Oyen O, Eskild W, Beebe S J, Hansson V, Jahnsen T
Institute of Pathology, Rikshospitalet, Oslo, Norway.
Mol Endocrinol. 1988 Nov;2(11):1070-6. doi: 10.1210/mend-2-11-1070.
In the present study we have examined the effect of long-term stimulation with (Bu)2cAMP on mRNA levels for the hormone responsive regulatory subunit (RII beta) of cAMP-dependent protein kinase in cultured rat Sertoli cells. The effects of the same treatment on two other mRNAs [androgen binding protein (ABP) and cellular retinol binding protein (cRBP)], shown to be regulated by cAMP, were examined simultaneously. The addition of (Bu)2cAMP (0.1 mM) to primary Sertoli cell cultures, for 14 and 24 h, caused a 50- to 60-fold stimulation in the steady state levels of mRNA for RII beta. During the same period of stimulation, we also observed a significant increase (2- to 3-fold) in the mRNA levels for ABP, and a 80% decrease in the mRNA levels for cRBP. Continued stimulation for 36 and 48 h was associated with a significant time-dependent decrease in the mRNA level for RII beta, in spite of the continuous presence of (Bu)2cAMP (0.1 mM) in the medium. This reduced response by long term stimulation with (Bu)2cAMP appears to be specific for RII beta, since mRNA for ABP remained elevated and mRNA for cRBP remained depressed during the entire period of cAMP stimulation. Our data demonstrate the presence of a biphasic type of regulation at the mRNA level, specific for the regulatory subunit RII beta of cAMP-dependent protein kinase. This response may be analogous to the desensitization mechanisms observed at other levels of the cAMP signalling pathway. For proteins constituting part of the signal transduction pathway this type of biphasic regulation, may be particularly important in maintaining homeostasis in the cell.
在本研究中，我们检测了用（二丁酰）环磷腺苷（（Bu）2cAMP）长期刺激对培养的大鼠支持细胞中依赖环磷腺苷的蛋白激酶的激素反应性调节亚基（RIIβ）mRNA水平的影响。同时检测了相同处理对另外两种已证明受环磷腺苷调节的mRNA[雄激素结合蛋白（ABP）和细胞视黄醇结合蛋白（cRBP）]的影响。将（Bu）2cAMP（0.1 mM）添加到原代支持细胞培养物中14小时和24小时，导致RIIβmRNA的稳态水平增加了50至60倍。在相同的刺激期间，我们还观察到ABP的mRNA水平显著增加（2至3倍），而cRBP的mRNA水平下降了80%。尽管培养基中持续存在（Bu）2cAMP（0.1 mM），但持续刺激36小时和48小时与RIIβmRNA水平随时间显著下降有关。用（Bu）2cAMP长期刺激导致的这种反应降低似乎对RIIβ具有特异性，因为在整个环磷腺苷刺激期间，ABP的mRNA水平仍然升高，而cRBP的mRNA水平仍然降低。我们的数据证明在mRNA水平存在一种双相调节类型，这对依赖环磷腺苷的蛋白激酶的调节亚基RIIβ具有特异性。这种反应可能类似于在环磷腺苷信号通路其他水平观察到的脱敏机制。对于构成信号转导通路一部分的蛋白质，这种双相调节类型在维持细胞内稳态方面可能特别重要。
