Dopamine (DA) homeostasis is essential for a variety of brain activities. Dopamine transporter (DAT)-mediated DA reuptake is one of the most critical mechanisms for normal DA homeostasis. However, the molecular mechanisms underlying the regulation of DAT activity in the brain remain poorly understood. Here we show that the Rho-family guanine nucleotide exchange factor protein Vav2 is required for DAT cell surface expression and transporter activity modulated by glial cell line-derived neurotrophic factor (GDNF) and its cognate receptor Ret. Mice deficient in either Vav2 or Ret displayed elevated DAT activity, which was accompanied by an increase in intracellular DA selectively in the nucleus accumbens. Vav2(-/-) mice exposed to cocaine showed reduced DAT activity and diminished behavioral cocaine response. Our data demonstrate that Vav2 is a determinant of DAT trafficking in vivo and contributes to the maintenance of DA homeostasis in limbic DA neuron terminals.

This work was designed to evaluate the coverage of data-dependent acquisition (DDA) extensively utilized in the untargeted metabolite/component identification in the food sciences and pharmaceutical analysis. Using saponins from the flower buds of Panax ginseng (PGF) as an example, precursor ions list (PIL)-including DDA on a Q-Orbitrap mass spectrometer could enable higher coverage than the other four MS 2 acquisition approaches in characterizing PGF ginsenosides. A "Virtual Library of Ginsenoside" containing 13,536 ginsenoside molecules was established by C-language-programmed large-scale molecular prediction, which in combination with mass defect filtering could create a new PIL involving 1859 PGF saponin precursors. We could newly obtain the MS 2 spectra of at least 17 components and characterize 36 ginsenosides with unknown masses, among the 164 compounds identified from PGF. Conclusively, a molecular-prediction-oriented PIL in DDA can assist to discover more potentially novel molecules benefiting to the development of functional foods and new drugs.

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