Glycosylation and palmitoylation of Wnt-3a are coupled to produce an active form of Wnt-3a
Glycosylation and palmitoylation of Wnt-3a are coupled to produce an active form of Wnt-3a
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DOI：
10.1111/j.1365-2443.2007.01068.x
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发表时间：
2007-04-01
期刊：
影响因子：
2.1
通讯作者：
Kikuchi, Akira
中科院分区：
文献类型：
--
作者：
Komekado, Hideyuki;Yamamoto, Hideki;Kikuchi, Akira
Wnt-3a 是一种代表性配体，可激活 Wnt 信号传导中的 β-连环蛋白依赖性途径，并用聚糖和棕榈酸酯进行修饰。在本研究中，我们分析了Wnt-3a的糖基化和脂化之间的关系。缺乏糖基化的 Wnt-3a 突变体 (Wnt-3a NQ) 的分泌受到损害。 Wnt-3a C77A 在 Cys77 处缺乏棕榈酰化，其分泌效率与野生型 Wnt-3a (Wnt-3a WT) 相似，但不会诱导低密度脂蛋白受体相关蛋白 6 (LRP6) 的内化。此外，从 Wnt-3a 中去除棕榈酸酯抑制了与其受体 Frizzled8 和 LRP6 结合的能力。 Wnt-3a C77A 的糖基化程度与 Wnt-3a WT 相似，而 Wnt-3a NQ 未用棕榈酸酯修饰。豪猪（一种推定的酰基转移酶）的表达大大增强了 Wnt-3a WT 的棕榈酰化，但略微增强了 Wnt-3a NQ 的棕榈酰化。 Wnt-3a WT 在内质网 (ER) 和高尔基体中均存在，而 Wnt-3a NQ 仅位于 ER 中。此外，在用布雷菲德菌素 A 处理的细胞中，Wnt-3a 没有被棕榈酰化，而是被糖基化，从而抑制囊泡从内质网转运到高尔基体。这些结果表明Wnt-3a的糖基化先于棕榈酰化，并且两种修饰对于活性Wnt-3a的分泌都是必需的。
Wnt-3a is a representative ligand that activates the beta-catenin-dependent pathway in Wnt signaling and is modified with glycans and palmitate. In this study, we analyzed the relationship between glycosylation and lipidation of Wnt-3a. Secretion of a Wnt-3a mutant that lacks glycosylation (Wnt-3a NQ) was impaired. Wnt-3a C77A, which lacks palmitoylation at Cys77, was secreted with similar efficiency to wild-type Wnt-3a (Wnt-3a WT), but did not induce the internalization of low-density lipoprotein receptor-related protein 6 (LRP6). Furthermore, removal of palmitate from Wnt-3a suppressed the ability to bind to its receptors Frizzled8 and LRP6. Wnt-3a C77A was glycosylated to an extent similar to Wnt-3a WT, while Wnt-3a NQ was not modified with palmitate. Expression of porcupine, which is a putative acyltransferase, enhanced palmitoylation of Wnt-3a WT greatly, but that of Wnt-3a NQ slightly. While Wnt-3a WT was present in both the endoplasmic reticulum (ER) and Golgi, Wnt-3a NQ was located to the ER only. Furthermore, Wnt-3a was not palmitoylated but was glycosylated in the cells treated with Brefeldin A, which inhibits transport of vesicles from the ER to the Golgi. These results indicate that glycosylation of Wnt-3a precedes palmitoylation and that both modifications are necessary for secretion of an active Wnt-3a.