Modulation of Notch-ligand binding by protein O-Fucosyltransferase 1 and Fringe
Modulation of Notch-ligand binding by protein O-Fucosyltransferase 1 and Fringe
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DOI：
10.1074/jbc.m308687200
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发表时间：
2003-10-24
影响因子：
4.8
通讯作者：
Irvine, KD
中科院分区：
文献类型：
--
作者：
Okajima, T;Xu, AG;Irvine, KD
Notch受体是介导广泛发育过程的糖蛋白。Notch在其表皮生长因子样结构域中通过向丝氨酸或苏氨酸残基添加岩藻糖来修饰。O-岩藻糖基化由蛋白质O-岩藻糖基转移酶1介导，并且通过RNA干扰或果蝇中Ofut 1基因的突变或通过小鼠中Pofut 1基因的突变来下调该酶阻止Notch信号传导。为了研究Notch上需要O-连接岩藻糖的分子基础，我们测定了标记的可溶形式的Notch胞外结构域结合其配体Delta和Serrate的能力。在Notch分泌细胞中通过RNA干扰下调OFUT 1抑制Delta-Notch和Serrate-Notch结合，表明Notch与其配体有效结合需要O-连接的岩藻糖。相反，培养细胞中OFUT 1的过表达增加了Serrate-Notch结合，但抑制了Delta-Notch结合。OFUT 1的这些作用与体内OFUT 1过表达对Notch信号传导的结果一致。有趣的是，它们也与糖基转移酶Fringe的表达相反，并受到其抑制，Fringe特异性修饰O-连接的岩藻糖。因此，Notch-配体相互作用取决于O-岩藻糖聚糖的存在和类型。
Notch receptors are glycoproteins that mediate a wide range of developmental processes. Notch is modified in its epidermal growth factor-like domains by the addition of fucose to serine or threonine residues. O-Fucosylation is mediated by protein O-fucosyltransferase 1, and down-regulation of this enzyme by RNA interference or mutation of the Ofut1 gene in Drosophila or by mutation of the Pofut1 gene in mouse prevents Notch signaling. To investigate the molecular basis for the requirement for O-linked fucose on Notch, we assayed the ability of tagged, soluble forms of the Notch extracellular domain to bind to its ligands, Delta and Serrate. Down-regulation of OFUT1 by RNA interference in Notch-secreting cells inhibits both Delta-Notch and Serrate-Notch binding, demonstrating a requirement for O-linked fucose for efficient binding of Notch to its ligands. Conversely, overexpression of OFUT1 in cultured cells increases Serrate-Notch binding but inhibits Delta-Notch binding. These effects of OFUT1 are consistent with the consequences of OFUT1 overexpression on Notch signaling in vivo. Intriguingly, they are also opposite to, and are suppressed by, expression of the glycosyltransferase Fringe, which specifically modifies O-linked fucose. Thus, Notch-ligand interactions are dependent upon both the presence and the type of O-fucose glycans.