Biosynthetic incorporation of unnatural sialic acids into polysialic acid on neural cells

In this study we demonstrate that polysialyltransferases are capable of accepting unnatural substrates in terminally differentiated human neurons. Polysialyltransferases catalyze the glycosylation of the neural cell adhesion molecule (NCAM) with polysialic acid (PSA). The unnatural sialic acid analo...

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Bibliographic Details
Published in:Glycobiology (Oxford) 2000-10, Vol.10 (10), p.1049-1056
Main Authors: Charter, N W, Mahal, L K, Koshland, Jr, D E, Bertozzi, C R
Format: Article
Language:English
Subjects:
Cell Compartmentation
Cell Differentiation
Cell Membrane - metabolism
Cytidine Monophosphate N-Acetylneuraminic Acid - metabolism
Glycoconjugates - biosynthesis
Hexosamines - metabolism
Humans
Neural Cell Adhesion Molecules - biosynthesis
Neurons - cytology
Neurons - metabolism
Polysaccharides - metabolism
Sialic Acids - metabolism
Sialyltransferases - metabolism
Substrate Specificity
Tumor Cells, Cultured
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Summary:In this study we demonstrate that polysialyltransferases are capable of accepting unnatural substrates in terminally differentiated human neurons. Polysialyltransferases catalyze the glycosylation of the neural cell adhesion molecule (NCAM) with polysialic acid (PSA). The unnatural sialic acid analog, N-levulinoyl sialic acid (SiaLev), was incorporated into cell surface glycoconjugates including PSA by the incubation of cultured neurons with the metabolic precursor N-levulinoylmannosamine (ManLev). The ketone group within the levulinoyl side chain of SiaLev was then used as a chemical handle for detection using a biotin probe. The incorporation of SiaLev residues into PSA was demonstrated by protection from sialidases that can cleave natural sialic acids but not those bearing unnatural N-acyl groups. The presence of SiaLev groups on the neuronal cell surface did not impede neurite outgrowth or significantly affect the distribution of PSA on neuronal compartments. Since PSA is important in neural plasticity and development, this mechanism for modulating PSA structure might be useful for functional studies.
ISSN:0959-6658
1460-2423
DOI:10.1093/glycob/10.10.1049