Resolving the continuous high-order organization of the exocyst during vesicle tethering

Abstract

Constitutive exocytosis is an essential and highly-conserved trafficking pathway for the delivering of cargo to the plasma membrane and the extracellular space. During this pathway, cargo-loaded vesicles are tethered to the plasma membrane by the exocyst, an heterodiramic complex, prior the vesicle fusion. Despite exocyst-mediated vesicle tethering represents a crucial stage, how multiple exocysts organize in space and time remains poorly understood. Here, we employed an integrative approach to unveil the dynamic architecture of exocyst-mediated vesicle tethering. To achieve this goal, we developed a computational workflow for the analysis of datasets from live-cell imaging, super-resolution microscopy and correlative cryo-electron tomography. We demonstrated that the exocyst high-order structure consists on seven exocyst, on average, assembled into in ring-like shapes. The radius of those rings expand from 18 to 38 nm following a saturated-exponential function defined by a characteristic time of 3.1 s.