Structure of the DDB1–CRBN E3 ubiquitin ligase in complex with thalidomide

Immunomodulatory drugs (IMiDs) are a family of compounds derived from thalidomide. Binding of the IMiD molecule to the Lon protease Cereblon initiates the degradation of substrates via the ubiquitin proteasome pathway. Here, we show that Cereblon forms a complex with Rabex-5, a regulator of immune homeostasis. Treatment with lenalidomide prevented the association of Cereblon with Rabex-5. Conversely, mutation of the IMiD binding site increased Cereblon–Rabex-5 coimmunoprecipitation. The thalidomide binding region of Cereblon therefore regulates the formation of this complex. Knockdown of Rabex-5 in the THP-1 macrophage cell line up-regulated Toll-like receptor (TLR)-induced cytokine and type 1 IFN production via a STAT1/IRF activating pathway. Thus, we identify Rabex-5 as a IMiD target molecule that functions to restrain TLR activated auto-immune promoting pathways. We propose that release of Rabex-5 from complex with Cereblon enables the suppression of immune responses, contributing to the antiinflammatory properties of IMiDs.

Section: Discussioncontrasting

confidence: 53%

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

Millrine

Tei

Gemechu

et al. 2016

“…4A). Moreover, the DNA-binding motif of CRBN is situated in an area in which substrates generally bind to WD40 DDB1/CUL4-associated factors, such as DDB2, to engage DNA (16). Therefore, we tested whether this potential DNA-binding motif of CRBN is required for binding to the Kcna3 R4 region.…”

Section: The C-terminal Domain Of Crbn Is Crucial For Crbn Enrichment Onmentioning

confidence: 99%

Epigenetic regulation of Kcna3 -encoding Kv1.3 potassium channel by cereblon contributes to regulation of CD4 ⁺ T-cell activation

Kang

Park

Jeong

et al. 2016

The role of cereblon (CRBN) in T cells is not well understood. We generated mice with a deletion in Crbn and found cereblon to be an important antagonist of T-cell activation. In mice lacking CRBN, CD4+ T cells show increased activation and IL-2 production on T-cell receptor stimulation, ultimately resulting in increased potassium flux and calcium-mediated signaling. CRBN restricts T-cell activation via epigenetic modification of Kcna3, which encodes the Kv1.3 potassium channel required for robust calcium influx in T cells. CRBN binds directly to conserved DNA elements adjacent to Kcna3 via a previously uncharacterized DNA-binding motif. Consequently, in the absence of CRBN, the expression of Kv1.3 is derepressed, resulting in increased Kv1.3 expression, potassium flux, and CD4+ T-cell hyperactivation. In addition, experimental autoimmune encephalomyelitis in T-cell–specific Crbn-deficient mice was exacerbated by increased T-cell activation via Kv1.3. Thus, CRBN limits CD4+ T-cell activation via epigenetic regulation of Kv1.3 expression.

“…(S)-pomalidomide was originally advanced into clinical trials as ENMD 0995 (39) but soon abandoned because of the rapid racemization of the exchangeable chiral center (28,29). Finally, it has recently been shown by X-ray crystallography that the (S)-enantiomers of thalidomide, lenalidomide, and pomalidomide preferentially bind a newly identified target, cereblon (CRBN), believed to be responsible for their efficacy and teratogenicity in a cocrystal with the DDB1-CRBN complex, where DDB1 stands for DNA damage-binding protein 1 (40).…”

mentioning

confidence: 99%

Differentiation of antiinflammatory and antitumorigenic properties of stabilized enantiomers of thalidomide analogs

Jacques¹,

Czarnik²,

Judge³

et al. 2015

Therapeutics developed and sold as racemates can exhibit a limited therapeutic index because of side effects resulting from the undesired enantiomer (distomer) and/or its metabolites, which at times, forces researchers to abandon valuable scaffolds. Therefore, most chiral drugs are developed as single enantiomers. Unfortunately, the development of some chirally pure drug molecules is hampered by rapid in vivo racemization. The class of compounds known as immunomodulatory drugs derived from thalidomide is developed and sold as racemates because of racemization at the chiral center of the 3-aminoglutarimide moiety. Herein, we show that replacement of the exchangeable hydrogen at the chiral center with deuterium allows the stabilization and testing of individual enantiomers for two thalidomide analogs, including CC-122, a compound currently in human clinical trials for hematological cancers and solid tumors. Using “deuterium-enabled chiral switching” (DECS), in vitro antiinflammatory differences of up to 20-fold are observed between the deuterium-stabilized enantiomers. In vivo, the exposure is dramatically increased for each enantiomer while they retain similar pharmacokinetics. Furthermore, the single deuterated enantiomers related to CC-122 exhibit profoundly different in vivo responses in an NCI-H929 myeloma xenograft model. The (−)-deuterated enantiomer is antitumorigenic, whereas the (+)-deuterated enantiomer has little to no effect on tumor growth. The ability to stabilize and differentiate enantiomers by DECS opens up a vast window of opportunity to characterize the class effects of thalidomide analogs and improve on the therapeutic promise of other racemic compounds, including the development of safer therapeutics and the discovery of new mechanisms and clinical applications for existing therapeutics.