The interaction of the general anesthetic etomidate with the gamma-aminobutyric acid type A receptor is influenced by a single amino acid
The interaction of the general anesthetic etomidate with the gamma-aminobutyric acid type A receptor is influenced by a single amino acid
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DOI：
10.1073/pnas.94.20.11031
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发表时间：
1997-09-30
影响因子：
11.1
通讯作者：
Whiting, PJ
中科院分区：
文献类型：
--
作者：
Belelli, D;Lambert, JJ;Whiting, PJ
γ-氨基丁酸A型（GABA（A））受体是一种递质门控离子通道，介导脑内大多数快速抑制性突触传递。（alpha（1-6）、beta（1-3）、gamma（1-3）、delta（1）和delta（1）），全身麻醉药对GABA（A）受体活性的正向变构调节代表了中枢神经系统抑制的一种逻辑机制，静脉全身麻醉剂依托咪酯调节和激活GABA（A）受体的能力独特地依赖于受体内存在的β亚单位亚型，含有β（2）-或β（3）-亚基，但不含β（1）亚基的受体对该试剂高度敏感。在此，在非洲爪蟾卵母细胞中与人α（6）和γ（2）亚基共表达的嵌合β（1）/β（2）亚基鉴定了细胞外N-末端结构域远端的区域作为依托咪酯选择性的决定因素，β（3）亚基通道结构域内存在的氨基酸（Asn-289）突变为Ser（β（1）中的同源残基），强烈抑制依托咪酯的GABA调节和GABA模拟作用，Asn取代β（1）亚基Ser-290产生匡威的作用，当细胞内应用于稳定表达α（6）β（3）γ（2）亚基组合的小鼠L（tk-）细胞时，依托咪酯呈惰性。因此，临床上使用的全身麻醉剂对生理学相关靶蛋白的作用受到单个氨基酸的显著影响。加上细胞内依托咪酯缺乏效果，这些数据反对单一的基于脂质的麻醉理论。
The gamma-aminobutyric acid type A (GABA(A)) receptor is a transmitter-gated ion channel mediating the majority of fast inhibitory synaptic transmission within the brain, The receptor is a pentameric assembly of subunits drain from multiple classes (alpha(1-6), beta(1-3), gamma(1-3), delta(1), and epsilon(1)), Positive allosteric modulation of GABA(A) receptor activity by general anesthetics represents one logical mechanism for central nervous system depression, The ability of the intravenous general anesthetic etomidate to modulate and activate GABA(A) receptors is uniquely dependent upon the beta subunit subtype present within the receptor, Receptors containing beta(2)- or beta(3)-, but not beta(1) subunits, are highly sensitive to the agent, Here, chimeric beta(1)/beta(2) subunits coexpressed in Xenopus laevis oocytes with human alpha(6) and gamma(2) subunits identified a region distal to the extracellular N-terminal domain as a determinant of the selectivity of etomidate, The mutation of an amino acid (Asn-289) present within the channel domain of the beta(3) subunit to Ser (the homologous residue in beta(1)), strongly suppressed the GABA-modulatory and GABA mimetic effects of etomidate, The replacement of the beta(1) subunit Ser-290 by Asn produced the converse effect, When applied intracellularly to mouse L(tk-) cells stably expressing the alpha(6) beta(3) gamma(2) subunit combination, etomidate was inert. Hence, the effects of a clinically utilized general anesthetic upon a physiologically relevant target protein are dramatically influenced by a single amino acid. Together with the lack of effect of intracellular etomidate, the data argue against a unitary, lipid-based theory of anesthesia.