Cationic modulation of rho 1-type gamma-aminobutyrate receptors expressed in Xenopus oocytes.
Cationic modulation of rho 1-type gamma-aminobutyrate receptors expressed in Xenopus oocytes.
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DOI：
10.1073/pnas.91.26.12725
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发表时间：
1994-12
影响因子：
11.1
通讯作者：
D. Calvo;A. E. Vazquez;R. Miledi
中科院分区：
文献类型：
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作者：
D. Calvo;A. E. Vazquez;R. Miledi
研究了二价和三价阳离子对非洲爪蟾卵母细胞注射编码γ-氨基丁酸（GABA rho 1）亚基的mRNA后表达的同型rho 1型GABA rho 1受体的影响。GABA引起大电流，Kd约为1 μ M。这些GABA rho 1受体的性质与视网膜mRNA表达的天然荷包牡丹碱抗性GABA受体的性质相似。GABA rho 1电流表现出非常少的脱敏，被阻断印防己毒素，但不是由荷包牡丹碱，并没有调制巴比妥类药物，苯二氮卓类药物，或β-咔啉。Zn 2+可逆性降低GABA rho 1反应（IC 50 = 22 μ M）。还测试了其他二价阳离子，并且它们的效力等级顺序为：Zn 2+约Ni 2+约Cu 2 + >> Cd 2+，而Ba 2+、Co 2+、Sr 2+、Mn 2+、Mg 2+和Ca 2+显示出很小的作用或没有作用。相反，镧3+可逆地增强由同型GABA rho 1受体介导的GABA电流，EC 50 = 135 μ M，最大增强约为100%（GABA，1 μ M;镧3+，1 mM）。其它镧系元素也表现出类似的效果（Lu 3 + > Eu 3 + > Tb 3 + > Gd 3 + > Er 3 +> Nd 3 + > La 3 + > Ce 3+）。因此，GABA rho 1受体含有阳离子识别位点，特别是，Zn 2+可能在视网膜突触传递过程中发挥作用。
A study was made of the effects of di- and trivalent cations on homomeric rho 1-type gamma-aminobutyrate (GABA rho 1) receptors expressed in Xenopus oocytes after injection of mRNA coding for the GABA rho 1 subunit. GABA elicited large currents with a Kd approximately 1 microM. The properties of these GABA rho 1 receptors were similar to those of native bicuculline-resistant GABA receptors expressed by retinal mRNA. GABA rho 1 currents showed very little desensitization, were blocked by picrotoxin but not by bicuculline, and were not modulated by barbiturates, benzodiazepines, or beta-carbolines. Zn2+ reversibly decreased GABA rho 1 responses (IC50 = 22 microM). Other divalent cations were also tested and their rank order of potency was: Zn2+ approximately Ni2+ approximately Cu2+ >> Cd2+, whereas Ba2+, Co2+, Sr2+, Mn2+, Mg2+, and Ca2+ showed little or no effect. In contrast, La3+ reversibly potentiated the GABA currents mediated by homomeric GABA rho 1 receptors, with an EC50 = 135 microM and a maximal potentiation of about 100% (GABA, 1 microM; La3+, 1 mM). Other lanthanides showed similar effects (Lu3+ > Eu3+ > Tb3+ > Gd3+ > Er3% > Nd3+ > La3+ > Ce3+). Thus, GABA rho 1 receptors contain sites for cationic recognition, and in particular, Zn2+ may play a role during synaptic transmission in the retina.