Association of polyalanine and polyglutamine coiled coils mediates expansion disease-related protein aggregation and dysfunction.
The expansion of homopolymeric glutamine (polyQ) or alanine (polyA) repeats in certain proteins owing to genetic mutations induces protein aggregation and toxicity, causing at least 18 human diseases. PolyQ and polyA repeats can also associate in the same proteins, but the general extent of their association in proteomes is unknown. Furthermore, the structural mechanisms by which their expansion causes disease are not well understood, and these repeats are generally thought to misfold upon expansion into aggregation-prone β-sheet structures like amyloids. However, recent evidence indicates a critical role for coiled-coil (CC) structures in triggering aggregation and toxicity of polyQ-expanded proteins, raising the possibility that polyA repeats may as well form these structures, by themselves or in association with polyQ. We found through bioinformatics screenings that polyA, polyQ and polyQA repeats have a phylogenetically graded association in human and non-human proteomes and associate/overlap with CC domains. Circular dichroism and cross-linking experiments revealed that polyA repeats can form--alone or with polyQ and polyQA--CC structures that increase in stability with polyA length, forming higher-order multimers and polymers in vitro. Using structure-guided mutagenesis, we studied the relevance of polyA CCs to the in vivo aggregation and toxicity of RUNX2--a polyQ/polyA protein associated with cleidocranial dysplasia upon polyA expansion--and found that the stability of its polyQ/polyA CC controls its aggregation, localization and toxicity. These findings indicate that, like polyQ, polyA repeats form CC structures that can trigger protein aggregation and toxicity upon expansion in human genetic diseases.
Department of Neuroscience and.
Ilaria
I
Pelassa
Center for Molecular Systems Biology, University of Torino, Torino 10123, Italy.
Davide
D
Corà
Department of Chemistry, University of Torino, Torino 10125, Italy.
Federico
F
Cesano
Department of Neurophysiology and Neuropharmacology, Medical University of Vienna, Vienna 1090, Austria.
Francisco J
FJ
Monje
Department of Neuroscience and National Institute of Neuroscience (INN), Torino 10125, Italy.
Pier Giorgio
PG
Montarolo
Department of Neuroscience and ferdinando.fiumara@unito.it.
Ferdinando
F
Fiumara
D002460:Cell Line; D002942:Circular Dichroism; D002973:Cleidocranial Dysplasia / Q000235:genetics / Q000378:metabolism; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics / Q000378:metabolism; D006801:Humans; D018613:Microscopy, Confocal; D010455:Peptides / Q000737:chemistry*; D010802:Phylogeny; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism*
D050659:Core Binding Factor Alpha 1 Subunit; D010455:Peptides; D011506:Proteins; C019529:polyalanine; C097188:polyglutamine