Identification of human proteins that modify misfolding and proteotoxicity of pathogenic ataxin-1

• Published in: PLoS genetics Vol. 8; no. 8; p. e1002897
• Main Authors: Petrakis, Spyros, Raskó, Tamás, Russ, Jenny, Friedrich, Ralf P, Stroedicke, Martin, Riechers, Sean-Patrick, Muehlenberg, Katja, Möller, Angeli, Reinhardt, Anita, Vinayagam, Arunachalam, Schaefer, Martin H, Boutros, Michael, Tricoire, Hervé, Andrade-Navarro, Miguel A, Wanker, Erich E
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.08.2012; Public Library of Science (PLoS)
• Subjects: Amino acids; Animals; Ataxin-1; Ataxins; Biology; Cercopithecus aethiops; COS Cells; Disease; Escherichia coli - genetics; Experiments; Humans; Hydrogen bonds; Mediator Complex - chemistry; Mediator Complex - genetics; Medicine; Mutation; Nerve Tissue Proteins - chemistry; Nerve Tissue Proteins - genetics; Nuclear Proteins - chemistry; Nuclear Proteins - genetics; Pathogenesis; Peptides - chemistry; Peptides - genetics; Plasmids; Polymerization; Protein Folding; Protein Structure, Secondary; Protein Structure, Tertiary; Proteins; Proteomics; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - genetics; RNA-Binding Proteins - chemistry; RNA-Binding Proteins - genetics; Structure-Activity Relationship; Studies; Transfection; France; Germany
• ISSN: 1553-7404; 1553-7390; 1553-7404
• DOI: 10.1371/journal.pgen.1002897

Proteins with long, pathogenic polyglutamine (polyQ) sequences have an enhanced propensity to spontaneously misfold and self-assemble into insoluble protein aggregates. Here, we have identified 21 human proteins that influence polyQ-induced ataxin-1 misfolding and proteotoxicity in cell model systems. By analyzing the protein sequences of these modifiers, we discovered a recurrent presence of coiled-coil (CC) domains in ataxin-1 toxicity enhancers, while such domains were not present in suppressors. This suggests that CC domains contribute to the aggregation- and toxicity-promoting effects of modifiers in mammalian cells. We found that the ataxin-1-interacting protein MED15, computationally predicted to possess an N-terminal CC domain, enhances spontaneous ataxin-1 aggregation in cell-based assays, while no such effect was observed with the truncated protein MED15ΔCC, lacking such a domain. Studies with recombinant proteins confirmed these results and demonstrated that the N-terminal CC domain of MED15 (MED15CC) per se is sufficient to promote spontaneous ataxin-1 aggregation in vitro. Moreover, we observed that a hybrid Pum1 protein harboring the MED15CC domain promotes ataxin-1 aggregation in cell model systems. In strong contrast, wild-type Pum1 lacking a CC domain did not stimulate ataxin-1 polymerization. These results suggest that proteins with CC domains are potent enhancers of polyQ-mediated protein misfolding and aggregation in vitro and in vivo.