Localization of adducin in epidermis.

On the cytoplasmic side of the plasma membrane of erythrocytes there is a dense protein filament matrix that maintains the shape of the cells. The main constituents of this system, actin and spectrin, which have also been detected in keratinocytes and fibroblasts, are known to be linked in erythrocytes in a network structure by additional proteins such as band 4.1 and adducin. The interaction between actin and spectrin, mediated by adducin, is regulated by calmodulin and protein kinase C. Because we have previously found adducin in cultured keratinocytes, we investigated epidermis by immunochemical techniques. We found adducin to be localized at cell-cell contact sites in epidermis using affinity-purified antibodies against human erythrocyte adducin. Immunofluorescence of epidermis revealed an intense fluorescence in the basal layer, whereas stratum spinosum and stratum granulosum showed moderate staining. There was intense staining at sites of cell-cell contact in cultured human keratinocytes. Immunoblot analysis indicated the presence of adducin polypeptides of 103 kd and 97 kd in epidermis, but in cultured keratinocytes only the higher molecular weight form could be detected. This study indicates adducin, a regulatory protein in erythrocytes, is also present in epidermis. Its localization suggests that it may be involved in the formation of the microfilament matrix of the membrane skeleton at cell-cell contact sites.