Enhanced expression of β3-galactosyltransferase 5 activity is sufficient to induce in vivo synthesis of extended type 1 chains on lactosylceramides of selected human colonic carcinoma cell lines

Chi Hung Lin, Yao Yun Fan, Yen Ying Chen, Shih Hsin Wang, Chun I. Chen, Lung Chih Yu, Kay Hooi Khoo*

*Corresponding author for this work

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

In general, an elevated expression of β3-galactosyltrans-ferase (β3GalT) activity contributed by β3GalT5 correlates well with increased biosynthesis and expression of type 1 chain (Galβ1-3GlcNAcβ1-) derivatives such as Lewis A and sialyl Lewis A, which are mostly recognized as terminal epitopes and not further extended. Most known β3-N-acetylglucosaminyltransferases show a higher activity toward extending type 2 chain (Galβ1-4GlcNAcβ1-), and an over-expression of β3GalT5 could suppress the formation of the type 2 chain poly-N- acetyllactosaminoglycans. The potential of extending instead the predominant type 1 chain termini synthesized under such circumstances was, however, not investigated, partly due to technical difficulty in unambiguous identification of extended type 1 chains. Using an advanced mass spectrometry-based glycomic mapping and glycan sequencing approach, we show here that type 1 chains carried on the lacto-series glycosphingolipids of colonic carcinoma cells can be extended when the endogenous β3GalT activity relative to competing β4GalT activity, as defined against a common GlcNAcβ1-3Galβ1-4Glc acceptor, is sufficiently high, as found in Colo205 and SW1116, but not in DLD-1 cells. In support of this positive correlation, the lacto-series glycosphingolipids isolated from stably transfected DLD-1 clones over-expressing β3GalT5 were shown to comprise fucosylated dimeric type 1 chains, whereas a mock transfectant and the DLD-1 parent carried only fucosylated dimeric type 2 chains on their lactosylceramides. It suggests that while the natural expression of extended type 1 chain is likely to be determined by many contributing factors including the relative amounts of competing glycosyltransferases and the UDP-Gal level, the enhanced expression of β3GalT5 is sufficient to promote in vivo extension of type 1 chains by furnishing a significantly higher amount of type 1 chain precursors relative to competing type 2 chains.

Original languageEnglish
Pages (from-to)418-427
Number of pages10
JournalGlycobiology
Volume19
Issue number4
DOIs
Publication statusPublished - 2009

Keywords

  • β3-galactosyltransferase
  • β3GalT5
  • Extended type 1 chain
  • Glycomics
  • Mass spectrometry

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