The DEP domain of Dishevelled (Dvl) proteins transduces signals to effector proteins downstream of Dvl in the Wnt pathway. Here we report that DEP-containing mutants inhibit Wnt-induced, but not Dvl-induced, activation of the transcription factor Lef-1. This inhibitory effect is weakened by a K434M mutation. Nuclear magnetic resonance spectroscopy revealed that the DEP domain of mouse Dvl1 comprises a three-helix bundle, a β-hairpin 'arm' and two short β-strands at the Cterminal region. Lys 434 is located at the tip of the β-hairpin 'arm'. Based on our findings, we conclude that DEP interacts with regulators upstream of Dvl via a strong electric dipole on the molecule's surface created by Lys 434, Asp 445 and Asp 448; the electric dipole and the putative membrane binding site are at two different locations.The Wnt signaling pathway is a key regulatory pathway for cellular development and growth. Wnt signaling has been extensively studied in Drosophila, Caenorhabditis elegans, Xenopus, and mammalian systems [1][2][3][4][5] . Through genetic studies, a working model of the Wnt signaling pathway has been established. Secreted Wnt proteins bind to Frizzled transmembrane receptors. The receptor-ligand complex activates the Dishevelled (Dsh and Dvl) proteins, which suppress the activity of glycogen synthase kinase-3β (GSK-3β). If its activity is not suppressed, GSK-3β binds to adenomatous polyposis coli (APC) protein and axin and then phosphorylates specific Ser and Thr residues at the N-terminus of β-catenin. In turn, the ubiquitin-proteasome pathway rapidly degrades hyperphosphorylated β-catenin. Wnt activation prevents this process by promoting the cytosolic accumulation and subsequent translocation of β-catenin into the nucleus. Once in the nucleus, β-catenin binds to the transcription factors T-cell factor (Tcf) or lymphoid enhancer factor (Lef) and acts as a transcriptional coactivator 5 . The result is increased expression of Tcf or Lef regulated target genes, such as Myc 6 and the gene encoding cyclin D 7 .© 2000 Nature America Inc. Correspondence should be addressed to: J.Z. Jie.Zheng@stjude.org.
HHS Public Access
DEP domain interacts with upstream regulators of DvlWe and others have demonstrated that Wnt-1 or Dvl1, when expressed in NIH3T3 cells, can activate the transcription regulator 16,28,29). This activation depends on β-catenin and is suppressed by GSK-3β and axin. To characterize the role of the mDvl1 DEP domain in Wnt signaling, we examined the effect of the Dvl1 N-terminal truncation mutant, DvlC1, on Wnt-induced activation of the transcription factor Lef-1. In Lef dependent reporter gene assays, DvlC1 inhibited Wnt-1 induced Lef-1 activation but not Dvl1 induced Lef-1 activation (Fig. 2). To further characterize the specific sequences that inhibit the Wnt-induced activation, we generated two additional mutants of mDvl1: DvlDEP, which contains only the DEP domain; and DvlC2, which encompasses the sequence downstream of the DEP domain. When expressed in NIH3T3 cells, DvlDEP, like DvlC1, bloc...