Ligand-mediated protein degradation reveals functional conservation among sequence variants of the CUL4-type E3 ligase substrate receptor cereblon

• DOI: 10.1074/jbc.m117.816868
• Publication Date: 2018-02-15T21:15:13Z
• Authors: Afua A. Akuffo; Aileen Y. Alontaga; Rainer Metcalf; Matthew S. Beatty; Andreas Becker; Jessica M. McDaniel; Rebecca S. Hester...; William E. Goodheart; Steven Gunawan; Muhammad Ayaz; Yan Yang; Md Rezaul Karim; Morgan E. Orobello; Kenyon Daniel; Wayne Guida; Jeffrey A. Yoder; Anjali M. Rajadhy...; Ernst Schönbrunn; Harshani R. Lawrence; Nicholas J. Lawrence; Pearlie K. Epling...
• Keywords: Cereblon; Ubiquitin-Protein Ligases; DDB1

Upon binding to thalidomide and other immunomodulatory drugs, the E3 ligase substrate receptor cereblon (CRBN) promotes proteosomal destruction by engaging DDB1-CUL4A-Roc1-RBX1 ubiquitin in human cells but not mouse cells, suggesting that sequence variations CRBN may cause its inactivation. Therapeutically, engagers have potential for broad applications cancer immune therapy specifically reducing protein expression through targeted ubiquitin-mediated degradation. To examine effects of defined changes on CRBN's activity, we performed a comprehensive study using complementary theoretical, biophysical, biological assays aimed at understanding nonprimate variations. With series recombinant thalidomide-binding domain (TBD) proteins, show variants retain their drug-binding properties both classical drugs dBET1, chemical compound targeting ligand designed degrade bromodomain-containing 4 (BRD4) via CRBN-dependent mechanism. We further dBET1 stimulates ubiquitin-conjugating function degrades BRD4 cells. This insight paves way studies proteasome-targeting molecules models provides new substrate-recruiting function.