title: Mammalian PIG-X and yeast Pbn1p are the essential components of glycosylphosphatidylinositol-mannosyltransferase I.
abstract: Within the endoplasmic reticulum (ER), mannoses and glucoses, donated from dolichol-phosphate-mannose and -glucose, are transferred to N-glycan and GPI-anchor precursors, and serine/threonine residues in many proteins. Glycosyltransferases that mediate these reactions are ER-resident multitransmembrane proteins with common characteristics, forming a superfamily of >10 enzymes. Here, we report an essential component of glycosylphosphatidylinositol-mannosyltransferase I (GPI-MT-I), which transfers the first of the four mannoses in the GPI-anchor precursors. We isolated a Chinese hamster ovary (CHO) cell mutant defective in GPI-MT-I but not its catalytic component PIG-M. The mutant gene, termed phosphatidylinositolglycan-class X (PIG-X), encoded a 252-amino acid ER-resident type I transmembrane protein with a large lumenal domain. PIG-X and PIG-M formed a complex, and PIG-M expression was <10% in the absence of PIG-X, indicating that PIG-X stabilizes PIG-M. We found that Saccharomyces cerevisiae Pbn1p/YCL052Cp, which was previously reported to be involved in autoprocessing of proproteinase B, is the functional homologue of PIG-X; Pbn1p is critical for Gpi14p/YJR013Wp function, the yeast homologue of PIG-M. This is the first report of an essential subcomponent of glycosyltransferases using dolichol-phosphate-monosaccharide.
authors.affiliation: Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Ashida
authors.forename: Yeongjin
authors.initials: Y
authors.lastname: Hong
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Murakami
authors.forename: Nobue
authors.initials: N
authors.lastname: Shishioh
authors.forename: Nakaba
authors.initials: N
authors.lastname: Sugimoto
authors.forename: Youn Uck
authors.initials: YU
authors.lastname: Kim
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Maeda
authors.forename: Taroh
authors.initials: T
authors.lastname: Kinoshita
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology; D001483:Base Sequence; D015153:Blotting, Western; D018957:CD59 Antigens / Q000096:biosynthesis; D016466:CHO Cells; D002384:Catalysis; D002460:Cell Line; D002469:Cell Separation; D002470:Cell Survival; D003001:Cloning, Molecular; D018387:Codon, Initiator; D006224:Cricetinae; D004286:Dolichols / Q000737:chemistry; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005434:Flow Cytometry; D005947:Glucose / Q000737:chemistry; D016695:Glycosyltransferases / Q000737:chemistry; D006801:Humans; D008055:Lipids / Q000737:chemistry; D008364:Mannosyltransferases / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000502:physiology*; D008565:Membrane Proteins / Q000737:chemistry*; D051379:Mice; D008969:Molecular Sequence Data; D009005:Monosaccharides / Q000737:chemistry; D009154:Mutation; D009844:Oligosaccharides / Q000737:chemistry; D010641:Phenotype; D010710:Phosphates / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry; D014162:Transfection
chemical_list: D000890:Anti-Infective Agents; D018957:CD59 Antigens; D018387:Codon, Initiator; D004286:Dolichols; D008055:Lipids; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009005:Monosaccharides; D009844:Oligosaccharides; C113817:PBN1 protein, S cerevisiae; D010710:Phosphates; D029701:Saccharomyces cerevisiae Proteins; D016695:Glycosyltransferases; D008364:Mannosyltransferases; C486036:PIGM protein, human; C502828:PIGX protein, human; C423034:glycosylphosphatidylinositol mannosyltransferase I; D012697:Serine Endopeptidases; C023302:yeast proteinase B; D005947:Glucose