Implication of tissue transglutaminase and desmoplakin in cell adhesion mechanism in human epidermis

The distribution patterns of both tissue and keratinocyte transglutaminases (TGase), as well as that of desmoplakin (DP), have been immunohistochemica lly investigated in human skin cultured in the absence or presence of cysta mine and enalapril, two acantholytic agents. In the control samples, tissue TGase is predominantly expressed in lower layers of the epidermis and is l ocated intercellularly. Conversely, in tissues cultured with cystamine or e nalapril, a diffuse cytoplasmatic staining was observed. Similarly, DP, det ected on the cell membrane in the control, shifts into the cytosol of the k eratinocytes following treatment. The distribution pattern of the keratinoc yte enzyme in the acantholytic epidermis was identical to that observed in the normal one. Since cystamine and enalapril are TGase inhibitors and DP w as shown to act as a TGase substrate in vitro, we suggest that DP and tissu e enzyme may participate in cell adhesion at the intraepidermal level.