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Evidence for Early Endosome‐like Fusion of Recently Endocytosed Synaptic Vesicles
Author(s) -
Rizzoli Silvio O.,
Bethani Ioanna,
Zwilling Daniel,
Wenzel Dirk,
Siddiqui Tabrez J.,
Brandhorst Dorothea,
Jahn Reinhard
Publication year - 2006
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2006.00466.x
Subject(s) - endosome , vesicle , endocytic cycle , synaptic vesicle , exocytosis , microbiology and biotechnology , vesicle fusion , biology , lipid bilayer fusion , endocytosis , synapse , synaptic vesicle recycling , bulk endocytosis , kiss and run fusion , cell , biochemistry , neuroscience , membrane , intracellular
Early endosomes are well‐established acceptor compartments of endocytic vesicles in many cell types. Little evidence of their existence or function has been obtained in synapses, and it is generally believed that synaptic vesicles recycle without passing through an endosomal intermediate. We show here that the early endosomal SNARE proteins are enriched in synaptic vesicles. To investigate their function in the synapse, we isolated synaptic nerve terminals (synaptosomes), stimulated them in presence of different fluorescent markers to label the recycling vesicles and used these vesicles in in vitro fusion assays. The recently endocytosed vesicles underwent homotypic fusion. They also fused with endosomes from PC12 and BHK cells. The fusion process was dependent upon NSF activity. Moreover, fusion was dependent upon the early endosomal SNAREs but not upon the SNAREs involved in exocytosis. Our results thus show that at least a fraction of the vesicles endocytosed during synaptic activity are capable of fusing with early endosomes and lend support to an involvement of endosomal intermediates during recycling of synaptic vesicles.