Properties of two classes of rat brain acidic amino acid receptors induced by distinct mRNA populations in Xenopus oocytes.
Properties of two classes of rat brain acidic amino acid receptors induced by distinct mRNA populations in Xenopus oocytes.
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爪蟾卵母细胞中不同 mRNA 群体诱导的两类大鼠脑酸性氨基酸受体的特性。
DOI：
10.1002/syn.890020613
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
Lester,HA
中科院分区：
文献类型：
--
作者：
Fong,TM;Davidson,N;Lester,HA
用非洲爪蟾卵母细胞表达系统研究了大鼠脑酸性氨基酸（AA）受体基因的分子组成，注射poly（A）mRNA的非洲爪蟾卵母细胞表达两类AA受体。一类由AA门控阳离子通道组成。反应由N-甲基-D-天冬氨酸（NMDA）、红藻氨酸以及在较小程度上由L-谷氨酸或使君子酸引起。第二类受体与细胞内第二信使途径偶联，激活卵母细胞编码的Ca 2+激活的Cl−电导。这种第二信使偶联AA受体可以被L-谷氨酸或使君子酸激活。DL-2-氨基-5-膦酸戊酸和D-α-氨基己二酸以不同效力抑制由NMDA或红藻氨酸盐激活的AA门控阳离子电导，但不抑制第二信使偶联AA受体。对NMDA的反应通过微摩尔水平的甘氨酸增强，并被Mg 2+、Zn 2+或MK-801抑制。剂量反应分析表明，红藻氨酸激活的AA门控阳离子电导需要两个激动剂分子的结合。为了研究分子组成，通过变性琼脂糖凝胶电泳对mRNA进行大小分级。实现了编码第二信使偶联AA受体的mRNA的比活性（nA/ng注射的mRNA）的约20倍纯化。相比之下，仅观察到编码AA门控通道的mRNA的轻微富集。这表明第二信使偶联AA受体由单一大小类别的mRNA编码，而AA门控阳离子通道由多种mRNA或大小分布不均匀的mRNA编码。
TheXenopus laevisoocyte expression system was used to study the molecular composition of mRNAs encoding acidic amino acid (AA) receptors from rat brain.Xenopusoocytes injected with poly(A) mRNA express two general classes of AA receptors. One class consists of AA‐gated cation channels. Responses are evoked by N‐methyl‐D‐aspartate (NMDA), by kainate, and to a lesser extent by L‐glutamate or quisqualate. The second class of receptor is coupled to an intracellular second messenger pathway activating an oocyte‐encoded Ca2+‐activated Cl−conductance. This second messenger‐coupled AA receptor can be activated by L‐glutamate or quisqualate. DL‐2‐amino‐5‐phosphonopentanoic acid and D‐α‐aminohexanedioic acid inhibit the AA‐gated cation conductances activated by NMDA or kainate with different potencies but do not inhibit the second messenger‐coupled AA receptor. Responses to NMDA are enhanced by micromolar level of glycine and are inhibited by Mg2+, Zn2+, or MK‐801. Dose‐response analysis reveals that the AA‐gated cation conductance activated by kainate requires the binding of two agonist molecules. To study the molecular composition, the mRNAs were size fractionated by denaturing agarose gel electrophoresis. About20‐fold purification in specific activity (nA/ng of mRNA injected) of mRNAs encoding the second messenger coupled AA receptor was achieved. In contrast, only a slight enrichment of the mRNAs encoding the AA‐gated channel was observed. This suggests that the second messenger coupled AA receptor is encoded by a single size class of mRNA, whereas the AA‐gated cation channel(s) is encoded by multiple species of mRNAs or by mRNAs whose size distribution is heterogeneous.