Nature Cell Biology2, 288 - 295 (2000)
Published online: 7 April 2000; | doi:10.1038/35010558
Dynamics and retention of misfolded proteins in native ER membranes
Sarah Nehls1, Erik L. Snapp1, Nelson B. Cole1, Kristien J.M. Zaal1, Anne K. Kenworthy1, Theresa H. Roberts1, Jan Ellenberg2, John F. Presley1, Eric Siggia3
& Jennifer Lippincott-Schwartz1
1
Cell Biology and Metabolism Branch, National Institute
of Child Health and Human Development, Building 18T, National Institute of
Health, Bethesda, Maryland 20892,
USA
2
Gene Expression and Cell Biology Program, European
Molecular Biology Laboratory, Heidelberg, Germany
3
Center for Studies in Physics and Biology, Rockefeller
University, New York, New York 10021, USA
Correspondence should be addressed to Jennifer Lippincott-Schwartz jlippin@helix.nih.gov
When co-translationally inserted into endoplasmic reticulum (ER) membranes,
newly synthesized proteins encounter the lumenal environment of the ER, which
contains chaperone proteins that facilitate the folding reactions necessary
for protein oligomerization, maturation and export from the ER. Here we show,
using a temperature-sensitive variant of vesicular stomatitis virus G protein
tagged with green fluorescent protein (VSVG−GFP), and fluorescence recovery
after photobleaching (FRAP), the dynamics of association of folded and misfolded
VSVG complexes with ER chaperones. We also investigate the potential mechanisms
underlying protein retention in the ER. Misfolded VSVG−GFP complexes
at 40 °C are highly mobile in ER membranes and do not reside in post-ER
compartments, indicating that they are not retained in the ER by immobilization
or retrieval mechanisms. These complexes are immobilized in ATP-depleted or
tunicamycin-treated cells, in which VSVG−chaperone interactions are
no longer dynamic. These results provide insight into the mechanisms of protein
retention in the ER and the dynamics of protein-folding complexes in native
ER membranes.
