Functional analysis of novel G-coupled receptor candidate for L-DOPA and structural determination of its ligands

我们提出L-3，4-二羟基苯丙氨酸(DOPA)作为终止于孤束核(NTS)的压力感受性传入神经元的候选神经递质。通过非洲爪哇非洲爪哇细胞的表达筛选，我们分离到线虫C06H5.7基因作为DOPA的候选受体。C06H5.7的电生理分析表明，C06H5.7对DOPA的非胺代谢产物有反应，但对自身没有反应。此前，我们曾报道3，4-二羟基苯甲醛(DHBALD)是C06H5.7的活性配体之一。一种气味苯甲醛，在化学结构上与DHBALD相似，具有电生理活性C06H5.7。虽然AWC感觉神经元能感受到低浓度的苯甲醛，但在AWC中尚未检测到C06H5.7的表达。C06H5.7的一个零突变候选Nj66在苯甲醛的诱变作用下没有缺陷。另一方面，在ASH感觉神经元感受到的高浓度苯甲醛是线虫的一种化学反应物，但其受体尚未确定。为了测试C06H5.7参与厌恶机制的可能性，我们进行了Nj66的厌恶实验，并检测了C06H5.7在ASH中的表达。然而，当这些配体被微量注射到孤束核中时，对麻醉大鼠的血压和心率没有影响。

We proposed L-3,4-dihydroxyphenylalanine (DOPA) as a neurotransmitter candidate of baroreceptor afferent neurons terminating in the nucleus tractus solitarii (NTS). We have isolated C.elegans C06H5.7 gene as a receptor candidate for DOPA through expression screening using Xenopus laevisoocytes. Electrophysiological analyses of C06H5.7 showed that C06H5.7 responded to non-amine metabolites of DOPA, but did not to itself. Previously, we have reported that 3,4-dihydroxybenzaldehyde (DHBALD) acts as one of active ligands for C06H5.7. An odorant benzaldehyde that is similar to DHBALD in the chemical structure electrophysiologically activated C06H5.7. Although benzaldehyde at low concentrations sensed by AWC sensory neurons is a chemoattractants in C.eleagans, expression of C06H5.7 have not yet been detected in AWC. A null mutant candidate for C06H5.7, nj66,was not defective in the attraction by benzaldehyde. On the other hand, benzaldehyde at high concentrations sensed by ASH sensory neurons is a chemorepellent in C.eleagans, but its receptor has not yet been identified. To test the possibility that C06H5.7 is involved in the aversive mechanisms, we are performing the aversion assay of nj66 and detecting the expression of C06H5.7 in the ASH. However, these ligands produced no effects on blood pressure and hear rates of anesthetized rats, when these were microinjected into the nucleus tractus solitarii.