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Synaptotagmin I and IV define distinct populations of neuronal transport vesicles
Author(s) -
Berton Frédérique,
Cornet Véronique,
Iborra Cécile,
Garrido Juan,
Dargent Bénédicte,
Fukuda Mitsunori,
Seagar Michael,
Marquèze Béatrice
Publication year - 2000
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.2000.00013.x
Subject(s) - synaptotagmin 1 , synaptotagmin i , microbiology and biotechnology , biology , synaptic vesicle , synapsin i , synaptophysin , vesicle , biochemistry , membrane , immunology , immunohistochemistry
Mammalian synaptotagmins constitute a multigene family of at least 11 membrane proteins. We have characterized synaptotagmin IV using antibodies directed against the C2A domain of the protein. Antibodies reacted specifically with a protein band that migrated as a 41–44 kDa doublet. Synaptotagmin IV expression was regulated throughout development. A strong decrease in the amount detected by Western blotting occurred between postnatal day 5 and adulthood, in agreement with studies on the expression of synaptotagmin IV transcripts. In subcellular fractionation, synaptotagmin IV was not detected in the synaptic vesicle‐enriched fraction. Immunofluorescence microscopy was concordant with this finding. In 6‐day‐old rat cerebellum and cultured hippocampal neurons the subcellular distribution of synaptotagmin IV was clearly different from that of synaptotagmin I. Synaptotagmin IV displayed a punctate non‐polarized distribution on neuronal extensions, whereas synaptotagmin I staining was essentially synaptic. Synaptotagmin IV staining was also observed in the soma in strong perinuclear fluorescent puncta superimposed on that of Golgi/TGN markers. Furthermore, synaptotagmin IV was seen in the proximal part of the growth cone domain and not in the microfilament‐rich region which includes filopodia. Co‐localizations with the adhesion molecules vinculin and zyxin at the proximal part of growth cones were observed. Synaptotagmin IV may thus be involved in the regulation of specific membrane‐trafficking pathways during brain development.