The nanoscale molecular morphology of docked exocytic dense-core vesicles in neuroendocrine cells

Nat Commun. 2021 Jun 25;12(1):3970. doi: 10.1038/s41467-021-24167-9.


Rab-GTPases and their interacting partners are key regulators of secretory vesicle trafficking, docking, and fusion to the plasma membrane in neurons and neuroendocrine cells. Where and how these proteins are positioned and organized with respect to the vesicle and plasma membrane are unknown. Here, we use correlative super-resolution light and platinum replica electron microscopy to map Rab-GTPases (Rab27a and Rab3a) and their effectors (Granuphilin-a, Rabphilin3a, and Rim2) at the nanoscale in 2D. Next, we apply a targetable genetically-encoded electron microscopy labeling method that uses histidine based affinity-tags and metal-binding gold-nanoparticles to determine the 3D axial location of these exocytic proteins and two SNARE proteins (Syntaxin1A and SNAP25) using electron tomography. Rab proteins are distributed across the entire surface and t-SNARE proteins at the base of docked vesicles. We propose that the circumferential distribution of Rabs and Rab-effectors could aid in the efficient transport, capture, docking, and rapid fusion of calcium-triggered exocytic vesicles in excitable cells.

Publication types

  • Research Support, N.I.H., Intramural
  • Video-Audio Media

MeSH terms

  • Animals
  • Carbocyanines / chemistry
  • Cells, Cultured
  • Exocytosis
  • Gold
  • HeLa Cells
  • Humans
  • Imaging, Three-Dimensional
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Metal Nanoparticles / chemistry
  • Microscopy / methods
  • Molecular Imaging / methods*
  • Neuroendocrine Cells / cytology*
  • Neuroendocrine Cells / metabolism
  • PC12 Cells
  • Rats
  • Red Fluorescent Protein
  • SNARE Proteins / metabolism
  • Secretory Vesicles / metabolism*
  • Vesicular Transport Proteins / genetics
  • Vesicular Transport Proteins / metabolism
  • rab GTP-Binding Proteins / metabolism*


  • Alexa Fluor 647
  • Carbocyanines
  • Luminescent Proteins
  • SNARE Proteins
  • Sytl4 protein, rat
  • Vesicular Transport Proteins
  • Gold
  • rab GTP-Binding Proteins