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SV2 and o-rab3 remain associated with recycling synaptic vesicles
B Wittich1, W Volknandt, H Zimmermann
1AK Neurochemie, Zoologisches Institut, Biozentrum der J. W. Goethe-Universität, Frankfurt am Main, F.R.G.
Journal of Neurochemistry
|September 1, 1994
Summary
O-rab3, a GTP-binding protein, remains associated with synaptic vesicles during exocytosis and endocytosis. This protein may be lost only when vesicles enter the prelysosomal pathway.
Area of Science:
- Neurobiology
- Cell Biology
- Molecular Biology
Background:
- O-rab3 is a GTP-binding protein homologous to mammalian rab3 proteins.
- It is believed to play a role in the exocytosis of secretory vesicles.
Purpose of the Study:
- To investigate the association of o-rab3 with synaptic vesicles during stimulation.
- To compare the behavior of o-rab3 with that of synaptic vesicle protein 2 (SV2).
Main Methods:
- Immunoelectron microscopy with colloidal gold labeling.
- Density-gradient centrifugation and column chromatography.
- Analysis of synaptic vesicles, multivesicular bodies, and vacuoles in nerve terminals.
Main Results:
- O-rab3 and SV2 were localized to the synaptic vesicle membrane compartment.
- Recycled synaptic vesicles under low-frequency stimulation retained both SV2 and o-rab3.
- No stimulation-dependent release of o-rab3 from synaptic vesicles was observed.
- Multivesicular bodies and vacuoles contained SV2 but minimal o-rab3.
Conclusions:
- O-rab3 remains associated with synaptic vesicles throughout stimulation-induced exo- and endocytosis cycles.
- O-rab3 may be degraded or lost upon entry into the prelysosomal pathway.