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Published on: March 26, 2014
Epidithiodiketopiperazines Inhibit Protein Degradation by Targeting Proteasome Deubiquitinase Rpn11
Jing Li1, Yaru Zhang1, Bruno Da Silva Sil Dos Santos2
1Division of Biology and Biological Engineering, California Institute of Technology, Box 114-96, Pasadena, CA 91125, USA; Amgen Discovery Research, One Amgen Center Drive MS 29-M-B, Thousand Oaks, CA 91320, USA.
Abstract:
The 26S proteasome is the major proteolytic machine for breaking down cytosolic and nuclear proteins in eukaryotes. Due to the lack of a suitable assay, it is difficult to measure routinely and quantitatively the breakdown of proteins by the 26S proteasome in vitro. In the present study, we developed an assay to monitor proteasome-mediated protein degradation. Using this assay, we discovered that epidithiodiketopiperazine (ETPs) blocked the degradation of our model substrate in vitro. Further characterization revealed that ETPs inhibited proteasome function by targeting the essential proteasomal deubiquitinase Rpn11 (POH1/PSMD14). ETPs also inhibited other JAMM (JAB1/MPN/Mov34 metalloenzyme) proteases such as Csn5 and AMSH. An improved ETP with fewer non-specific effects, SOP11, stabilized a subset of proteasome substrates in cells, induced the unfolded protein response, and led to cell death. SOP11 represents a class of Rpn11 inhibitor and provides an alternative route to develop proteasome inhibitors.
Insights
Researchers developed a new assay to measure proteasome activity. They found that epidithiodiketopiperazines (ETPs) inhibit the proteasome by targeting Rpn11, a key deubiquitinase, offering a new strategy for proteasome inhibitor development.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- The 26S proteasome is crucial for protein homeostasis in eukaryotes.
- Quantitative assays for in vitro proteasome activity are limited.
Purpose of the Study:
- Develop a novel assay to monitor proteasome-mediated protein degradation.
- Investigate the inhibitory effects of epidithiodiketopiperazines (ETPs) on proteasome function.
Main Methods:
- Development of a quantitative in vitro assay for 26S proteasome activity.
- Characterization of ETPs as inhibitors of the proteasome.
- Identification of Rpn11 (POH1/PSMD14) as the specific target of ETPs.
- Evaluation of an improved ETP derivative, SOP11, in cellular contexts.
Main Results:
- ETPs were identified as inhibitors of proteasome-mediated protein degradation in vitro.
- ETPs specifically inhibit the proteasomal deubiquitinase Rpn11.
- ETPs also inhibit other JAMM metalloproteases, including Csn5 and AMSH.
- SOP11, an improved ETP, stabilized proteasome substrates, induced the unfolded protein response, and caused cell death in cells.
Conclusions:
- A new assay enables quantitative measurement of proteasome activity.
- ETPs are potent inhibitors of the 26S proteasome via Rpn11 targeting.
- SOP11 demonstrates therapeutic potential as a proteasome inhibitor, offering a new class of drugs.
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