The synaptic vesicle proteins SV2, synaptotagmin and synaptophysin are sorted to separate cellular compartments in CHO fibroblasts.
We expressed the synaptic vesicle proteins SV2, synaptotagmin, and synaptophysin in CHO fibroblasts to investigate the targeting information contained by each protein. All three proteins entered different cellular compartments. Synaptotagmin was found on the plasma membrane. Both SV2 and synaptophysin were sorted to small intracellular vesicles, but synaptophysin colocalized with early endosomal markers, while SV2 did not. SV2-containing vesicles did not have the same sedimentation characteristics as authentic synaptic vesicles, even though transfected SV2 was sorted from endosomal markers. We also created cell lines expressing both SV2 and synaptotagmin, both synaptotagmin and synaptophysin, and lines expressing all three synaptic vesicle proteins. In all cases, the proteins maintained their distinct compartmentalizations, were not found in the same organelle, and did not created synaptic vesicle-like structures. These results have important implications for models of synaptic vesicle biogenesis.
Feany
M B
MB
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115.
Yee
A G
AG
Delvy
M L
ML
Buckley
K M
KM
D000818:Animals; D001921:Brain / Q000378:metabolism*; D016466:CHO Cells; D002135:Calcium-Binding Proteins; D002499:Centrifugation, Density Gradient; D006224:Cricetinae; D004330:Drosophila / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006801:Humans; D008562:Membrane Glycoproteins / Q000032:analysis / Q000096:biosynthesis / Q000378:metabolism*; D008854:Microscopy, Electron; D016253:Microscopy, Immunoelectron; D009419:Nerve Tissue Proteins / Q000032:analysis / Q000096:biosynthesis / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000378:metabolism; D051381:Rats; D013347:Subcellular Fractions / Q000378:metabolism / Q000648:ultrastructure; D013572:Synaptic Vesicles / Q000378:metabolism*; D016708:Synaptophysin / Q000032:analysis / Q000096:biosynthesis / Q000378:metabolism*; D050857:Synaptotagmins; D014162:Transfection
D002135:Calcium-Binding Proteins; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D018377:Neurotransmitter Agents; C489618:Sv2a protein, rat; D016708:Synaptophysin; D050857:Synaptotagmins; C076414:SV2A protein, human