Abstract
A single GAG codon deletion in the gene encoding torsinA is linked to most cases of early-onset torsion dystonia. TorsinA is an ER-localized membrane-associated ATPase from the AAA+ superfamily with an unknown biological function. We investigated the formation of oligomeric complexes of torsinA in cultured mammalian cells and found that wild type torsinA associates into a complex with a molecular weight consistent with that of a homohexamer. Interestingly, the dystonia-linked variant torsinAΔE displayed a reduced propensity to form the oligomers compared to the wild type protein. We also discovered that the deletion of the N-terminal membrane-associating region of torsinA abolished oligomer formation. Our results demonstrate that the dystonia-linked mutation in the torsinA gene produces a protein variant that is deficient in maintaining its oligomeric state and suggest that ER membrane association is required to stabilize the torsinA complex.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-3-743) contains supplementary material, which is available to authorized users.
Highlights
Early-onset torsion dystonia (EOTD) is the most common and severe form of primary dystonia, a neurological disorder that manifests as uncontrollable movements and abnormal body postures
To determine whether human torsinA and the dystonialinked torsinAΔE variant oligomerize in the cell, we expressed each protein in two cell lines, HEK293 and CHO cells
The migration of the torsinA oligomer in BN-PAGE is consistent with that of a homohexamer and is consistent with the formation of a species of similar size in BN-PAGE using lysates prepared from U2OS cells (Vander Heyden et al 2009)
Summary
Early-onset torsion dystonia (EOTD) is the most common and severe form of primary dystonia, a neurological disorder that manifests as uncontrollable movements and abnormal body postures. TorsinA assemblies ranging from monomers and dimers to hexamers were detected in lysates from mammalian cells (Kustedjo et al 2000; Gordon and Gonzalez-Alegre 2008; Vander Heyden et al 2009; Jungwirth et al 2010). How these assemblies are affected by the disease-causing mutation or the hydrophobic membrane anchor has not yet been established. To this end, we investigated the size of human torsinA complexes after isolation from cultured mammalian cells. These data add fundamental new insights to our understanding of torsinA structure and suggest why the loss of a single amino acid can exhibit profound cellular effects
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