Cerebellar soluble lectin is responsible for cell adhesion and participates in myelin compaction in cultured rat oligodendrocytes.

Cultures of rat oligodendrocytes were used to test the possible role of the cerebellar soluble lectin (CSL) in myelin formation. Immunocytochemistry at the ultrastructural level showed that the lectin is present in the cytoplasm of the perikaryon of cultured oligodendrocytes and also on the plasma membrane of the cell body and processes. It is present in compact myelin and in the zones of contacts between different myelin sheaths or oligodendrocyte membranes. Staining of blots of the cultures with iodinated CSL indicated that endogenous glycoprotein ligands for CSL are present in the culture, rendering probable the hypothesis that cell contacts between different oligodendrocytes or between adjacent lamellae in myelin are mediated by lectin-glycoprotein interactions. This hypothesis was demonstrated by two effects of anti-CSL Fab fragments (4 micrograms/ml) on oligodendrocyte cultures: (1) the almost complete detachment of the cell layer from the culture substratum, and (2) the loss of myelin compaction by a separation of lamellae at the intraperiod line. The present findings could explain the complexity of the contacts between cultured oligodendrocyte processes by the formation of CSL bridges between glycoproteins of the membranes of these cells. CSL seems to be a key molecule in adhesion both for intercellular contacts and fixation of cells to the substratum. The small number of glycoprotein subunits found in oligodendrocytes that interact with CSL suggests that CSL-mediated cell adhesion involves a special class of glycoprotein glycans.