AURION R-Gent SE-EM
ER exit site in 60 nm-thin cryosection of Hepg2 cells, labeled for COPII (primary antibody against sec23 was obtained by ABR) and detected with Fab-goat-anti-rabbit, conjugated to ultra-small gold, silver enhanced for 30 minutes (from Aurion).
The arrows point to labeled COPII-coats on vesicular and tubular membranes, which are located close to the ER.
The information of a thin section is not sufficient to conclude how the membranes are related to each other- if they are still connected to the ER, or if they are free.
Therefore we performed 3D electron tomography on 400nm thick cryosections, which were labeled similar for COPII. (see next picture).
ER= endoplasmic reticulum
PM= plasma membrane
MVB= multi-vesicular body
Bar = 100 mikrometer
2 views of a model of a COPII-labeled ER-exit site, resolved from 400nm thick cryo-sections of Hepg2 cells, labeled like described for the ultrathin section before.
Note that the labeling for COPII is assessable throughout the section.
Free membrane carriers of vesicular and tubular shape, partially labeled for COPII=yellow
Courtesy of: Dagmar Zeuschner, Judith Klumperman (Department of Cell Biology, UMC Utrecht, The Netherlands) and Willie Geerts, Abraham Koster (Molecular Cell Biology, Utrecht University, The Netherlands)