Dishevelled-3 C-terminal His single amino acid repeats are obligate for Wnt5a activation of non-canonical signaling

BACKGROUND The Wnt non-canonical pathway (Wnt5a > Frizzled-2 > cyclic GMP phosphodiesterase/Ca2+-mobilization pathway regulates the activation of NF-AT) is mediated by three mammalian Dishevelleds (Dvl1, Dvl2, and Dvl3) and the role of the C-terminal region unique to Dvl3 was interrogated. RESULTS Dvl1, Dvl2, and Dvl3 are expressed at varying levels in mouse totipotent F9 embryonal teratocarcinoma cells. The expression of each endogenous Dvl isoform, as defined by knock-down with siRNA, was obligate for Wnt5a to activate NF-AT-sensitive transcription. Elements upstream of effectors, e.g., cGMP phosphodiesterase and Ca2+-mobilization, were blocked by knock-down of any one of the Dvls; thus, with respect to Wnt5a activation of NF-AT Dvls are not redundant. Among the three Dvl isoforms, the C-terminal sequence of Dvl3 is the most divergent. Deletion of region of Dvl3 abolishes Wnt5a-stimulated signaling. Alanine (Ala)-substitution of histidine (His) single amino acid repeats at 637,638 and/or 647,648 in Dvl3, like C-terminal deletion, abolishes Wnt 5a signal propagation. Phenylalanine (Phe)-substitution of the same His-repeats in Dvl3 mimics Wnt5a stimulated NF-AT-sensitive transcription. CONCLUSIONS The C-terminal third of Dvl3 and His single amino acid repeats 637,638 and 647,648 (which are unique to and conserved in Dvl3) are essential for Wnt5a activation of the non-canonical pathway, but not the Wnt3a activation of the canonical pathway.