Postsynaptic glutamate receptor δ family contributes to presynaptic terminal differentiation and establishment of synaptic transmission
Postsynaptic glutamate receptor δ family contributes to presynaptic terminal differentiation and establishment of synaptic transmission
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DOI：
10.1073/pnas.0900892106
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发表时间：
2009-03-24
影响因子：
11.1
通讯作者：
Hirano, Tomoo
中科院分区：
文献类型：
--
作者：
Kuroyanagi, Tomoaki;Yokoyama, Marie;Hirano, Tomoo
突触粘附分子如神经连接素参与突触形成，而离子型递质受体介导快速突触传递。在谷氨酸受体δ 2亚单位（δ 2）缺陷的突变小鼠中，小脑中颗粒神经元（GN）和浦肯野神经元（PN）之间的突触数量减少。在这里，我们已经研究了三角洲2在突触形成中的作用，使用文化准备。首先，我们发现，在原代培养制备的敲除小鼠的PN上的GN突触前末梢的大小和数量小于对照培养。接下来，我们在非神经元的人胚肾（HEK）细胞中表达delta 2，并将其与GN共培养。HEK细胞周围聚集了表达突触前神经末梢标记蛋白的点状结构。此外，HEK细胞同时表达δ 2和GluR 1（一种形成功能性谷氨酸门控离子通道的谷氨酸受体亚单位），显示突触后电流。缺失δ 2的胞外亮氨酸/异亮氨酸/缬氨酸结合蛋白（LIVBP）结构域消除了诱导能力，并且直接融合到跨膜序列的LIVBP结构域足以诱导突触前分化。此外，LIVBP结构域被Δ 2 LIVBP结构域取代的突变型GluR 1本身足以建立突触传递。δ谷氨酸受体家族的另一个成员δ 1也诱导突触前分化。因此，δ谷氨酸受体亚家族可以诱导谷氨酸能突触前末梢的分化，并有助于突触传递的建立。
Synaptic adhesion molecules such as neuroligin are involved in synapse formation, whereas ionotropic transmitter receptors mediate fast synaptic transmission. In mutant mice deficient in the glutamate receptor delta 2 subunit (delta 2), the number of synapses between granule neurons (GNs) and a Purkinje neuron (PN) in the cerebellum is reduced. Here, we have examined the role of delta 2 in synapse formation using culture preparations. First, we found that the size and number of GN presynaptic terminals on a PN in the primary culture prepared from knockout mice were smaller than those in control culture. Next we expressed delta 2 in nonneuronal human embryonic kidney (HEK) cells and cocultured them with GNs. Punctate structures expressing marker proteins for glutamatergic presynaptic terminals were accumulated around the HEK cells. Furthermore, HEK cells expressing both delta 2 and GluR1, a glutamate receptor subunit forming a functional glutamate- gated ion channel, showed postsynaptic current. Deletion of the extracellular leucine/isoleucine/valine binding protein (LIVBP) domain of delta 2 abolished the induction ability, and the LIVBP domain directly fused to a transmembrane sequence was sufficient to induce presynaptic differentiation. Furthermore, a mutant GluR1 whose LIVBP domain was replaced with the delta 2 LIVBP domain was sufficient by itself to establish synaptic transmission. Another member of delta glutamate receptor family delta 1 also induced presynaptic differentiation. Thus, the delta glutamate receptor subfamily can induce the differentiation of glutamatergic presynaptic terminals and contribute to the establishment of synaptic transmission.