Transmembrane BAX inhibitor motif containing (TMBIM) family proteins perturbs a trans-Golgi network enzyme, Gb3 synthase, and reduces Gb3 biosynthesis.
Globotriaosylceramide (Gb3) is a well known receptor for Shiga toxin (Stx), produced by enterohemorrhagic Escherichia coli and Shigella dysenteriae. The expression of Gb3 also affects several diseases, including cancer metastasis and Fabry disease, which prompted us to look for factors involved in its metabolism. In the present study, we isolated two cDNAs that conferred resistance to Stx-induced cell death in HeLa cells by expression cloning: ganglioside GM3 synthase and the COOH terminus region of glutamate receptor, ionotropic, N-methyl-D-asparate-associated protein 1 (GRINA), a member of the transmembrane BAX inhibitor motif containing (TMBIM) family. Overexpression of the truncated form, named GRINA-C, and some members of the full-length TMBIM family, including FAS inhibitory molecule 2 (FAIM2), reduced Gb3, and lactosylceramide was accumulated instead. The change of glycolipid composition was restored by overexpression of Gb3 synthase, suggesting that the synthase is affected by GRINA-C and FAIM2. Interestingly, the mRNA level of Gb3 synthase was unchanged. Rather, localization of the synthase as well as TGN46, a trans-Golgi network marker, was perturbed to form punctate structures, and degradation of the synthase in lysosomes was enhanced. Furthermore, GRINA-C was associated with Gb3 synthase. These observations may demonstrate a new type of posttranscriptional regulation of glycosyltransferases.
Yamaji
Toshiyuki
T
Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan. tyamaji@nih.go.jp
Nishikawa
Kiyotaka
K
Hanada
Kentaro
K
D000595:Amino Acid Sequence; D017209:Apoptosis / Q000235:genetics; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000235:genetics; D004351:Drug Resistance / Q000235:genetics; D005700:Galactosyltransferases / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D005915:Globosides / Q000096:biosynthesis*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D011485:Protein Binding; D016194:Receptors, N-Methyl-D-Aspartate / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D022622:Shiga Toxin 1 / Q000494:pharmacology; D014162:Transfection; D014281:Trihexosylceramides / Q000096:biosynthesis*; D021601:trans-Golgi Network / Q000201:enzymology / Q000378:metabolism*
D051017:Apoptosis Regulatory Proteins; D005700:Galactosyltransferases; D005915:Globosides; D049452:Green Fluorescent Proteins; D008565:Membrane Proteins; D016194:Receptors, N-Methyl-D-Aspartate; D022622:Shiga Toxin 1; D014281:Trihexosylceramides; C400427:FAIM2 protein, human; C514780:globotrihexosylceramide; C045097:UDP-galactose-lactosylceramide alpha 1-4-galactosyltransferase