title: Two distinct pathways for O-fucosylation of epidermal growth factor-like or thrombospondin type 1 repeats.
abstract: Epidermal growth factor-like (EGF) repeats and thrombospondin type 1 repeats (TSRs) are both small cysteine-knot motifs known to be O-fucosylated. The enzyme responsible for the addition of O-fucose to EGF repeats, protein O-fucosyltransferase 1 (POFUT1), has been identified and shown to be essential in Notch signaling. Fringe, an O-fucose beta1,3-N-acetylglucosaminyltransferase, elongates O-fucose on specific EGF repeats from Notch to form a disaccharide that can be further elongated to a tetrasaccharide. TSRs are found in many extracellular matrix proteins and are involved in protein-protein interactions. The O-fucose moiety on TSRs can be further elongated with glucose to form a disaccharide. The discovery of O-fucose on TSRs raised the question of whether POFUT1, or a different enzyme, adds O-fucose to TSRs. Here we demonstrate the existence of a TSR-specific O-fucosyltransferase distinct from POFUT1. Similar to POFUT1, the novel TSR-specific O-fucosyltransferase is a soluble enzyme that requires a properly folded TSR as an acceptor substrate. In addition, we found that a previously identified fucose-specific beta1,3-glucosyltransferase adds glucose to O-fucose on TSRs, but it does not modify O-fucose on an EGF repeat. Similarly, Lunatic fringe, Manic fringe, and Radical fringe are all capable of modifying O-fucose on an EGF repeat, but not on a TSR. Taken together, these results suggest that two distinct O-fucosylation pathways exist in cells, one specific for EGF repeat and the other for TSRs.
authors.affiliation: Department of Biochemistry and Cell Biology, Institute for Cell and Developmental Biology, Stony Brook University, Stony Brook, New York 11794-5215.
authors.forename: Yi
authors.initials: Y
authors.lastname: Luo
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Nita-Lazar
authors.forename: Robert S
authors.initials: RS
authors.lastname: Haltiwanger
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D004815:Epidermal Growth Factor / Q000378:metabolism*; D004926:Escherichia coli; D005643:Fucose / Q000378:metabolism; D005647:Fucosyltransferases / Q000378:metabolism*; D005964:Glucosyltransferases / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D017510:Protein Folding; D051880:Receptors, Notch / Q000502:physiology; D015398:Signal Transduction; D019700:Thrombospondin 1 / Q000737:chemistry / Q000378:metabolism*
chemical_list: D051880:Receptors, Notch; D019700:Thrombospondin 1; D005643:Fucose; D004815:Epidermal Growth Factor; D005647:Fucosyltransferases; D005964:Glucosyltransferases