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Vol. 20, Issue 11, 2661-2672, June 1, 2009

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LULL1 Retargets TorsinA to the Nuclear Envelope Revealing an Activity That Is Impaired by the DYT1 Dystonia Mutation

Abigail B. Vander Heyden^*, Teresa V. Naismith^*, Erik L. Snapp, Didier Hodzic^*, and Phyllis I. Hanson^*

*Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110; and Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461

Submitted January 30, 2009; Revised March 16, 2009; Accepted March 25, 2009
Monitoring Editor: Ramanujan S. Hegde

TorsinA (TorA) is an AAA+ ATPase in the endoplasmic reticulum (ER) lumen that is mutated in early onset DYT1 dystonia. TorA is an essential protein in mice and is thought to function in the nuclear envelope (NE) despite localizing throughout the ER. Here, we report that transient interaction of TorA with the ER membrane protein LULL1 targets TorA to the NE. FRAP and Blue Native PAGE indicate that TorA is a stable, slowly diffusing oligomer in either the absence or presence of LULL1. Increasing LULL1 expression redistributes both wild-type and disease-mutant TorA to the NE, while decreasing LULL1 with shRNAs eliminates intrinsic enrichment of disease-mutant TorA in the NE. When concentrated in the NE, TorA displaces the nuclear membrane proteins Sun2, nesprin-2G, and nesprin-3 while leaving nuclear pores and Sun1 unchanged. Wild-type TorA also induces changes in NE membrane structure. Because SUN proteins interact with nesprins to connect nucleus and cytoskeleton, these effects suggest a new role for TorA in modulating complexes that traverse the NE. Importantly, once concentrated in the NE, disease-mutant TorA displaces Sun2 with reduced efficiency and does not change NE membrane structure. Together, our data suggest that LULL1 regulates the distribution and activity of TorA within the ER and NE lumen and reveal functional defects in the mutant protein responsible for DYT1 dystonia.

Address correspondence to: Phyllis I. Hanson (phanson22{at}wustl.edu)

Abbreviations used: AAA+, ATPases associated with a variety of cellular activities; BN-PAGE, Blue Native-PAGE; DDM, dodecylmaltoside; ER, endoplasmic reticulum; FRAP, fluorescence recovery after photobleaching; INM, inner nuclear membrane; LINC, linker of the nucleoskeleton and cytoskeleton; mGFP, monomeric green fluorescent protein; NE, nuclear envelope; ONM, outer nuclear membrane; RFP, red fluorescent protein; TorA, TorsinA.

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