Primate involucrins: antigenic relatedness and detection of multiple forms

Hominoid apes (gorilla, chimpanzee, orangutan, gibbon), Old World monkeys (rhesus, cynomolgus), New World monkeys (owl, cebus), and a prosimian (lemur) express involucrin-like proteins in cultured keratinocytes. Primate involucrins can be precipitated with trichloroacetic acid, resolubilized at pH 8, and subsequently retain aqueous solubility in 67% ethanol. Polyacrylamide gel electrophoresis of keratinocyte extracts after this rapid partial purification has revealed in each species tested one (chimpanzee, orangutan, gibbon) or two (gorilla, rhesus, owl, cebus) antigenically crossreactive proteins that migrate in the vicinity of human involucrin. In the species examined further (gorilla, chimpanzee, rhesus), poly(A)+ mRNA isolated from the cultures directed the cell-free translation of polypeptides with mobilities similar to those extracted from the cells. From five cynomolgus monkeys, three different electrophoretic profiles were obtained, suggesting the existence of different alleles. Quantitative comparisons by a sensitive enzyme-linked immunosorbent assay indicated that certain primate involucrins have a higher density of antigenic determinants than the human protein, whereas others lack some determinant(s). In contrast to those from other species, all of which showed substantial crossreactivity, the lemur protein was minimally immunoreactive by immunoblotting and not clearly detected by solid-phase assay. The electrophoretic and antigenic differences displayed throughout the primate order suggest that this protein has been subject to relatively rapid evolution.