Evidence for efficient uptake and incorporation of sialic acid by eukaryotic cells

摘要: Sialic acids are the most abundant terminal carbohydrate moiety on cell surface glycoconjugates in eukaryotic cells and of functional importance for many biological ligand-receptor interactions. It is a widely accepted view that sialic cannot be efficiently taken up from extracellular space by cells. To test this assumption, we cultivated two recently identified human hematopoetic lines which hyposialylated due to deficiency de novo acid biosynthesis presence N-acetylneuraminic (NeuAc), frequently found acid. Surprisingly, NeuAc medium supplementation rapidly potently compensated endogenous hyposialylation concentration-dependent manner, resulting presentation sialoglycans involved adhesion, virus infection signal transduction. We provide several experimental evidence all suggest was neither extracellularly incorporated nor degraded less complex sugar before uptake. Importantly, induced marked increase intracellular CMP-NeuAc levels both primary regardless prior sialylation status Studies employing 9-[3H]NeuAc revealed an uptake consistent with observed incorporation unlabeled NeuAc. propose existence efficient mechanism