Structure of the human Cereblon–DDB1–lenalidomide complex reveals basis for responsiveness to thalidomide analogs

Abstract

The Cul4-Rbx1-DDB1-Cereblon E3 ubiquitin ligase complex is the target of thalidomide, lenalidomide and pomalidomide, therapeutically important drugs for multiple myeloma and other B-cell malignancies. These drugs directly bind Cereblon (CRBN) and promote the recruitment of substrates Ikaros (IKZF1) and Aiolos (IKZF3) to the E3 complex, thus leading to substrate ubiquitination and degradation. Here we present the crystal structure of human CRBN bound to DDB1 and the drug lenalidomide. A hydrophobic pocket in the thalidomide-binding domain (TBD) of CRBN accommodates the glutarimide moiety of lenalidomide, whereas the isoindolinone ring is exposed to solvent. We also solved the structures of the mouse TBD in the apo state and with thalidomide or pomalidomide. Site-directed mutagenesis in lentiviral-expression myeloma models showed that key drug-binding residues are critical for antiproliferative effects.

Rabex-5 is a lenalidomide target molecule that negatively regulates TLR-induced type 1 IFN production

“…S3). This region is within the DDB1 binding portion and serves to connect Cereblon to the wider CUL4A CRBN complex (13). Collectively, these data identify Rabex-5 as a specific (among A20 homology proteins) CUL4A CRBN -interacting protein.…”

“…The IMiD-induced degradation of substrates does not occur in murine systems (13,17). Therefore, we next compared the effect of IMiD treatment on the Cereblon-Rabex-5 interaction using human and murine recombinant protein.…”

“…Ikaros, which is degraded following IMiD treatment, functions as a transcriptional repressor of the regulatory T-cell-promoting cytokine IL2 (9)(10)(11)(12). Consequently, treatment with pomalidomide up-regulates IL2 production in a Cereblon-dependent manner (11,13). Cereblon therefore contributes to the antiinflammatory properties of IMiDs by mediating the degradation of proteins with functions in the immune system.…”

Aiolos Overexpression in Systemic Lupus Erythematosus B Cell Subtypes and BAFF-Induced Memory B Cell Differentiation Are Reduced by CC-220 Modulation of Cereblon Activity

“…Although thalidomide and related compounds bind both murine and human CRBN, only human CRBN induces ubiquitination and degradation of Aiolos and Ikaros (58). CC-220 has a similar binding mechanism and also does not induce murine aiolos and ikaros degradation (data not shown), precluding mouse cell or SLE disease model testing.…”

Recognition of substrate degrons by E3 ubiquitin ligases and modulation by small-molecule mimicry strategies

“…4c). IMiD-binding by CRL4 CRBN prevents engagement of its endogenous substrate MEIS2; it also re-directs effective recruitment and CRBN-dependent degradation of the transcription factors Ikaros and Aiolos as well as Casein kinase 1α (CK1α) [57][58][59][60]. Additionally, lenalidomide derivative CC-885 was shown to induce recruitment and degradation of the translation termination factor GSPT1 [61].…”