INTERACTIONS OF THE CYTOPLASMIC DOMAIN OF THE DESMOSOMAL CADHERIN DSG1 WITH PLAKOGLOBIN

Dsg1 is a 165-kDa glycoprotein component of suprabasal epidermal desmo somes and the prototype of a subset of the cadherin superfamily of cel l-cell adhesion proteins known as desmogleins. The adhesive function o f classical cadherins is known to be dependent upon their association with cytoplasmic components called catenins. In the case of desmoglein s, a single interaction has been described with a protein called plako globin that is found in desmosomal plaques, adherens junctions, and th e cytosol. Several proteins with homology to plakoglobin have been des cribed that regulate junction assembly and implement morphoregulatory signals. To address the functional significance of plakoglobin-desmogl ein interaction, we have mapped the sequences of Dsg1 that are crucial for this association by using blot overlay techniques. By examining t he binding of plakoglobin to a deletion series of the Dsg1 cytoplasmic domain expressed as fusion proteins, we have defined a 19-amino acid sequence that is important for association. This region of Dsg1 sequen ce shows significant similarity to the catenin-binding domain of class ical cadherins, suggesting a common mechanism for the association of p lakoglobin with desmosomes and adherens junctions.