Class-Wide Analysis of Frizzled-Dishevelled Interactions Using BRET Biosensors Reveals Functional Differences among Receptor Paralogs

Wingless/Int-1 (WNT) signaling is mediated by WNT binding to 10 Frizzleds (FZD_1-10), which propagate the signal inside the cell by interacting with different transducers, most prominently the phosphoprotein Dishevelled (DVL). Despite recent progress, questions about WNT/FZD selectivity and paralog-dependent differences in the FZD/DVL interaction remain unanswered. Here, we present a class-wide analysis of the FZD/DVL interaction using the DEP domain of DVL as a proxy in bioluminescence resonance energy transfer (BRET) techniques. Most FZDs engage in a constitutive high-affinity interaction with DEP. Stimulation of unimolecular FZD/DEP BRET sensors with different ligands revealed that most paralogs are dynamic in the FZD/DEP interface, showing distinct profiles in terms of ligand selectivity and signal kinetics. This study underlines mechanistic differences in terms of how allosteric communication between FZDs and their main signal transducer DVL occurs. Moreover, the unimolecular sensors represent the first receptor-focused biosensors to surpass the requirements for high-throughput screening, facilitating FZD-targeted drug discovery.