Hamilton P J, Campbell N G, Sharma S, Erreger K, Herborg Hansen F, Saunders C, Belovich A N, Sahai M A, Cook E H, Gether U, McHaourab H S, Matthies H J G, Sutcliffe J S, Galli A
Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville, TN, USA.
Mol Psychiatry. 2013 Dec;18(12):1315-23. doi: 10.1038/mp.2013.102. Epub 2013 Aug 27.
De novo genetic variation is an important class of risk factors for autism spectrum disorder (ASD). Recently, whole-exome sequencing of ASD families has identified a novel de novo missense mutation in the human dopamine (DA) transporter (hDAT) gene, which results in a Thr to Met substitution at site 356 (hDAT T356M). The dopamine transporter (DAT) is a presynaptic membrane protein that regulates dopaminergic tone in the central nervous system by mediating the high-affinity reuptake of synaptically released DA, making it a crucial regulator of DA homeostasis. Here, we report the first functional, structural and behavioral characterization of an ASD-associated de novo mutation in the hDAT. We demonstrate that the hDAT T356M displays anomalous function, characterized as a persistent reverse transport of DA (substrate efflux). Importantly, in the bacterial homolog leucine transporter, substitution of A289 (the homologous site to T356) with a Met promotes an outward-facing conformation upon substrate binding. In the substrate-bound state, an outward-facing transporter conformation is required for substrate efflux. In Drosophila melanogaster, the expression of hDAT T356M in DA neurons-lacking Drosophila DAT leads to hyperlocomotion, a trait associated with DA dysfunction and ASD. Taken together, our findings demonstrate that alterations in DA homeostasis, mediated by aberrant DAT function, may confer risk for ASD and related neuropsychiatric conditions.
新生基因变异是自闭症谱系障碍（ASD）的一类重要风险因素。最近，对ASD家庭进行的全外显子组测序在人类多巴胺（DA）转运体（hDAT）基因中发现了一种新的新生错义突变，该突变导致356位点的苏氨酸被甲硫氨酸取代（hDAT T356M）。多巴胺转运体（DAT）是一种突触前膜蛋白，通过介导突触释放的DA的高亲和力再摄取来调节中枢神经系统中的多巴胺能张力，使其成为DA稳态的关键调节因子。在此，我们报告了hDAT中与ASD相关的新生突变的首次功能、结构和行为特征。我们证明hDAT T356M表现出异常功能，其特征为DA的持续逆向转运（底物外流）。重要的是，在细菌同源物亮氨酸转运体中，用甲硫氨酸取代A289（T356的同源位点）会促进底物结合后向外的构象。在底物结合状态下，底物外流需要向外的转运体构象。在果蝇中，在缺乏果蝇DAT的DA神经元中表达hDAT T356M会导致运动亢进，这是一种与DA功能障碍和ASD相关的特征。综上所述，我们的研究结果表明，由异常的DAT功能介导的DA稳态改变可能会增加患ASD和相关神经精神疾病的风险。
