earticle

영어

Sialic acids are typically found as terminal monosaccharides attached to the cell surface glycoconjugates and play important roles in many physiological and pathological processes, including microbe binding that leads to infections, regulation of the immune response, the progression and spread of human malignancies, differentiation, development, canceration, and degenerative diseases (1-3). UDP-GlcNAc is a metabolic precursor of sialic acids. Thus, glucose metabolism and regulation of metabolic flux of UDT-GlcNAc critically affect the expression of cell surface sialic acid and nervous system function (4,5). Here, we investigated the expression of sialic acid in human neuroblastoma cell, SK-N-SH, in response to glucose deprivation. When subjected to a glucose-free environment for 24 h, SK-N-SH cells showed severe defects in neurite development and eventually died. During glucose limitation, the expression level of sialic acid of total cellular proteins was examined by lectin blotting using Maackia amunrensis(MAA) lectin and Sambucus nigra(SNA) lectin, which are specific for α-2,3 sialic acid and α-2,6 sialic acid, respectively. Glucose deprivation caused increase in MAA binding to several major proteins (especially, 45 and 75 kDa), suggesting an increased α-2,3 sialylation on these proteins. Lectin histochemistry using MAA lectin also showed a significant increase in surface α,2-3 sialylation upon glucose deprivation. In addition, glucose deprivation resulted in a dose-dependant increase in the mRNA level of ST3GAL4 sialyltransferase by 2.3 folds comparing to that cultured in 2 mg/ml glucose medium, whereas expressions of other sialyltransferases (ST3GAL3, ST3GAL6, and ST6GAL1) were not significantly influenced. These results suggest that glucose deprivation upregulates the α,2-3 sialylation on several cell surface glycoproteins and this phenomenon may be involved in neural cell death by glucose deprivation.