Differential effects of unnatural sialic acids on the polysialylation of the neural cell adhesion molecule and neuronal behavior.
In this study we have examined how unnatural sialic acids can alter polysialic acid expression and influence the adhesive properties of the neural cell adhesion molecule (NCAM). Unnatural sialic acids are generated by metabolic conversion of synthetic N-acyl mannosamines and are typically incorporated into cell-surface glycoconjugates. However, N-butanoylmannosamine and N-pentanoylmannosamine are effective inhibitors of polysialic acid (PSA) synthesis in stably transfected HeLa cells expressing NCAM and the polysialyltransferase STX. These cells were used as substrates to examine the effect of inhibiting PSA synthesis on the development of neurons derived from the chick dorsal root ganglion. N-butanoylmannosamine blocked polysialylation of NCAM and significantly reduced neurite outgrowth comparable with enzymatic removal of PSA by endoneuraminidases. As a result, neurite outgrowth was similar to that observed for non-polysialylated NCAM. In contrast, previous studies have shown that N-propanoyl sialic acid (SiaProp), generated from N-propanoylmannosamine, is readily accepted by polysialyltransferases and permits the extension of poly(SiaProp) on NCAM. Despite being immunologically distinct, poly(SiaProp) can promote neurite outgrowth similarly to natural polysialic acid. Thus, subtle structural differences in PSA resulting from the incorporation of SiaProp residues do not alter the antiadhesive properties of polysialylated NCAM.
Charter
Neil W
NW
Department of Chemistry, University of California, Berkeley, California 94720, USA. ncharter@uclink4.berkeley.edu
Mahal
Lara K
LK
Koshland
Daniel E
DE
Bertozzi
Carolyn R
CR
D000107:Acetylation; D000818:Animals; D002645:Chickens; D005727:Ganglia, Spinal / Q000502:physiology; D006367:HeLa Cells; D006595:Hexosamines / Q000494:pharmacology; D006801:Humans; D039842:Neural Cell Adhesion Molecule L1; D019006:Neural Cell Adhesion Molecules / Q000378:metabolism*; D016501:Neurites / Q000187:drug effects* / Q000502:physiology; D012794:Sialic Acids / Q000096:biosynthesis* / Q000378:metabolism* / Q000494:pharmacology*
D006595:Hexosamines; C116505:N-butanoylmannosamine; D039842:Neural Cell Adhesion Molecule L1; D019006:Neural Cell Adhesion Molecules; D012794:Sialic Acids; C021319:polysialic acid; C103469:polysialyl neural cell adhesion molecule