title: Prefoldin Promotes Proteasomal Degradation of Cytosolic Proteins with Missense Mutations by Maintaining Substrate Solubility.
abstract: Misfolded proteins challenge the ability of cells to maintain protein homeostasis and can accumulate into toxic protein aggregates. As a consequence, cells have adopted a number of protein quality control pathways to prevent protein aggregation, promote protein folding, and target terminally misfolded proteins for degradation. In this study, we employed a thermosensitive allele of the yeast Guk1 guanylate kinase as a model misfolded protein to investigate degradative protein quality control pathways. We performed a flow cytometry based screen to identify factors that promote proteasomal degradation of proteins misfolded as the result of missense mutations. In addition to the E3 ubiquitin ligase Ubr1, we identified the prefoldin chaperone subunit Gim3 as an important quality control factor. Whereas the absence of GIM3 did not impair proteasomal function or the ubiquitination of the model substrate, it led to the accumulation of the poorly soluble model substrate in cellular inclusions that was accompanied by delayed degradation. We found that Gim3 interacted with the Guk1 mutant allele and propose that prefoldin promotes the degradation of the unstable model substrate by maintaining the solubility of the misfolded protein. We also demonstrated that in addition to the Guk1 mutant, prefoldin can stabilize other misfolded cytosolic proteins containing missense mutations.
authors.affiliation: Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada.|Genome Science and Technology Program, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Sophie A
authors.identifier: 0000-0001-6259-9045
authors.initials: SA
authors.lastname: Comyn
authors.affiliation: Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Barry P
authors.initials: BP
authors.lastname: Young
authors.affiliation: Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Loewen
authors.affiliation: Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada.|Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Thibault
authors.initials: T
authors.lastname: Mayor
mesh_terms: D051528:Guanylate Kinases / Q000235:genetics*; D018832:Molecular Chaperones / Q000235:genetics*; D020125:Mutation, Missense; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism; D066329:Protein Aggregates / Q000235:genetics*; D017510:Protein Folding; D059748:Proteolysis; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D012995:Solubility; D044767:Ubiquitin-Protein Ligases / Q000235:genetics*; D054875:Ubiquitination
chemical_list: C000615831:Gim3 protein, S cerevisiae; C000615891:Guk1 protein, S cerevisiae; D018832:Molecular Chaperones; D066329:Protein Aggregates; D029701:Saccharomyces cerevisiae Proteins; C112806:prefoldin; C066066:UBR1 protein, S cerevisiae; D044767:Ubiquitin-Protein Ligases; D051528:Guanylate Kinases; D046988:Proteasome Endopeptidase Complex