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).
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
reticulumPM= plasma membraneMVB= multi-vesicular bodyBar = 100
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
Note that the labeling for COPII is assessable throughout the
section.ER=light blueFree membrane
carriers of vesicular and tubular shape, partially labeled for
Courtesy of: Dagmar Zeuschner,
Judith Klumperman (Department of Cell Biology, UMC Utrecht, The Netherlands)
and Willie Geerts, Abraham Koster (Molecular Cell Biology, Utrecht University,
© Aurion 2007 - 2010