Efflux of dopamine through the dopamine transporter (DAT) is critical for the psychostimulatory properties of amphetamines, but the underlying mechanism is unclear. Here we show that Ca2+/calmodulin-dependent protein kinase II (CaMKII) plays a key role in this efflux. CaMKIIα bound to the distal C terminus of DAT and colocalized with DAT in dopaminergic neurons. CaMKIIα stimulated dopamine efflux via DAT in response to amphetamine in heterologous cells and in dopaminergic neurons. CaMKIIα phosphorylated serines in the distal N terminus of DAT in vitro, and mutation of these serines eliminated the stimulatory effects of CaMKIIα. A mutation of the DAT C terminus impairing CaMKIIα binding also impaired amphetamine-induced dopamine efflux. An in vivo role for CaMKII was supported by chronoamperometry measurements showing reduced amphetamine-induced dopamine efflux in response to the CaMKII inhibitor KN93. Our data suggest that CaMKIIα binding to the DAT C terminus facilitates phosphorylation of the DAT N terminus and mediates amphetamine-induced dopamine efflux.
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