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Rab1 interaction with a GM130 effector complex regulates COPII vesicle cis--Golgi tethering
B D Moyer1, B B Allan, W E Balch
1Department of Cell and Molecular Biology, The Institute for Childhood and Neglected Diseases, The Scripps Research Institute, 10550 N. Torrey Pines Road, San Diego, California 92037, USA.
Traffic (Copenhagen, Denmark)
|April 4, 2001
Summary
Rab GTPases regulate membrane fusion. A novel Rab1 effector complex involving GM130 and GRASP65 is crucial for targeting vesicles from the endoplasmic reticulum to the Golgi apparatus.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Rab GTPases are key regulators of membrane trafficking along the biosynthetic and endocytic pathways.
- Previous work established Rab1's role in programming COPII vesicles for fusion with the Golgi via p115 recruitment.
- The precise mechanisms of Rab regulation at the Golgi acceptor compartment remained unclear.
Purpose of the Study:
- To elucidate the molecular mechanisms by which Rab proteins regulate Golgi acceptor compartment function.
- To identify novel Rab1 effector complexes involved in endoplasmic reticulum to Golgi transport.
- To investigate the role of cis-Golgi tethering proteins in Rab-mediated membrane fusion.
Main Methods:
- Biochemical assays to identify and characterize protein complexes.
- Analysis of Rab1-GTP interactions with tethering factors.
- Functional studies assessing vesicle targeting and fusion with the cis-Golgi.
Main Results:
- A novel Rab1 effector complex, including GM130 and GRASP65, was identified at the cis-Golgi.
- This complex directly interacts with activated Rab1-GTP in a p115-independent manner.
- The GM130-based complex is essential for the targeting and fusion of COPII vesicles with the cis-Golgi.
Conclusions:
- The cis-Golgi tethering protein GM130, complexed with GRASP65, forms a Rab1 effector complex.
- This complex mediates p115-independent Rab1 function in COPII vesicle fusion with the cis-Golgi.
- A 'homing hypothesis' is proposed where Rab proteins interact with distinct tethering factors to ensure directional membrane fusion.