Zhang Long, Gao Xia, Wen Jun, Ning Yuanheng, 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. 2006 Mar 31;281(13):8607-12. doi: 10.1074/jbc.M600274200. Epub 2006 Jan 30.
Wnt signaling plays pivotal roles in the regulation of embryogenesis and cancer development. Xenopus Dapper (Dpr) was identified as an interacting protein for Dishevelled (Dvl), a Wnt signaling mediator, and modulates Wnt signaling. However, it is largely unclear how Dpr regulates Wnt signaling. Here, we present evidence that human Dpr1, the ortholog of Xenopus Dpr, inhibits Wnt signaling. We have identified the regions responsible for the Dpr-Dvl interaction in both proteins and found that the interaction interface is formed between the DEP (Dishevelled, Egl-10, and pleckstrin) domain of Dvl and the central and the C-terminal regions of Dpr1. The inhibitory function of human Dpr1 requires both its N and C terminus. Overexpression of the C-terminal region corresponding to the last 225 amino acids of Dpr1, in contrast to wild-type Dpr1, enhances Wnt signaling, suggesting a dominant negative function of this region. Furthermore, we have shown that Dpr1 induces Dvl degradation via a lysosome inhibitor-sensitive and proteasome inhibitor-insensitive mechanism. Knockdown of Dpr1 by RNA interference up-regulates endogenous Dvl2 protein. Taken together, our data indicate that the inhibitory activity of Dpr on Wnt signaling is conserved from Xenopus to human and that Dpr1 antagonizes Wnt signaling by inducing Dvl degradation.
Wnt信号通路在胚胎发育和癌症发展的调控中发挥着关键作用。非洲爪蟾的Dapper（Dpr）被鉴定为Wnt信号传导介质Dishevelled（Dvl）的相互作用蛋白，并调节Wnt信号通路。然而，目前尚不清楚Dpr如何调节Wnt信号通路。在此，我们提供证据表明，非洲爪蟾Dpr的直系同源物人类Dpr1可抑制Wnt信号通路。我们已经确定了两种蛋白质中负责Dpr-Dvl相互作用的区域，发现相互作用界面形成于Dvl的DEP（Dishevelled、Egl-10和普列克底物蛋白）结构域与Dpr1的中央区域和C末端区域之间。人类Dpr1的抑制功能需要其N末端和C末端。与野生型Dpr1相比，对应于Dpr1最后225个氨基酸的C末端区域的过表达增强了Wnt信号通路，表明该区域具有显性负功能。此外，我们已经表明，Dpr1通过一种对溶酶体抑制剂敏感而对蛋白酶体抑制剂不敏感的机制诱导Dvl降解。通过RNA干扰敲低Dpr1可上调内源性Dvl2蛋白。综上所述，我们的数据表明，Dpr对Wnt信号通路的抑制活性从非洲爪蟾到人类都是保守的，并且Dpr1通过诱导Dvl降解来拮抗Wnt信号通路。
