Dynamic recruitment of axin by Dishevelled protein assemblies

Dishevelled (Dvl) proteins are cytoplasmic components of the Wnt signalling pathway, which controls numerous cell fate decisions during animal development. During Wnt signalling, Dvl binds to the intracellular domain of the frizzled transmembrane receptors, and also to axin to block its activity, which results in the activation of beta-catenin and, consequently, in a transcriptional switch. We have previously reported that the DIX domain of mammalian Dvl2 allows it to form dynamic protein assemblies. Here, we show that these Dvl2 assemblies recruit axin, and also casein kinase I epsilon. Using photobleaching experiments of GFP- tagged Dvl2 and axin to study the dynamics of their interaction, we found that the recruitment of axin- GFP by Dvl2 assemblies is accompanied by a striking acceleration of the dynamic properties of axin-GFP. We also show that the interaction between Dvl2 and axin remains highly dynamic even after Wnt- induced relocation to the plasma membrane. We discuss how the recruitment of casein kinase I epsilon by Dvl2 assemblies might impact on the recruitment of axin to the plasma membrane during Wnt signalling.