Mandy Hiu Yi Lam

Targeted protein degradation and stabilization are promising therapeutic modalities because of their potency, versatility and their potential to expand the druggable target space^1,2. However, only a few of the hundreds of E3 ligases and deubiquitinases in the human proteome have been harnessed for this purpose, which substantially limits the potential of the approach. Moreover, there may be other protein classes that could be exploited for protein stabilization or degradation^3,4,5, but there are currently no methods that can identify such effector proteins in a scalable and unbiased manner. Here we established a synthetic proteome-scale platform to functionally identify human proteins that can promote the degradation or stabilization of a target protein in a proximity-dependent manner. Our results reveal that the human proteome contains a large cache of effectors of protein stability. The approach further enabled us to comprehensively compare the activities of human E3 ligases and deubiquitinases, identify and characterize non-canonical protein degraders and stabilizers and establish that effectors have vastly different activities against diverse targets. Notably, the top degraders were more potent against multiple therapeutically relevant targets than the currently used E3 ligases cereblon and VHL. Our study provides a functional catalogue of stability effectors for targeted protein degradation and stabilization and highlights the potential of induced proximity screens for the discovery of new proximity-dependent protein modulators.

SUMMARY: Targeted protein degradation and stabilization are promising therapeutic modalities due to their potency and versatility. However, only few E3 ligases and deubiquitinases have been harnessed for this purpose. Moreover, there may be other protein classes that could be exploited for protein stabilization or degradation. Here, we used a proteome-scale platform to identify hundreds of human proteins that can promote the degradation or stabilization of a target protein in a proximity-dependent manner. This allowed us to comprehensively compare the activities of human E3s and deubiquitinases, characterize non-canonical protein degraders and stabilizers, and establish that effectors have vastly different activities against diverse targets. Notably, the top degraders were more potent against multiple therapeutically relevant targets than the currently used E3s CBRN and VHL. Our study provides a functional catalogue of effectors for targeted protein degradation and stabilization and highlights the potential of induced proximity screens for discovery of novel proximity-dependent protein modulators.