Shen Y, Monsma F J, Metcalf M A, Jose P A, Hamblin M W, Sibley D R
Molecular Neuropharmacology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
J Biol Chem. 1993 Aug 25;268(24):18200-4.
We have utilized the polymerase chain reaction technique to selectively amplify a G protein-coupled receptor cDNA from rat kidney proximal convoluted tubule mRNA, which exhibits high homology with previously cloned serotonin receptors. Sequencing of a full-length clone isolated from a rat hippocampal cDNA library revealed an open reading frame of 1,212 base pairs encoding a 404-residue protein with seven hydrophobic regions predicted to represent transmembrane-spanning domains. Within the transmembrane regions, this receptor was found to be 44-50% identical with various members of the 5-HT1, 5-HT5, and 5-HT6 subfamilies with lower (37-40%) homology to the 5-HT2-like receptors. Northern blots revealed a approximately 3.6-kilobase transcript localized in various brain regions with the following rank order of abundance: hypothalamus > hippocampus = mesencephalon > cerebral cortex = olfactory bulb > olfactory tubercle. Expression of this clone in COS-7 cells resulted in the appearance of high affinity, saturable binding of [3H]lysergic acid diethylamide ([3H]LSD; KD = 5 nM) and [3H]serotonin ([3H]5-HT; KD = 1 nM). Among endogenous biogenic amines, only 5-HT completely inhibited radioligand binding. The inhibition of radioligand binding by other serotonergic agents revealed a pharmacological profile that does not correlate with any previously described serotonin receptor subtype. In addition, this receptor exhibits high affinity for a number of tricyclic antipsychotic and antidepressant drugs including clozapine, loxapine, and amitriptyline. In HEK-293 cells stably transfected with this receptor, serotonin elicits a potent stimulation of adenylylcyclase activity. The distinct structural and pharmacological properties of this receptor suggests that it represents a completely novel serotonin receptor subtype, which we propose to designate 5-HT7. Based on its pharmacology and its localization to limbic and cortical regions of the brain, it is likely that this receptor may play a role in several neuropsychiatric disorders that involve serotonergic systems.
我们利用聚合酶链反应技术，从大鼠肾近端曲管mRNA中选择性扩增出一种G蛋白偶联受体cDNA，该cDNA与先前克隆的5-羟色胺受体具有高度同源性。对从大鼠海马cDNA文库中分离出的一个全长克隆进行测序，发现其开放阅读框为1212个碱基对，编码一个404个氨基酸残基的蛋白质，该蛋白质有7个疏水区域，预计代表跨膜结构域。在跨膜区域内，发现该受体与5-HT1、5-HT5和5-HT6亚家族的各个成员有44%-50%的同一性，与5-HT2样受体的同源性较低（37%-40%）。Northern印迹显示，在不同脑区有一个约3.6千碱基的转录本，其丰度顺序如下：下丘脑>海马=中脑>大脑皮层=嗅球>嗅结节。该克隆在COS-7细胞中的表达导致出现了对[3H]麦角酰二乙胺（[3H]LSD；KD = 5 nM）和[3H]5-羟色胺（[3H]5-HT；KD = 1 nM）的高亲和力、可饱和结合。在内源性生物胺中，只有5-羟色胺能完全抑制放射性配体结合。其他5-羟色胺能药物对放射性配体结合的抑制作用显示出一种药理学特征，与任何先前描述的5-羟色胺受体亚型均不相关。此外，该受体对包括氯氮平、洛沙平及阿米替林在内的多种三环类抗精神病药和抗抑郁药具有高亲和力。在用该受体稳定转染的HEK-293细胞中，5-羟色胺能有效刺激腺苷酸环化酶活性。该受体独特的结构和药理学特性表明它代表一种全新的5-羟色胺受体亚型，我们建议将其命名为5-HT7。基于其药理学特性及其在脑边缘和皮质区域的定位，该受体很可能在涉及5-羟色胺能系统的多种神经精神疾病中发挥作用。
