α-synuclein produces a long-lasting increase in neurotransmitter release

Wild-type α-synuclein, a protein of unknown function, has received much attention because of its involvement in a series of diseases that are known as synucleinopathies. We find that long-lasting potentiation of synaptic transmission between cultured hippocampal neurons is accompanied by an increase in the number of α-synuclein clusters. Conversely, suppression of α-synuclein expression through antisense nucleotide and knockout techniques blocks the potentiation, as well as the glutamate-induced increase in presynaptic functional bouton number. Consistent with these findings, α-synuclein introduction into the presynaptic neuron of a pair of monosynaptically connected cells causes a rapid and long-lasting enhancement of synaptic transmission, and rescues the block of potentiation in α-synuclein null mouse cultures. Also, we report that the application of nitric oxide (NO) increases the number of α-synuclein clusters, and inhibitors of NO-synthase block this increase, supporting the hypothesis that NO is involved in the enhancement of the number of α-synuclein clusters. Thus, α-synuclein is involved in synaptic plasticity by augmenting transmitter release from the presynaptic terminal.