Catenins as mediators of the cytoplasmic functions of cadherins.

The catenins are polypeptides that bind to the conserved cytoplasmic tail of cadherins and are required for cadherin function. alpha-Catenin is related to vinculin and seems to be required for the interaction of cadherins with the actin cytoskeleton. beta-Catenin is homologous to armadillo, a segment polarity gene in Drosophila that participates in developmental signaling. Recent findings indicate that beta-catenin also participates in developmental signaling and embryonic patterning in Xenopus laevis. At least a portion of the electrophoretic band migrating at the position of gamma-catenin consists of plakoglobin, a desmosomal and zonula adherens protein that has high sequence similarity to beta-catenin and armadillo. The catenins may be involved in the regulation of cadherin function during tissue morphogenesis and tumorigenesis.