Kazanskaya Olga, Glinka Andrei, del Barco Barrantes Ivan, Stannek Peter, Niehrs Christof, Wu Wei
Division of Molecular Embryology, Deutsches Krebsforschungszentrum, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany.
Dev Cell. 2004 Oct;7(4):525-34. doi: 10.1016/j.devcel.2004.07.019.
We have carried out a small pool expression screen for modulators of the Wnt/beta-catenin pathway and identified Xenopus R-spondin2 (Rspo2) as a secreted activator of this cascade. Rspo2 is coexpressed with and positively regulated by Wnt signals and synergizes with Wnts to activate beta-catenin. Analyses of functional interaction with components of the Wnt/beta-catenin pathway suggest that Rspo2 functions extracellularly at the level of receptor ligand interaction. In addition to activating the Wnt/beta-catenin pathway, Rspo2 overexpression blocks Activin, Nodal, and BMP4 signaling in Xenopus, raising the possibility that it may negatively regulate the TGF-beta pathway. Antisense Morpholino experiments in Xenopus embryos and RNAi experiments in HeLa cells reveal that Rspo2 is required for Wnt/beta-catenin signaling. In Xenopus embryos depleted of Rspo2, the muscle markers myoD and myf5 fail to be activated and later muscle development is impaired. Thus, Rspo2 functions in a positive feedback loop to stimulate the Wnt/beta-catenin cascade.
我们针对Wnt/β-连环蛋白信号通路的调节剂进行了一项小规模的细胞池表达筛选，并确定非洲爪蟾R-spondin2（Rspo2）是该信号级联反应的一种分泌型激活剂。Rspo2与Wnt信号共同表达且受其正向调控，并与Wnt协同作用以激活β-连环蛋白。对其与Wnt/β-连环蛋白信号通路各组分的功能相互作用分析表明，Rspo2在受体配体相互作用水平发挥细胞外功能。除了激活Wnt/β-连环蛋白信号通路外，Rspo2过表达还会阻断非洲爪蟾中的激活素、Nodal和BMP4信号传导，这增加了其可能对转化生长因子-β（TGF-β）信号通路产生负调控的可能性。在非洲爪蟾胚胎中进行的反义吗啉代寡核苷酸实验以及在HeLa细胞中进行的RNA干扰实验表明，Wnt/β-连环蛋白信号传导需要Rspo2。在缺乏Rspo2的非洲爪蟾胚胎中，肌肉标志物肌分化抗原（MyoD）和肌原性决定因子5（Myf5）无法被激活，随后的肌肉发育受损。因此，Rspo2在一个正反馈环中发挥作用，以刺激Wnt/β-连环蛋白信号级联反应。
