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

Item Type:Article
Title:Prion-like proteins sequester and suppress the toxicity of huntingtin exon 1
Creators Name:Kayatekin, C. and Matlack, K.E.S. and Hesse, W.R. and Guan, Y. and Chakrabortee, S. and Russ, J. and Wanker, E.E. and Shah, J.V. and Lindquist, S.
Abstract: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.
Keywords:Protein Misfolding, Prions
Source:Proceedings of the National Academy of Sciences of the United States of America
ISSN:0027-8424
Publisher:National Academy of Sciences (U.S.A.)
Volume:111
Number:33
Page Range:12085-12090
Date:19 August 2014
Official Publication:https://doi.org/10.1073/pnas.1412504111
PubMed:View item in PubMed

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