Systematic identification of 20S proteasome targets

ABSTRACT: For many years, the ubiquitin-26S proteasome degradation pathway was considered the principal route for proteasomal degradation. However, it is now becoming clear that proteins can also be targeted for degradation by an ubiquitin-independent mechanism mediated by the core 20S proteasome itself. The fact that half of cellular proteasomes are free 20S complexes suggests that degradation by this complex is not limited to rare cases. Identifying 20S proteasome substrates is challenging, as different pools of the same protein can be sent to degradation via either 20S or 26S proteasomes. Hence, current knowledge regarding the repertoire of 20S proteasome substrates mainly originates from individual case studies. Here, in an effort to unravel the global repertoire of substrates degraded by the 20S proteasome, we used an advanced mass spectrometry approach coupled with biochemical and cellular analysis. Our analysis enabled the identification of hundreds of 20S proteasome substrates. In addition to proteins that are degraded to completion, we also identified proteins that undergo specific cleavage by the 20S proteasome, at their N- or C- termini, to possibly tune their function. We also found that 20S substrates are significantly enriched with RNA- and DNA-binding proteins that contain intrinsically disordered regions. The vast majority of them are localized in the nucleus and stress granules. Further, we demonstrate that oxidized proteasomes have reduced proteolytic activity compared to naïve proteasomes, which we propose is an adaptive advantage under conditions of cellular stress. Whereas oxidized protein substrates, rather than being folded proteins that lost their native structure due to the stress, actually display a higher degree of structural-disorder than naïve proteins. In summary, here we shed light on the nature of the 20S substrates, providing critical insight into the biological role of the 20S proteasome.

INSTRUMENT(S): Orbitrap Fusion Lumos, Orbitrap Exploris 480

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Michal sharon  

LAB HEAD: Michal Sharon

PROVIDER: PXD044399 | Pride | 2023-12-21

REPOSITORIES: Pride