Roles of O‐Fucose Glycans in Notch Signaling Revealed by Mutant Mice
Section snippets
Overview
Notch receptors belong to a family of single transmembrane glycoproteins containing 29–36 EGF repeats in their extracellular domain (ECD). Notch receptor signaling is critical for cell fate determination, cell growth control, and development in metazoans. In mammals, there are four Notch receptors (Notch1–Notch4) and five Notch ligands (Jagged1, Jagged2, Delta1, Delta3, and Delta4). Each Notch receptor is synthesized in the endoplasmic reticulum (ER) as a single polypeptide and later cleaved in
Glycosylation of Notch Receptors and Notch Ligands
The extracellular domain of Notch receptors is glycosylated with N‐glycans (Johansen et al., 1989) and O‐glycans, including O‐fucose and O‐glucose glycans (Moloney et al., 2000b). O‐glucosylation occurs at Ser or Thr in the consensus sequence C1XXPS/TC2 between the first and second Cys residue in Notch EGF repeats. A trisaccharide may be present at O‐glucose sites. Although the structure of the trisaccharide is unknown, it is predicted to contain xylose in the structure Xylβ1,3Xylβ1,3Glc (Fig. 1
Pofut1 Is an Essential Component of the Canonical Notch Signaling Pathway
O‐Fucose on Notch receptors was first shown to play a role in Notch signaling in Lec13 Chinese hamster ovary (CHO) cells that make very low amounts of GDP‐fucose (Moloney 2000a, Chen 2001). Jagged1‐induced Notch signaling in a co‐culture reporter assay is markedly reduced in Lec13 cells. These cells transfer little fucose to glycoproteins but can be corrected by exogenous fucose and thus have normal function of fucosyltransferases including Pofut1. The fact that Lec13 cells exhibit little Notch
Fringe Is a Modulator of Notch Signaling
Fringe is a β1,3N‐acetylglucosaminyltransferase (β1,3GlcNAcT) that transfers GlcNAc to O‐fucose on EGF repeats of Notch receptors (Haines and Irvine, 2003). In mammals, there are three Fringe homologs, Lunatic, Manic, and Radical Fringe (Lfng, Mfng, and Rfng). They function in the Golgi, but all of them are also secreted.
Lfng is expressed in many cell types during embryonic stages, but its dynamic expression in mouse somites indicated a functional role during segmentation (Johnston et al., 1997
β4GalT‐1 Is a Novel Regulator of Notch Signaling
The elongation of the GlcNAcβ3Fuc disaccharide on Notch EGF repeats by β4GalT‐1 was found to be required for Lfng and Mfng inhibition of Jagged1‐induced Notch signaling in a co‐culture assay (Chen et al., 2001). Neither the Lec20 CHO mutant that lacks β4GalT‐1 and β4GalT‐6 nor the Lec8 CHO mutant that cannot transport UDP‐Gal into the Golgi exhibits Lfng or Mfng modulation of Notch signaling. When corrected with a cDNA encoding β4GalT‐1, Lec20 cells are rescued for Fng effects. To investigate
Mutations in Other Glycosyltransferase Genes
There are now many strains of mice that have a null mutation in a glycosyltransferases gene that affects the synthesis of N‐glycans or mucin O‐glycans or O‐Mannose glycans (Lowe and Marth, 2003). Although Notch receptors and their ligands carry N‐glycans, none of the mutant mice defective in N‐glycan synthesis with the exception of the mice lacking β4GalT‐1 described previously have been found to exhibit an overt phenotype consistent with defective Notch signaling. However, they may well have a
Acknowledgments
This work was supported by NCI grant RO1 95022 to PS.
References (48)
- et al.
Intracellular cleavage of Notch leads to a heterodimeric receptor on the plasma membrane
Cell
(1997) - et al.
Expression of Notch signaling pathway genes in mouse embryos lacking beta4galactosyltransferase‐1
Gene Expr. Patterns
(2006) - et al.
Clock regulatory elements control cyclic expression of Lunatic fringe during somitogenesis
Dev. Cell.
(2002) - et al.
Waves of mouse Lunatic fringe expression, in four‐hour cycles at two‐hour intervals, precede somite boundary formation
Curr. Biol.
(1998) - et al.
Subversion of the T/B lineage decision in the thymus by lunatic fringe‐mediated inhibition of Notch‐1
Immunity
(2001) - et al.
Targeted mutation in beta1,4‐galactosyltransferase leads to pituitary insufficiency and neonatal lethality
Dev. Biol.
(1997) - et al.
Mammalian Notch1 is modified with two unusual forms of O‐linked glycosylation found on epidermal growth factor‐like modules
J. Biol. Chem.
(2000) - et al.
Periodic lunatic fringe expression is controlled during segmentation by a cyclic transcriptional enhancer responsive to notch signaling
Dev. Cell
(2002) - et al.
Lunatic fringe, FGF, and BMP regulate the Notch pathway during epithelial morphogenesis of teeth
Dev. Biol.
(2002) - et al.
Notch ligands are substrates for protein O‐fucosyltransferase‐1 and Fringe
J. Biol. Chem.
(2002)
Highly conserved O‐fucose sites have distinct effects on Notch1 function
J. Biol. Chem.
Fringe modifies O‐fucose on mouse Notch1 at epidermal growth factor‐like repeats within the ligand‐binding site and the Abruptex region
J. Biol. Chem.
Manic fringe and lunatic fringe modify different sites of the Notch2 extracellular region, resulting in different signaling modulation
J. Biol. Chem.
Mutation of the Lunatic Fringe gene in humans causes spondylocostal dysostosis with a severe vertebral phenotype
Am. J. Hum. Genet.
A mutation in the Lunatic fringe gene suppresses the effects of a Jagged2 mutation on inner hair cell development in the cochlea
Curr. Biol.
Growth retardation and early death of beta‐1,4‐galactosyltransferase knockout mice with augmented proliferation and abnormal differentiation of epithelial cells
EMBO J.
Strain‐specific modification of lethality in fucose‐deficient mice
Mamm. Genome.
Periodic repression by the bHLH factor Hes7 is an essential mechanism for the somite segmentation clock
Genes Dev.
Negative feedback loop formed by Lunatic fringe and Hes7 controls their oscillatory expression during somitogenesis
Genesis
Fringe modulation of Jagged1‐induced Notch signaling requires the action of beta4galactosyltransferase‐1
Proc. Natl. Acad. Sci. USA
Specification of vertebral identity is coupled to Notch signalling and the segmentation clock
Development
lunatic fringe is an essential mediator of somite segmentation and patterning
Nature
Lunatic fringe null female mice are infertile due to defects in meiotic maturation
Development
A loss of lunatic fringe is associated with female infertility
Development
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