Unique allosteric regulation of 5-hydroxytryptamine receptor-mediated signal transduction by oleamide
Unique allosteric regulation of 5-hydroxytryptamine receptor-mediated signal transduction by oleamide
复制标题
DOI：
10.1073/pnas.94.25.14115
复制
发表时间：
1997-12-09
影响因子：
11.1
通讯作者：
Sutcliffe, JG
中科院分区：
文献类型：
--
作者：
Thomas, EA;Carson, MJ;Sutcliffe, JG
在培养的哺乳动物细胞中研究了油酰胺（一种从睡眠剥夺的猫的脑脊液中分离的酰胺化脂质）对5-羟色胺受体介导的反应的影响。在内源性表达5-羟色胺（2A）（5 HT（2A））受体的大鼠P11细胞中，油酰胺显着增强5 HT诱导的磷酸肌醇水解。在表达5 HT（7）受体亚型的HeLa细胞中，油酰胺引起cAMP积累的浓度依赖性增加，但疗效低于5 HT。在未转染的HeLa细胞中未观察到这种效应。氯氮平不能阻止由油酰胺引起的cAMP增加，酮色林引起约65%的下降。在5-HT存在下，油酰胺对cAMP有相反的作用，对5-HT的量效曲线产生难以克服的拮抗作用，但对异丙肾上腺素或毛喉素引起的cAMP水平没有影响。这些结果表明，油酰胺可以调节5 HT介导的信号转导在不同亚型的哺乳动物5 HT受体。此外，我们的数据表明，油酰胺作用于5 HT（7）受体上的一个明显的变构位点，并通过激活该位点来激发功能反应。这代表了5 HT G蛋白偶联受体的独特激活机制，并表明G蛋白偶联神经递质受体可能像它们的离子型对应物一样起作用（即，γ-氨基丁酸A型受体），因为在受体上可能存在几个结合位点，其以不同的功效调节功能活性。
The effects of oleamide, an amidated lipid isolated from the cerebrospinal fluid of sleep-deprived cats, on serotonin receptor-mediated responses were investigated in cultured mammalian cells. In rat P11 cells, which endogenously express the 5-hydroxytryptamine(2A) (5HT(2A)) receptor, oleamide significantly potentiated 5HT-induced phosphoinositide hydrolysis. In HeLa cells expressing the 5HT(7) receptor subtype, oleamide caused a concentration-dependent increase in cAMP accumulation but with lower efficacy than that observed by 5HT. This effect was not observed in untransfected HeLa cells. Clozapine did not prevent the increase in cAMP elicited by oleamide, and ketanserin caused an approximate to 65% decrease. In the presence of 5HT, oleamide had the opposite effect on cAMP, causing insurmountable antagonism of the concentration-effect curve to 5HT, but had no effect on cAMP levels elicited by isoproterenol or forskolin. These results indicate that oleamide can modulate 5HT-mediated signal transduction at different subtypes of mammalian 5HT receptors. Additionally, our data indicate that oleamide acts at an apparent allosteric site on the 5HT(7) receptor and elicits functional responses via activation of this site. This represents a unique mechanism of activation for 5HT G protein-coupled receptors and suggests that G protein-coupled neurotransmitter receptors may act like their iontropic counterparts (i.e., gamma-aminobutyric acid type A receptors) in that there may be several binding sites on the receptor that regulate functional activity with varying efficacies.