Related Experiment Videos
Rab GDI: a solubilizing and recycling factor for rab9 protein
T Soldati1, M A Riederer, S R Pfeffer
1Department of Biochemistry, Stanford University School of Medicine, California 94028.
Molecular Biology of the Cell
|April 1, 1993
Summary
Cytosolic rab9 forms complexes with GDP dissociation inhibitors (GDIs), similar to other rab proteins. GDI proteins solubilize rab9GDP from membranes, suggesting a role in recycling rab proteins for intracellular transport regulation.
Area of Science:
- Cell Biology
- Molecular Biology
- Protein Biochemistry
Background:
- Rab proteins regulate vesicle transport by mediating membrane identification and fusion.
- Cytosolic rab proteins, including rab3A, rab11, and Sec4, associate with GDP dissociation inhibitors (GDIs).
Purpose of the Study:
- To investigate the association of rab9, crucial for endosome-to-Golgi transport, with GDI-like proteins.
- To elucidate the mechanisms and requirements for rab9-GDI complex formation and its functional implications.
Main Methods:
- In vitro reconstitution of rab9-GDI complex formation using recombinant proteins and cytosol.
- Analysis of rab9 carboxy terminus and geranylgeranylation requirements for complex assembly.
- Investigation of rab3A-GDI's ability to solubilize rab9GDP and rab9GTP from membranes.
Main Results:
- Cytosolic rab9 forms an 80-kD complex with a GDI-like protein.
- Complex formation requires an intact rab9 carboxy terminus and geranylgeranylation; monoprenylation is sufficient.
- Purified rab9 and rab3A-GDI can assemble into 80-kD complexes in vitro.
- rab3A-GDI solubilizes rab9GDP, but not rab9GTP, from cytoplasmic membranes.
Conclusions:
- GDI proteins associate with rab9, extending their known function to endosome-to-Golgi transport.
- GDIs likely facilitate the recycling of rab proteins from target membranes after transport cycles.
- GDI proteins play a regulatory role in intracellular transport by controlling the availability of rab proteins.