Molecular Basis of Wnt Activation via the DIX Domain Protein Ccd1
Molecular Basis of Wnt Activation via the DIX Domain Protein Ccd1
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通过 DIX 结构域蛋白 Ccd1 激活 Wnt 的分子基础
DOI：
10.1074/jbc.m110.186742
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发表时间：
2011-03-11
影响因子：
4.8
通讯作者：
Wu, Jia-Wei
中科院分区：
文献类型：
--
作者：
Liu, Yi-Tong;Dan, Qiong-Jie;Wu, Jia-Wei
Wnt信号在胚胎发育和癌症中起着关键作用，而DVL、Axin和Ccd1这三个含有DIX结构域的蛋白在规范的Wnt信号的启动和调控中发挥着不同的作用。过度表达的DVL倾向于在细胞质中形成大分子聚合物，而具有生物活性的DVL实际上形成低分子量低聚物。DVL蛋白的聚合体大小如何控制Wnt信号的分子基础仍不清楚。在这里，我们展示了CCD1通过与DVL协同作用上调规范的Wnt信号。我们测定了野生型Ccd1-DIX和突变型Dvl1-DIX(Y17D)的晶体结构，它们包装成“头到尾”的螺旋细丝。结构分析揭示了丝内同质和异质相互作用的两个关键部位和细丝间同质组装的第三个部位。系统的突变研究确定了DVL同源寡聚、斑点形成和刺激Wnt信号所需的所有三个位点的关键残基。值得注意的是，CCD1通过DVL-DIX的“头”和CCD1-DIX的“尾”与DVL形成杂化络合物，解聚DVL均一组分，从而控制DVL聚合物的大小。这些数据共同提示了CCD1介导的Wnt活化的分子机制，即CCD1将潜伏的聚合物DVL转化为具有生物活性的寡聚体(S)。
The Wnt signaling plays pivotal roles in embryogenesis and cancer, and the three DIX domain-containing proteins, Dvl, Axin, and Ccd1, play distinct roles in the initiation and regulation of canonical Wnt signaling. Overexpressed Dvl has a tendency to form large polymers in a cytoplasmic punctate pattern, whereas the biologically active Dvl in fact forms low molecular weight oligomers. The molecular basis for how the polymeric sizes of Dvl proteins are controlled upon Wnt signaling remains unclear. Here we show that Ccd1 up-regulates canonical Wnt signaling via acting synergistically with Dvl. We determined the crystal structures of wild type Ccd1-DIX and mutant Dvl1-DIX(Y17D), which pack into "head-to-tail" helical filaments. Structural analyses reveal two sites crucial for intra-filament homo-and hetero-interaction and a third site for inter-filament homo-assembly. Systematic mutagenesis studies identified critical residues from all three sites required for Dvl homo-oligomerization, puncta formation, and stimulation of Wnt signaling. Remarkably, Ccd1 forms a hetero-complex with Dvl through the "head" of Dvl-DIX and the "tail" of Ccd1-DIX, depolymerizes Dvl homo-assembly, and thereby controls the size of Dvl polymer. These data together suggest a molecular mechanism for Ccd1-mediated Wnt activation in that Ccd1 converts latent polymeric Dvl to a biologically active oligomer(s).