Hong Senlian, Feng Lei, Yang Yi, Jiang Hao, Hou Xiaomeng, Guo Peng, Marlow Florence L, Stanley Pamela, Wu Peng
Department of Molecular Medicine, The Scripps Research Institute, La Jolla CA 92037, USA.
Department of Biochemistry, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY 10461, USA.
Cell Chem Biol. 2020 Sep 17;27(9):1140-1150.e4. doi: 10.1016/j.chembiol.2020.06.015. Epub 2020 Jul 9.
Wnt/β-catenin signaling regulates critical, context-dependent transcription in numerous physiological events. Among the well-documented mechanisms affecting Wnt/β-catenin activity, modification of N-glycans by L-fucose is the newest and the least understood. Using a combination of Chinese hamster ovary cell mutants with different fucosylation levels and cell-surface fucose editing (in situ fucosylation [ISF]), we report that α(1-3)-fucosylation of N-acetylglucosamine (GlcNAc) in the Galβ(1-4)-GlcNAc sequences of complex N-glycans modulates Wnt/β-catenin activity by regulating the endocytosis of low-density lipoprotein receptor-related protein 6 (LRP6). Pulse-chase experiments reveal that ISF elevates endocytosis of lipid-raft-localized LRP6, leading to the suppression of Wnt/β-catenin signaling. Remarkably, Wnt activity decreased by ISF is fully reversed by the exogenously added fucose. The combined data show that in situ cell-surface fucosylation can be exploited to regulate a specific signaling pathway via endocytosis promoted by a fucose-binding protein, thereby linking glycosylation of a receptor with its intracellular signaling.
Wnt/β-连环蛋白信号通路在众多生理事件中调控关键的、依赖于背景的转录。在影响Wnt/β-连环蛋白活性的诸多已被充分记录的机制中，L-岩藻糖对N-聚糖的修饰是最新且了解最少的。通过结合使用具有不同岩藻糖基化水平的中国仓鼠卵巢细胞突变体和细胞表面岩藻糖编辑（原位岩藻糖基化[ISF]），我们报告称，复杂N-聚糖的Galβ(1-4)-GlcNAc序列中N-乙酰葡糖胺（GlcNAc）的α(1-3)-岩藻糖基化通过调节低密度脂蛋白受体相关蛋白6（LRP6）的内吞作用来调节Wnt/β-连环蛋白活性。脉冲追踪实验表明，ISF提高了脂筏定位的LRP6的内吞作用，导致Wnt/β-连环蛋白信号通路受到抑制。值得注意的是，外源性添加岩藻糖可完全逆转ISF降低的Wnt活性。综合数据表明，原位细胞表面岩藻糖基化可用于通过岩藻糖结合蛋白促进的内吞作用来调节特定的信号通路，从而将受体的糖基化与其细胞内信号传导联系起来。
