Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, CP 76230 Queretaro, Mexico.
Proc Natl Acad Sci U S A. 2010 Oct 12;107(41):17780-4. doi: 10.1073/pnas.1012540107. Epub 2010 Sep 27.
The Cys-loop family of receptors mediates synaptic neurotransmission in the central nervous system of vertebrates. These receptors share several structural characteristics and assemble in the plasma membrane as multimers with fivefold symmetry. Of these, the ionotropic GABA receptors are key players in the pathogenesis of diseases like epilepsy, anxiety, and schizophrenia. Different experimental approaches have shed some light on the mechanisms behind the function of these receptors; but little is known about their structure at high resolution. Sequence homology with the nicotinic acetylcholine receptor predicts that ionotropic GABA receptors possess four transmembrane segments (TM1-4) and that TM2 forms the wall of the ion channel. However, the role of the other three segments is unclear. The GABAρ1 receptor plays a fundamental role in the regulation of neurotransmission along the visual pathway, is highly sensitive to GABA, and exhibits little desensitization. In our recent investigations of the role of TM4 in receptor function, a key residue in this domain (W475) was found to be involved in activation of the receptor. Here we have generated a structural model of the GABAρ1 receptor in silico and assessed its validity by electrophysiologically testing nine amino acid substitutions of W475 and deletions of the neighboring residues (Y474 and S476). The results identify a critical linkage between the ligand-binding domain and the TM4 domain and provide a framework for more detailed structure-function analyses of ionotropic GABA receptors.
Cys 环家族受体介导脊椎动物中枢神经系统的突触神经传递。这些受体具有一些共同的结构特征，并在质膜上组装成具有五重对称性的多聚体。其中，离子型 GABA 受体是癫痫、焦虑和精神分裂症等疾病发病机制的关键因素。不同的实验方法已经揭示了这些受体功能背后的一些机制；但它们的高分辨率结构知之甚少。与烟碱型乙酰胆碱受体的序列同源性表明，离子型 GABA 受体具有四个跨膜片段（TM1-4），TM2 形成离子通道的壁。然而，其他三个片段的作用尚不清楚。GABAρ1 受体在视觉通路中神经传递的调节中起着重要作用，对 GABA 高度敏感，并且几乎没有脱敏现象。在我们最近对 TM4 在受体功能中的作用的研究中，发现该结构域中的一个关键残基（W475）参与了受体的激活。在这里，我们通过对 W475 的九个氨基酸取代和相邻残基（Y474 和 S476）的缺失进行电生理学测试，在计算机上生成了 GABAρ1 受体的结构模型，并评估了其有效性。结果确定了配体结合域和 TM4 域之间的关键联系，并为离子型 GABA 受体的更详细的结构-功能分析提供了框架。
