Dynamics and Composition of Small Heat Shock Protein Condensates and Aggregates.

Autor: Joosten J; Biomolecular Chemistry, Radboud University Institute for Molecular and Materials, Nijmegen, the Netherlands; Physical Organic Chemistry, Radboud University Institute for Molecular and Materials, Nijmegen, the Netherlands; Synthetic Organic Chemistry, Radboud University Institute for Molecular and Materials, the Netherlands. Electronic address: joep.joosten@ru.nl., van Sluijs B; Physical Organic Chemistry, Radboud University Institute for Molecular and Materials, Nijmegen, the Netherlands., Vree Egberts W; Biomolecular Chemistry, Radboud University Institute for Molecular and Materials, Nijmegen, the Netherlands., Emmaneel M; Biomolecular Chemistry, Radboud University Institute for Molecular and Materials, Nijmegen, the Netherlands., Jansen PWTC; Molecular Biology, Radboud University Institute for Molecular Life Sciences, Nijmegen, the Netherlands., Vermeulen M; Molecular Biology, Radboud University Institute for Molecular Life Sciences, Nijmegen, the Netherlands. Electronic address: https://twitter.com/LabVermeulen., Boelens W; Biomolecular Chemistry, Radboud University Institute for Molecular and Materials, Nijmegen, the Netherlands., Bonger KM; Synthetic Organic Chemistry, Radboud University Institute for Molecular and Materials, the Netherlands. Electronic address: https://twitter.com/kimbonger., Spruijt E; Physical Organic Chemistry, Radboud University Institute for Molecular and Materials, Nijmegen, the Netherlands. Electronic address: https://twitter.com/SpruijtLab.
Jazyk: angličtina
Zdroj: Journal of molecular biology [J Mol Biol] 2023 Jul 01; Vol. 435 (13), pp. 168139. Date of Electronic Publication: 2023 May 03.
DOI: 10.1016/j.jmb.2023.168139
Abstrakt: Small heat shock proteins (sHSPs) are essential ATP-independent chaperones that protect the cellular proteome. These proteins assemble into polydisperse oligomeric structures, the composition of which dramatically affects their chaperone activity. The biomolecular consequences of variations in sHSP ratios, especially inside living cells, remain elusive. Here, we study the consequences of altering the relative expression levels of HspB2 and HspB3 in HEK293T cells. These chaperones are partners in a hetero-oligomeric complex, and genetic mutations that abolish their mutual interaction are associated with myopathic disorders. HspB2 displays three distinct phenotypes when co-expressed with HspB3 at varying ratios. Expression of HspB2 alone leads to formation of liquid nuclear condensates, while shifting the stoichiometry towards HspB3 resulted in the formation of large solid-like aggregates. Only cells co-expressing HspB2 with a limited amount of HspB3 formed fully soluble complexes that were distributed homogeneously throughout the nucleus. Strikingly, both condensates and aggregates were reversible, as shifting the HspB2:HspB3 balance in situ resulted in dissolution of these structures. To uncover the molecular composition of HspB2 condensates and aggregates, we used APEX-mediated proximity labelling. Most proteins interact transiently with the condensates and were neither enriched nor depleted in these cells. In contrast, we found that HspB2:HspB3 aggregates sequestered several disordered proteins and autophagy factors, suggesting that the cell is actively attempting to clear these aggregates. This study presents a striking example of how changes in the relative expression levels of interacting proteins affects their phase behavior. Our approach could be applied to study the role of protein stoichiometry and the influence of client binding on phase behavior in other biomolecular condensates and aggregates.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)
Databáze: MEDLINE
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