Dendritic Assembly of Heteromeric γ-Aminobutyric Acid Type B Receptor Subunits in Hippocampal Neurons
Dendritic Assembly of Heteromeric γ-Aminobutyric Acid Type B Receptor Subunits in Hippocampal Neurons
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DOI：
10.1074/jbc.m900575200
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发表时间：
2009-05-08
影响因子：
4.8
通讯作者：
Couve, Andres
中科院分区：
文献类型：
--
作者：
Ramirez, Omar A.;Vidal, Rene L.;Couve, Andres
了解通过神经递质受体的可用性控制突触功效的机制取决于揭示其特定的细胞内运输途径。γ-氨基丁酸B型（GABA（B））受体（GABA（B）Rs）是存在于树突兴奋性和抑制性突触后位点的专性异聚体。目前尚不清楚GABA（B）Rs的合成和组装是否发生在体细胞内质网（ER）中，然后通过囊泡运输到树突，或者体细胞合成之后是否通过独立运输的亚基组装和ER出口到整个体细胞树突隔室。为了区分这些可能性，我们研究了GABA（B）R亚基在海马神经元树突结合活荧光显微镜，生物化学，定量共定位，和双分子荧光互补的协会。我们证明，GABA（B）R亚基的分离和差异移动的在树突细胞内室和非相关的细胞内亚基的高比例存在于大脑中。组装的异聚体优先位于质膜上，但ER出口的阻断导致它们在细胞体和树突中的细胞内积累。我们认为GABA（B）R亚单位在内质网中组装，并在插入质膜之前从内质网输出到整个神经元。我们的研究结果是一致的，通过ER和排除后高尔基体囊泡运输的预组装GABA（B）Rs的隔离亚基的大规模流动。
Understanding the mechanisms that control synaptic efficacy through the availability of neurotransmitter receptors depends on uncovering their specific intracellular trafficking routes. gamma-Aminobutyric acid type B (GABA(B)) receptors (GABA(B)Rs) are obligatory heteromers present at dendritic excitatory and inhibitory postsynaptic sites. It is unknown whether synthesis and assembly of GABA(B)Rs occur in the somatic endoplasmic reticulum (ER) followed by vesicular transport to dendrites or whether somatic synthesis is followed by independent transport of the subunits for assembly and ER export throughout the somatodendritic compartment. To discriminate between these possibilities we studied the association of GABA(B)R subunits in dendrites of hippocampal neurons combining live fluorescence microscopy, biochemistry, quantitative colocalization, and bimolecular fluorescent complementation. We demonstrate that GABA(B)R subunits are segregated and differentially mobile in dendritic intracellular compartments and that a high proportion of non-associated intracellular subunits exist in the brain. Assembled heteromers are preferentially located at the plasma membrane, but blockade of ER exit results in their intracellular accumulation in the cell body and dendrites. We propose that GABA(B)R subunits assemble in the ER and are exported from the ER throughout the neuron prior to insertion at the plasmamembrane. Our results are consistent with a bulk flow of segregated subunits through the ER and rule out a post-Golgi vesicular transport of preassembled GABA(B)Rs.