Dual and Direction-Selective Mechanisms of Phosphate Transport by the Vesicular Glutamate Transporter
Dual and Direction-Selective Mechanisms of Phosphate Transport by the Vesicular Glutamate Transporter
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DOI：
10.1016/j.celrep.2018.03.055
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发表时间：
2018-04-10
期刊：
影响因子：
8.8
通讯作者：
Ahnert-Hilger, Gudrun
中科院分区：
文献类型：
--
作者：
Preobraschenski, Julia;Cheret, Cyril;Ahnert-Hilger, Gudrun
囊泡谷氨酸转运体（VGLUT）使突触囊泡充满谷氨酸，因此对于谷氨酸能神经传递是必需的。然而，VGLUT最初被发现为对无机磷酸盐（Pi）特异性的转运蛋白亚家族的成员。目前还不清楚VGLUT如何适应谷氨酸转运偶联到电化学质子梯度Δ μ H+与反向P-1转运偶联到Na+梯度和膜电位。使用功能重建和异源表达，我们表明，VGLUT转运谷氨酸和P-1使用一个单一的底物结合位点，但不同的耦合阳离子梯度。当面对细胞质时，两种离子都以Delta mu H+依赖性方式转运到突触囊泡中，其中谷氨酸优先于Pi。当面对细胞外空间时，Pi以Na+偶联的方式转运，谷氨酸竞争结合，但亲和力较低。我们的结论是，VGLUTs具有双重功能，在囊泡递质的负载和P-i内稳态的多巴胺能神经元。
Vesicular glutamate transporters (VGLUTs) fill synaptic vesicles with glutamate and are thus essential for glutamatergic neurotransmission. However, VGLUTs were originally discovered as members of a transporter subfamily specific for inorganic phosphate (P-i). It is still unclear how VGLUTs accommodate glutamate transport coupled to an electrochemical proton gradient Delta mu H+ with inversely directed P-i transport coupled to the Na+ gradient and the membrane potential. Using both functional reconstitution and heterologous expression, we show that VGLUT transports glutamate and P-i using a single substrate binding site but different coupling to cation gradients. When facing the cytoplasm, both ions are transported into synaptic vesicles in a Delta mu H+-dependent fashion, with glutamate preferred over P-i. When facing the extracellular space, P-i is transported in a Na+-coupled manner, with glutamate competing for binding but at lower affinity. We conclude that VGLUTs have dual functions in both vesicle transmitter loading and P-i homeostasis within glutamatergic neurons.