{beta}-galactoside {alpha}2,6 sialyltranferase 1 promotes transforming growth factor-{beta}-mediated epithelial-mesenchymal transition [Glycobiology and Extracellular Matrices]

October 24th, 2014 by Lu, J., Isaji, T., Im, S., Fukuda, T., Hashii, N., Takakura, D., Kawasaki, N., Gu, J.

β-galactoside α2,6 sialyltranferase 1 (ST6GAL1) catalyzes the addition of terminal α2,6 sialylation to N-glycans. Increased expression of ST6GAL1 has been reported in diverse carcinomas, and highly correlates with tumor progression. Here, we report that St6gal1 transcription and α2,6 sialylated N-glycans are up-regulated during TGF-β-induced Epithelial-mesenchymal transition (EMT) in GE11 cells, requiring Sp1 element within St6gal1 promoter. Knockdown of St6gal1 strongly suppressed TGF-β-induced EMT with a concomitant increase in E-cadherin expression, a major determinant of epithelial cell adherens junctions. Conversely, overexpression of ST6GAL1 increased the turnover of cell surface E-cadherin and promoted TGF-β-induced EMT. Overexpressing β-galactoside α2,3 sialyltranferase 4 had little influence on EMT, indicating specificity for α2,6 sialylation. The basal mesenchymal phenotype of MDA-MB-231 human breast cancer cells was partially reversed by ST6GAL1 silencing. Moreover, ST6GAL1 knockdown inhibited the phosphorylation of Akt, but not Smad2, suggesting ST6GAL1 contributes to EMT through a non-Smad signaling pathway. Taken together, our data indicate that ST6GAL1 promotes TGF-β dependent EMT, as well as maintenance of mesenchymal state by growth signaling, providing a plausible mechanism whereby up-regulated ST6GAL1 may promote malignant progression.
  • Posted in Journal of Biological Chemistry, Publications
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