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Published on: September 3, 2014
Rab4 regulates formation of synaptic-like microvesicles from early endosomes in PC12 cells
H de Wit1, Y Lichtenstein, R B Kelly
1Department of Biochemistry and Biophysics, Hormone Research Institute, University of California, San Francisco, California 94143-0534.
Molecular Biology of the Cell
|November 6, 2001
Summary
The small GTPase rab4 plays a key role in forming synaptic-like microvesicles and recycling vesicles from early endosomes in PC12 cells. Its different forms influence vesicle number and tubule length, impacting protein localization.
Area of Science:
- Cell Biology
- Molecular Biology
- Cellular Trafficking
Background:
- Early endosomes are crucial for vesicle formation and protein sorting.
- The small GTPase rab4 is implicated in intracellular transport.
- PC12 cells are a model system for studying neuronal differentiation and vesicle trafficking.
Purpose of the Study:
- To investigate the role of rab4 in the formation of synaptic-like microvesicles and constitutive recycling vesicles from early endosomes.
- To elucidate the function of different rab4 isoforms (GTP-bound vs. GDP-bound) in vesicle dynamics.
Main Methods:
- Immunogold electron microscopy to localize rab4 in PC12 cells.
- Overexpression of GTPase-deficient (Q67Lrab4) and GDP-bound (S22Nrab4) rab4 mutants.
- Early endosome budding assays to assess vesicle formation.
Main Results:
- Rab4 localizes to early endosomes and peripheral vesicles.
- Q67Lrab4 increased vesicle numbers and shifted rab4, VAMP2, and TfR to peripheral locations.
- S22Nrab4 increased early endosomal tubule length and enhanced labeling of rab4, VAMP2, and TfR on early endosomes.
Conclusions:
- Rab4 is essential for the formation of synaptic-like microvesicles from early endosomes.
- Rab4's GTP/GDP status regulates the morphology and protein content of early endosomes and associated vesicles.
- This study reveals a novel function for rab4 in constitutive recycling vesicle biogenesis.
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