Cellular Validation of a Chemically Improved Inhibitor Identifies Monoubiquitination on OTUB2

Area of Science:

• Biochemistry
• Molecular Biology
• Oncology

Background:

• Ovarian tumor (OTU) deubiquitinase 2 (OTUB2) is a cysteine protease frequently overexpressed in tumors, driving progression and metastasis.
• Targeting OTUB2 with small-molecule inhibitors is therapeutically significant, but potent and selective options are limited.

Purpose of the Study:

• To develop an improved, potent, and selective small-molecule inhibitor for OTUB2.
• To investigate the mechanism of action and cellular effects of the novel OTUB2 inhibitor.

Main Methods:

• Design and synthesis of a novel OTUB2 inhibitor, LN5P45, featuring a chloroacethydrazide moiety for covalent active-site targeting.
• Assessment of target engagement and proteome-wide selectivity using cellular assays.
• Analysis of OTUB2 post-translational modifications, specifically monoubiquitination at lysine 31, upon inhibitor treatment.

Main Results:

• LN5P45 demonstrated excellent target engagement and high proteome-wide selectivity in living cells.
• LN5P45 and other OTUB2 inhibitors effectively induced monoubiquitination of OTUB2 on lysine 31.
• The study identified a potential therapeutic strategy and highlighted LN5P45's utility in exploring OTUB2 biology.

Conclusions:

• LN5P45 represents a promising lead compound for developing novel OTUB2-targeted cancer therapeutics.
• OTUB2 inhibition influences its post-translational modification status, specifically inducing monoubiquitination at K31.
• This work provides a foundation for further research into OTUB2 regulation and therapeutic targeting in cancer.