Dynamics of the Functional Activity and Expression of Proteasome Subunits during Cellular Adaptation to Heat Shock
The ubiquitin-proteasome system (UPS) performs proteolysis of most intracellular proteins. The key components of the UPS are the proteasomes, multi-subunit protein complexes, playing an important role in cellular adaptation to various types of stress. We analyzed the dynamics of the proteasome activity, the content of proteasome subunits, and the expression levels of genes encoding catalytic subunits of proteasomes in the human histiocytic lymphoma U937 cell line immediately, 2, 4, 6, 9, 24, and 48 h after a heat shock (HS). The initial decrease (up to 62%) in the proteasome activity in cellular lysates was revealed, then 10 h after HS the activity began to recover. The amount of proteasomal α-subunits in the cells decreased 2 h after HS, and was restored to 24–48 h after HS. Fluctuations in the levels of mRNAs encoding proteasome catalytic subunits with the maximum expression 2 h after HS and a gradual decrease to 48 h after HS were observed. The average estimated number of mRNA copies per cell ranged from 10 for weakly to 150 for highly expressed proteasome genes. Thus, the recovery efficiency of UPS functionality after HS, which reflects the important role of proteasomes in maintaining cell homeostasis, was evaluated.
Keywords:ubiquitin-proteasome system proteasome heat shock
The authors thank V.A. Morozov for participating in the discussion of the results.
An RT-PCR system for the quantification of the expression levels of proteasome genes was designed, tested, and tuned with the financial support of the Russian Science Foundation (grant no. 18-74-10095). The studies on the proteasomal activity and their subunit composition in lysates of U937 cells were supported by the grant of the President of the Russian Federation for young PhD scientists (grant no. MK3613.2017.4) and financially supported under the Program of Fundamental Research of the State Academies of Sciences for 2013–2020, subject no. 01201363823.
COMPLIANCE WITH ETHICAL STANDARDS
Conflict of interest. The authors declare that they have no conflict of interest.
Statement of the welfare of animals. This article does not contain any studies involving animals or human participants performed by any of the authors.
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