USP7 small-molecule inhibitors interfere with ubiquitin binding.

Area of Science:

• Biochemistry
• Molecular Biology
• Drug Discovery

Background:

• The ubiquitin system is crucial for cellular processes, with deubiquitinase enzymes like ubiquitin-specific protease-7 (USP7) regulating protein stability.
• USP7 plays a role in cancer by controlling the stability of tumor suppressors like p53, but selective inhibitors have been difficult to develop.

Purpose of the Study:

• To develop novel, selective inhibitors of USP7.
• To elucidate the mechanism of inhibition and explore therapeutic applications of these inhibitors.

Main Methods:

• Nuclear magnetic resonance (NMR)-based screening and structure-based drug design were employed to identify and optimize USP7 inhibitors.
• Co-crystal structures were used to understand the non-covalent binding of inhibitors to USP7.
• Di-ubiquitin chain assays with isotopic labeling were performed to study USP7 substrate preference.

Main Results:

• Two selective USP7 inhibitors, GNE-6640 and GNE-6776, were developed.
• These compounds bind non-covalently to USP7 at a site distinct from the catalytic cysteine, attenuating ubiquitin binding.
• Inhibitors enhance the cytotoxicity of chemotherapeutic agents and PIM kinase inhibitors, inducing tumor cell death.
• USP7 preferentially binds and cleaves Lys48-linked ubiquitin chains, a mechanism elucidated through di-ubiquitin chain analysis.

Conclusions:

• GNE-6640 and GNE-6776 represent a new class of USP7 inhibitors targeting ubiquitin binding, offering a promising strategy for cancer therapy.
• The findings suggest a broader applicability of targeting protein-ubiquitin interactions for developing inhibitors against other deubiquitinases and related proteins.