Pearson D, Nigg E A, Nagamine Y, Jans D A, Hemmings B A
Friedrich Miescher-Institut, Basel, Switzerland.
Exp Cell Res. 1991 Jan;192(1):315-8. doi: 10.1016/0014-4827(91)90193-x.
The precise mechanistic role of the cAMP-dependent protein kinase (cAMP-PK) in cAMP-mediated gene induction remains unclear. Renal epithelial cell mutants were compared to the LLC-PK1 parental cell line for induction of the cAMP-responsive urokinase-type plasminogen activator (uPA) gene, as quantitated by the technique of mRNA solution hybridization. The FIB4 and FIB6 mutants, which possess less than 10% parental cAMP-PK catalytic (C) subunit activity, showed markedly diminished uPA mRNA induction in response to agents elevating intracellular cAMP such as the cAMP analogue 8-bromo-cAMP and the adenylate cyclase-stimulating hormones vasopressin and calcitonin. In contrast, the mutant cells responded to a similar or greater extent than the parental cells in terms of uPA mRNA induction following treatment with the Ca2+/phospholipid-dependent protein kinase activator phorbol 12-myristate 13-acetate (PMA). Elevation of intracellular cAMP was found to induce a translocation of the cAMP-PK C subunit from the perinuclear Golgi region to the nucleus in both parental and mutant cell lines, as shown by immunocytochemical techniques. Results argue for the role of the cAMP-PK C subunit activity and possibly nuclear translocation of the C subunit in cAMP-mediated uPA induction, which is mechanistically distinct from the PMA-stimulated response.
环磷酸腺苷依赖性蛋白激酶（cAMP-PK）在cAMP介导的基因诱导中的确切机制作用尚不清楚。通过mRNA溶液杂交技术进行定量，将肾上皮细胞突变体与LLC-PK1亲本细胞系进行比较，以检测cAMP反应性尿激酶型纤溶酶原激活剂（uPA）基因的诱导情况。FIB4和FIB6突变体的cAMP-PK催化（C）亚基活性不到亲本的10%，在响应升高细胞内cAMP的试剂（如cAMP类似物8-溴-cAMP以及刺激腺苷酸环化酶的激素血管加压素和降钙素）时，uPA mRNA的诱导明显减弱。相反，在用钙/磷脂依赖性蛋白激酶激活剂佛波醇12-肉豆蔻酸酯13-乙酸酯（PMA）处理后，突变细胞在uPA mRNA诱导方面的反应程度与亲本细胞相似或更大。免疫细胞化学技术显示，细胞内cAMP升高会诱导亲本细胞系和突变细胞系中的cAMP-PK C亚基从核周高尔基体区域转位至细胞核。结果表明，cAMP-PK C亚基活性以及可能的C亚基核转位在cAMP介导的uPA诱导中发挥作用，这在机制上与PMA刺激的反应不同。
