Institute for Integrative Neuroanatomy, Charité, Medical University of Berlin, 10115 Berlin, Germany.
Laboratory of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, and University of Göttingen, 37077 Göttingen, Germany.
Cell Rep. 2021 Jan 12;34(2):108623. doi: 10.1016/j.celrep.2020.108623.
Vesicular glutamate transporters (VGLUTs) fill synaptic vesicles with glutamate. VGLUTs were originally identified as sodium-dependent transporters of inorganic phosphate (Pi), but the physiological relevance of this activity remains unclear. Heterologous expression of all three VGLUTs greatly augments intracellular Pi levels. Using neuronal models, we show that translocation of VGLUTs to the plasma membrane during exocytosis results in highly increased Pi uptake. VGLUT-mediated Pi influx is counteracted by Pi efflux. Synaptosomes prepared from perinatal VGLUT2 mice that are virtually free of VGLUTs show drastically reduced cytosolic Pi levels and fail to import Pi. Glutamate partially competes with sodium (Na)/Pi (NaPi)-uptake mediated by VGLUTs but does not appear to be transported. A nanobody that blocks glutamate transport by binding to the cytoplasmic domain of VGLUT1 abolishes Pi transport when co-expressed with VGLUT1. We conclude that VGLUTs have a dual function that is essential for both vesicular glutamate loading and Pi restoration in neurons.
囊泡谷氨酸转运体 (VGLUTs) 使突触小泡充满谷氨酸。VGLUTs 最初被鉴定为无机磷酸盐 (Pi) 的钠依赖性转运体，但这种活性的生理相关性仍不清楚。所有三种 VGLUTs 的异源表达都大大增加了细胞内 Pi 水平。使用神经元模型，我们表明，在胞吐作用期间 VGLUTs 向质膜的易位导致 Pi 摄取的显著增加。VGLUT 介导的 Pi 内流被 Pi 外排所抵消。来自 VGLUT2 出生后小鼠的突触小体几乎不含 VGLUTs，其细胞质 Pi 水平明显降低，并且无法摄取 Pi。谷氨酸部分与 VGLUTs 介导的钠/磷酸盐 (NaPi) 摄取竞争，但似乎不被运输。当与 VGLUT1 共表达时，一种结合 VGLUT1 胞质结构域阻断谷氨酸转运的纳米抗体可阻止 Pi 转运。我们得出结论，VGLUTs 具有双重功能，这对神经元中囊泡谷氨酸的装载和 Pi 的恢复都是必不可少的。
