G-protein α subunit isoforms couple differentially to receptors that mediate presynaptic inhibition at rat hippocampal synapses
G-protein α subunit isoforms couple differentially to receptors that mediate presynaptic inhibition at rat hippocampal synapses
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DOI：
10.1523/jneurosci.22-07-02460.2002
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发表时间：
2002-04-01
影响因子：
5.3
通讯作者：
Sullivan, JM
中科院分区：
文献类型：
--
作者：
Straiker, AJ;Borden, CR;Sullivan, JM
与异源三聚体G蛋白偶联的突触前受体遍布大脑，负责调节突触传递。至少有10个G蛋白偶联受体（GPCR）减少海马神经元中的传递。此外，海马神经元表达多达17种不同的G α、G β和G γ亚基，这使得可能的异源三聚体组合物和GPCR-异源三聚体相互作用形成了惊人的阵列。Galpha亚基的身份可能是GPCR与其介导突触前抑制的分子效应器之间偶联特异性的关键决定因素。我们通过表达百日咳毒素不敏感（PTx-ins）Galpha（i/o）突变体研究了四种Galpha（i/o）亚基（Galpha（o 1）、Galpha（i1）、Galpha（i2）和Galpha（i3））在介导海马神经元突触前抑制中的作用。这些细胞的PTx处理破坏了内源性亚基的偶联，仅留下突变体Ga亚基与天然GPCR和β γ亚基偶联。突触前抑制的成功拯救表明表达的突变体G α亚基可以偶联到感兴趣的GPCR。所有四个PTX-ins G α亚基都能通过腺苷A1受体挽救突触前抑制。PTX-ins G α亚基也挽救了腺苷A1介导的自发囊泡融合频率抑制。在测试的其余GPCR中，大麻素CB 1、生长抑素和GABA（B）受体在与G蛋白异源三聚体结合时显示出α亚基依赖性选择性，而III组代谢型谷氨酸受体介导的抑制并不被四种PTX-ins α亚基中的任何一种表达所拯救。G蛋白α亚基的差异偶联可能是实现不同GPCR与其介导突触前抑制的分子靶点之间特异性的手段。
Presynaptic receptors that are coupled to heterotrimeric G-proteins are found throughout the brain and are responsible for modulating synaptic transmission. At least 10 G-protein-coupled receptors (GPCRs) reduce transmission in hippocampal neurons. Additionally, hippocampal neurons express up to 17 different Galpha, Gbeta, and Ggamma subunits, making for a striking array of possible heterotrimer compositions and GPCR-heterotrimer interactions. The identity of the Galpha subunit is likely a critical determinant in coupling specificity between GPCRs and their molecular effectors mediating presynaptic inhibition. We studied the role of four Galpha(i/o) subunits (Galpha(o1),Galpha(i1), Galpha(i2), and Galpha(i3)) in mediating presynaptic inhibition in hippocampal neurons by expressing pertussis toxin-insensitive (PTx-ins) Galpha(i/o) mutants. PTx treatment of these cells disrupts coupling of endogenous subunits, leaving only the mutant Galpha subunits to couple with native GPCRs and betagamma subunits. Successful rescue of presynaptic inhibition indicates that the expressed mutant Galpha subunit can couple to the GPCR of interest. All four PTx-ins Galpha subunits rescued presynaptic inhibition by adenosine A1 receptors. A PTx-ins Galpha subunit also rescued adenosine A1-mediated inhibition of spontaneous vesicle fusion frequency. Of the remaining GPCRs tested, cannabinoid CB1, somatostatin, and GABA(B) receptors displayed an alpha subunit-dependent selectivity in binding to G-protein heterotrimers, whereas group III metabotropic glutamate receptor-mediated inhibition was not rescued by expression of any of the four PTx-ins Galpha subunits. Differential coupling of G-protein alpha subunits may be a means of achieving specificity between different GPCRs and their molecular targets for mediating presynaptic inhibition.