Exocyst dynamics during vesicle tethering and fusion

Nat Commun. 2018 Dec 3;9(1):5140. doi: 10.1038/s41467-018-07467-5.


The exocyst is a conserved octameric complex that tethers exocytic vesicles to the plasma membrane prior to fusion. Exocyst assembly and delivery mechanisms remain unclear, especially in mammalian cells. Here we tagged multiple endogenous exocyst subunits with sfGFP or Halo using Cas9 gene-editing, to create single and double knock-in lines of mammary epithelial cells, and interrogated exocyst dynamics by high-speed imaging and correlation spectroscopy. We discovered that mammalian exocyst is comprised of tetrameric subcomplexes that can associate independently with vesicles and plasma membrane and are in dynamic equilibrium with octamer and monomers. Membrane arrival times are similar for subunits and vesicles, but with a small delay (~80msec) between subcomplexes. Departure of SEC3 occurs prior to fusion, whereas other subunits depart just after fusion. About 9 exocyst complexes are associated per vesicle. These data reveal the mammalian exocyst as a remarkably dynamic two-part complex and provide important insights into assembly/disassembly mechanisms.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms
  • Animals
  • Cell Line
  • Epithelial Cells / metabolism
  • Exocytosis*
  • Female
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • HEK293 Cells
  • Humans
  • Mammary Glands, Animal / cytology
  • Membrane Fusion
  • Mice
  • Microscopy, Confocal
  • Models, Biological
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / metabolism*
  • Protein Transport
  • Secretory Vesicles / metabolism*
  • Vesicular Transport Proteins / genetics
  • Vesicular Transport Proteins / metabolism*


  • Multiprotein Complexes
  • Vesicular Transport Proteins
  • Green Fluorescent Proteins