Molecular interaction between fukutin and POMGnT1 in the glycosylation pathway of alpha-dystroglycan |
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Authors: | Xiong Hui Kobayashi Kazuhiro Tachikawa Masaji Manya Hiroshi Takeda Satoshi Chiyonobu Tomohiro Fujikake Nobuhiro Wang Fan Nishimoto Akemi Morris Glenn E Nagai Yoshitaka Kanagawa Motoi Endo Tamao Toda Tatsushi |
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Affiliation: | Division of Clinical Genetics, Department of Medical Genetics, Osaka University Graduate School of Medicine, 2-2-B9 Yamadaoka, Suita, Osaka 565-0871, Japan. |
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Abstract: | The recent identification of mutations in genes encoding demonstrated or putative glycosyltransferases has revealed a novel mechanism for congenital muscular dystrophy. Hypoglycosylated alpha-dystroglycan (alpha-DG) is commonly seen in Fukuyama-type congenital muscular dystrophy (FCMD), muscle-eye-brain disease (MEB), Walker-Warburg syndrome (WWS), and Large(myd) mice. POMGnT1 and POMTs, the gene products responsible for MEB and WWS, respectively, synthesize unique O-mannose sugar chains on alpha-DG. The function of fukutin, the gene product responsible for FCMD, remains undetermined. Here we show that fukutin co-localizes with POMGnT1 in the Golgi apparatus. Direct interaction between fukutin and POMGnT1 was confirmed by co-immunoprecipitation and two-hybrid analyses. The transmembrane region of fukutin mediates its localization to the Golgi and participates in the interaction with POMGnT1. Y371C, a missense mutation found in FCMD, retains fukutin in the ER and also redirects POMGnT1 to the ER. Finally, we demonstrate reduced POMGnT1 enzymatic activity in transgenic knock-in mice carrying the retrotransposal insertion in the fukutin gene, the prevalent mutation in FCMD. From these findings, we propose that fukutin forms a complex with POMGnT1 and may modulate its enzymatic activity. |
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Keywords: | Fukutin POMGnT1 Fukuyama-type congenital muscular dystrophy Muscle-eye-brain disease α-Dystroglycan |
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