Cellular localization of epidermal transglutaminase: a histochemical and immunochemical study.

Abstract

Sites of transglutaminase activity in epidermis and hair follicle were visualized histochemically by exposure of frozen tissue sections to dansyl cadaverine in the presence of Ca. Fluorescence, resulting from crosslinking of dansyl cadaverine to tissue acceptor (glutamine-containing) sites, was limited to upper Malpighian and granular cells of bovine snout epidermis, granular cells of normal human epidermis and cells of the keratinizing zone of the inner sheath of bovine vibrissa or hair follicles. No fluorescence was seen incompletely keratinized or parakeratotic human epidermis obtained from biopsies of diseased skin. Direct immunochemical identification of epidermal transglutaminase in bovine epidermis, by using fluorescein-conjugated antiserum to the enzyme, confirmed histochemical localization studies. The antiserum did not cross-react with isolated bovine hair follicle transglutaminase nor did it label bovine hair follicles, newborn rat or human epidermis. These observations indicate that epidermal transglutaminase functions in the later phases of differentiation in epidermis and hair follicle inner root sheath, and that epidermal and hair follicle transglutaminases are isoenzymes.