Constitutively Active Mutant N111G of Angiotensin II Type 1 (AT1) Receptor Induces Homologous Internalization Through Mediation of AT1-Receptor Antagonist
Constitutively Active Mutant N111G of Angiotensin II Type 1 (AT1) Receptor Induces Homologous Internalization Through Mediation of AT1-Receptor Antagonist
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DOI：
10.1254/jphs.09202fp
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发表时间：
2009-11-01
影响因子：
3.5
通讯作者：
Nagatomo, Takafumi
中科院分区：
文献类型：
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作者：
Bhuiyan, Mohiuddin Ahmed;Hossain, Murad;Nagatomo, Takafumi
本研究探讨了血管紧张素Ⅱ 1型（AT（1））受体组成型活性突变体（CAM）N111 G的内化行为，并将结果与突变体的组成型活性机制相关联。还通过磷酸肌醇（IP）蓄积研究以及受体内化试验检查了缬沙坦、氯沙坦、坎地沙坦和替米沙坦的反向激动剂活性。野生型（WT）和N111 G突变体受体在COS-7细胞中瞬时表达，并测定了与激动剂和这四种AT（1）拮抗剂的结合亲和力。在存在和不存在化合物的情况下测量总IP的产生。还研究了WT和N111 G突变体受体的激动剂诱导的受体内化。尽管突变体显示出与用作WT的激动剂和拮抗剂相似的结合特征，但突变体的内化（19.56 +/-2.87%）远低于WT受体的内化（74.63 +/-1.00%）。在缬沙坦存在下，突变体的内化显著增加（63.22 +/- 0.03%），其在N111 G突变体中也显示出显著的反向激动剂活性。结果表明，缬沙坦可诱导AT（1）受体的CAM N111 G内化，这可能是AT（1）拮抗剂N111 G反向激动活性的重要特征。
The present study investigated the internalization behavior of the constitutively active mutant (CAM) N111G of angiotensin II type 1 (AT(1)) receptor and correlated the result with the mechanism of the constitutive activity of the mutant. The inverse agonist activity of valsartan, losartan, candesartan, and telmisartan was also examined by inositol phosphate (IP) accumulation study as well as receptor-internalization assay. Both wild-type (WT) and N111G Mutant receptors were transiently expressed in COS-7 cells and the binding affinities towards the agonist and these four AT(1) antagonists were determined. Production of total IP was measured in the presence and absence of the compounds. The agonist-induced receptor internalization of both WT and N111G mutant receptors was also investigated. Although the mutant showed similar binding characteristics with agonist and the antagonists used as WT, the internalization of the mutant was much lower (19.56 +/- 2.87%) than that of the WT receptor (74.63 +/- 1.00%). Internalization of the mutant significantly increased (63.22 +/- 0.03%) in the presence of valsartan, which also showed significant inverse agonist activity in the N111G mutant. The results indicate that internalization of CAM N111G of the AT(1) receptor is induced by the use of valsartan, which may be an important characteristic of inverse agonist activities of AT(1) antagonists in N111G.