EPISIALIN

(= polymorphic epithelial mucin, PEM; epithelial membrane antigen, EMA)

Heavily glycosylated membrane glycoprotein. Encoded by the MUC- 1 gene; has a molecular weight of around 300 kD, more than half of which is O -linked glycan. There is a 69 residue cytoplasmic domain and the extracellular domain may extend hundreds of nanometres beyond the plasma membrane; the increased expression in carcinoma cells may reduce the adhesion and mask antigenic properties of the cells. Similar functions are ascribed to ASGP, epiglycanin and leukosialin.