Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
Sci Rep. 2017 Jul 14;7(1):5399. doi: 10.1038/s41598-017-05637-x.
Dopamine transporter (DAT) has been shown to accumulate in filopodia in neurons and non-neuronal cells. To examine the mechanisms of DAT filopodial targeting, we used quantitative live-cell fluorescence microscopy, and compared the effects of the DAT inhibitor cocaine and its fluorescent analog JHC1-64 on the plasma membrane distribution of wild-type DAT and two non-functional DAT mutants, R60A and W63A, that do not accumulate in filopodia. W63A did not bind JHC1-64, whereas R60A did, although less efficiently compared to the wild-type DAT. Molecular dynamics simulations predicted that R60A preferentially assumes an outward-facing (OF) conformation through compensatory intracellular salt bridge formation, which in turn favors binding of cocaine. Imaging analysis showed that JHC1-64-bound R60A mutant predominantly localized in filopodia, whereas free R60A molecules were evenly distributed within the plasma membrane. Cocaine binding significantly increased the density of R60A, but not that of W63A, in filopodia. Further, zinc binding, known to stabilize the OF state, also increased R60A concentration in filopodia. Finally, amphetamine, that is thought to disrupt DAT OF conformation, reduced the concentration of wild-type DAT in filopodia. Altogether, these data indicate that OF conformation is required for the efficient targeting of DAT to, and accumulation in, filopodia.
多巴胺转运体(DAT)已被证明在神经元和非神经元细胞的丝状伪足中积累。为了研究 DAT 丝状伪足靶向的机制,我们使用定量活细胞荧光显微镜,比较了 DAT 抑制剂可卡因及其荧光类似物 JHC1-64 对野生型 DAT 和两种不能在丝状伪足中积累的无功能 DAT 突变体(R60A 和 W63A)的质膜分布的影响。W63A 不结合 JHC1-64,而 R60A 结合了 JHC1-64,尽管与野生型 DAT 相比结合效率较低。分子动力学模拟预测 R60A 通过补偿性的细胞内盐桥形成优先呈现外向(OF)构象,这反过来有利于可卡因的结合。成像分析表明,结合 JHC1-64 的 R60A 突变体主要定位于丝状伪足,而游离的 R60A 分子均匀分布在质膜内。可卡因结合显著增加了 R60A 在丝状伪足中的密度,但对 W63A 则没有。此外,已知稳定 OF 状态的锌结合也增加了丝状伪足中 R60A 的浓度。最后,安非他命,被认为会破坏 DAT 的 OF 构象,降低野生型 DAT 在丝状伪足中的浓度。总之,这些数据表明 OF 构象是 DAT 有效靶向并在丝状伪足中积累所必需的。