Chuang D M, Costa E
Neurochem Res. 1979 Dec;4(6):777-93. doi: 10.1007/BF00964474.
Following persistent stimulation of beta-adrenergic receptors of frog erythrocytes with (-)-isoproterenol, the cyclic adenosine 3',5'-monophosphate-dependent protein kinase (cAMP-dependent protein kinase) (EC 2.7.1.37) was activated for several hours. This activation outlasted the duration of the increase of cAMP content. Following a persistant stimulation of beta-adrenergic receptors with isoproterenol, the phosphorylation of selective membrane proteins was increased. This increase in phosphorylation lasted longer than 4 hr but less than 12 hr. Between 2 and 4 hr after receptor stimulation the loss of beta-adrenergic receptor from plasma membrane was maximal, and the phosphorylation of two membrane proteins characterized by molecular weights of 60,000 and 38,000 daltons was selectively enhanced. In addition we found that isolated erythrocytes are capable of synthesizing RNA and polypeptides and that incubation with (-)-isoproterenol indices a long-term delayed increase of the synthesis of erythrocyte proteins. This increase in the synthesis of proteins appears to require new RNA synthesis. Thus the possibility can be entertained that this delayed increase in protein synthesis participates in the new synthesis of receptor and is operative in the termination of beta-adrenergic receptor subsensitivity elicited by a persistent stimulation with (-)-isoproterenol.
用（-）-异丙肾上腺素持续刺激青蛙红细胞的β-肾上腺素能受体后，环腺苷酸依赖性蛋白激酶（cAMP依赖性蛋白激酶）（EC 2.7.1.37）被激活数小时。这种激活持续的时间超过了cAMP含量增加的持续时间。用异丙肾上腺素持续刺激β-肾上腺素能受体后，选择性膜蛋白的磷酸化增加。这种磷酸化增加持续超过4小时但少于12小时。在受体刺激后2至4小时之间，质膜上β-肾上腺素能受体的丢失达到最大，并且分子量为60,000和38,000道尔顿的两种膜蛋白的磷酸化被选择性增强。此外，我们发现分离的红细胞能够合成RNA和多肽，并且用（-）-异丙肾上腺素孵育会导致红细胞蛋白合成的长期延迟增加。这种蛋白质合成的增加似乎需要新的RNA合成。因此，可以设想这种蛋白质合成的延迟增加参与了受体的新合成，并在由（-）-异丙肾上腺素持续刺激引起的β-肾上腺素能受体亚敏感性的终止中起作用。
