Striatal Dopamine Transporter Function Is Facilitated by Converging Biology of α-Synuclein and Cholesterol

Abstract

Striatal dopamine transporters (DAT) powerfully regulate dopamine signaling, and can contribute risk to degeneration in Parkinson's disease (PD). DATs can interact with the neuronal protein α-synuclein, which is associated with the etiology and molecular pathology of idiopathic and familial PD. Here, we tested whether DAT function in governing dopamine (DA) uptake and release is modified in a human-α-synuclein-overexpressing (<i>SNCA</i>-OVX) transgenic mouse model of early PD. Using fast-scan cyclic voltammetry (FCV) in <i>ex vivo</i> acute striatal slices to detect DA release, and biochemical assays, we show that several aspects of DAT function are promoted in <i>SNCA</i>-OVX mice. Compared to background control α-synuclein-null mice (<i>Snca</i>-null), the <i>SNCA</i>-OVX mice have elevated DA uptake rates, and more pronounced effects of DAT inhibitors on evoked extracellular DA concentrations ([DA]_o) and on short-term plasticity (STP) in DA release, indicating DATs play a greater role in limiting DA release and in driving STP. We found that DAT membrane levels and radioligand binding sites correlated with α-synuclein level. Furthermore, DAT function in <i>Snca</i>-null and <i>SNCA</i>-OVX mice could also be promoted by applying cholesterol, and using Tof-SIMS we found genotype-differences in striatal lipids, with lower striatal cholesterol in <i>SNCA</i>-OVX mice. An inhibitor of cholesterol efflux transporter ABCA1 or a cholesterol chelator in <i>SNCA</i>-OVX mice reduced the effects of DAT-inhibitors on evoked [DA]_o. Together these data indicate that human α-synuclein in a mouse model of PD promotes striatal DAT function, in a manner supported by extracellular cholesterol, suggesting converging biology of α-synuclein and cholesterol that regulates DAT function and could impact DA function and PD pathophysiology.