Entactin, a novel basal lamina-associated sulfated glycoprotein.

A sulfated glycoprotein, entactin, of apparent molecular weight 158,000 has been isolated from an extracellular basement membrane-like matrix. This matrix is elaborated in cell culture by a mouse endodermal cell line. Antibodies prepared in rabbits against this sulfated glycoprotein react with mouse and rat basement membranes from a variety of tissues. These antibodies also react in a specific manner with a discrete component of mouse and rat kidney glomeruli. The electrophoretic mobility of this component is identical to that of entactin. The mouse kidney antigen, as shown by immunoelectron microscopic studies, is predominantly localized at the surface of epithelial cells of tubules and glomeruli adjacent to the basement membrane. Some antigen is also present in the basal lamina adjacent to the epithelial cells. Entactin is distinct from the basement membrane-associated protein GP-2, a protein similar to laminin. Entactin differs from GP-2 in electrophoretic mobility, cyanogen bromide peptide fragmentation pattern, immunological cross-reactivity, and incorporation of H235SO4. Entactin is insensitive to treatment with chrondroitinase ABC. It is suggested that this molecule plays a role in the interaction of the extracellular matrix and the cell surface.