Regulation of sialic acid 9-O-acetylation during the growth and differentiation of murine erythroleukemia cells.
Abstract
Sialic acids are typically found at the terminal position on vertebrate oligosaccharides. They are sometimes modified by an O-acetyl ester at the 9-position, potentially altering recognition of sialic acid by antibodies, lectins, and viruses. 9-O-Acetylation is known to be selectively expressed on gangliosides in melanoma cells and on N-linked chains in hepatocytes. Using a recently developed probe, we show here that in murine erythroleukemia cells, this modification is selectively expressed on another class of oligosaccharides, O-linked chains carried on cell surface sialomucins. These cells also express 9-O-acetylation on the ganglioside GD3, but this modification appears to be undetectable on the cell surface. Increasing cell density in culture is associated with a decrease in cell surface 9-O-acetylation of sialomucins. This change correlates with the spontaneous differentiation toward a mature erythroid phenotype. This down-regulation upon differentiation and entry into the G0/G1 stage of the cell cycle is confirmed by differentiation-inducing agents. In contrast, cells arrested in G2/M by the microtubule depolymerizing agent nocodazole show increased expression of cell surface 9-O-acetylated sialomucins (but not the 9-O-a...Continue Reading
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Characterization of the sialate-7(9)-O-acetyltransferase from the microsomes of human colonic mucosa
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