Aberrant cellular behavior of mutant torsinA implicates nuclear envelope dysfunction in DYT1 dystonia.
Torsion dystonia-1 (DYT1) dystonia, the most common inherited form of dystonia, is caused by a three base pair deletion that eliminates a single amino acid from the disease protein, torsinA. TorsinA is an "AAA" protein thought to reside in the endoplasmic reticulum (ER), yet both its cellular function and the basis for neuronal dysfunction in DYT1 remain unknown. A clue to disease pathogenesis is the fact that mutant, but not wild-type, torsinA forms membranous inclusions in cell culture. To explore the pathobiology of DYT1 dystonia, we generated PC12 neural cell lines that inducibly express wild-type or mutant torsinA. Although in this model torsinA displays some properties consistent with ER localization, mutant torsinA also accumulates in the nuclear envelope (NE), a structure contiguous with cytoplasmic ER. Consistent with this, membranous inclusions formed by mutant torsinA are shown to derive not from the ER, as thought previously, but from the NE. We demonstrate further that torsinA forms different disulfide-linked complexes that may be linked functionally to subcellular localization in the NE versus cytoplasmic ER. Despite mutant TA accumulation in NE structures, nucleocytoplasmic transport of a reporter protein was unaffected. These findings, together with parallel studies failing to demonstrate perturbation of ER function, implicate the NE as a primary site of dysfunction in DYT1. DYT1 dystonia can be added to the growing list of inherited neurological disorders involving the NE.
Gonzalez-Alegre
Pedro
P
Department of Neurology, Carver College of Medicine at the University of Iowa, Iowa City, Iowa 52242, USA. gonzalezp@mail.medicine.uiowa.edu
Paulson
Henry L
HL
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002999:Clone Cells; D050483:Dopamine Plasma Membrane Transport Proteins; D020821:Dystonic Disorders / Q000209:etiology* / Q000503:physiopathology*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D049452:Green Fluorescent Proteins; D006801:Humans; D002479:Inclusion Bodies / Q000378:metabolism* / Q000648:ultrastructure; D008164:Luminescent Proteins / Q000235:genetics; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D009685:Nuclear Envelope / Q000378:metabolism*; D016716:PC12 Cells; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics; D014162:Transfection
D002352:Carrier Proteins; D050483:Dopamine Plasma Membrane Transport Proteins; D008164:Luminescent Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D018832:Molecular Chaperones; D009419:Nerve Tissue Proteins; D011993:Recombinant Fusion Proteins; C108175:TOR1A protein, human; C491549:Tor1a protein, rat; D049452:Green Fluorescent Proteins