Incorporation of N-propanoylneuraminic acid leads to calcium oscillations in oligodendrocytes upon the application of GABA

Sialylation of glycoproteins and glycolipids plays an important role during development, regeneration and pathogenesis, It has been shown that unnatur al sialylation within glial cell cultures can have distinct effects on thei r proliferation and antigenic profiles, These cultures metabolize N-propano ylman-nosamine (N-propanoylneuraminic acid precursor P-NAP), a synthetic no n-physiological precursor of neuraminic acid, resulting in the expression o f N-propanoylneuraminic acid in glycoconjugates of their cell membranes [Sc hmidt, C,, Stehling, P,, Schnitzer, J,, Reutter, W. and Horstkorte, R, (199 8) J, Biol, Chem. 273, 19146-19152]. To determine whether these biochemical ly engineered sialic acids influence calcium concentrations in cells of the oligodendrocyte lineage, mixed glial cultures of oligodendrocytes growing on top of an astrocyte monolayer were exposed to glutamate, histamine, adre naline, gamma-aminobutyric acid (GABA), high potassium (high K+) and ATP, C alcium responses in P-NAP-treated oligodendrocytes were determined by confo cal microscopy with the calcium indicator fluo-3 AM, and compared with cont rol cultures. We showed that P-NAP differentially modulated the calcium res ponses of individual oligodendrocytes when GABA nas applied. GABA induced c alcium oscillations with up to four spikes per min in 60% of oligodendrocyt es when treated with P-NAP. (C) 2000 Federation of European Biochemical Soc ieties. Published by Elsevier Science B.V. All rights reserved.