Abstract
Teratocarcinoma-derived endodermal PYS-2 cells are known to synthesize an extracellular matrix containing the basement membrane molecules laminin, type IV collagen, and heparan sulfate proteoglycan as major constituents (I. Leivo, K. Alitalo, L. Risteli, A. Vaheri, R. Timpl, J. Wartiovaara, Exp Cell Res 137:15-23, 1982). Immunoferritin techniques with specific antibodies were used in the present study to define the ultrastructural localization of the above constituents in the fibrillar network. Laminin was detected in matrix network adjacent to the basal cell membrane and in protruding matrix fibrils that connect the matrix to the cell membrane. Ruthenium red-stainable heparinase-sensitive 10- to 20-nm particles were often present at the junction of the attachment fibrils and the matrix network, or along the attachment fibrils. A corresponding distribution of ferritin label was observed for basement membrane heparan sulfate proteoglycan. Type IV collagen was found in the matrix network but not in the attachment fibrils. The results suggest that the PYS-2 cells are connected to their pericellular matrix by fibrils containing laminin associated with heparan sulfate-containing particles. These results may also have relevance for the attachment of epithelial cells to basement membranes.