Degradation of the Deubiquitinating Enzyme USP33 Is Mediated by p97 and the Ubiquitin Ligase HERC2

Because the deubiquitinating enzyme USP33 is involved in several important cellular processes (β-adrenergic receptor recycling, centrosome amplification, RalB signaling, and cancer cell migration), its levels must be carefully regulated. Using quantitative mass spectrometry, we found that the intracellular level of USP33 is highly sensitive to the activity of p97. Knockdown or chemical inhibition of p97 causes robust accumulation of USP33 due to inhibition of its degradation. The p97 adaptor complex involved in this function is the Ufd1-Npl4 heterodimer. Furthermore, we identified HERC2, a HECT domain-containing E3 ligase, as being responsible for polyubiquitination of USP33. Inhibition of p97 causes accumulation of polyubiquitinated USP33, suggesting that p97 is required for postubiquitination processing. Thus, our study has identified several key molecules that control USP33 degradation within the ubiquitin-proteasome system. Background: The deubiquitinating enzyme USP33 controls several important cellular functions. Results: HERC2 and p97 are critical for USP33 degradation. Conclusion: HERC2 and p97 constitute a novel pathway to degrade USP33. Significance: The HERC2/p97 degradative pathway may control USP33-dependent processes.