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Morphological and molecular heterogeneity in release sites of single neurons
Author(s) -
Morgenthaler Florence D.,
Knott Graham W.,
Floyd Sarria J.C.,
Wang Xin,
Staple Julie K.,
Catsicas Stefan,
Hirling Harald
Publication year - 2003
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.1460-9568.2003.02572.x
Subject(s) - synaptotagmin 1 , synaptic vesicle , synaptophysin , active zone , neuron , synapse , postsynaptic potential , biology , synaptotagmin i , vesicle , neurotransmission , neurotransmitter , synaptic vesicle recycling , microbiology and biotechnology , synapsin , synaptic cleft , neuroscience , biochemistry , receptor , membrane , central nervous system , immunohistochemistry , immunology
We have previously shown that labelling intensities for synaptic proteins vary strongly among synaptic boutons. Here we addressed the questions as to whether there are heterogeneous levels of integral membrane synaptic vesicle proteins at distinct active release sites of single neurons and if these sites possess the ultrastructural features of synapses. By double‐immunostaining with specific antibodies against synaptophysin, synaptotagmin I, VAMP1 and VAMP2, we identified different relative levels of these integral membrane proteins of synaptic vesicles in comparison to boutons of the same rat cortical neuron. This heterogeneity could also be observed between the two isoforms VAMP1 and VAMP2. By studying pairs of these proteins implicated in neurotransmitter release, including both VAMP isoforms, we also show that the sites that contained predominantly one protein were nevertheless functional, as they internalized and released FM1‐43 upon potassium stimulation. Using electron microscopy, we show that these active sites could have either synaptic specializations, or the features of vesicle‐containing varicosities without a postsynaptic target. Different varicosities of the same neuron showed different intensities for synaptic vesicle proteins; some varicosities were capable of internalizing and releasing FM1‐43, while others were silent. These results show that integral membrane synaptic vesicle proteins are differentially distributed among functional release sites of the same neuron.