α-catenin, a cadherin-associated protein, links cadherin/β-catenin and cadherin/plakoglobin complexes to the actin cytoskeleton. This protein is required for the function of cadherins, cell adhesion molecules. We transfected an α-catenin-deficient colon carcinoma line, which cannot organize desmosomes, with a series of α-catenin mutant constructs. We examined the formation of desmosomes in these cells by immunofluorescence staining using anti-desmoglein and anti-desmoplakin antibodies. The results demonstrated that either the middle or the carboxy-terminal region of α-catenin was required for desmosome formation. Immunoblot analysis revealed that the amounts of desmoglein and desmoplakin did not differ significantly between cells that were capable of forming desmosomes and those that failed to form desmosomes. Cell surface biotinylation revealed that desmoglein was retained intracellularly in cells that could not organize desmosomes. The internal domain binds vinculin and α-actinin, actin-binding proteins, while the carboxy-terminal domain has the ability to bind and bundle actin filaments. These results indicate that the interaction of α-catenin and actin functions in the assembly of desmosomes in epithelial cells.

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