Basement membrane glycoproteins in the extracellular matrix of a teratocarcinoma-derived differentiated cell line

Glycoproteins synthesized and deposited into extracellular matrix in cultures of a mouse teratocarcinoma-derived differentiated cell line (PYS-2) were studied by metabolic labeling and immunochemical methods, and by immunofluorescence and electron microscopy. PYS-2 cells synthesized two major high-molecular weight glycoproteins, laminin and type IV collagen, which were deposited in matrix form with no apparent processing. The lamellar subcellular matrix was composed of a loose network of fine fibrils and dense grains. Straight 60-80 nm fibrils attached the matrix to the plasma membranes and were decorated with ferritin-coupled antibodies for laminin. The cells did not synthesize fibronectin, but the matrix bound fibronectin from the culture medium. The PSY-2 matrix provides possibilities for in vitro studies on basal lamina components in early differentiation.