Two distinct pathways for cAMP-mediated down-regulation of the beta 2-adrenergic receptor. Phosphorylation of the receptor and regulation of its mRNA level.
Two distinct pathways for cAMP-mediated down-regulation of the beta 2-adrenergic receptor. Phosphorylation of the receptor and regulation of its mRNA level.
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cAMP 介导的 β2-肾上腺素能受体下调有两种不同的途径。
DOI：
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发表时间：
1989
影响因子：
4.8
通讯作者：
R. Lefkowitz
中科院分区：
文献类型：
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作者：
M. Bouvier;S. Collins;B. O'dowd;P. T. Campbell;A. Blasi;B. Kobilka;C. Macgregor;G. Irons;M. G. Caron;R. Lefkowitz
我们研究了环 AMP 介导的 β 2-肾上腺素受体 (β 2AR) 调节。在表达野生型人β2AR受体（CH-β2）或缺乏cAMP依赖性蛋白激酶磷酸化共有序列的突变型受体的中国仓鼠成纤维细胞（CHW）中评估了cAMP的作用。用cAMP类似物二丁酰cAMP (Bt2cAMP)处理CH-β2细胞会诱导β2AR数量的时间依赖性“下调”。受体的下调伴随着 β2AR mRNA 稳态水平的下降。此外，Bt2cAMP 处理会诱导膜相关 β2AR 磷酸化水平增加。 β2AR mRNA 的减少和受体磷酸化的增强都是快速的，并且发生在受体丧失之前。 Bt2cAMP 诱导的 β2AR 下调具有浓度依赖性，并可被其他生物活性环核苷酸类似物 8-Br-cAMP、毛喉素 (forskolin) 和磷酸二酯酶抑制剂异丁基甲基黄嘌呤所模拟。在表达缺乏推定蛋白激酶 A 磷酸化位点的受体的 CHW 细胞系中，Bt2cAMP 诱导的 β2AR 磷酸化被完全消除。在这些细胞中，cAMP 产生的 β2AR 受体数量的下调显着减慢，而 β2AR mRNA 水平的降低与在 CH-β2 细胞中观察到的相同。这些数据表明，cAMP 至少可以通过两种途径减少细胞中 β2AR 的数量：一种涉及 cAMP 依赖性蛋白激酶对受体的磷酸化，另一种导致稳态 β2AR mRNA 水平降低。
We have studied cyclic AMP-mediated regulation of the beta 2-adrenergic receptor (beta 2AR). The effects of cAMP were assessed in Chinese hamster fibroblast (CHW) cells expressing either the wild type human beta 2AR receptor (CH-beta 2) or mutated forms of the receptor lacking the consensus sequences for phosphorylation by the cAMP-dependent protein kinase. Treatment of the CH-beta 2 cells with the cAMP analogue dibutyryl cAMP (Bt2cAMP) induces a time-dependent "down-regulation" of the number of beta 2AR. This down-regulation of the receptors is accompanied by a decline in the steady state level of beta 2AR mRNA. Moreover, the treatment with Bt2cAMP induces an increase in the phosphorylation level of the membrane-associated beta 2AR. Both the reduction in beta 2AR mRNA and the enhanced phosphorylation of the receptor are rapid and precede the loss of receptor. The down-regulation of beta 2AR induced by Bt2cAMP is concentration-dependent and mimicked by the other biologically active cyclic nucleotide analogue, 8-Br-cAMP, by forskolin, and by the phosphodiesterase inhibitor, isobutylmethylxanthine. In the CHW cell lines expressing receptors lacking the putative protein kinase A phosphorylation sites, the Bt2cAMP-induced phosphorylation of beta 2AR is completely abolished. In these cells the down-regulation of beta 2AR receptor number produced by cAMP is significantly slowed, whereas the reduction in beta 2AR mRNA level is equivalent to that observed in CH-beta 2 cells. These data indicate that there are at least two pathways by which cAMP may decrease the number of beta 2ARs in cells: one involves phosphorylation of the receptor by the cAMP-dependent protein kinase and the other leads to a reduction in steady state beta 2AR mRNA levels.