Overexpression of the α2,6 (N) sialyltransferase enzyme in human and rat neural cell lines is associated with increased expression of the polysialic acid epitope

Abstract

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.

Retinoic acid‐induced changes in polysialyltransferase mRNA expression and NCAM polysialylation in human neuroblastoma cells

“…. In contrast to previous findings for SH-SY5Y cells using samples extracted by sonication (Hildebrandt et al, 1998a;Georgopoulou and Breen, 1999), we could not detect NCAM 120, even after extraction with octylglucoside, which is especially suited to extract GPI-anchored molecules like the 120 kD isoform of NCAM (Solomon et al, 1998; data not shown). Thus, the previously found band at 120 kD might have been a degradation artifact resulting from the extraction procedure.…”

“Juvenile stress” alters maturation‐related changes in expression of the neural cell adhesion molecule L1 in the limbic system: Relevance for stress‐related psychopathologies

“…Alternatively, insofar as adult juvenile‐stressed rats exhibit higher basal CORT levels than controls (Ilin and Richter‐Levin, 2009), it may be that in the current study a juvenile stress‐induced state of chronic elevated CORT levels in adulthood provoked an L1 neuroprotective reaction against the deleterious atrophic effects of chronic elevated CORT levels. Several studies indicated direct involvement of glucocorticoids in regulating NCAM and its polysialylated form PSA‐NCAM expression (Coughlan et al, 1996; Coughlan and Breen, 1998; Georgopoulou and Breen, 1999; Datson et al, 2001). Adult juvenile‐stressed rats were reported to exhibit altered expression ratio of PSA‐NCAM to NCAM (Tsoory et al, 2008a).…”

The role of post-translational modification in ϐ-amyloid precursor protein processing

“…Stably-transfected B104 rat neuroblastoma cells that overexpress the ST6N enzyme have been generated. These cells have specific enzyme activities reaching up to 20 times that of control (mock-transfected) cells and show a parallel increase in protein-bound ␣2,6 linked sialic acid [49,50]. There was a marked decrease in the levels of particulate (cellular) APP in the transfected cells, which was accompanied by an increase in the secreted form of the protein (Figure 4).…”