title: Overexpression of Q-rich prion-like proteins suppresses polyQ cytotoxicity and alters the polyQ interactome.
abstract: 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.
authors.affiliation: Departments of Cellular Biochemistry and.
authors.forename: Leslie
authors.initials: L
authors.lastname: Ripaud
authors.affiliation: Departments of Cellular Biochemistry and.
authors.forename: Victoria
authors.initials: V
authors.lastname: Chumakova
authors.affiliation: Departments of Cellular Biochemistry and.
authors.forename: Matthias
authors.initials: M
authors.lastname: Antonin
authors.affiliation: Departments of Cellular Biochemistry and.
authors.forename: Alex R
authors.initials: AR
authors.lastname: Hastie
authors.affiliation: Departments of Cellular Biochemistry and.
authors.forename: Stefan
authors.initials: S
authors.lastname: Pinkert
authors.affiliation: Departments of Cellular Biochemistry and.
authors.forename: Roman
authors.initials: R
authors.lastname: Körner
authors.affiliation: Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130.
authors.forename: Kiersten M
authors.initials: KM
authors.lastname: Ruff
authors.affiliation: Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130.
authors.forename: Rohit V
authors.initials: RV
authors.lastname: Pappu
authors.affiliation: Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany; and.
authors.forename: Daniel
authors.initials: D
authors.lastname: Hornburg
authors.affiliation: Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany; and.
authors.forename: Matthias
authors.initials: M
authors.lastname: Mann
authors.affiliation: Departments of Cellular Biochemistry and uhartl@biochem.mpg.de hipp@biochem.mpg.de.
authors.forename: F Ulrich
authors.initials: FU
authors.lastname: Hartl
authors.affiliation: Departments of Cellular Biochemistry and uhartl@biochem.mpg.de hipp@biochem.mpg.de.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Hipp
mesh_terms: D010455:Peptides / Q000378:metabolism*; D011328:Prions / Q000378:metabolism*; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000235:genetics
chemical_list: D010455:Peptides; D011328:Prions; C097188:polyglutamine
keywords: neurodegeneration; polyglutamine proteins; prion; protein aggregation; protein misfolding