title: The dystonia-associated protein torsinA modulates synaptic vesicle recycling.
abstract: The loss of a glutamic acid residue in the AAA-ATPase (ATPases associated with diverse cellular activities) torsinA is responsible for most cases of early onset autosomal dominant primary dystonia. In this study, we found that snapin, which binds SNAP-25 (synaptosome-associated protein of 25,000 Da) and enhances the association of the SNARE complex with synaptotagmin, is an interacting partner for both wild type and mutant torsinA. Snapin co-localized with endogenous torsinA on dense core granules in PC12 cells and was recruited to perinuclear inclusions containing mutant DeltaE-torsinA in neuroblastoma SH-SY5Y cells. In view of these observations, synaptic vesicle recycling was analyzed using the lipophilic dye FM1-43 and an antibody directed against an intravesicular epitope of synaptotagmin I. We found that overexpression of wild type torsinA negatively affects synaptic vesicle endocytosis. Conversely, overexpression of DeltaE-torsinA in neuroblastoma cells increases FM1-43 uptake. Knockdown of snapin and/or torsinA using small interfering RNAs had a similar inhibitory effect on the exo-endocytic process. In addition, down-regulation of torsinA causes the persistence of synaptotagmin I on the plasma membrane, which closely resembles the effect observed by the overexpression of the DeltaE-torsinA mutant. Altogether, these findings suggest that torsinA plays a role together with snapin in regulated exocytosis and that DeltaE-torsinA exerts its pathological effects through a loss of function mechanism. This may affect neuronal uptake of neurotransmitters, such as dopamine, playing a role in the development of dystonic movements.
authors.affiliation: Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3PX, United Kingdom.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Granata
authors.forename: Rose
authors.initials: R
authors.lastname: Watson
authors.forename: Lucy M
authors.initials: LM
authors.lastname: Collinson
authors.forename: Giampietro
authors.initials: G
authors.lastname: Schiavo
authors.forename: Thomas T
authors.initials: TT
authors.lastname: Warner
mesh_terms: D000818:Animals; D004298:Dopamine / Q000235:genetics / Q000378:metabolism; D004422:Dystonia Musculorum Deformans / Q000235:genetics / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D018698:Glutamic Acid / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018832:Molecular Chaperones / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D016716:PC12 Cells; D017354:Point Mutation; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D050600:SNARE Proteins / Q000235:genetics / Q000378:metabolism; D013572:Synaptic Vesicles / Q000378:metabolism*; D050825:Synaptosomal-Associated Protein 25 / Q000235:genetics / Q000378:metabolism; D050863:Synaptotagmin I / Q000235:genetics / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C491548:Dyt1 protein, mouse; D018832:Molecular Chaperones; D034741:RNA, Small Interfering; D050600:SNARE Proteins; C494210:Snap25 protein, rat; C498451:Snapin protein, mouse; C498452:Snapin protein, rat; D050825:Synaptosomal-Associated Protein 25; D050863:Synaptotagmin I; C494311:Syt1 protein, mouse; C494312:Syt1 protein, rat; C491549:Tor1a protein, rat; D033921:Vesicular Transport Proteins; D018698:Glutamic Acid; D004298:Dopamine