De Novo design of a potent Wnt Surrogate specific for the frizzled7 subtype members
In humans, 19 Wnt ligands interact with 10 Frizzled (Fzd) receptors and the co-receptors LRP5/6 to initiate signaling. Wnts and Fzds are highly promiscuous, making it challenging to dissect the specific outcomes of individual Wnt-Fzd interactions. Developing Wnt surrogates with specificity for individual Fzd subtypes could be pivotal. We present a modular, potent, and Fzd7-specific Wnt surrogate that consists of three de novo designed modules, a Fzd7 binder, an LRP6 binder and a homodimeric protein. The Fzd7-specific module was designed by targeting two less conserved surface patches on the cysteine-rich domain (CRD) of Fzds to achieve both selectivity and affinity. It exhibits a strong binding affinity (KD < 2.3 nM) for the very closely related Fzd7 subtype members (Fzd7, Fzd1, Fzd2) with no measurable binding to the CRDs of the other seven Fzd receptors. This Wnt surrogate induced spheroid organoid formation from intestinal stem cells at subnanomolar concentration, and promoted full hair follicle regeneration and robust hair growth in mice. These results suggest that our strategy could be extended to design modular Wnt surrogates capable of selectively activating individual Fzd receptors, providing a valuable tool kit for development and differentiation, organoid cultures and targeted regeneration.