Activity-dependent changes of the presynaptic synaptophysin-synaptobrevin complex in adult rat brain

The vesicular protein synaptobrevin contributes to two mutually exclusive c omplexes in mature synapses. Synaptobrevin tightly interacts with the plasm a membrane proteins syntaxin and SNAP 25 forming the SNARE complex as a pre requisite for exocytotic membrane fusion. Alternatively, synaptobrevin bind s to the vesicular protein synaptophysin. It is unclear whether SNARE compl ex formation is diminished or facilitated when synaptobrevin is bound to sy naptophysin. Here we show that the synaptophysin-synaptobrevin complex is i ncreased in adult rat brain after repeated synaptic hyperactivity in the ki ndling model of epilepsy. Two days after the last kindling-induced stage V seizure the relative amount of synaptophysin-synaptobrevin complex obtained by co-immunoprecipitation from cortical and hippocampal membranes was incr eased twofold compared to controls. By contrast the relative amounts of var ious synaptic proteins as well as that of the SNARE complex did not change in membrane preparations from kindled rats compared to controls. The increa sed amount of synaptophysin-synaptobrevin complex in kindled rats supports the idea that this complex represents a reserve pool for synaptobrevin enab ling synaptic vesicles to adjust to an increased demand for synaptic effici ency. We conclude that the synaptophysin-synaptobrevin interaction is invol ved in activity-dependent plastic changes in adult rat brain.