DEMONSTRATION OF TYPE-II HEMIDESMOSOMES IN A MAMMARY-GLAND EPITHELIAL-CELL LINE, BMGE-H

Hemidesmosomes (HDs) are specialized cell-substrate junctions with dis tinct cytoplasmic plaques where intermediate filaments (IFs) are ancho red. In our previous work, we described two types of HDs in terms of t heir molecular constituents, i.e. type I HD and type II HD [Hieda, Y., Nishizawa, Y., Uematsu, J., and Owaribe, K. (1992) J. Cell Biol. 116, 1497-1506]. In the present study we further characterized type II HDs in cultured cells, comparing their composition and function with thos e of conventional type I HDs. Although the two bovine mammary gland ep ithelial cell lines, BMGE+H and BMGE-H, were derived from the same tis sue, their cell-substrate adhesion properties are markedly different. Immunological examination showed that BMGE-H cells express HD1 and the integrin alpha 6 beta 4 complex but not bullous pemphigoid antigens, while BMGE+H cells express all these components, i.e. the former have type II HDs and the latter have type I HDs. GoH3, a monoclonal antibod y to the integrin alpha 6 subunit, inhibited BMGE-H cell adhesion to l aminin as a substrate, as also observed for BMGE+H cells. These and el ectron microscopic results indicate that BMGE-H cells form type II HD- like structures containing HD1 and alpha 6 beta 4 which are associated with Ifs. This structure mediates adhesion of the cell to laminin. Th is is the first demonstration of an adhesion function for type II HDs in cultured cells.