Evidence for the presence of N-CAM 180 on astrocytes from rat cerebellum and differences in glycan structures between N-CAM 120 and N-CAM 140

Abstract

Differences in the N-linked oligosaccharides on isoforms of the neural cell adhesion molecule (N-CAM) on astrocytes were found using a lectin, namely, Datura stramonium agglutinin (DSA). Integral proteins of astrocytes prepared from newborn rat cerebella were solubilized with Nonident P-40 and then separated into two fractions, an unbound fraction and a bound fraction, by a DSA-agarose column. Both fractions thus obtained were subjected to immunoblotting using an anti-N-CAM monoclonal antibody. In the DSA-bound fraction, N-CAM 180 was found as well as N-CAM 120 and N-CAM 140. On the other hand, N-CAM 180 was not detected in the unbound fraction, whereas N-CAM 120 and N-CAM 140 were. Furthermore, N-CAM 180 did not carry the HNK-1 epitope, whereas the other two isoforms did. Although the presence of N-CAM 180 on astrocytes was controversial until recently, the results shown here indicate that N-CAM 180 exists on rat astrocytes and exclusively carries a glycan structure reacting with DSA. This is the first demonstration of the production of N-CAM glycoforms carrying different oligosaccharides by a homogeneous astrocyte preparation. These results suggest that the glycosylation of each N-CAM isoform might be regulated independently. Whether each N-CAM with different glycans participates in different functions remains to be established.