Effect of N-glycosylation on turnover and subcellular distribution of N- acetylgalactosaminyltransferase I and sialyltransferase II in neuroblastoma cells

Erhard Bieberich, Tewin Tencomnao, Dmitri Kapitonov, Robert K. Yu

Research output: Contribution to journalArticle

22 Scopus citations

Abstract

Gangliosides are sialylated glycosphingolipids whose biosynthesis is catalyzed by a series of endoplasmic reticulum (ER)- and Golgi-resident glycosyltransferases. Protein expression, processing, and subcellular localization of the key regulatory enzymes for ganglioside biosynthesis, sialyltransferase II (ST-II) and N-acetylgalactosaminyltransferase I (GalNAcT), were analyzed upon transient expression of the two enzymes in the neuroblastoma cell lines NG108-15 and F-11. The enzymes were endowed with a C-terminal epitope tag peptide (FLAG) for immunostaining and immunoaffinity purification using a FLAG-specific antibody. Mature ST-II-FLAG and GalNAcT- FLAG were expressed as N-glycoproteins with noncomplex oligosaccharides. ST- II-FLAG was distributed to the Golgi apparatus, whereas GalNAcT-FLAG was found in the ER and Golgi. Inhibition of early N-glycoprotein processing with castanospermine resulted in a distribution of ST-II-FLAG to the ER, whereas that of GalNAcT-FLAG remained unaltered. In contrast to GalNAcT, the activity of ST-II and the amount of immunostained enzyme were reduced concomitantly by. 75% upon incubation with castanospermine. This was due to a fourfold increased turnover of ST-II-FLAG, which was not found with GalNAcT-FLAG. The ER retention and increased turnover of ST-II-FLAG were most likely due to its inability to bind to calnexin upon inhibition of early N-glycoprotein processing. Calnexin binding was not observed for GalNAcT-FLAG, indicating a differential effect of N-glycosylation on the turnover and subcellular localization of the two glycosyltransferases.

Original languageEnglish (US)
Pages (from-to)2359-2364
Number of pages6
JournalJournal of Neurochemistry
Volume74
Issue number6
DOIs
StatePublished - Jun 5 2000

Keywords

  • Chaperones
  • Gangliosides
  • Glycosylation
  • Glycosyltransferases
  • Posttranslational modification
  • Subcellular localization

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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