ORIGINAL RESEARCH article

Front. Cell Dev. Biol.

Sec. Signaling

Volume 13 - 2025 | doi: 10.3389/fcell.2025.1570499

This article is part of the Research TopicUbiquitin Proteasome System (UPS) and Ubiquitin-Independent Proteasome-Mediated Proteolysis (UIPP) Crosstalk in Development and DiseaseView all 4 articles

Proteasome Caspase-Like Activity Regulates Stress Granules and Proteasome Condensates

Provisionally accepted
  • Weizmann Institute of Science, Rehovot, Israel

The final, formatted version of the article will be published soon.

The 20S proteasome maintains cellular protein homeostasis, particularly during stress responses. In a previous study, we identified numerous 20S proteasome substrates through mass spectrometry analysis of peptides generated from cellular extracts degraded by purified 20S proteasome. Many substrates were found to be components of liquid-phase separation, such as stress granules (SGs). Here, we demonstrate that the degradation products arise from the caspase-like (CL) proteasomal activity. To investigate the functional implications of CL activity, we generated cell lines devoid of CL function by introducing the PSMB6 T35A mutation. These mutant cells exhibited slower growth rates, heightened sensitivity to stress, and activation of the unfolded protein response (UPR), as indicated by elevated levels of spliced XBP1 (sXBP1) and stress markers. Cells were subjected to arsenite and osmotic stress to assess their responses. Our findings reveal that CL activity is crucial for efficient SG assembly but does not significantly affect SG clearance. Interestingly, in these mutant cells, proteasomes were more cytoplasmic under normal conditions but formed nuclear condensates/granules (PGs) upon NaCl osmotic stress. However, the PGs were unstable and rapidly dispersed. These findings underscore the important role of the proteasome's CL activity in managing stress-induced dynamics of liquid-liquid phase, highlighting its importance in cellular adaptation to proteotoxic and genotoxic stress conditions.

Keywords: stress granules,, proteasome condensates, proteasome caspase-like activity, intrinsically disordered proteins, 20S proteasome

Received: 03 Feb 2025; Accepted: 26 May 2025.

Copyright: © 2025 Steinberger, Adler, Myers and Shaul. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Yosef Shaul, Weizmann Institute of Science, Rehovot, Israel

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