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Updated: Nov 30, 2025
Purification of Hsp104, a Protein Disaggregase
Published on: September 30, 2011
Mutable yeast prion variants are stabilized by a defective Hsp104 chaperone
Yu-Wen Huang1,2, Vitaly V Kushnirov3, Chih-Yen King2
1Molecular Cell Biology, Taiwan International Graduate Program, Academia Sinica and National Defense Medical Center, Taipei, Taiwan.
Abstract:
Gorkovskiy et al. observed that many [PSI+ ] prion isolates, obtained in yeast with the mutant Hsp104T160M chaperone, propagate poorly in wild-type cells and suggested that Hsp104 is part of the cellular anti-prion system, curing many nascent [PSI+ ] variants. Here, we argue that the concept may require reassessment. We induced [PSI+ ] variants in both the wild-type and the mutant background. Three new variants were isolated in the T160M background. They exhibited lower thermostability, possessed novel structural features, and were inherently mutable, changing to well-characterized VH, VK, and VL variants in wild-type cells. In contrast, VH, VK, and VL of the wild-type background, could not change freely and were lost in the mutant, due to insufficient chaperone activity. Thus, mutant Hsp104 can impose as much restriction against emerging prion variants as the wild-type protein. Such restriction conserved the transmutable variants in the T160M background, since new structures mis-templated from them could not gain a foothold. We further demonstrate excess Hsp104T160M or Hsp104∆2-147 can eliminate nearly all of the [PSI+ ] variants in their native background. This finding contradicts the generally held belief that Hsp104-induced [PSI+ ] curing requires its N-terminal domain, and may help settling the current contention regarding how excess Hsp104 cures [PSI+ ].
Insights
The yeast chaperone Hsp104, even in a mutant form, restricts the emergence of new prion variants. Excess amounts of mutant Hsp104 can cure existing prions, challenging previous assumptions about its function.
Area of Science:
- Protein misfolding and aggregation
- Yeast genetics and molecular biology
- Prion biology
Background:
- The Hsp104 chaperone is implicated in prion propagation and curing.
- Previous studies suggested Hsp104 acts as an anti-prion system, curing nascent variants.
- The role of Hsp104 in prion variant stability and emergence requires further investigation.
Purpose of the Study:
- To reassess the role of Hsp104 in prion variant dynamics.
- To investigate the impact of mutant Hsp104 on the emergence and stability of [PSI+] prion variants.
- To clarify the mechanism of Hsp104-induced prion curing.
Main Methods:
- Induction of [PSI+] variants in wild-type and Hsp104 mutant yeast strains.
- Characterization of prion variant properties including thermostability and mutability.
- Assessment of prion curing by excess amounts of wild-type and mutant Hsp104.
Main Results:
- Mutant Hsp104 restricted the emergence of new, mutable prion variants.
- Newly identified variants in the mutant background showed lower thermostability and changed to known variants in wild-type cells.
- Excess Hsp104 (mutant or truncated) effectively cured [PSI+] variants, independent of its N-terminal domain.
Conclusions:
- Mutant Hsp104 can restrict prion variant emergence, conserving transmutable variants.
- The findings challenge the necessity of the Hsp104 N-terminal domain for prion curing.
- This study provides new insights into Hsp104's complex role in prion biology and curing mechanisms.
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