Characterization of a 125K glycoprotein associated with bovine epithelial desmosomes

An analysis of the concanavalinA binding polypeptide components of bovine tongue epithelial desmosomes reveals that in addition to the known desmosomal glycoproteins of 100/115K (the 'desmocollins'), 140K and 160/165K ('desmoglein 1') there is an uncharacterized glycoprotein of 125K (K = Mr x 10(-3). This latter polypeptide is immunologically distinct from known desmosomal glycoproteins, as determined by Western immunoblotting, but is recognized by an antibody preparation directed against the epithelial cell adhesion molecule E-cadherin. Moreover, the cadherin antibodies recognize a polypeptide present in bovine muzzle desmosomes that co-migrates with the 125K glycoprotein component of bovine tongue epithelial desmosomes. Upon treatment of bovine tongue desmosomes with a solution containing 9.5 M-urea, the 125K polypeptide becomes enriched in a urea-insoluble, membrane-enriched pelletable desmosomal fraction. Cadherin antibodies and antibodies directed against the 100/115K and 160/165K desmosomal glycoproteins generate similar immunofluorescence staining patterns in cryostat sections of bovine tongue epithelium. However, immunoelectron microscopic analysis of bovine tongue epithelium reveals that cadherin antibodies recognize components located both along the intercellular region of the desmosome and along nondesmosomal cell surfaces whereas antibodies directed against the 100/115K and the 160/165K desmosomal glycoproteins bind specifically to desmosomes. These results suggest that a cadherin-like glycoprotein component may play a role in the adhesive properties of the desmosomes of stratified squamous epithelia.