Localization of UDP-GlcNAc 2-epimerase/ManAc kinase (GNE) in the Golgi complex and the nucleus of mammalian cells (2005)

Author(s): Krause S, Hinderlich S, Amsili S, Horstkorte R, Wiendl H, Argov Z, Mitrani-Rosenbaum S, Lochmuller H

    Abstract: The bifunctional enzyme UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (GNE) is essential for early embryonic development and catalyzes the rate limiting step in sialic acid biosynthesis. Although epimerase and kinase activities have been attributed to GNE, little is known about the regulation, differential expression, and subcellular localization of GNE in vivo. Mutations in GNE cause a rare inherited muscle disorder in humans called hereditary inclusion body myopathy (HIBM). However, the role of GNE in HIBM pathogenesis has not been defined yet. Here, we show that the GNE protein is expressed in various mammalian cells and tissues with highest levels found in cancer cells and liver. In human skeletal muscle, GNE protein is developmentally regulated: high levels are found in immature myoblasts but low levels in mature skeletal muscle. The GNE protein colocalizes with resident proteins of the Golgi compartment in a variety of human cells including muscle. Drug-induced disruption of the Golgi and subsequent recovery reveals co-distribution of GNE along with Golgi-targeted proteins. This subcellular localization of GNE is in good agreement with its established role as the key enzyme of sialic acid biosynthesis, since the sialylation of glycoconjugates takes place in the Golgi complex. Surprisingly, GNE is also detected in the nucleus. Upon nocodazole treatment, GNE redistributes to the cytoplasm suggesting that GNE may act as a nucleocytoplasmic shuttling protein. A regulatory role for GNE shifting between the nuclear and the Golgi compartment is proposed. Further insight into GNE regulation may promote the understanding of HIBM pathogenesis.

      • Date: 01-04-2005
      • Journal: Experimental Cell Research
      • Volume: 304
      • Issue: 2
      • Pages: 365-379
      • Publisher: Academic Press
      • Publication type: Article
      • Bibliographic status: Published

      Keywords: Active Transport, Cell Nucleus/drug effects/physiology Animals Antineoplastic Agents/pharmacology Brefeldin A/pharmacology Cell Compartmentation/physiology Cell Nucleus/ enzymology Cytoplasm/enzymology Glycoconjugates/ biosynthesis Golgi Apparatus/ enzymology Hela Cells Humans Jurkat Cells K562 Cells Mice Multienzyme Complexes/ metabolism Muscle, Skeletal/enzymology/growth & development Myoblasts/enzymology Myositis, Inclusion Body/congenital/enzymology N-Acetylneuraminic Acid/ biosynthesis Neoplasms/enzymology/physiopathology Nocodazole/pharmacology Pluripotent Stem Cells Protein Synthesis Inhibitors/pharmacology Protein Transport/drug effects/physiology


      Professor Hanns Lochmuller
      Professor of Experimental Myology