Ogreid D, Cho-Chung Y S, Ekanger R, Vintermyr O, Haavik J, Døskeland S O
Cancer Res. 1987 May 15;47(10):2576-82.
We have compared the properties of cyclic adenosine 3':5'-monophosphate (cAMP)-dependent protein kinases I and II in hormone-dependent/cAMP-sensitive (DMBA tumor) and hormone-independent/cAMP-resistant (DMBA 1 tumor) rat mammary carcinomas. cAMP-resistance was not due to less total kinase in the hormone-independent tumor, grossly altered distribution between soluble and particulate forms of the kinase (80% soluble in either tumor), alteration in the relative proportion of isozymes I and II of the protein kinase (the soluble and the particulate fraction from both tumors contained about 50% of either isozyme), or a decreased sensitivity towards cAMP (both isozymes had affinities for cAMP and its derivatives that corresponded closely with those of isozymes from normal tissues). Furthermore, the sensitivity of the enzymes towards thermal denaturation was identical for samples from the two tumor types. Subtle differences did, however, exist between the regulatory moieties [regulatory subunit of cAMP-dependent protein kinase II (RII)] of isozyme II from the two tumors: autophosphorylated RII from the hormone-independent tumor migrated as a doublet corresponding to Mrs 54,000 and 52,000 on sodium dodecyl sulfate-polyacrylamide gels, against Mrs 53,000 and 52,000 for RII from the hormone-dependent tumor; RII from the two tumors showed different elution profiles upon DEAE-cellulose chromatography; a considerable proportion of the soluble RII in the hormone-independent tumor formed supramolecular aggregates as judged by size-exclusion chromatography. No such microheterogeneity was noted for isozyme I. This study thus shows that the lack of cAMP-responsiveness of one tumor is related either to a defect distal to the cAMP-dependent protein kinases or to the appearance of the new subtype of RII in the resistant tumor. If the latter explanation is correct, it means that the part of the RII molecule responsible for interaction with other proteins rather than that responsible for cAMP-binding and control of protein kinase activity modulates the growth-inhibiting response to cAMP.
我们比较了环磷酸腺苷（cAMP）依赖性蛋白激酶I和II在激素依赖性/cAMP敏感型（DMBA肿瘤）和激素非依赖性/cAMP抗性型（DMBA 1肿瘤）大鼠乳腺癌中的特性。cAMP抗性并非由于激素非依赖性肿瘤中总激酶含量减少、激酶在可溶性和颗粒性形式之间的分布发生显著改变（两种肿瘤中80%为可溶性）、蛋白激酶同工酶I和II的相对比例改变（两种肿瘤的可溶性和颗粒性部分均含有约50%的任一同工酶）或对cAMP的敏感性降低（两种同工酶对cAMP及其衍生物的亲和力与正常组织中的同工酶密切对应）。此外，两种肿瘤类型的样品中酶对热变性的敏感性相同。然而，两种肿瘤中同工酶II的调节部分[依赖cAMP的蛋白激酶II的调节亚基（RII）]之间确实存在细微差异：激素非依赖性肿瘤中自磷酸化的RII在十二烷基硫酸钠-聚丙烯酰胺凝胶上迁移为双峰，对应分子量为54,000和52,000，而激素依赖性肿瘤中RII的分子量为53,000和52,000；两种肿瘤的RII在DEAE-纤维素色谱上显示出不同的洗脱图谱；通过尺寸排阻色谱法判断，激素非依赖性肿瘤中相当一部分可溶性RII形成了超分子聚集体。同工酶I未观察到这种微观异质性。因此，本研究表明，一种肿瘤缺乏cAMP反应性要么与cAMP依赖性蛋白激酶下游的缺陷有关，要么与抗性肿瘤中出现新的RII亚型有关。如果后一种解释正确，这意味着RII分子中负责与其他蛋白质相互作用的部分而非负责cAMP结合和蛋白激酶活性控制的部分调节了对cAMP的生长抑制反应。
