Effect of the A118G polymorphism on binding affinity, potency and agonist-mediated endocytosis, desensitization, and resensitization of the human mu-opioid receptor
Effect of the A118G polymorphism on binding affinity, potency and agonist-mediated endocytosis, desensitization, and resensitization of the human mu-opioid receptor
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DOI：
10.1111/j.1471-4159.2004.02340.x
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发表时间：
2004-05-01
影响因子：
4.7
通讯作者：
Höllt, V
中科院分区：
文献类型：
--
作者：
Beyer, A;Koch, T;Höllt, V
人类mu-阿片受体基因中最普遍的单核苷酸多态性（SNP） A118G预测了氨基酸位置40从天冬酰胺残基到天冬氨酸残基的氨基酸变化。这种N40D突变与阿片类药物成瘾的发展有关，先前有报道称其导致β -内啡肽结合亲和力增加和吗啡-6-葡萄糖醛酸盐效力降低。因此，在本研究中，我们研究了这种突变是否会影响人胚胎肾293细胞中稳定表达的人mu-阿片受体的结合亲和力、效力和/或激动剂诱导的脱敏、内化和再敏。除了在HEK293细胞中N40D的表达水平低于人mu-阿片受体（hMOR）外，我们的分析显示N40D与野生型受体之间没有明显的功能差异。吗啡、吗啡-6-葡糖苷和β -内啡肽对两种受体显示出相似的结合亲和力和效力。在阿片肽[D-Ala(2),N-MePhe(4)，甘油(5)]脑啡肽（DAMGO）和β -内啡肽]存在的情况下，n40d变体受体和hMOR都表现出强大的受体内化，但对吗啡或吗啡-6-葡萄糖醛酸盐没有反应。在长期使用吗啡治疗后，吗啡-6-葡糖苷或-内啡肽两种受体表现出相似的脱敏时间过程。此外，两种受体类型的受体再敏化率几乎相同。
The most prevalent single-nucleotide polymorphism (SNP) A118G in the human mu-opioid receptor gene predicts an amino acid change from an asparagine residue to an aspartatic residue in amino acid position 40. This N40D mutation, which has been implicated in the development of opioid addiction, was previously reported to result in an increased beta-endorphin binding affinity and a decreased potency of morphine-6-glucuronide. Therefore, in the present study we have investigated whether this mutation might affect the binding affinity, potency, and/or the agonist-induced desensitization, internalization and resensitization of the human mu-opioid receptor stably expressed in human embryonic kidney 293 cells. With the exception of a reduced expression level of N40D compared to human mu-opioid receptor (hMOR) in HEK293 cells, our analyses revealed no marked functional differences between N40D and wild-type receptor. Morphine, morphine-6-glucuronide and beta-endorphin revealed similar binding affinities and potencies for both receptors. Both the N40D-variant receptor and hMOR exhibited robust receptor internalization in the presence of the opioid peptide [D-Ala(2),N-MePhe(4),Glyol(5)]enkephalin (DAMGO) and beta-endorphin but not in response to morphine or morphine-6-glucuronide. After prolonged treatment with morphine, morphine-6-glucuronide or beta-endorphin both receptors showed similiar desensitization time courses. In addition, the receptor resensitization rates were nearly identical for both receptor types.