Gerhardt C C, Bakker R A, Piek G J, Planta R J, Vreugdenhil E, Leysen J E, Van Heerikhuizen H
Department of Biochemistry and Molecular Biology, Research Institute Neurosciences, Vrije Universiteit, Amsterdam, The Netherlands.
Mol Pharmacol. 1997 Feb;51(2):293-300. doi: 10.1124/mol.51.2.293.
We describe the cloning and functional expression of a cDNA encoding a novel G protein-coupled receptor, which was isolated from the central nervous system of the pond snail Lymnaea stagnalis. The amino acid sequence predicted by this cDNA shows highest similarity with the sequence of the Locusta tyramine receptor, the Drosophila tyramine/octopamine receptor, and the mammalian alpha-adrenergic receptors. On expression in mammalian cells, [3H]rauwolscine, an alpha2-adrenergic receptor antagonist, binds with high affinity (K(D) = 2.9 x 10(-9) M) to the receptor. Of several tested neurotransmitters, octopamine (which is considered to be the invertebrate counterpart of norepinephrine) showed the highest affinity (1.9 x 10(-6) M) for the receptor. Therefore, we consider this receptor to be the first true octopamine receptor to be cloned. The ligand binding properties of the novel receptor, designated Lym oa1, seem to be distinct from any of the binding profiles described for octopamine receptors in tissue preparations. Although the pharmacological profile of Lym oa1 shows some similarity with that of Tyr/Oct-Dro and Tyr-Loc, there are also clear differences. In particular, phentolamine, chlorpromazine, and mianserine display markedly higher affinities for Lym oa1 than for the insect receptors. As far as the vertebrate adrenergic receptors are concerned, the ligand binding properties of Lym oa1 resemble alpha2-adrenergic receptors more than they do alpha- or beta-adrenergic receptors. Octopaminergic stimulation of Lym oa1 induces an increase in both inositol phosphates and cAMP (EC50 = 9.1 x 10(-7) M and 5.1 x 10(-6) M, respectively). This is in contrast to the signal transduction pathways described for the related tyramine- and alpha2-adrenergic receptors, which couple in an inhibitory way to adenylyl cyclase.
我们描述了从池塘蜗牛椎实螺的中枢神经系统中分离出的一种编码新型G蛋白偶联受体的cDNA的克隆及功能表达。该cDNA预测的氨基酸序列与飞蝗酪胺受体、果蝇酪胺/章鱼胺受体以及哺乳动物α-肾上腺素能受体的序列具有最高的相似性。在哺乳动物细胞中表达时，α2-肾上腺素能受体拮抗剂[3H]萝芙木碱以高亲和力（K(D)=2.9×10(-9)M）与该受体结合。在几种经过测试的神经递质中，章鱼胺（被认为是去甲肾上腺素在无脊椎动物中的对应物）对该受体显示出最高的亲和力（1.9×10(-6)M）。因此，我们认为该受体是第一个被克隆的真正的章鱼胺受体。这种被命名为Lym oa1的新型受体的配体结合特性似乎与组织制剂中描述的任何章鱼胺受体的结合模式都不同。尽管Lym oa1的药理学特征与Tyr/Oct-Dro和Tyr-Loc的药理学特征有一些相似之处，但也存在明显差异。特别是，酚妥拉明、氯丙嗪和米安色林对Lym oa1的亲和力明显高于对昆虫受体的亲和力。就脊椎动物肾上腺素能受体而言，Lym oa1的配体结合特性与α2-肾上腺素能受体的相似性高于与α-或β-肾上腺素能受体的相似性。对Lym oa1的章鱼胺能刺激会导致肌醇磷酸和cAMP均增加（EC50分别为9.1×10(-7)M和5.1×10(-6)M）。这与相关酪胺和α2-肾上腺素能受体所描述的信号转导途径相反，后者以抑制方式与腺苷酸环化酶偶联。
