The synaptic vesicle protein synaptotagmin promotes formation of filopodia in fibroblasts.
Neuronal filopodia are actin-rich cytoplasmic extensions that are involved in motility and recognition in growth cones and maturing axonal endings. A detailed understanding of neuronal growth will depend on clarification of the membrane fusion events occurring during filopodial extension. The synaptic vesicle protein synaptotagmin seems to be intimately involved in exocytotic membrane fusion. Here we show that fibroblast cell lines transfected with synaptotagmin form long, highly branched, actin-rich filopodial processes, with the expressed synaptotagmin being incorporated into the plasma membrane. In contrast, cell lines expressing either of two other synaptic vesicle proteins, SV2 or synaptophysin, generate only rudimentary processes, and, like neurons, sort SV2 and synaptophysin to small intracellular vesicles. As presynaptic calcium entry regulates synaptic vesicle fusion, our results indicate that synaptotagmin might link neuronal activity with synaptic growth.
Feany
M B
MB
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115.
Buckley
K M
KM
D000818:Animals; D016466:CHO Cells; D002135:Calcium-Binding Proteins; D002455:Cell Division / Q000235:genetics / Q000502:physiology; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology / Q000648:ultrastructure; D006224:Cricetinae; D004330:Drosophila; D005347:Fibroblasts; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000502:physiology*; D009474:Neurons / Q000166:cytology; D011554:Pseudopodia / Q000502:physiology* / Q000648:ultrastructure; D051381:Rats; D016708:Synaptophysin / Q000235:genetics / Q000502:physiology; D050857:Synaptotagmins; D014162:Transfection
D002135:Calcium-Binding Proteins; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; C489618:Sv2a protein, rat; D016708:Synaptophysin; D050857:Synaptotagmins; C076414:SV2A protein, human