Polyglutamine Toxicity Is Controlled by Prion Composition and Gene Dosage in Yeast

Gong, He; Romanova, Nina V.; Allen, Kim D.; Chandramowlishwaran, Pavithra; Gokhale, Kavita Chandan; Newnam, Gary P.; Mieczkowski, Piotr A.; Sherman, Michael Y.; Chernoff, Yury O.

doi:10.1371/journal.pgen.1002634

Cited by 48 publications

(57 citation statements)

References 80 publications

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“…The neurodegeneration caused by various polyQ expansion proteins is highly cell specific, despite the fact that these proteins are broadly expressed throughout the body. Thus, toxicity in any particular cell type must be influenced by the sequences flanking the polyQ segments and the unique proteomes of the susceptible cell types (5,18,19). We do not, therefore, suggest that our yeast suppressors are directly relevant to human disease.…”

Section: Resultsmentioning

confidence: 92%

Prion-like proteins sequester and suppress the toxicity of huntingtin exon 1

Kayatekin

Matlack

Hesse

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Expansions of preexisting polyglutamine (polyQ) tracts in at least nine different proteins cause devastating neurodegenerative diseases. There are many unique features to these pathologies, but there must also be unifying mechanisms underlying polyQ toxicity. Using a polyQ-expanded fragment of huntingtin exon-1 (Htt103Q), the causal protein in Huntington disease, we and others have created tractable models for investigating polyQ toxicity in yeast cells. These models recapitulate key pathological features of human diseases and provide access to an unrivalled genetic toolbox. To identify toxicity modifiers, we performed an unbiased overexpression screen of virtually every protein encoded by the yeast genome. Surprisingly, there was no overlap between our modifiers and those from a conceptually identical screen reported recently, a discrepancy we attribute to an artifact of their overexpression plasmid. The suppressors of Htt103Q toxicity recovered in our screen were strongly enriched for glutamine-and asparagine-rich prion-like proteins. Separated from the rest of the protein, the prion-like sequences of these proteins were themselves potent suppressors of polyQ-expanded huntingtin exon-1 toxicity, in both yeast and human cells. Replacing the glutamines in these sequences with asparagines abolished suppression and converted them to enhancers of toxicity. Replacing asparagines with glutamines created stronger suppressors. The suppressors (but not the enhancers) coaggregated with Htt103Q, forming large foci at the insoluble protein deposit in which proteins were highly immobile. Cells possessing foci had fewer (if any) small diffusible oligomers of Htt103Q. Until such foci were lost, cells were protected from death. We discuss the therapeutic implications of these findings.protein misfolding | prions P rotein misfolding and aggregation underlie many neurodegenerative diseases. The causes of protein misfolding are numerous and include single amino acid changes and expansions of amino acid repeats. Polyglutamine (polyQ) expansions are an infamous example of the latter and are responsible for at least nine neurodegenerative conditions, including Huntington disease (HD). In most of these diseases the polyQ-expanded protein is expressed throughout the body, but tissue damage is restricted to the nervous system and, often, to a subset of cells depending on the causal protein. Thus, there are important cell type-specific determinants of toxicity, and these are specific to particular proteins. Despite these differences, disease severity is tightly linked to the number of glutamines. Progressively earlier onset occurs as the number of glutamines increases beyond a critical threshold of ∼35-45 residues (1). Moreover, in all cases, pathology is associated with misfolded forms of the polyQ-expanded protein.Thus, common features that arise from the expansions and result from shared aspects of polyQ-driven protein misfolding must contribute to pathology. Given the diverse nature of both the proteins bearing the polyQ tract and t...

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Section: Resultsmentioning

confidence: 92%

Prion-like proteins sequester and suppress the toxicity of huntingtin exon 1

Kayatekin

Matlack

Hesse

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…Previous studies have shown that overproduction of Sup35NM and expression of expanded polyglutamine in yeast can cause cytotoxicity through sequestration of the termination factors Sup35 and Sup45. 57,70 Thus, it is possible that the absence of RAC function enhances sequestration of essential factors by Sup35NM and polyglutamine. Regardless of the mechanism, the potential for cytotoxicity may be partially abrogated by the reduction in protein synthesis that occurs during the kinds of stresses that may trigger RAC dissociation from ribosomes.…”

Section: Discussionmentioning

confidence: 99%

The ribosome-associated complex antagonizes prion formation in yeast

Amor

Castanzo

Delany

et al. 2015

Prion

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ABSTRACT. The number of known fungal proteins capable of switching between alternative stable conformations is steadily increasing, suggesting that a prion-like mechanism may be broadly utilized as a means to propagate altered cellular states. To gain insight into the mechanisms by which cells regulate prion formation and toxicity we examined the role of the yeast ribosome-associated complex (RAC) in modulating both the formation of the [PSI C ] prion -an alternative conformer of Sup35 protein -and the toxicity of aggregation-prone polypeptides. The Hsp40 RAC chaperone Zuo1 anchors the RAC to ribosomes and stimulates the ATPase activity of the Hsp70 chaperone Ssb. We found that cells lacking Zuo1 are sensitive to over-expression of some aggregation-prone proteins, including the Sup35 prion domain, suggesting that co-translational protein misfolding increases in Dzuo1 strains. Consistent with this finding, Dzuo1 cells exhibit higher frequencies of spontaneous and induced prion formation. Cells expressing mutant forms of Zuo1 lacking either a C-terminal charged region required for ribosome association, or the J-domain responsible for Ssb ATPase stimulation, exhibit similarly high frequencies of prion formation. Our findings are consistent with a role for the RAC in chaperoning nascent Sup35 to regulate folding of the N-terminal prion domain as it emerges from the ribosome.

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“…As a result, the association of molecular chaperones of the Hsp70 and Hsp90 systems with the polyQ aggregates was enhanced, and their ability to sequester nuclear proteins was strongly reduced. Protein sequestration into aggregates may lead to an impairment of multiple key cellular pathways and is considered an important mechanism of aggregate toxicity (7,9,10,32,50,(53)(54)(55)(56)(57)(58).…”

Section: Discussionmentioning

confidence: 99%

Overexpression of Q-rich prion-like proteins suppresses polyQ cytotoxicity and alters the polyQ interactome

Ripaud¹,

Chumakova²,

Antonin³

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Expansion of a poly-glutamine (polyQ) repeat in a group of functionally unrelated proteins is the cause of several inherited neurodegenerative disorders, including Huntington's disease. The polyQ length-dependent aggregation and toxicity of these disease proteins can be reproduced in Saccharomyces cerevisiae. This system allowed us to screen for genes that when overexpressed reduce the toxic effects of an N-terminal fragment of mutant huntingtin with 103 Q. Surprisingly, among the identified suppressors were three proteins with Q-rich, prion-like domains (PrDs): glycine threonine serine repeat protein (Gts1p), nuclear polyadenylated RNA-binding protein 3, and minichromosome maintenance protein 1. Overexpression of the PrD of Gts1p, containing an imperfect 28 residue glutamine-alanine repeat, was sufficient for suppression of toxicity. Association with this discontinuous polyQ domain did not prevent 103Q aggregation, but altered the physical properties of the aggregates, most likely early in the assembly pathway, as reflected in their increased SDS solubility. Molecular simulations suggested that Gts1p arrests the aggregation of polyQ molecules at the level of nonfibrillar species, acting as a cap that destabilizes intermediates on path to form large fibrils. Quantitative proteomic analysis of polyQ interactors showed that expression of Gts1p reduced the interaction between polyQ and other prion-like proteins, and enhanced the association of molecular chaperones with the aggregates. These findings demonstrate that short, Q-rich peptides are able to shield the interactive surfaces of toxic forms of polyQ proteins and direct them into nontoxic aggregates.protein aggregation | protein misfolding | neurodegeneration | prion | polyglutamine proteins

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Polyglutamine Toxicity Is Controlled by Prion Composition and Gene Dosage in Yeast

Cited by 48 publications

References 80 publications

Prion-like proteins sequester and suppress the toxicity of huntingtin exon 1

Prion-like proteins sequester and suppress the toxicity of huntingtin exon 1

The ribosome-associated complex antagonizes prion formation in yeast

Overexpression of Q-rich prion-like proteins suppresses polyQ cytotoxicity and alters the polyQ interactome

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