Initial enzyme for glycosylphosphatidylinositol biosynthesis requires PIG-P and is regulated by DPM2.
Glycosylphosphatidylinositols (GPIs) are attached to the C-termini of many proteins, thereby acting as membrane anchors. Biosynthesis of GPI is initiated by GPI-N-acetylglucosaminyltransferase (GPI-GnT), which transfers N-acetylglucosamine from UDP- N-acetylglucosamine to phosphatidylinositol. GPI-GnT is a uniquely complex glycosyltransferase, consisting of at least four proteins, PIG-A, PIG-H, PIG-C and GPI1. Here, we report that GPI-GnT requires another component, termed PIG-P, and that DPM2, which regulates dolichol-phosphate-mannose synthase, also regulates GPI-GnT. PIG-P, a 134-amino acid protein having two hydrophobic domains, associates with PIG-A and GPI1. PIG-P is essential for GPI-GnT since a cell lacking PIG-P is GPI-anchor negative. DPM2, but not two other components of dolichol-phosphate-mannose synthase, associates with GPI-GnT through interactions with PIG-A, PIG-C and GPI1. Lec15 cell, a null mutant of DPM2, synthesizes early GPI intermediates, indicating that DPM2 is not essential for GPI-GnT; however, the enzyme activity is enhanced 3-fold in the presence of DPM2. These results reveal new essential and regulatory components of GPI-GnT and imply co-regulation of GPI-GnT and the dolichol-phosphate-mannose synthase that generates a mannosyl donor for GPI.
Watanabe
R
R
Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan.
Murakami
Y
Y
Marmor
M D
MD
Inoue
N
N
Maeda
Y
Y
Hino
J
J
Kangawa
K
K
Julius
M
M
Kinoshita
T
T
D000595:Amino Acid Sequence; D000818:Animals; D018957:CD59 Antigens / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002469:Cell Separation; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004287:Dolichol Monophosphate Mannose / Q000378:metabolism; D020224:Expressed Sequence Tags; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D005656:Fungal Proteins / Q000737:chemistry; D017261:Glycosylphosphatidylinositols / Q000096:biosynthesis* / Q000235:genetics; D006602:Hexosyltransferases; D006801:Humans; D008364:Mannosyltransferases; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D017351:N-Acetylglucosaminyltransferases / Q000737:chemistry / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014162:Transfection
D018957:CD59 Antigens; D002352:Carrier Proteins; D018076:DNA, Complementary; C485893:Dscr5 protein, mouse; D005656:Fungal Proteins; D017261:Glycosylphosphatidylinositols; D008565:Membrane Proteins; C414442:PIGH protein, human; D010940:Plant Proteins; C080086:phosphatidylinositol glycan-class A protein; D004287:Dolichol Monophosphate Mannose; C115077:DPM2 protein, human; D006602:Hexosyltransferases; D008364:Mannosyltransferases; D017351:N-Acetylglucosaminyltransferases; C037649:N-acetyllactosaminide beta-1,6-N-acetylglucosaminyltransferase; C101351:PIGC protein, human; C414441:PIGP protein, human