Notch deficiency implicated in the pathogenesis of congenital disorder of glycosylation IIc
Notch deficiency implicated in the pathogenesis of congenital disorder of glycosylation IIc
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DOI：
10.1073/pnas.0504115102
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发表时间：
2005-12-20
影响因子：
11.1
通讯作者：
Matsuno, K
中科院分区：
文献类型：
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作者：
Ishikawa, HO;Higashi, S;Matsuno, K
先天性糖基化IIc障碍（CIDG IIc），也称为白细胞粘附缺陷II，是一种隐性综合征，其特征是生长缓慢、智力迟钝和严重免疫缺陷。最近，发现负责CDG IIc的基因编码GDP-岩藻糖转运蛋白。在这里，我们调查了可能的原因CDG IIc患者的发育缺陷，通过使用果蝇模型。在生物化学方面，我们证明了果蝇的GDP-岩藻糖转运蛋白，高尔基体的GDP-岩藻糖转运蛋白（GFR）的同源物，专门在体外转运GDP-岩藻糖。为了了解Gfr基因的功能，我们在果蝇中产生了Gfr的无效突变体。人GDP-岩藻糖转运蛋白转基因挽救了果蝇Gfr突变体的表型。我们的表型分析显示，Notch（N）信号在这些GFR突变体中是缺陷的。已知GDP-岩藻糖对于N-连接聚糖的岩藻糖基化和O-岩藻糖基化至关重要，并且两种岩藻糖修饰均存在于N上。我们的研究结果表明，Gfr参与N上的Winked聚糖的岩藻糖基化及其O-岩藻糖基化，以及散装蛋白质的岩藻糖基化。然而，尽管IN O-岩藻糖基化在发育过程中起着重要作用，但Gfr纯合子是可行的。因此，我们的研究结果还表明，果蝇基因组编码至少另一种GDP-岩藻糖转运蛋白，参与N。最后，我们发现哺乳动物GFR是哺乳动物培养细胞中IN信号传导所必需的。因此，我们的研究结果表明，减少在CDG IIc的病理IN信号。
Congenital disorder of glycosylation IIc (CIDG IIc), also termed leukocyte adhesion deficiency II, is a recessive syndrome characterized by slowed growth, mental retardation, and severe immunodeficiency. Recently, the gene responsible for CDG IIc was found to encode a GDP-fucose transporter. Here, we investigated the possible cause of the developmental defects in CDG IIc patients by using a Drosophila model. Biochemically, we demonstrated that a Drosophila homolog of the GDP-fucose transporter, the Golgi GDP-fucose transporter (Gfr), specifically transports GDP-fucose in vitro. To understand the function of the Gfr gene, we generated null mutants of Gfr in Drosophila. The phenotypes of the Drosophila Gfr mutants were rescued by the human GDP-fucose transporter transgene. Our phenotype analyses revealed that Notch (N) signaling was deficient in these Gfr mutants. GDP-fucose is known to be essential for the fucosylation of N-linked glycans and for O-fucosylation, and both fucose modifications are present on N. Our results suggest that Gfr is involved in the fucosylation of Winked glycans on N and its O-fucosylation, as well as those of bulk proteins. However, despite the essential role of IN O-fucosylation during development, the Gfr homozygote was viable. Thus, our results also indicate that the Drosophila genome encodes at least another GDP-fucose transporter that is involved in the O-fucosylation of N. Finally, we found that mammalian Gfr is required for IN signaling in mammalian cultured cells. Therefore, our results implicate reduced IN signaling in the pathology of CDG IIc.