PIG-S and PIG-T, essential for GPI anchor attachment to proteins, form a complex with GAA1 and GPI8.
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.
Ohishi
K
K
Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan.
Inoue
N
N
Kinoshita
T
T
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
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