Journal Article

Identification of Human Proteins That Modify Misfolding and Proteotoxicity of Pathogenic Ataxin-1

Muehlenberg, Katja, Russ, Jenny, Schaefer, Martin H., Riechers, Sean-Patrick, Reinhardt, Anita, Vinayagam, Arunachalam, Raskó, Tamás, Möller, Angeli, Tricoire, Hervé, Friedrich, Ralf P., Petrakis, Spyros, Stroedicke, Martin, Wanker, Erich E., Andrade-Navarro, Miguel A., Boutros, Michael

2012

Overview

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.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: 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