On the structure of the ‘synaptosecretosome’ Evidence for a neurexin/synaptotagmin/syntaxin/Ca2+channel complex

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Abstract
Recent experiments have identified interactions between presynaptic and synaptic vesicle membrane proteins, that might be important in organizing the components of the fast neurotransmitter release mechanism to ensure that the process follows a rapid time course. Here we extend previous investigations to show that in addition to the α-latrotoxin receptor (neurexin) and synaptotagmin another presynaptic protein, syntaxin, co-purifies on a α-latrotoxin affinity column. This implies that syntaxin is associated with these two molecules in a complex; a conclusion supported by the immunoprecipitation of [125I]latrotoxin binding by syntaxin antibodies. In addition, antibodies against syntaxin and the α-latrotoxin receptor immunoprecipitate [125I]ω-conotoxin binding sites, indicating that calcium channels are associated with this complex. Thus, neurexin, synaptotagmin, syntaxin, and calcium channels can be found in a structure we propose to call the ‘synaptosecretosome’. The components of the synaptosecretosome, in association with additional proteins, are postulated to organize the process of neurotransmitter release.