The structure and function of presynaptic and postsynaptic components of the synapse are highly coordinated. How such coordination is achieved and the molecules involved in this process have not been clarified. Several lines of evidence suggest that presynaptic functionalities are regulated by retrograde mechanisms from the postsynaptic side. We therefore sought postsynaptic mechanisms responsible for trans-synaptic regulation of presynaptic function at excitatory synapses in rat hippocampal CA1 pyramidal neurons. We show here that the postsynaptic complex of scaffolding protein PSD-95 and neuroligin can modulate the release probability of transmitter vesicles at synapse in a retrograde way, resulting in altered presynaptic short-term plasticity. Presynaptic β-neurexin serves as a likely presynaptic mediator of this effect. Our results indicate that trans-synaptic protein-protein interactions can link postsynaptic and presynaptic function.
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