Subtype-specific desensitization of human endothelin ETA and ETB receptors reflects differential receptor phosphorylation
Subtype-specific desensitization of human endothelin ETA and ETB receptors reflects differential receptor phosphorylation
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DOI：
10.1021/bi9708848
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发表时间：
1997-10-28
期刊：
影响因子：
2.9
通讯作者：
Schroeder, C
中科院分区：
文献类型：
--
作者：
Cramer, H;MullerEsterl, W;Schroeder, C
内皮素通过G蛋白偶联受体调节哺乳动物的血压。存在两种受体亚型，ETA和ETB，其激动剂特征不同。在这里，我们展示了这些内皮素受体失活的亚型特异性差异。使用改良的磷酸肌醇积累测定，我们发现内皮素-I刺激ETA导致该亚型的持续活化，甚至在激动剂施用后20分钟仍保持其初始活性的>30%，而ETB在激动剂刺激后迅速失活，在内皮素应用后5分钟内失去其初始活性的>80%。受体失活的差异反映在受体磷酸化的亚型特异性差异。而ETA未能进行配体诱导的磷酸化，ETB迅速磷酸化的激动剂刺激。相比之下，配体诱导的内化的动力学基本上是相同的受体亚型，这表明内皮素受体内化是独立的配体诱导的受体磷酸化。有趣的是，在ETA失活的时间过程和ETA内化之间观察到强相关性。因此，我们的数据表明人内皮素受体的亚型特异性失活：ETB的情况下受体磷酸化快，ETA的情况下受体内化慢。内皮素受体的亚型特异性调节可能通过快速下调ETB受体解释内皮素的短期降压作用，以及由于持续的ETA激活引起的孤独持续的高血压作用。
Endothelins regulate blood pressure in mammals through G protein-coupled receptors. Two receptor subtypes, ETA and ETB, exist which differ by their agonist profiles. Here we show subtype-specific differences in the inactivation of these endothelin receptors. Using a modified inositol phosphate accumulation assay, we found that stimulation of ETA by endothelin-l results in sustained activation of the subtype, retaining >30% of its initial activity even 20 min after agonist administration, whereas the ETB rapidly deactivated after agonist stimulation, losing >80% of its initial activity within 5 min after endothelin application. The discrepancy in receptor inactivation is reflected by subtype-specific differences in receptor phosphorylation. Whereas ETA failed to undergo ligand-induced phosphorylation, the ETB was rapidly phosphorylated in response to agonist stimulation. BY contrast, the kinetics of ligand-induced internalization were essentially identical for the receptor subtypes, suggesting endothelin receptor internalization being independent of ligand-induced receptor phosphorylation. Interestingly, a strong correlation was observed between the time course of ETA inactivation and ETA internalization. Therefore, our data suggest a subtype-specific inactivation of human endothelin receptors: fast receptor phosphorylation in the case of ETB and slow receptor internalization in the case of ETA. Subtype-specific modulation of endothelin receptors may account for the short-term hypotensive effects of endothelins via rapidly downregulating ETB receptors and the lone-lasting hypertensive effects due to sustained ETA activation.