim et al.

    Enhancement of the adenoviral sensitivity of human ovarian cancer cells by transient expression of coxsackievirus and adenovirus receptor (CAR)

    Gynecol. Oncol.

    (2002)
  • R. Xu et al.

    Expression and distribution of the receptors for coxsackievirus B3 during fetal development of the Balb/c mouse and of their brain cells in culture

    Virus Res.

    (1996)
  • Y. Hotta et al.

    Developmental distribution of coxsackie virus and adenovirus receptor localized in the nervous system

    Brain Res. Dev. Brain Res.

    (2003)
  • R. Feuer et al.

    Coxsackievirus B3 and the neonatal CNS: the roles of stem cells, developing neurons, and apoptosis in infection, viral dissemination, and disease

    Am. J. Pathol.

    (2003)
  • J.E. Mapoles et al.

    Purification of a HeLa cell receptor protein for the group B coxsackieviruses

    J. Virol.

    (1985)
  • J.M. Bergelson et al.

    Isolation of a common receptor for Coxsackie B viruses and adenoviruses 2 and 5

    Science

    (1997)
  • R.P. Tomko et al.

    HCAR and MCAR: the human and mouse cellular receptors for subgroup C adenoviruses and group B coxsackieviruses

    Proc. Natl. Acad. Sci. U. S. A.

    (1997)
  • C.J. Cohen et al.

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

    Proc. Natl. Acad. Sci. U. S. A.

    (2001)
  • W. van't Hof et al.

    Fatty acid modification of the coxsackievirus and adenovirus receptor

    J. Virol.

    (2002)
  • Y. Xie et al.

    Identification of a human LNX protein containing multiple PDZ domains

    Biochem. Genet.

    (2001)
  • Y. He et al.

    Interaction of coxsackievirus B3 with the full length coxsackievirus–adenovirus receptor

    Nat. Struct. Biol.

    (2001)
  • M.C. Bewley et al.

    Structural analysis of the mechanism of adenovirus binding to its human cellular receptor, CAR

    Science

    (1999)
  • T. Okegawa et al.

    The mechanism of the growth-inhibitory effect of coxsackie and adenovirus receptor (CAR) on human bladder cancer: a functional analysis of car protein structure

    Cancer Res.

    (2001)
  • P.A. van der Merwe et al.

    Transient intercellular adhesion: the importance of weak protein–protein interactions

    Trends Biochem. Sci.

    (1994)
  • P.A. van der Merwe et al.

    Human cell-adhesion molecule CD2 binds CD58 (LFA-3) with a very low affinity and an extremely fast dissociation rate but does not bind CD48 or CD59

    Biochemistry

    (1994)
  • D. Kostrewa et al.

    X-ray structure of junctional adhesion molecule: structural basis for homophilic adhesion via a novel dimerization motif

    EMBO J.

    (2001)
  • A.E. Prota et al.

    Crystal structure of human junctional adhesion molecule 1: implications for reovirus binding

    Proc. Natl. Acad. Sci. U. S. A.

    (2003)
  • K.R. Bowles et al.

    Genomic organization and chromosomal localization of the human coxsackievirus B–adenovirus receptor gene

    Hum. Genet.

    (1999)
  • J.W. Chen et al.

    Structure and chromosomal localization of the murine coxsackievirus and adenovirus receptor gene

    DNA Cell Biol.

    (2003)
  • Cited by (0)

    View full text