Regulated oligomerization induces uptake of a membrane protein into COPII vesicles independent of its cytosolic tail.
Export of transmembrane proteins from the endoplasmic reticulum (ER) is driven by directed incorporation into coat protein complex II (COPII)-coated vesicles. The sorting of some cargo proteins into COPII vesicles was shown to be mediated by specific interactions between transmembrane and COPII-coat-forming proteins. But even though some signals for ER exit have been identified on the cytosolic domains of membrane proteins, the general signaling and sorting mechanisms of ER export are still poorly understood. To investigate the role of cargo protein oligomer formation in the export process, we have created a transmembrane fusion protein that - owing to its FK506-binding protein domains - can be oligomerized in isolated membranes by addition of a small-molecule dimerizer. Packaging of the fusion protein into COPII vesicles is strongly enhanced in the presence of the dimerizer, demonstrating that the oligomeric state is an ER export signal for this membrane protein. Surprisingly, the cytosolic tail is not required for this oligomerization-dependent effect on protein sorting. Thus, an alternative mechanism, such as membrane bending, must account for ER export of the fusion protein.
Biochemistry and Cell Biology, Jacobs University Bremen, Bremen, Germany.
Sebastian
S
Springer
Per
P
Malkus
Britta
B
Borchert
Ursula
U
Wellbrock
Rainer
R
Duden
Randy
R
Schekman
D022181:COP-Coated Vesicles / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D050576:Membrane Fusion Proteins / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D055503:Protein Multimerization / Q000502:physiology*; D021381:Protein Transport / Q000502:physiology*; D022021:Tacrolimus Binding Proteins / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000378:metabolism*; D015003:Yeasts / Q000378:metabolism / Q000502:physiology
D002352:Carrier Proteins; D050576:Membrane Fusion Proteins; D033921:Vesicular Transport Proteins; D022021:Tacrolimus Binding Proteins
ER export; in vitro COPII vesicle generation assay; membrane bending; oligomerization; transmembrane protein