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COPII vesicles derived from mammalian endoplasmic reticulum microsomes recruit COPI
T Rowe1, M Aridor, J M McCaffery
1Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
The Journal of Cell Biology
|November 1, 1996
Summary
ER to Golgi transport relies on COPII for cargo export and COPI for vesicle targeting. This study reveals coat exchange as an early event, crucial for directing vesicles to pre-Golgi intermediates.
Area of Science:
- Cell Biology
- Molecular Biology
- Protein Transport
Background:
- ER to Golgi transport is essential for protein trafficking.
- Two main vesicle coat complexes, COPI and COPII, regulate this process.
- Small GTPases ADP-ribosylation factor 1 (ARF1) and Sar1 control coat assembly.
Purpose of the Study:
- To investigate the distinct roles of COPI and COPII in ER to Golgi transport.
- To develop a novel in vitro assay for studying ER-derived vesicle formation.
- To elucidate the sequence of coat complex recruitment during vesicular transport.
Main Methods:
- Developed a mammalian microsomal assay to reconstitute ER-derived vesicle formation.
- Utilized vesicular stomatitis virus glycoprotein (VSV-G) and p58 as cargo molecules.
- Employed a trans-dominant ARF1 mutant and immunoisolation to study coat recruitment.
Main Results:
- Cargo (VSV-G, p58) was efficiently sorted from resident ER proteins during vesicle formation.
- COPII exclusively mediated the export of cargo from the ER.
- ARF1-GDP mutant blocked vesicle movement to the Golgi, indicating COPI's role in later stages.
- Vesicles recruited COPI in an ARF1-dependent manner after ER export.
Conclusions:
- COPII is responsible for cargo export from the ER.
- Coat exchange, involving COPI recruitment, occurs early in vesicular transport.
- This coat exchange precedes the targeting of ER-derived vesicles to pre-Golgi intermediates.