Proteome-wide identification of the druggable CRBN interactome.

Molecular glue degraders (MGDs), such as pomalidomide, induce degradation of non-native substrates by the cullin-RING E3 ligase 4 (CRL4) through its substrate receptor cereblon (CRBN). Here, to explore CRBN programmability, we tested whether reported CRBN-MGD substrates are part of a network of latent CRBN interactors, proteins capable of MGD-induced CRBN binding without detectable degradation. Leveraging a highly parallel protein complementation assay (GluePCA) to measure MGD-induced interaction between CRBN and zinc fingers, we identified ~210 zinc fingers bound to CRBN-pomalidomide, where top binders are already reported as degraded by dedicated MGDs. To map latent CRBN-MGD interactions proteome-wide and define the accessible CRBN interaction space, we combined artificial intelligence-derived protein surface queries (MaSIF-mimicry) with GluePCA. This pipeline identified 6 known and 43 novel CRBN-pomalidomide binders, including orthogonally validated hits. We find that these binders provide privileged starting points for MGD development. We expect this binding-focused workflow to be applicable to other MGD-E3 ligase systems, potentially extending the scope of this emerging drug class.