Ubiquitin E3 ligases are crucial for eliminating misfolded proteins before they form cytotoxic aggregates that threaten cell fitness and survival. However, it remains unclear how emerging misfolded proteins in the cytoplasm can be selectively recognized and eliminated by E3 ligases in plants. We found that Misfolded Protein Sensing RING E3 ligase 1 (MPSR1) is an indispensable E3 ligase required for plant survival after protein-damaging stress. Under no stress, MPSR1 is prone to rapid degradation by the 26S proteasome, concealing its protein quality control (PQC) E3 ligase activity. Upon proteotoxic stress, MPSR1 directly senses incipient misfolded proteins and tethers ubiquitins for subsequent degradation. Furthermore, MPSR1 sustains the structural integrity of the proteasome complex at the initial stage of proteotoxic stress. Here, we suggest that the MPSR1 pathway is a constitutive mechanism for proteostasis under protein-damaging stress, as a front-line surveillance system in the cytoplasm.
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|Publication status||Published - 2017 Nov 14|
Bibliographical noteFunding Information:
ACKNOWLEDGMENTS. This work was supported by National Research Foundation Projects 2014R1A2A2A01003891 and NRF-2017R1A2B2006750, a Republic of Korea grant (to W.T.K.), and by Radiation Technology R&D Program Project NRF-2015M2A2B2066120 through the National Research Foundation of Korea funded by the Ministry of Science, ICT & Future Planning (S.W.Y.).
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