Cloning and characterization of a novel epidermal cell surface antigen (ESA)

We report here the isolation and characterization of a cDNA that encodes a novel extracellular epidermal molecule, epidermal surface antigen (ESA), which is thought to play a role in intercellular epidermal adhesion. Sequence analysis reveals that the 379 amino acid ESA has a molecular mass of about 41.7 kDa and an alpha-helix-rich secondary conformation. Much of this also has an heptad substructure, consistent with the formation of several bundles of alpha-helices in a compact globular structure. The ESA protein appears to consist of an NH2-terminal hydrophobic region with mixed alpha and beta structure followed by a more hydrophilic COOH-terminal region which is very rich in alpha-helix. The 2.5-kilobase ESA mRNA is expressed in cultured keratinocytes, melanocytes, 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 epidermis, the appearance of ESA protein early in human development, and conservation of the ESA gene throughout mammalian evolution suggest that the novel ESA protein plays a vital role in epidermal structure and maintenance.