Functional consequences of Wnt-induced dishevelled 2 phosphorylation in canonical and non-canonical Wnt signaling

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Dishevelled (Dvl) proteins are intracellular effectors of Wnt signaling that have essential roles in both canonical and noncanonical Wnt pathways. It has long been known that Wnts stimulate Dvl phosphorylation, but relatively little is known about its functional significance. We have previously reported that both Wnt3a and Wnt5a induce Dvl2 phosphorylation that is associated with an electrophoretic mobility shift and loss of recognition by monoclonal antibody 10B5. In the present study, we mapped the 10B5 epitope to a 16-amino acid segment of human Dvl2 (residues 594-609) that contains four Ser/Thr residues. Alanine substitution of these residues (P4m) eliminated the mobility shift induced by either Wnt3a or Wnt5a. The Dvl2P4m mutant showed a modest increase in canonical Wnt/β-catenin signaling activity relative to wild type. Consistent with this finding, Dvl2 4Pm preferentially localized to cytoplasmic puncta. In contrast to wild-type Dvl2, however, the P4m mutant was unable to rescue Wnt3a-dependent neurite outgrowth in TC-32 cells following suppression of endogenous Dvl2/3. Earlier work has implicated casein kinase 1δ/ε as responsible for the Dvl mobility shift, and a CK1δ in vitro kinase assay confirmed that Ser594, Thr595, and Ser597 of Dvl2 are CK1 targets. Alanine substitution of these three residues was sufficient to abrogate the Wnt-dependent mobility shift. Thus, we have identified a cluster of Ser/Thr residues in the C-terminal domain of Dvl2 that are Wnt-induced phosphorylation (WIP) sites. Our results indicate that phosphorylation at theWIPsites reduces Dvl accumulation in puncta and attenuates β-catenin signaling, whereas it enables noncanonical signaling that is required for neurite outgrowth. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.
This work was supported, in whole or in part, by National Institutes of Health Grant R01 CA123238 (to A. M. C. B.) and Postdoctoral Fellowship F32 CA117662 (to C. L. A.). This work was also supported by a fellowship from the Ministerio de Educación, Cultura, y Deportes, of Spain (to J. M. G.-S.), by New York State Department of Health postdoctoral Fellowship NYS C021339 (to Y. T.), and by charitable donations to Strang Cancer Prevention Center. This research also was supported in part by the Intramural Research Program of the National Institutes of Health, National Cancer Institute.