RESUMO
Chaperones and autophagy are components of the protein quality control system that contribute to the management of proteins that are misfolded and aggregated. Here, we use yeast prions, which are self-perpetuating aggregating proteins, as a means to understand how these protein quality control systems influence aggregate loss. Chaperones, such as Hsp104, fragment prion aggregates to generate more prion seeds for propagation. While much is known about the role of chaperones, little is known about how other quality control systems contribute to prion propagation. We show that the aprotic solvent dimethyl sulfoxide (DMSO) cures a range of [PSI+] prion variants, which are related to several misfolded aggregated conformations of the Sup35 protein. Our studies show that DMSO-mediated curing is quicker and more efficient than guanidine hydrochloride, a prion curing agent that inactivates the Hsp104 chaperone. Instead, DMSO appears to induce Hsp104 expression. Using the yTRAP system, a recently developed transcriptional reporting system for tracking protein solubility, we found that DMSO also rapidly induces the accumulation of soluble Sup35 protein, suggesting a potential link between Hsp104 expression and disassembly of Sup35 from the prion aggregate. However, DMSO-mediated curing appears to also be associated with other quality control systems. While the induction of autophagy alone does not lead to curing, we found that DMSO-mediated curing is dramatically impaired in autophagy related (atg) gene mutants, suggesting that other factors influence this DMSO mechanism of curing. Our data suggest that DMSO-mediated curing is not simply dependent upon Hsp104 overexpression alone, but may further depend upon other aspects of proteostasis.
