RT Journal Article
SR Electronic
T1 Exocyst stimulates each step of exocytic SNARE complex assembly and vesicle fusion
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2022.01.16.476540
DO 10.1101/2022.01.16.476540
A1 Lee, Chanwoo
A1 Lepore, Dante
A1 Munson, Mary
A1 Yoon, Tae-Young
YR 2022
UL http://biorxiv.org/content/early/2022/01/17/2022.01.16.476540.abstract
AB The exocyst is a large multisubunit tethering complex essential for targeting and fusion of secretory vesicles in eukaryotic cells. Although the assembled exocyst complex is proposed to tether vesicles to the plasma membrane and activate the SNARE proteins for membrane fusion, only little is known about the key biochemical steps that exocyst stimulates in the course of SNARE complex assembly, a critical question defining the essential molecular role of the exocyst complex. Here, we use a combination of single molecule and bulk fluorescence assays with purified octameric yeast exocyst complexes to examine the role of exocyst in a reconstituted SNARE assembly and fusion system. We show that the exocyst complex simulates multiple steps spanning from SNARE protein activation to ternary complex assembly, rather than affecting only a specific subset of steps. We also observed that the exocyst has important downstream roles in driving membrane fusion, up to full content mixing of vesicle lumens. Our results suggest that the exocyst complex provides extensive chaperoning functions for the entire process of SNARE complex assembly, presumably using its multi-faceted structure provided by the eight subunits.Competing Interest StatementThe authors have declared no competing interest.