LOCALIZATION OF ADDUCIN IN EPIDERMIS

On the cytoplasmic side of the plasma membrane of erythrocytes there i s a dense protein filament matrix that maintains the shape of the cell s. The-main constituents of this system, actin and spectrin, which hav e 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 spectr in, 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 add ucin to be localized at cell-cell contact sites in epidermis using aff inity-purified antibodies against human erythrocyte adducin. Immunoflu orescence of epidermis revealed an intense fluorescence in the basal l ayer, 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 presen ce of adducin polypeptides of 103 kd and 97 kd in epidermis, but in cu ltured keratinocytes only the higher molecular weight form could be de tected. This study indicates adducin, a regulatory protein in erythroc ytes, is also present in epidermis. Its localization suggests that it may be involved in the formation of the microfilament matrix of the me mbrane skeleton at cell-cell contact sites.