title: PIG-S and PIG-T, essential for GPI anchor attachment to proteins, form a complex with GAA1 and GPI8.
abstract: Many eukaryotic cell surface proteins are anchored to the plasma membrane via glycosylphosphatidylinositol (GPI). The GPI transamidase mediates GPI anchoring in the endoplasmic reticulum, by replacing a protein's C-terminal GPI attachment signal peptide with a pre-assembled GPI. During this transamidation reaction, the GPI transamidase forms a carbonyl intermediate with a substrate protein. It was known that the GPI transamidase is a complex containing GAA1 and GPI8. Here, we report two new components of this enzyme: PIG-S and PIG-T. To determine roles for PIG-S and PIG-T, we disrupted these genes in mouse F9 cells by homologous recombination. PIG-S and PIG-T knockout cells were defective in transfer of GPI to proteins, particularly in formation of the carbonyl intermediates. We also demonstrate that PIG-S and PIG-T form a protein complex with GAA1 and GPI8, and that PIG-T maintains the complex by stabilizing the expression of GAA1 and GPI8. Saccharomyces cerevisiae Gpi16p (YHR188C) and Gpi17p (YDR434W) are orthologues of PIG-T and PIG-S, respectively.
authors.affiliation: Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ohishi
authors.forename: N
authors.initials: N
authors.lastname: Inoue
authors.forename: T
authors.initials: T
authors.lastname: Kinoshita
mesh_terms: D000217:Acyltransferases / Q000378:metabolism* / Q000502:physiology; D000595:Amino Acid Sequence; D019881:Aminoacyltransferases; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D006224:Cricetinae; D018076:DNA, Complementary; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D002352:Carrier Proteins; D015815:Cell Adhesion Molecules; D018076:DNA, Complementary; C486254:GAA1 protein, S cerevisiae; C093316:GPAA1 protein, human; D017261:Glycosylphosphatidylinositols; C486253:Gpaa1 protein, mouse; D008562:Membrane Glycoproteins; C491190:PIGK protein, human; D029701:Saccharomyces cerevisiae Proteins; D000217:Acyltransferases; D019881:Aminoacyltransferases; C081007:COOH-terminal signal transamidase; C103133:GPI8 protein, S cerevisiae