Impaired formation of beta-adrenergic receptor-nucleotide regulatory protein complexes in pseudohypoparathyroidism.
Impaired formation of beta-adrenergic receptor-nucleotide regulatory protein complexes in pseudohypoparathyroidism.
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假性甲状旁腺功能减退症中β-肾上腺素能受体-核苷酸调节蛋白复合物的形成受损。
DOI：
10.1172/jci111336
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
Lefkowitz,RJ
中科院分区：
文献类型：
--
作者：
Heinsimer,JA;Davies,AO;Downs,RW;Levine,MA;Spiegel,AM;Drezner,MK;DeLean,A;Wreggett,KA;Caron,MG;Lefkowitz,RJ
一些假性甲状旁腺功能减退症（PHP-Ia）患者的细胞膜中存在腺苷酸环化酶系统的鸟嘌呤核苷酸调节蛋白（N）活性降低，而其他患者的N活性正常（PHP-Ib）。PHP-Ia中低N活性导致各种组织中激素（H）可刺激的腺苷酸环化酶减少，这可能是由于形成由H、受体（R）和N组成的激动剂特异性高亲和力复合物的能力降低。为了验证这一假设，我们比较了5例PHP-Ia患者（N = 45%的对照），5例PHP-Ib患者（N = 97%）和5例对照受试者红细胞膜中β-肾上腺素能激动剂的特异性结合特性。通过增加与[125 I]吲哚洛尔竞争的β-激动剂异丙肾上腺素的浓度产生的竞争曲线是浅的（斜率因子小于1），并且计算机拟合到具有对激动剂的相应高和低亲和力的双态模型。PHP-Ia患者的激动剂竞争曲线显著向右移动（P <0.02），这是由于高亲和力状态的β-肾上腺素能受体百分比显著降低（P <0.01）的结果，从PHP-Ib的64 +/- 22%和对照组的56 +/- 5%降低到PHP-Ia的10 +/- 8%。激动剂竞争曲线被计算机拟合为两步反应的“三元复合物”模型：平衡中的H + R + N HR +平衡HRN中的N。建模是一致的功能浓度的N减少60%，并在与生化测定的红细胞N蛋白活性的降低是很好的协议。这些在红细胞中的体外发现与最近的观察结果结合在一起，即在患有PHP的患者中体内异丙肾上腺素刺激的腺苷酸环化酶活性降低（Carlson，H. E、和A. S. Brickman，1983，J. Clin. Endocrinol. Metab. 56：1323-1326）与N是与R和腺苷酸环化酶两者相互作用的双功能蛋白的概念一致。在PHP-Ia患者中，可能是单一的分子和遗传缺陷导致HRN形成减少和腺苷酸环化酶活性降低，而在PHP-Ib患者中，生化损伤似乎不影响HRN复合物的形成。
Decreased activity of the guanine nucleotide regulatory protein (N) of the adenylate cyclase system is present in cell membranes of some patients with pseudohypoparathyrodism (PHP-Ia) whereas others have normal activity of N (PHP-Ib). Low N activity in PHP-Ia results in a decrease in hormone (H)-stimulatable adenylate cyclase in various tissues, which might be due to decreased ability to form an agonist-specific high affinity complex composed of H, receptor (R), and N. To test this hypothesis, we compared beta-adrenergic agonist-specific binding properties in erythrocyte membranes from five patients with PHP-Ia (N = 45% of control), five patients with PHP-Ib (N = 97%), and five control subjects. Competition curves that were generated by increasing concentrations of the beta-agonist isoproterenol competing with [125I]pindolol were shallow (slope factors less than 1) and were computer fit to a two-state model with corresponding high and low affinity for the agonist. The agonist competition curves from the PHP-Ia patients were shifted significantly (P less than 0.02) to the right as a result of a significant (P less than 0.01) decrease in the percent of beta-adrenergic receptors in the high affinity state from 64 +/- 22% in PHP-Ib and 56 +/- 5% in controls to 10 +/- 8% in PHP-Ia. The agonist competition curves were computer fit to a "ternary complex" model for the two-step reaction: H + R + N in equilibrium HR + N in equilibrium HRN. The modeling was consistent with a 60% decrease in the functional concentration of N, and was in good agreement with the biochemically determined decrease in erythrocyte N protein activity. These in vitro findings in erythrocytes taken together with the recent observations that in vivo isoproterenol-stimulated adenylate cyclase activity is decreased in patients with PHP (Carlson, H. E., and A. S. Brickman, 1983, J. Clin. Endocrinol. Metab. 56:1323-1326) are consistent with the notion that N is a bifunctional protein interacting with both R and the adenylate cyclase. It may be that in patients with PHP-Ia a single molecular and genetic defect accounts for both decreased HRN formation and decreased adenylate cyclase activity, whereas in PHP-Ib the biochemical lesion(s) appear not to affect HRN complex formation.