PT  - JOURNAL ARTICLE
AU  - Xiuxiu Lu
AU  - Venkata R. Sabbasani
AU  - Vasty Osei-Amponsa
AU  - Christine N. Evans
AU  - Julianna C. King
AU  - Sergey G. Tarasov
AU  - Marzena Dyba
AU  - King C. Chan
AU  - Charles D. Schwieters
AU  - Sulbha Choudhari
AU  - Caroline Fromont
AU  - Yongmei Zhao
AU  - Bao Tran
AU  - Xiang Chen
AU  - Hiroshi Matsuo
AU  - Thorkell Andresson
AU  - Raj Chari
AU  - Rolf E. Swenson
AU  - Nadya I. Tarasova
AU  - Kylie J. Walters
TI  - Structure-guided bifunctional molecules hit a DEUBAD-lacking hRpn13 species upregulated in multiple myeloma
AID  - 10.1101/2021.07.16.452547
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.07.16.452547
4099  - http://biorxiv.org/content/early/2021/07/17/2021.07.16.452547.short
4100  - http://biorxiv.org/content/early/2021/07/17/2021.07.16.452547.full
AB  - Proteasome substrate receptor hRpn13 is a promising anti-cancer target. By integrated in silico and biophysical screening, we identified a chemical scaffold that binds hRpn13 with non-covalent interactions that mimic the proteasome and a weak electrophile for Michael addition. hRpn13 Pru domain binds proteasomes and ubiquitin whereas its DEUBAD domain binds deubiquitinating enzyme UCHL5. NMR revealed lead compound XL5 to interdigitate into a hydrophobic pocket created by lateral movement of a Pru β-hairpin with an exposed end for Proteolysis Targeting Chimeras (PROTACs). Implementing XL5-PROTACs as chemical probes identified a DEUBAD-lacking hRpn13 species (hRpn13Pru) present naturally with cell type-dependent abundance. XL5-PROTACs preferentially target hRpn13Pru, causing its ubiquitination. Gene-editing and rescue experiments established hRpn13 requirement for XL5-PROTAC-triggered apoptosis and increased p62 levels. These data establish hRpn13 as an anti-cancer target for multiple myeloma and introduce an hRpn13-targeting scaffold that can be optimized for preclinical trials against hRpn13Pru-producing cancer types.Competing Interest StatementThe authors have declared no competing interest.