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Stress-inducible phosphoprotein 1 (Sti1/Stip1/Hop) sequesters misfolded proteins during stress
Benjamin S Rutledge1, Young J Kim2, Donovan W McDonald2
1Department of Biochemistry, The University of Western Ontario, London, Canada.
The FEBS Journal
|December 31, 2024
Summary
Stress-inducible phosphoprotein 1 (Sti1) sequesters misfolded proteins during cellular stress, acting independently of Hsp90 regulation. This crucial role in proteostasis prevents toxic protein accumulation and aids cellular recovery.
Area of Science:
- Cellular Biology
- Molecular Biology
- Protein Homeostasis
Background:
- Co-chaperones like stress-inducible phosphoprotein 1 (Sti1) and activator of Hsp90 ATPase protein 1 (Aha1) are vital for cellular protein quality control.
- These co-chaperones collaborate with heat shock proteins Hsp70 and Hsp90 to maintain protein folding and prevent the aggregation of misfolded proteins.
Purpose of the Study:
- To investigate the role of Sti1 and Aha1 in cellular proteostasis.
- To elucidate the function of Sti1 in Hsp90-mediated protein folding and quality control.
Main Methods:
- Analysis of yeast and mammalian cell models with altered Sti1 and Aha1 expression.
- Investigating the impact of STI1 deletion on protein aggregation and heat shock response.
- Microscopic examination of Sti1 localization during proteostatic stress.
Main Results:
- Misbalanced Sti1 and Aha1 expression leads to significant growth defects in both yeast and mammalian cells.
- Deletion of STI1 results in the accumulation of misfolded, ubiquitinated proteins and heightened heat shock response.
- During proteostatic stress, Sti1 forms cytoplasmic inclusions that co-localize with misfolded proteins.
Conclusions:
- Sti1 plays a critical role in maintaining proteostasis by sequestering misfolded proteins during stress.
- This function of Sti1 is independent of its previously known Hsp90 ATPase regulatory activities.
- Sti1 acts as a key component in cellular defense against proteotoxic stress.
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