Figure 7.

Model for dual regulatory functions of DP1. (A) In the absence or below the activation threshold of Wnt, DP1 prevents from aberrant (noisy) activation, by interfering Dvl–Axin interaction. Therefore, the destruction complex remains intact and it facilitates β-catenin degradation. This negative function of DP1 stabilizes Wnt-off state. (B) In the presence or above the activation threshold of Wnt, DP1 further enhances the signalling via increasing cytosolic β-catenin level and antagonizing kinase activity of NLK. The mechanism how and the location where DP1 increases β-catenin level are uncertain. Nevertheless, this positive function stabilizes Wnt-on state. (C) Morphogen gradient of Wnt is translated into biphasic on and off states by the proposed dual regulatory functions of DP1. In general term, morphogen gradient can be translated into biphasic states by the action of on/off states stabilizer. This would in turn make sharp boundary between cells and allow them to take different cell fates.