The actions of sevoflurane and desflurane on the gamma-aminobutyric acid receptor type A: effects of TM2 mutations in the alpha and beta subunits.
The actions of sevoflurane and desflurane on the gamma-aminobutyric acid receptor type A: effects of TM2 mutations in the alpha and beta subunits.
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发表时间：
2003
期刊：
影响因子：
8.8
通讯作者：
K. Nishikawa;N. Harrison
中科院分区：
文献类型：
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作者：
K. Nishikawa;N. Harrison
背景先前的研究表明，A型γ-氨基丁酸受体(GABAA)受体推定的第二跨膜片段(TM2)中的特定氨基酸残基在氟烷、安氟烷和异氟烷增强GABAA受体功能中发挥关键作用。然而，关于七氟烷和地氟烷对重组 GABAA 受体的作用知之甚少。本研究的目的是检查七氟醚和地氟醚对野生型 GABAA 受体和 α1、α2 或 β2 亚基 TM2 突变受体中 GABA 诱导反应增强的影响。方法通过转染人胚肾293细胞表达GABAA受体α1或α2、β2或β3和γ2s亚基cDNA用于药理学研究，并使用全细胞电压钳技术进行测定。激动剂的浓度-反应曲线和 EC50 值在野生型 α 1 beta 2 gamma 2s 和 alpha 2 beta 3 gamma 2s 受体以及带有 TM2 突变的受体中测定，例如 alpha1(S270W)beta 2 gamma 2s、alpha 1 beta 2(N265W)gamma 2s 和 TM2 突变受体。 α2(S270I)β 3 伽玛 2s。比较临床相关浓度的挥发性麻醉剂（异氟烷、七氟烷和地氟烷）对野生型和突变型 GABAA 受体中 GABA 激活的 Cl-电流的作用。结果 七氟醚和地氟醚均增强野生型 GABAA α 1 β 2 γ 2s 受体和 α 2 β 3 γ 2s 受体中的次最大 GABA 电流。将 α 亚基 TM2 中的 Ser270 替换为更大的氨基酸、色氨酸 (W) 或异亮氨酸 (I)，如 alpha1(S270W)beta 2 gamma 2s 和 alpha 2(S270I)beta 3 gamma 2s，完全消除了这些麻醉剂对 GABA 诱导电流的增强作用。相比之下，β亚基TM2中的Asn265突变为色氨酸(W)并不能阻止GABA诱导的反应的增强。七氟醚和地氟醚在野生型受体和突变受体中的作用在定性和定量上与异氟醚观察到的相似。结论 GABAA α1 和 α2 亚基的 Ser270 位点（而非 β2 亚基的 TM2 中的 Asn265）对于七氟烷、地氟烷以及异氟烷对 GABAA 受体的调节至关重要，这与这三种挥发性麻醉剂在 α 亚基上具有共同作用位点的观点一致。 GABAA 受体。
BACKGROUND Previous studies have shown that specific amino acid residues in the putative second transmembrane segment (TM2) of the gamma-aminobutyric acid receptor type A (GABAA) receptor play a critical role in the enhancement of GABAA receptor function by halothane, enflurane, and isoflurane. However, very little is known about the actions of sevoflurane and desflurane on recombinant GABAA receptors. The aim of this study was to examine the effects of sevoflurane and desflurane on potentiation of GABA-induced responses in the wild-type GABAA receptor and in receptors mutated in TM2 of the alpha1, alpha 2, or beta 2 subunits. METHODS GABAA receptor alpha 1 or alpha 2, beta 2 or beta 3, and gamma 2s subunit cDNAs were expressed for pharmacologic study by transfection of human embryonic kidney 293 cells and assayed using the whole cell voltage clamp technique. Concentration-response curves and EC50 values for agonist were determined in the wild-type alpha 1 beta 2 gamma 2s and alpha 2 beta 3 gamma 2s receptors, and in receptors harboring mutations in TM2, such as alpha1(S270W)beta 2 gamma 2s, alpha 1 beta 2(N265W)gamma 2s, and alpha2(S270I)beta 3 gamma 2s. The actions of clinically relevant concentration of volatile anesthetics (isoflurane, sevoflurane, and desflurane) on GABA activated Cl- currents were compared in the wild-type and mutant GABAA receptors. RESULTS Both sevoflurane and desflurane potentiated submaximal GABA currents in the wild-type GABAA alpha 1 beta 2 gamma 2s receptor and alpha 2 beta 3 gamma 2s receptor. Substitution of Ser270 in TM2 of the alpha subunit by a larger amino acid, tryptophan (W) or isoleucine (I), as in alpha1(S270W)beta 2 gamma 2s and alpha 2(S270I)beta 3 gamma 2s, completely abolished the potentiation of GABA-induced currents by these anesthetic agents. In contrast, mutation of Asn265 in TM2 of the beta subunit to tryptophan (W) did not prevent potentiation of GABA-induced responses. The actions of sevoflurane and desflurane in the wild-type receptor and in mutated receptors were qualitatively and quantitatively similar to those observed for isoflurane. CONCLUSIONS Positions Ser270 of the GABAA alpha1 and alpha2 subunits, but not Asn265 in the TM2 of the beta2 subunit, are critical for regulation of the GABAA receptor by sevoflurane and desflurane, as well as isoflurane, consistent with the idea that these three volatile anesthetics share a common site of actions on the alpha subunit of the GABAA receptor.