Genetic analysis of beta-adrenergic receptor internalization and down-regulation.
Genetic analysis of beta-adrenergic receptor internalization and down-regulation.
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β-肾上腺素能受体内化和下调的遗传分析。
DOI：
10.1073/pnas.82.1.129
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发表时间：
1985
影响因子：
11.1
通讯作者：
Insel,PA
中科院分区：
文献类型：
--
作者：
Mahan,LC;Koachman,AM;Insel,PA
我们使用野生型和变异的t淋巴瘤细胞系S49来探索腺苷酸环化酶连接的β -肾上腺素能受体的内化和下调。内化被定义为在4℃时完整细胞上通过拮抗剂[3H] cbp -12177或[125I]iodocyanopindolol检测到的“表面受体”的损失，而下调被定义为受体总细胞含量的损失[（125I]iodocyanopindolol结合在37℃时测定）。在野生型细胞中，β -肾上腺素能激动剂异丙肾上腺素诱导了表面受体的快速（t1 /2，大约等于1分钟）和可逆的损失。表面位点丢失的速率与S49细胞β -肾上腺素能受体介导的环AMP的脱敏速率相似。一系列S49变异体（cyc-， UNC, H21a）在NS（鸟嘌呤核苷酸结合蛋白，将β受体与腺苷酸环化酶偶联）中发生病变或缺乏camp依赖性蛋白激酶活性（kin-），其表面位点的损失与野生型细胞相当。相比之下，NS病变的S49变异细胞表现出不同程度的β -肾上腺素能受体下调率。在野生型和kin- S49细胞中，β受体下调了大约等于4小时的1/2。在改变受体与NS耦合的cyc-和UNC变体中，下调被减弱，但在保留受体与NS相互作用的H21a变体中，下调速度更快。在野生型、UNC和H21a细胞中，下调后受体的恢复速度相似（t1 /2，大约等于6小时）。这些结果表明β -肾上腺素能受体的内化可能是必要的，但不足以解释S49细胞中激动剂诱导的受体下调。S49变异体下调过程中的可变表达表明，受体-神经神经系统相互作用调节了与腺苷酸环化酶刺激相关的受体的命运。
We have used wild-type and variants of the T-lymphoma cell line S49 to explore internalization and down-regulation of adenylate cyclase-linked beta-adrenergic receptors. Internalization was defined by the loss in "surface receptors" detected at 4 degrees C on intact cells by the antagonists [3H]CGP-12177 or [125I]iodocyanopindolol, whereas down-regulation was defined as the loss in total cellular content of receptors [( 125I]iodocyanopindolol binding assayed at 37 degrees C). In wild-type cells, the beta-adrenergic agonist isoproterenol induced a rapid (t 1/2, approximately equal to 1 min) and reversible loss in surface receptors. The surface sites were lost at a rate similar to the rate of desensitization of beta-adrenergic receptor-mediated cyclic AMP generation of S49 cells. A series of S49 variants (cyc-, UNC, H21a) having lesions in NS (the guanine nucleotide binding protein that couples beta-receptors to adenylate cyclase) or with absent cAMP-dependent protein kinase activity (kin-), had a loss in surface sites that was equivalent to that of wild-type cells. By contrast, S49 variant cells having lesions in NS showed variable rates and extents of down-regulation of beta-adrenergic receptors. In wild-type and kin- S49 cells, beta-receptors down-regulated with a t 1/2 of approximately equal to 4 hr. Down-regulation was blunted in the cyc- and UNC variants that have altered coupling of receptors to NS, but it was faster in the H21a variant that retains receptor-NS interaction. Recovery of receptors after down-regulation occurred at a similar rate (t 1/2, approximately equal to 6 hr) in wild-type, UNC, and H21a cells. These results demonstrate that internalization of beta-adrenergic receptors may be necessary, but is not sufficient, to explain agonist-induced receptor down-regulation in S49 cells. The variable expression in the development of down-regulation in S49 variants implies that receptor-NS interaction regulates the fate of receptors linked to the stimulation of adenylate cyclase.