Identification and immunolocalization of a new component of human cardiac muscle intercalated disc

A new protein was found at the site of interaction of cytoskeletal filaments and the plasma membrane in desmosomes of human cardiac muscle intercalated discs. As revealed by the indirect immunofluorescence method, monoclonal antibody XVE2 was able to stain intercalated discs of cardiac muscle and desmosomes of human skin epidermal cells, whereas it did not react with sections from human uterine smooth muscle, vascular tissue and liver. Western immunoblot analysis of extracts of total human heart and uterus demonstrated that a doublet of 65 kDa and 70 kDa polypeptides were the major proteins recognized by the monoclonal antibody XVE2. These 65 kDa and 70 kDa proteins are immunologically distinct from other known intercalated disc proteins such as vinculin, meta-vinculin, filamin, talin, alpha-actinin, desmin and desmoplakins. The distribution of the XVE2 monoclonal antibody antigens raises the possibility that these polypeptides are involved in linking intermediate filaments to the dense plaque of desmosomes of cardiac muscle intercalated discs.