N-cadherin in adult rat cardiomyocytes in culture. I. Functional role of N-cadherin and impairment of cell-cell contact by a truncated N-cadherin mutant.
N-cadherin is a transmembrane Ca(2+)-dependent glycoprotein that is part of adherens junctions. It functions with the cell adhesion N-terminal extracellular domain as a site of homophilic cell-cell contacts. The intracellular C-terminal domain provides via a catenin complex the interaction with the cytoskeleton. Ectopic expression of chicken N-cadherin in adult rat cardiomyocytes (ARC) in culture was obtained after microinjection into non-dividing cardiomyocytes; it was demonstrated that the exogenous protein colocalized with the endogenous N-cadherin at the plasma membrane of the cell and formed contact sites. A dominant negative chicken N-cadherin mutant was constructed by a large deletion of the extracellular domain. This mutant was expressed and inhibited the function of the endogenous rat N-cadherin probably by competing for the catenin complex binding domain, which is essential for the formation of a stable cell-cell contact of ARC. The injected cells lost contact with neighbouring cells and retracted; the connexons of the gap junctions were pulled out as well. This could be avoided by another N-cadherin mutation, which, in addition to the N-terminal truncation, contained a deletion of the catenin binding domain. In the case of the truncated N-cadherin at the N terminus, the sarcomeric structure of the myofibrils of ARC was also affected. Myofibrils were the most vulnerable cytoskeletal structures affected by the overexpressed dominant negative N-cadherin mutation. Similar behaviour was shown when cardiomyocytes separated following Ca2+ depletion and when new cell-cell contacts were formed after Ca2+ replenishment. N-cadherin is thought to be the essential component for establishing new cell-cell contacts which eventually led to a new formation of intercalated disc-like structures in the cardiac cell culture.
Hertig
C M
CM
Institute for Cell Biology, Swiss Federal Institute of Technology, Zürich, Switzerland.
Eppenberger-Eberhardt
M
M
Koch
S
S
Eppenberger
H M
HM
D000818:Animals; D001483:Base Sequence; D015820:Cadherins / Q000235:genetics / Q000378:metabolism*; D002450:Cell Communication; D002478:Cells, Cultured; D002645:Chickens; D017931:DNA Primers; D017353:Gene Deletion; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism*; D008969:Molecular Sequence Data; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D015820:Cadherins; D017931:DNA Primers