Isolation of the intercellular glycoproteins of desmosomes.

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Abstract
To characterize the demosome components that mediate intercellular adhesion and cytoskeletal-plasma membrane attachment, whole desmosomes and isolated desmosomal intercellular regions (desmosomal cores) were prepared from the living cell layers of bovine muzzle epidermis. The tissue was disrupted in a nonionic detergent at low pH, sonciated, and the insoluble residue fractionated by differential centrifugation and metrizamide gradient centrifugation. Transmission electron microscopic analyses reveal that a fraction obtained after differential centrifugation is greatly enriched in whole desmosomes that possess intracellular plaques. Metrizamide gradient centrifugation removes most of the plaque material, leaving the intercellular components and the adjoining plasma membranes. Sodium dodecyl sulfate polyacrylamide gel electrophoresis coupled with methods that reveal carbohydrate-containing moieties on gels demonstrate that certain proteins present in whole desmosomes are clycosylated. These glycoproteins are specifically and greatly enriched in the desmosome cores of which they are the principal protein contituents, and may function as the intercellular adhesive of the desmosome.