CLONING AND CHARACTERIZATION OF A NOVEL EPIDERMAL-CELL SURFACE-ANTIGEN (ESA)

We report here the isolation and characterization of a cDNA that encod es a novel extracellular epidermal molecule, epidermal surface antigen (ESA), which is thought to play a role in intercellular epidermal adh esion. Sequence analysis reveals that the 379 amino acid ESA has a mol ecular mass of about 41.7 kDa and an alpha-helix-rich secondary confor mation. Much of this also has an heptad substructure, consistent with the formation of several bundles of alpha-helices in a compact globula r structure. The ESA protein appears to consist of an NH2-terminal hyd rophobic region with mixed alpha and beta structure followed by a more hydrophilic COOH-terminal region which is very rich in alpha-helix. T he 2.5-kilobase ESA mRNA is expressed in cultured keratinocytes, melan ocytes, fibroblasts, carcinoma, and melanoma cell lines. The ESA gene is conserved in all mammalian species examined and has been localized to human chromosome 17 (M17S1) in the same region as the gene for von Recklinghausen neurofibromatosis. The high level of expression of the ESA mRNA in human skin and in cultured cells derived from the epidermi s, the appearance of ESA protein early in human development, and conse rvation of the ESA gene throughout mammalian evolution suggest that th e novel ESA protein plays a vital role in epidermal structure and main tenance.