Subtype-specific kinetics of inhibitory adenosine receptor internalization are determined by sensitivity to phosphorylation by G protein-coupled receptor kinases
Subtype-specific kinetics of inhibitory adenosine receptor internalization are determined by sensitivity to phosphorylation by G protein-coupled receptor kinases
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DOI：
10.1124/mol.57.3.546
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发表时间：
2000-03-01
影响因子：
3.6
通讯作者：
Palmer, TM
中科院分区：
文献类型：
--
作者：
Ferguson, G;Watterson, KR;Palmer, TM
尽管与相同种类的抑制性G蛋白偶联并结合相同的生理配体，但人A（1）和大鼠A（3）腺苷受体（AR）对持续的激动剂暴露的反应以不同的速率脱敏。这是由于A（3）AR（而不是A（1）AR）能够作为G蛋白偶联受体激酶（GRK）家族成员快速磷酸化和脱敏的底物。本研究的目的是调查这些差异是否也表现在他们的能力进行激动剂依赖性受体内化。我们首次报道了A（3）AR在短期暴露于第二信使调节激酶的激动剂而不是激活剂时发生了深刻的内化。A（3）AR选择性拮抗剂MRS 1523阻断A（3）AR磷酸化和内化。此外，与A（1）AR的内化非常缓慢（t（1/2）= 90分钟）相反，A（3）AR在受体磷酸化开始后的一段时间内迅速内化（t（1/2）= 10分钟）。一个非磷酸化的A（3）AR突变体在60分钟内不能内化，这表明受体磷酸化是A（3）AR快速内化的必要条件。此外，融合到A（1）AR上的A（3）AR C-末端结构域包含GRKs磷酸化位点，在所得嵌合AR上赋予快速激动剂诱导的内化动力学（t（1/2）= 10 min）。总之，这些数据表明GRK刺激的A（3）AR C-末端结构域内苏氨酸残基的磷酸化是观察受体快速激动剂介导的内化的必要条件。
Despite coupling to the same class of inhibitory G proteins and binding the same physiological ligand, the human A(1) and rat A(3) adenosine receptors (ARs) desensitize at different rates in response to sustained agonist exposure. This is due to the ability of the A(3)AR, but not the A(1)AR, to serve as a substrate for rapid phosphorylation and desensitization by members of the G protein-coupled receptor kinase (GRK) family. The aim of this study was to investigate whether these differences were also manifested in their abilities to undergo agonist-dependent receptor internalization. For the first time, we report that A(3)ARs internalize profoundly in response to short-term exposure to agonist but not activators of second messenger-regulated kinases. The A(3)AR-selective antagonist MRS1523 blocked both A(3)AR phosphorylation and internalization. Moreover, in contrast to the A(1)AR, which internalized quite slowly (t(1/2) = 90 min), A(3)ARs internalized rapidly (t(1/2) = 10 min) over a time frame that followed the onset of receptor phosphorylation. A nonphosphorylated A(3)AR mutant failed to internalize over a 60-min time course, suggesting that receptor phosphorylation was essential for rapid A(3)AR internalization to occur. In addition, fusion onto the A(1)AR of the A(3)AR C-terminal domain containing the sites for phosphorylation by GRKs conferred rapid agonist-induced internalization kinetics (t(1/2) = 10 min) on the resulting chimeric AR. In conclusion, these data suggest that GRK-stimulated phosphorylation of threonine residues within the C-terminal domain of the A(3)AR is obligatory to observe rapid agonist-mediated internalization of the receptor.