The luminal AAA+ ATPase torsinA mediates distinct mechanisms of nuclear-cytoplasmic communication by adopting different functional assembly states

Abstract

ABSTRACTChemical and mechanical nuclear-cytoplasmic communication across the nuclear envelope (NE) is largely mediated by the nuclear pore complex (NPC) and the linker of nucleoskeleton and cytoskeleton (LINC) complex, respectively. While NPC and LINC complex assembly are functionally related, the mechanisms responsible for this relationship remain poorly understood. Here, we investigated how the luminal ATPases associated with various cellular activities (AAA+) protein torsinA promotes NPC and LINC complex assembly using fluorescence fluctuation spectroscopy (FFS), quantitative photobleaching analyses, and functional cellular assays. We report that torsinA controls LINC complex-dependent nuclear-cytoskeletal coupling as a soluble hexameric AAA+ protein and interphase NPC biogenesis as a membrane-associated helical polymer. These findings help resolve the conflicting models of torsinA function that were recently proposed based on in vitro structural studies. Our results will enable future studies of the role of defective nuclear-cytoplasmic communication in DYT1 dystonia and other diseases caused by mutations in torsinA.