Identification of human proteins that modify misfolding and proteotoxicity of pathogenic ataxin-1.
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.
Neuroproteomics, Max Delbrueck Center for Molecular Medicine, Berlin, Germany.
Spyros
S
Petrakis
Tamás
T
Raskó
Jenny
J
Russ
Ralf P
RP
Friedrich
Martin
M
Stroedicke
Sean-Patrick
SP
Riechers
Katja
K
Muehlenberg
Angeli
A
Möller
Anita
A
Reinhardt
Arunachalam
A
Vinayagam
Martin H
MH
Schaefer
Michael
M
Boutros
Hervé
H
Tricoire
Miguel A
MA
Andrade-Navarro
Erich E
EE
Wanker
D000818:Animals; D000067696:Ataxin-1; D000067528:Ataxins; D019556:COS Cells; D002522:Chlorocebus aethiops; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D056892:Mediator Complex / Q000737:chemistry* / Q000235:genetics; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics; D010455:Peptides / Q000737:chemistry* / Q000235:genetics; D010957:Plasmids; D058105:Polymerization; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics; D013329:Structure-Activity Relationship; D014162:Transfection
C000593749:ATXN1 protein, human; D000067696:Ataxin-1; D000067528:Ataxins; C416944:MED15 protein, human; D056892:Mediator Complex; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; C471242:PUM1 protein, human; D010455:Peptides; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; C097188:polyglutamine