Abstract
Sialylation of glycoproteins and glycolipids plays an important role during development, regeneration, and pathogenesis of diseases. During times of intense plasticity within the nervous system, such as development and regeneration, sialylation of neural cells is distinct from the time of its maintenance. In this study, a synthetic precursor of neuraminic acid, N-propanoylmannosamine (N-propanoyl neuraminic acid precursor (P-NAP)), is applied to the culture medium of oligodendrocyte progenitor cells, microglia, astrocytes, and neurons from neonatal rat brains to alter sialylation of glycoconjugates within these cells. P-NAP is metabolized and incorporated as N-propanoyl neuraminic acid into glycoproteins of the cell membrane. P-NAP stimulates the proliferation of astrocytes and microglia but not of oligodendrocyte progenitor in vitro. However, P-NAP increases the number of oligodendrocyte progenitor cells expressing the early oligodendroglial surface marker A2B5 epitope. In the presence of P-NAP, cerebellar neurons (but not astrocytes) in microexplant cultures start to express the oligodendroglial progenitor marker A2B5 epitope, which is normally undetectable on these cells. The controls, which were performed in the absence of any additive or in the presence of the physiological precursor of neuraminic acid, N-acetylmannosamine, did not show any increase in A2B5 expression.
Highlights
Cell surface components such as terminal neuraminic acids of glycoconjugates orchestrate a variety of biological functions such as proliferation, cell-cell interaction, and migration
Cerebellar Microexplants Treated with propanoyl neuraminic acid from the appropriate precursor (P-NAP) Show Early A2B5-positive Oligodendrocyte Progenitor Cells That Migrated from the Explant Cores—Cerebellar microexplants from neonatal brains mostly consist of small cerebellar neurons, astrocytes, and oligodendrocytes [14, 15]
When the explants were treated with 5 mM P-NAP (Fig. 1D), there was no significant difference in the outgrowth pattern of these neurons when compared with the control in the absence of neuraminic acid precursors (Fig. 1A)
Summary
P-NAP, N-propanoyl neuraminic acid precursor; A-NAP, N-acetylneuraminic acid precursor; PBS, phosphatebuffered saline; GFAP, glial fibrillary acidic protein; BrdUrd, 5-bromo2Ј-deoxyuridine; HPLC, high pressure liquid chromatography. This paper is available on line at http://www.jbc.org the outgrowth pattern of oligodendrocyte progenitor cells, astrocytes, and neurons as well as neurite fasciculation [14, 15]. They were maintained in the presence of synthetic neuraminic acid precursors to study some of these aspects. Cerebellar neurons do not express the A2B5 epitope under the culture conditions of our experiments, they start to express this epitope on their neurites after application of P-NAP
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