Laminin and other basal lamina proteins with neurite promoting activity in medium conditioned by C6 glioma cells.

Neurite promoting activities (NPFs) are essential factors in neuronal differentiation. Some of them are associated with proteins of the extracellular matrix (ECM). C6 cells, a rat glioma cell line, release NPF activities into the cell culture medium. We used antibodies against ECM-proteins for enrichment and partial characterization of these activities. Results show that, (1) C6 cells express and release laminin; (2) the C6-laminin consists of 260 kD chains only and is therefore different from typical basal lamina laminin (220 and 440 kD chains), but comparable to other laminins of glial origin (chains in the 200 kD range only); (3) C6-laminin partially purified by affinity chromatography shows NPF-activity; (4) laminin concentration in C6 cell-conditioned medium is not sufficient to account for the total neurite promoting activity of the medium, and (5) in addition to laminin C6 cells express and release fibronectin and possibly type IV collagen.