Polysialylation of NCAM by a single enzyme.
The addition of poly-alpha2,8-N-acetylneuraminic acid (polysialic acid; PSA) to the neural cell adhesion molecule NCAM plays a crucial role in neural development [1-3], neural regeneration [4], and plastic processes in the vertebrate brain associated with neurite outgrowth [5], axonal pathfinding [6], and learning and memory [7,-9]. PSA levels are decreased in people affected by schizophrenia [10], and PSA has been identified as a specific marker for some neuroendocrine and lymphoblastoid tumours [11-13]; expression of PSA on the surface of these tumour cells modulates their metastatic potential [11-13]. Studies aimed at understanding PSA biosynthesis and the dynamics of its production have largely been promoted by the cloning of polysialyltransferases (PST-1 in hamster; PST in human and mouse) [14-16]. However, the number of enzymes involved in the biosynthesis of PSA has not been identified. Using incompletely glycosylated NCAM variants and soluble recombinant glycosyltransferases, we reconstituted the site at which PST-1 acts to polysialylate NCAM in vitro. The data presented here clearly demonstrate that polysialylation of NCAM is catalyzed by a single enzyme, PST-1, and that terminal sialylation of the N-glycan core is sufficient to generate the PSA acceptor site. Our results also show that PST-1 can act on core structures with the terminal sialic acid connected to galactose via an alpha2,3 or alpha2,6 linkage.
Mühlenhoff
M
M
Institut für Medizinische Mikrobiologie, Medizinische Hochschule Hannover, Konstanty-Gutschow-Str. 8, 30625 Hannover, Germany.
Eckhardt
M
M
Bethe
A
A
Frosch
M
M
Gerardy-Schahn
R
R
D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D006801:Humans; D051379:Mice; D019006:Neural Cell Adhesion Molecules / Q000378:metabolism*; D012794:Sialic Acids / Q000378:metabolism*; D012799:Sialyltransferases / Q000378:metabolism*; D013379:Substrate Specificity
D019006:Neural Cell Adhesion Molecules; D012794:Sialic Acids; C021319:polysialic acid; C046778:CMP-N-acetylneuraminate-poly-alpha-2,8-sialosyl sialyltransferase; D012799:Sialyltransferases