Assembling the presynaptic active zone: A characterization of an active zone precursor vesicle

The active zone is a specialized region of the presynaptic plasma membrane where synaptic vesicles dock and fuse. In this study, we have investigated the cellular mechanism underlying the transport and recruitment of the acti ve zone protein Piccolo into nascent synapses. Our results show that Piccol o is transported to nascent synapses on an similar to 80 nm dense core gran ulated vesicle together with other constituents of the active zone, includi ng Bassoon, Syntaxin, SNAP-25, and N-cadherin, as well as chromogranin B. C omponents of synaptic vesicles, such as VAMP 2/synaptobrevin II, synaptophy sin, synaptotagmin, or proteins of the perisynaptic plasma membrane such as GABA transporter 1 (GAT1), were not present. These studies demonstrate tha t the presynaptic active zone is formed in part by the fusion of an active zone precursor vesicle with the presynaptic plasma membrane.