Inverse Agonism of SQ 29,548 and Ramatroban on Thromboxane A2 Receptor
Inverse Agonism of SQ 29,548 and Ramatroban on Thromboxane A2 Receptor
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DOI：
10.1371/journal.pone.0085937
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发表时间：
2014-01-23
期刊：
影响因子：
3.7
通讯作者：
Chelikani, Prashen
中科院分区：
文献类型：
--
作者：
Chakraborty, Raja;Bhullar, Rajinder P.;Chelikani, Prashen
G蛋白偶联受体（gpcr）即使在没有激动剂的情况下也表现出一定程度的基础活性，这种现象被称为构成活性。已知gpcr中的这种组成活性在人类疾病中具有重要的病理生理作用。血栓素A2受体（thromboxane A2 receptor， TP）是一种GPCR，通过与类前列腺素血栓素A2的结合促进血栓形成。TP功能障碍广泛涉及诸如出血性疾病、高血压和心血管疾病等病理生理状况。最近，我们报道了TP中几个组成型活性突变体（CAMs）的特征，包括一个遗传变异A160T。使用这些CAMs作为报告者，我们现在在HEK293T细胞中测试TP， SQ 29,548, Ramatroban， L-670596和双氯芬酸的已知拮抗剂的逆激动剂特性。有趣的是，SQ 29,548降低了WT-TP和CAMs的基础活性，而Ramatroban只能降低CAMs的基础活性。双氯芬酸和L-670596对WT-TP或CAMs基础活性的降低没有统计学意义。为了研究这些化合物对人类血小板功能的作用，我们测试了它们对人类巨核细胞为基础的血小板激活系统的影响。SQ 29,548和Ramatroban均可降低A160T基因变异的血小板活性。综上所述，我们的研究结果表明SQ 29,548和Ramatroban是TP的反向激动剂，而L-670596和双氯芬酸是中性拮抗剂。我们的发现在TP介导的病理生理条件的治疗中具有重要的治疗应用。
G protein-coupled receptors (GPCRs) show some level of basal activity even in the absence of an agonist, a phenomenon referred to as constitutive activity. Such constitutive activity in GPCRs is known to have important pathophysiological roles in human disease. The thromboxane A2 receptor (TP) is a GPCR that promotes thrombosis in response to binding of the prostanoid, thromboxane A2. TP dysfunction is widely implicated in pathophysiological conditions such as bleeding disorders, hypertension and cardiovascular disease. Recently, we reported the characterization of a few constitutively active mutants (CAMs) in TP, including a genetic variant A160T. Using these CAMs as reporters, we now test the inverse agonist properties of known antagonists of TP, SQ 29,548, Ramatroban, L-670596 and Diclofenac, in HEK293T cells. Interestingly, SQ 29,548 reduced the basal activity of both, WT-TP and the CAMs while Ramatroban was able to reduce the basal activity of only the CAMs. Diclofenac and L-670596 showed no statistically significant reduction in basal activity of WT-TP or CAMs. To investigate the role of these compounds on human platelet function, we tested their effects on human megakaryocyte based system for platelet activation. Both SQ 29,548 and Ramatroban reduced the platelet hyperactivity of the A160T genetic variant. Taken together, our results suggest that SQ 29,548 and Ramatroban are inverse agonists for TP, whereas, L-670596 and Diclofenac are neutral antagonists. Our findings have important therapeutic applications in the treatment of TP mediated pathophysiological conditions.