Overexpression of the alpha2,6 (N) sialyltransferase enzyme in human and rat neural cell lines is associated with increased expression of the polysialic acid epitope

The function of the neural cell adhesion molecule, NCAM, is modulated by the expression of the N-linked polysialic acid (PSA) oligosaccharide chain, with PSA serving to decrease the adhesive potential of the protein backbone. In this study, we have generated clonal cells of the rat B104 and human SH-SY5Y neuroblastoma cell lines that over-express the alpha2,6(N) sialyltransferase (ST6N) enzyme in order to investigate the role of this enzyme in PSA biosynthesis. The clonal cells exhibited ST enzyme activities of up to 20-times control levels, which remained stable throughout the duration of the study. The increase in enzyme activity paralleled an increase in enzyme protein levels, as determined by Western blot analysis, and immunocytochemical analysis confirmed the Golgi localisation of the enzyme. The induction of PSA-NCAM expression in the cells expressing high levels of ST6N was confirmed both by using anti-PSA antisera and by specific digestion with endo-N-acetylneuraminidase E, whose actions are specific for alpha2, 8-linked PSA chains. These results demonstrate that the cellular ST6N activity serves to positively influence the expression of PSA in neuronal cells.