The participation of a putative cell surface receptor for laminin and fibronectin in peripheral neurite extension

We have used the CSAT (cell substrate attachment) monoclonal antibody (Mab), which is directed against a putative laminin and fibronectin receptor, to examine its role in the adhesive phenomena of neurons. This antibody was previously found to disturb the adhesion of several classes of fibroblasts and muscle. Here we report its effects upon neuronal-substrate adhesion. Two sources of neurons were investigated--the dorsal root and ciliary ganglia. Both responded similarly. Neurons plated in the presence of the CSAT Mab did not adhere to the substratum and process formation was inhibited completely for at least 24-48 hr. In explant cultures, when neurons were first allowed to extend processes prior to addition of the CSAT Mab, the results depended on the particular substrate. With some substrates, the neurites bundled and detached from the substratum; with others, they retracted and regrew to form large fascicles or bundles of processes. In dissociated cultures that already had extended processes, neurites fasciculated and cell bodies aggregated in response to the presence of the CSAT Mab. The magnitude of this response varied, depending upon the substrate. The antigen was localized, using immunofluorescence, on neuronal cell bodies, axons, and growth cones. This distribution correlated with its biological effects on all parts of the neuron. The antigen was isolated from neuronal cultures by immunoaffinity purification. It migrated in the molecular weight range of 140 kDa on reducing SDS-PAGE. This antigen is very similar to that isolated from fibroblasts, which is an integral membrane glycoprotein complex. The data presented implicate the participation of the CSAT antigen in neurite extension and fasciculation.