Cross-regulation between G-protein-mediated pathways. Stimulation of adenylyl cyclase increases expression of the inhibitory G-protein, Gi alpha 2.
Cross-regulation between G-protein-mediated pathways. Stimulation of adenylyl cyclase increases expression of the inhibitory G-protein, Gi alpha 2.
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DOI：
10.1016/s0021-9258(18)77181-0
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发表时间：
1990-09
期刊：
影响因子：
--
通讯作者：
J. Hadcock;M. Ros;D. C. Watkins;C. Malbon
中科院分区：
文献类型：
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作者：
J. Hadcock;M. Ros;D. C. Watkins;C. Malbon
激素敏感的腺苷酸环化酶系统受到双重控制，接受刺激和抑制输入。鸟嘌呤核苷酸结合调节蛋白（g蛋白）将细胞表面受体的信号传递给腺苷酸环化酶等效应器。激素刺激通过Gs传播，抑制通过Gi。在S49小鼠淋巴瘤细胞中，二萜福斯克林或β -肾上腺素能激动剂异丙肾上腺素持续（24小时）激活腺苷酸环化酶刺激通路可增强经腺苷酸环化酶抑制通路介导的生长抑素的作用。免疫印迹定量显示，用福斯克林或异丙肾上腺素刺激细胞24小时，可导致Gi α 2稳态水平增加3倍，Gs α下降25%。在刺激腺苷酸环化酶12小时内，通过dna过量溶液杂交检测，Gi α 2 mRNA水平增加了4倍。相比之下，Gs α mRNA水平最初升高（25%），但随后下降至对照组的75%。在缺乏功能性蛋白激酶A （kin-）的S49变异体中，异丙肾上腺素刺激无法改变Gi α 2蛋白或mRNA水平的表达。在福斯克林刺激下，Gi α 2的相对合成速率增加了3倍，半衰期（约80 h）没有变化。虽然在福斯克林刺激下，Gs α的合成适度增加（70%），但Gs α的半衰期实际上从未处理细胞的55小时减少到处理细胞的34小时。因此，控制腺苷酸环化酶的两种g蛋白介导途径表现出“交叉调节”。刺激通路的持续激活增加了Gi α 2 mRNA和表达。短暂升高的Gs α mRNA水平被蛋白质半衰期的减少所抵消。
The hormone-sensitive adenylyl cyclase system is under dual control, receiving both stimulatory and inhibitory inputs. Guanine nucleotide-binding regulatory proteins (G-proteins) transduce signals from cell surface receptors to effectors such as adenylyl cyclase. Hormonal stimulation is propagated via Gs, inhibition by Gi. Persistent (24-h) activation of the stimulatory pathway of adenylyl cyclase by the diterpene forskolin or the beta-adrenergic agonist isoproterenol in S49 mouse lymphoma cells enhanced the effects of somatostatin mediated via the inhibitory pathway of adenylyl cyclase. Stimulating cells with forskolin or isoproterenol for 24 h resulted in a 3-fold increase in the steady-state levels of Gi alpha 2 and a 25% decline in Gs alpha, as quantified by immunoblotting. Within 12 h of stimulation of adenylyl cyclase, Gi alpha 2 mRNA levels increased 4-fold, measured by DNA-excess solution hybridization. Gs alpha mRNA levels, in contrast, increased initially (25%), but then declined to 75% of control. In S49 variants that lack functional protein kinase A (kin-), stimulation by isoproterenol failed to alter Gi alpha 2 expression at either the protein or the mRNA levels. A 3-fold increase in relative synthesis rate and no change in the half-life (approximately 80 h) of Gi alpha 2 was observed in response to forskolin stimulation. Although Gs alpha synthesis increased (70%) modestly in response to forskolin stimulation, the half-life of Gs alpha actually decreased from 55 h in naive cells to 34 h in treated cells. Thus, the two G-protein-mediated pathways controlling adenylyl cyclase display “cross-regulation.” Persistent activation of the stimulatory pathway increases Gi alpha 2 mRNA and expression. Transiently elevated Gs alpha mRNA levels are counterbalanced by a reduction in the half-life of the protein.