Gao Xia, Wen Jun, Zhang Long, Li Xiang, Ning Yuanheng, Meng Anming, Chen Ye-Guang
State Key Laboratory of Biomembrane and Membrane Biotechnology, Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China.
J Biol Chem. 2008 Dec 19;283(51):35679-88. doi: 10.1074/jbc.M804088200. Epub 2008 Oct 20.
Wnt signaling, via the activation of the canonical beta-catenin and lymphoid enhancer factor (LEF)/T-cell factor pathway, plays an important role in embryogenesis and cancer development by regulating the expression of genes involved in cell proliferation, differentiation, and survival. Dapper (Dpr), as a Dishevelled interactor, has been suggested to modulate Wnt signaling by promoting Dishevelled degradation. Here, we provide evidence that Dpr1 shuttles between the cytoplasm and the nucleus. Although overexpressed Dpr1 was mainly found in the cytoplasm, endogenous Dpr1 was localized over the cell, and Wnt1 induced its nuclear export. Treatment with leptomycin B induced nuclear accumulation of both endogenous and overexpressed Dpr1. We further identified the nuclear localization signal and the nuclear export signal within Dpr1. Using reporter assay and in vivo zebrafish embryo assay, we demonstrated that the forced nuclearly localized Dpr1 possessed the ability to antagonize Wnt signaling. Dpr1 interacted with beta-catenin and LEF1 and disrupted their complex formation. Furthermore, Dpr1 could associate with histone deacetylase 1 (HDAC1) and enhance the LEF1-HDAC1 interaction. Together, our findings suggest that Dpr1 negatively modulates the basal activity of Wnt/beta-catenin signaling in the nucleus by keeping LEF1 in the repressive state. Thus, Dpr1 controls Wnt/beta-catenin signaling in both the cytoplasm and the nucleus.
Wnt信号通路通过激活经典的β-连环蛋白和淋巴样增强因子（LEF）/T细胞因子途径，在胚胎发育和癌症发展中发挥重要作用，其机制是调节参与细胞增殖、分化和存活的基因的表达。Dapper（Dpr）作为一种与Dishevelled相互作用的蛋白，被认为通过促进Dishevelled的降解来调节Wnt信号通路。在此，我们提供证据表明Dpr1在细胞质和细胞核之间穿梭。尽管过表达的Dpr1主要存在于细胞质中，但内源性Dpr1在细胞内广泛分布，并且Wnt1诱导其核输出。用放线菌酮B处理可诱导内源性和过表达的Dpr1在细胞核中积累。我们进一步鉴定了Dpr1内的核定位信号和核输出信号。通过报告基因检测和体内斑马鱼胚胎检测，我们证明了强制定位于细胞核的Dpr1具有拮抗Wnt信号的能力。Dpr1与β-连环蛋白和LEF1相互作用，并破坏它们的复合物形成。此外，Dpr1可以与组蛋白去乙酰化酶1（HDAC1）结合，并增强LEF1-HDAC1的相互作用。总之，我们的研究结果表明，Dpr1通过使LEF1处于抑制状态，在细胞核中负向调节Wnt/β-连环蛋白信号通路的基础活性。因此，Dpr1在细胞质和细胞核中均控制Wnt/β-连环蛋白信号通路。
