Neuron-derived D-serine release provides a novel means to activate N-methyl-D-aspartate receptors
Neuron-derived D-serine release provides a novel means to activate N-methyl-D-aspartate receptors
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DOI：
10.1074/jbc.m512927200
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发表时间：
2006-05-19
影响因子：
4.8
通讯作者：
Wolosker, Herman
中科院分区：
文献类型：
--
作者：
Kartvelishvily, Elena;Shleper, Maria;Wolosker, Herman
D-丝氨酸是N-甲基-D-天冬氨酸（NMDA）受体的促凝剂，在大脑中以高水平存在。D-丝氨酸的生物合成是通过丝氨酸消旋酶进行的，丝氨酸消旋酶将L-丝氨酸转化为D-丝氨酸。D-丝氨酸已被证明存在于神经胶质细胞中，从而提出星形胶质细胞是D-丝氨酸的唯一来源。我们现在报告大量的丝氨酸消旋酶和D-丝氨酸在原代神经元培养和神经元在体内。几种神经元培养类型表达丝氨酸消旋酶，和D-丝氨酸的合成与神经胶质细胞培养。用新抗体对脑切片进行免疫组织化学染色，发现神经元中存在丝氨酸消旋酶和D-丝氨酸。表达丝氨酸消旋酶的皮层神经元也原位表达NR 2a亚基。神经元衍生的D-丝氨酸有助于皮层神经元培养物中NMDA受体的激活。内源性D-丝氨酸的降解通过添加重组酶D-丝氨酸脱氨酶减少NMDA引起的兴奋性毒性。神经元D-丝氨酸的释放由离子型谷氨酸受体激动剂如NMDA、α-氨基-3-羟基-5-甲基异恶唑-4-丙酸和红藻氨酸介导。去除外部Ca ~（2+）或Na ~+可阻断D-丝氨酸的释放。D-丝氨酸的释放主要通过胞质途径，因为它对巴夫洛霉素A（一种有效的囊泡神经递质摄取抑制剂）不敏感（1）。D-丝氨酸也没有运输到纯化的突触囊泡的条件下，最佳的吸收已知的发射机。我们的研究结果表明，神经元是D-丝氨酸的主要来源。谷氨酸诱导的神经元D-丝氨酸释放为自分泌或旁分泌激活NMDA受体提供了一种新的机制。
D-Serine is a coagonist of N-methyl-D-aspartate ( NMDA) receptors that occurs at high levels in the brain. Biosynthesis of D-serine is carried out by serine racemase, which converts L-to D-serine. D-Serine has been demonstrated to occur in glial cells, leading to the proposal that astrocytes are the only source of D-serine. We now report significant amounts of serine racemase and D-serine in primary neuronal cultures and neurons in vivo. Several neuronal culture types expressed serine racemase, and D-serine synthesis was comparable with that in glial cultures. Immunohistochemical staining of brain sections with new antibodies revealed the presence of serine racemase and D-serine in neurons. Cortical neurons expressing serine racemase also expressed the NR2a subunit in situ. Neuron-derived D-serine contributes to NMDA receptor activation in cortical neuronal cultures. Degradation of endogenous D-serine by addition of the recombinant enzyme D-serine deaminase diminished NMDA-elicited excitotoxicity. Release of neuronal D-serine was mediated by ionotropic glutamate receptor agonists such as NMDA, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid, and kainate. Removal of either external Ca2+ or Na+ blocked D-serine release. Release of D-serine was mostly through a cytosolic route because it was insensitive to bafilomycin A(1), a potent inhibitor of vesicular neurotransmitter uptake. D-Serine was also not transported into purified synaptic vesicles under conditions optimal for the uptake of known transmitters. Our results suggest that neurons are a major source of D-serine. Glutamate-induced neuronal D-serine release provides a novel mechanism for activating NMDA receptors by an autocrine or paracrine way.