NSF/αSNAP2-mediated cis-SNARE complex disassembly precedes membrane fusion generating the cell plate during Arabidopsis cytokinesis

Abstract

SummaryEukaryotic membrane fusion requires trans-SNARE complexes bridging the gap between adjacent membranes (Jahn and Scheller, 2006). Fusion between a transport vesicle and its target membrane transforms the trans-into a cis-SNARE complex. The latter interacts with the hexameric AAA+-ATPase NSF and its co-factor αSNAP, forming a 20S complex (Zhou et al., 2015; Zhao and Brunner, 2016). ATPase activity disassembles the SNARE complex into Qa-SNARE, which folds back onto itself, and its partners (Huang et al., 2019; Kim et al., 2021). Fusion of identical membranes has a different sequence of events (Baker and Hughson, 2016). The fusion partners each have cis-SNARE complexes to be broken up by NSF and αSNAP. The Qa-SNARE monomers are then stabilized by interaction with Sec1-type regulators (SM proteins) to form trans-SNARE complexes, as shown for the yeast vacuole (Baker et al., 2015). Membrane fusion in Arabidopsis cytokinesis is formally akin to vacuolar fusion (Müller and Jürgens, 2016). Membrane vesicles fuse with one another to form the partitioning membrane known as cell plate. Cis-SNARE complexes of cytokinesis-specific Qa-SNARE KNOLLE and its SNARE partners are assembled at the ER and delivered by traffic via Golgi/TGN to the cell division plane (Karnahl and Park et al., 2017). SM protein KEULE is required for the formation of trans-SNARE complexes between adjacent membrane vesicles (Park et al., 2012). Here, we identify the missing NSF-type AAA+-ATPase and its adaptor αSNAP2 required for disassembly of KNOLLE cis-SNARE complexes. In addition, we show that NSF is also required for other trafficking pathways and interacts with the respective Q-SNAREs. In conclusion, the SNARE complex disassembly machinery is conserved in plants and plays a unique essential role in cytokinesis.