Structure of the Rpn13-Rpn2 complex provides insights for Rpn13 and Uch37 as anticancer targets

Area of Science:

• Molecular Biology
• Biochemistry
• Cancer Research

Background:

• The proteasome system degrades proteins, crucial for cellular regulation.
• hRpn13 (human Rad23 homologue) is a proteasome receptor that binds and activates Uch37 (UCHL5), a deubiquitinating enzyme.
• RA190 is a bis-benzylidine piperidone compound that restricts cancer growth.

Purpose of the Study:

• To elucidate the structural basis of hRpn13-hRpn2 interaction.
• To understand the mechanism of RA190 action on hRpn13 and Uch37.
• To investigate the role of hRpn13 in RA190-mediated cancer therapy.

Main Methods:

• X-ray crystallography to determine the structure of hRpn13 bound to hRpn2.
• Biophysical analyses (e.g., SPR, ITC) to quantify binding affinities.
• Cell-based assays (e.g., Western blotting, gene deletion) to assess functional consequences.

Main Results:

• The structure reveals hRpn2 binding to the hRpn13 Pru domain, with an hRpn2 extension blocking the RA190-binding site.
• hRpn13 shows preferential binding to hRpn2 and proteasomes over RA190.
• RA190 directly binds and inactivates Uch37, independent of hRpn13.
• hRpn13 deletion abolishes RA190-induced proteasome substrate accumulation.

Conclusions:

• RA190 targets hRpn13 and Uch37 via parallel mechanisms.
• At the proteasome, RA190-inactivated Uch37 cannot remove ubiquitin chains from hRpn13-bound substrates.
• This study provides insights into the mechanism of RA190 as a potential cancer therapeutic.