Second cysteine-rich domain of Dickkopf-2 activates canonical Wnt signaling pathway via LRP-6 independently of dishevelled
Second cysteine-rich domain of Dickkopf-2 activates canonical Wnt signaling pathway via LRP-6 independently of dishevelled
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DOI：
10.1074/jbc.m111131200
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发表时间：
2002-02-22
影响因子：
4.8
通讯作者：
Wu, DQ
中科院分区：
文献类型：
--
作者：
Li, L;Mao, JH;Wu, DQ
最近的证据表明Dickkopf （Dkk）家族成员可以直接结合ldl相关蛋白(LRP)-6，从而抑制wnt激活的信号传导。为了进一步表征Dkk和LRP蛋白之间的相互作用，制备了含有Dkk-1和Dkk-2各自保守的富含半胱氨酸结构域的条件培养基。虽然全长Dkk-1和Dkk-2以及两个Dkk分子的第二富半胱氨酸结构域抑制wnt -3a诱导的典型通路下游靶点淋巴细胞增强因子(LEF)-1的激活，但我们发现当lrp6在NIH3T3细胞中异位表达时，Dkk-2的第二富半胱氨酸结构域（Dkk- 2c2）能够刺激典型通路。Dkk-2C2的这种作用可以被LRP-5/6的第二个YWTD重复结构域特异性单克隆抗体阻断，这表明Dkk-2C2通过LRP-6起作用。我们还发现，虽然Axin和disheveled （Dvl）的DIX结构域都能抑制Dkk-2C2诱导的LEF-1的激活，但Dvl的DEP结构域抑制wnt诱导的LEF-1的激活，却不能抑制Dkk-2C2或LRP-5的激活形式LRPC2对LEF-1的激活。此外，糖原合成酶激酶-3 β，一种有效的Dvl和Writ抑制剂，也不能抑制LRPC2或Dkk-2C2。此外，通过Dvl特异性的短干扰rna敲低Dvl分子的表达，可以抑制wnt诱导的lev -1激活，但对lrpc2诱导的lev -1激活无效。所有证据表明，Dkk-2C2通过LRP蛋白进行信号传递，不需要Dvl，而Wnt蛋白可能同时使用Dvl（可能通过Fz）和LRP来实现更有效的信号转导。
Recent evidence suggests that members of the Dickkopf (Dkk) family can directly bind to LDL-related protein (LRP)-6, resulting in inhibition of Wnt-activated signaling. To further characterize the interactions between Dkk and LRP proteins, conditioned media containing individually conserved cysteine-rich domains of Dkk-1 and Dkk-2 were prepared. Although full-length Dkk-1 and Dkk-2 and the second cysteine-rich domains of both Dkk molecules inhibited Wnt-3a-induced activation of lymphoid enhancing factor (LEF)-1, a downstream target of the canonical pathway, we found that the second cysteine-rich domain of Dkk-2 (Dkk-2C2) was able to stimulate the canonical pathway when LRP-6 was ectopically expressed in NIH3T3 cells. This effect of Dkk-2C2 could be blocked by a monoclonal antibody specific to the second YWTD repeat domain of LRP-5/6, suggesting that Dkk-2C2 acts via LRP-6. We also showed that while both Axin and the DIX domain of Dishevelled (Dvl) could inhibit Dkk-2C2-induced activation of LEF-1, the DEP domain of Dvl, which inhibited Wnt-induced activation of LEF-1, failed to inhibit the activation of LEF-1 by Dkk-2C2 or by an activated form of LRP-5, LRPC2. In addition, glycogen synthase kinase-3beta, a potent inhibitor for both Dvl and Writ, also failed to inhibit LRPC2 or Dkk-2C2. Furthermore, knocking-down the expression of Dvl molecules by short interfering RNAs specific to Dvl inhibited Wnt-induced, but not LRPC2-induced, activation of LEF-1. All the evidence indicates that Dkk-2C2 signals through LRP proteins, which does not require Dvl, while Wnt protein may employ both Dvl, presumably through Fz, and LRP to achieve more efficient signal transduction.