Retinoic acid-induced changes in polysialyltransferase mRNA expression and NCAM polysialylation in human neuroblastoma cells.
Polysialic acid (PSA) is a dynamically regulated carbohydrate modification of the neural cell adhesion molecule NCAM, which is implicated in neural differentiation and cellular plasticity. The cloning and characterization of two polysialyltransferases, termed ST8SiaII (STX) and ST8SiaIV (PST), opened up new perspectives in the search for factors that control this unique cell surface glycosylation. In vitro and transfection approaches revealed that ST8SiaII and ST8SiaIV are independently capable of synthesizing PSA on NCAM with slightly different specificities towards the major NCAM isoforms and glycosylation sites. Their overlapping but distinct expression patterns during brain development point towards an independent transcriptional regulation. However, the factors driving their joint or distinct expression, as well as the significance of divergent expression patterns in vivo, are not yet understood. In the present study, the mRNA expression of ST8SiaII and ST8SiaIV was comparatively analyzed in neuronal differentiation of PSA-positive human neuroblastoma cell lines induced by retinoic acid (RA), phorbolester, or growth factors. Using a semiquantitative RT-PCR strategy, we demonstrated a general decrease in the mRNA level of ST8SiaII upon differentiation of SH-SY5Y and LAN-5 cells. In contrast, a drastic increase of ST8SiaIV was specifically induced by RA-treatment of SH-SY5Y cells. To explore the significance of these changes, the cellular capacity to perform PSA synthesis and the degree of NCAM polysialylation were analyzed. Our data indicate that the increased expression of ST8SiaIV enables an accelerated polysialylation of NCAM, which, however, is not converted into higher amounts of PSA.
Seidenfaden
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R
Institut für Zoologie (220), Universität Hohenheim, Garbenstr. 30, 70593 Stuttgart, Germany.
Hildebrandt
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H
D000954:Antigens, Surface / Q000187:drug effects / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects* / Q000235:genetics; D048429:Cell Size / Q000187:drug effects / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008970:Molecular Weight; D019006:Neural Cell Adhesion Molecules / Q000187:drug effects / Q000378:metabolism*; D009447:Neuroblastoma; D009473:Neuronal Plasticity / Q000187:drug effects / Q000235:genetics; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D012794:Sialic Acids / Q000096:biosynthesis*; D012799:Sialyltransferases / Q000235:genetics*; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
D000954:Antigens, Surface; D019006:Neural Cell Adhesion Molecules; D012333:RNA, Messenger; D012794:Sialic Acids; C021319:polysialic acid; D014212:Tretinoin; C046778:CMP-N-acetylneuraminate-poly-alpha-2,8-sialosyl sialyltransferase; D012799:Sialyltransferases