Coxsackievirus and adenovirus receptor (CAR) mediates atrioventricular-node function and connexin 45 localization in the murine heart
Byung-Kwan Lim, … , Toshitaka Yajima, Kirk U. Knowlton
Byung-Kwan Lim, … , Toshitaka Yajima, Kirk U. Knowlton
Published July 17, 2008
Citation Information: J Clin Invest. 2008;118(8):2758-2770. https://doi.org/10.1172/JCI34777.
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Coxsackievirus and adenovirus receptor (CAR) mediates atrioventricular-node function and connexin 45 localization in the murine heart

Abstract

The coxsackievirus and adenovirus receptor (CAR) is a transmembrane protein that belongs to the family of adhesion molecules. In the postnatal heart, it is localized predominantly at the intercalated disc, where its function is not known. Here, we demonstrate that a first degree or complete block of atrioventricular (AV) conduction developed in the absence of CAR in the adult mouse heart and that prolongation of AV conduction occurred in the embryonic heart of the global CAR-KO mouse. In the cardiac-specific CAR-KO (CAR-cKO) mouse, we observed the loss of connexin 45 localization to the cell-cell junctions of the AV node but preservation of connexin 40 and 43 in contracting myocardial cells and connexin 30.2 in the AV node. There was also a marked decrease in β-catenin and zonula occludens-1 (ZO-1) localization to the intercalated discs of CAR-cKO mouse hearts at 8 weeks before the mice developed cardiomyopathy at 21 weeks of age. We also found that CAR formed a complex with connexin 45 via its PSD-95/DigA/ZO-1–binding (PDZ-binding) motifs. We conclude that CAR expression is required for normal AV-node conduction and cardiac function. Furthermore, localization of connexin 45 at the AV-node cell-cell junction and of β-catenin and ZO-1 at the ventricular intercalated disc are dependent on CAR.

Authors

Byung-Kwan Lim, Dingding Xiong, Andrea Dorner, Tae-Jin Youn, Aaron Yung, Taylor I. Liu, Yusu Gu, Nancy D. Dalton, Adam T. Wright, Sylvia M. Evans, Ju Chen, Kirk L. Peterson, Andrew D. McCulloch, Toshitaka Yajima, Kirk U. Knowlton

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Figure 1

Generation of CAR-cKO mice.

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Generation of CAR-cKO mice. (A) Targeting strategy for deletion of C...
(A) Targeting strategy for deletion of CAR. Exon 2 of the murine CAR gene was flanked by loxP sites, and a neomycin (Neo) resistance cassette was inserted downstream, flanked by FRT sites. Sa, SalI; Nh, NheI; N, NotI. (B) Genomic Southern blot analysis of mutant floxed allele (M) or WT ES cells using probe shown in panel A, after digestion of genomic DNA with NheI. (C) PCR of WT, floxed heterozygous (H), or homozygous (M) mutant mice from extracted mouse-tail genomic DNA using primers P1 and P2. (D) Disruption of CAR expression in WT or CAR-cKO mice as measured by immunofluorescent staining and immunoblotting using an antibody specific for CAR (red) and γ-catenin (green) as marker of the cell-cell junction. The typical intercalated disc staining for CAR is noted in the WT mice (arrows) but absent in the CAR-cKO mice. Scale bar: 40 μm.