EXPRESSION PATTERNS OF LORICRIN IN VARIOUS SPECIES AND TISSUES

In this study we analyzed the expression patterns of loricrin in vario us species and tissues using immunohistochemistry, immunoblotting and Northern blots. Loricrin is a glycine-, serine- and cysteine-rich prot ein expressed very late in epidermal differentiation in the granular l ayers of normal mouse and human epidermis. Later on in differentiation , loricrin becomes cross-linked as a major component into the cornifie d cell envelope by the formation of N(epsilon)-(gamma-glutamyl)lysine isopeptide bonds. This process either occurs directly or by the interm ediate accumulation in L-keratohyaline granules of mouse epidermis and human acrosyringia. Loricrin was identified in all mammalian species analyzed by virtue of its highly conserved carboxy-terminal sequences revealing an electric mobility of approximately 60 kDa in rodents, rab bit and cow and of approximately 35 kDa in lamb and human on sodium do decyl sulfate polyacrylamide gel electrophoresis. Loricrin is expresse d in the granular layer of all mammalian orthokeratinizing epithelia t ested including oral, esophageal and fore-stomach mucosa of rodents, t racheal squamous metaplasia of vitamin A deficient hamster and estroge n induced squamous vaginal epithelium of ovary ectomized rats. Loricri n is also expressed in a few parakeratinizing epithelia such as BBN [N -butyl-N-(4-hydroxybutyl)nitrosamine]-induced murine bladder carcinoma and a restricted subset of oral and single vaginal epithelial cells i n higher mammals. Our results provide further evidence that the progra m of squamous differentiation in internal epithelia of the upper alime ntary tract in rodents and higher mammals differ remarkably. In additi on, we also have noted the distinct distribution patterns of human lor icrin and involucrin, another major precursor protein of the cornified cell envelope.