The catenin, p120^ctn, is a common membrane-associated protein in various epithelial and non-epithelial cells and tissues

Abstract.

The cadherin-binding catenin p120^ctn was originally identified as an Src-tyrosine kinase substrate. More recently, p120^ctn has been shown in some cell types to be associated with catenin/cadherin complexes of adherens junctions. To address the question whether p120^ctn is restricted to certain cell types or whether it is a general cellular component we investigated tissue distribution of p120^ctn by immunohistochemistry and immunoblotting in the rat. We found p120^ctn to be widely distributed in several tissues where it is mainly restricted to the plasma membrane. In various epithelia p120^ctn was found in association with different adherens junctions such as the zonula adherens and puncta adherentia. In addition, p120^ctn was localized along infoldings of the basal cell membrane, most prominently in renal proximal and distal tubules. p120^ctn was not restricted to epithelia. It was also found at intercalated discs of cardiomyocytes. In the nervous system, immunostaining was particularly prominent in areas rich in synapses suggesting that p120^ctn is a component of synaptic adherens junctions as well. By immunoblotting, four different isoforms of p120^ctn could be detected displaying similar electrophoretic mobilities as the isoforms 1A, 1B, 2A, and 2B reported from mice. Whereas all epithelia assayed contained at least two isoforms, testis, heart, brain, and retina contained a single 110-kDa band that corresponds to isoform 1B in mice.