Effects of altered sialic acid biosynthesis on N-linked glycan branching and cell surface interactions

Nam D. Pham, Poh Choo Pang, Soumya Krishnamurthy, Amberlyn M. Wands, Paola Grassi, Anne Dell, Stuart M. Haslam, Jennifer J. Kohler

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


GNE (UDP-GlcNAc 2-epimerase/ManNAc kinase) myopathy is a rare muscle disorder associated with aging and is related to sporadic inclusion body myositis, the most common acquired muscle disease of aging. Although the cause of sporadic inclusion body myositis is unknown, GNE myopathy is associated with mutations in GNE. GNE harbors two enzymatic activities required for biosynthesis of sialic acid in mammalian cells. Mutations to both GNE domains are linked to GNE myopathy. However, correlation between mutation-associated reductions in sialic acid production and disease severity is imperfect. To investigate other potential effects of GNE mutations, we compared sialic acid production in cell lines expressing wild type or mutant forms of GNE. Although we did not detect any differences attributable to disease-associated mutations, lectin binding and mass spectrometry analysis revealed that GNE deficiency is associated with unanticipated effects on the structure of cell-surface glycans. In addition to exhibiting low levels of sialylation, GNE-deficient cells produced distinct N-linked glycan structures with increased branching and extended poly-Nacetyllactosamine. GNE deficiency may affect levels of UDPGlcNAc, a key metabolite in the nutrient-sensing hexosamine biosynthetic pathway, but this modest effect did not fully account for the change in N-linked glycan structure. Furthermore, GNE deficiency and glucose supplementation acted independently and additively to increaseN-linked glycan branching. Notably, N-linked glycans produced by GNE-deficient cells displayed enhanced binding to galectin-1, indicating that changes inGNEactivity can alter affinity of cell-surface glycoproteins for the galectin lattice. These findings suggest an unanticipated mechanism by which GNE activity might affect signaling through cell-surface receptors.

Original languageEnglish (US)
Pages (from-to)9637-9651
Number of pages15
JournalJournal of Biological Chemistry
Issue number23
StatePublished - Jun 9 2017

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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