MECHANISM OF CAMP ACTION IN GROWTH CONTROL, DIFFERENTIATION, AND GENE REGULATION

CAMP 在生长控制、分化和基因调控中的作用机制

• 批准号: 3774316
• 负责人: Y S CHO-CHUNG
• 金额: --
• 依托单位: DIVISION OF CANCER BIOLOGY AND DIAGNOSIS
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/3774316
• 关键词: antineoplastics; biological signal transduction; cell differentiation; cell growth regulation; cellular oncology; cyclic AMP; cyclic AMP receptors; genetic regulatory element; genetic transcription; growth inhibitors; intracellular transport; isozymes; nucleotide analog; phosphorylation; protein kinase A; protein sequence; protein structure function; receptor binding; site directed mutagenesis; tissue /cell culture

The striking growth inhibitory effect of 8-Cl-cAMP has been related to its selective binding and activation of protein kinase isozymes: It binds to RII with a high affinity for Site B but with a low affinity for Site A, keeping type Il protein kinase in the holoenzyme form, while binding with moderately high affinity for both Site A and Site B to RI, facilitating dissociation of the RI subunit and down-regulation of type I protein kinase. The growth inhibition induced by 8-Cl-cAMP brought about various effects among the cell lines tested, including the suppression of oncogenes and transforming growth factor a (TGFalpha), and morphological changes, differentiation, and reverse transformation. Despite the appearance of markers of mature phenotype and definitive growth arrest, the 8-Cl-cAMP-treated leukemic cells exhibited no change in the cell cycle phase. 8-Cl-cAMP therefore produces growth inhibition while allowing the cells to progress through their normal cell cycle, albeit at a slower rate, and this may lead to eventual restoration of a balance between cell proliferation and differentiation in cancer cells. Thus, unlike cytotoxic drugs, 8-Cl-cAMP does not act to prevent mitosis but acts to alter the growth ratio, the ratio of cell births to cell deaths, via restoration of the RI/RII balance in cancer cells. The cellular events underlying growth inhibition and differentiation of cancer cells induced by 8-Cl-cAMP include a rapid nuclear translocation of RIIbeta, and such translocation of RIIbeta into the nucleus correlates with an increase n transcription factors in cancer cells that bind specifically to cAMP response element (CRE). Thus, the mechanism of action of 8-Cl-cAMP in the suppression of malignancy may involve the restoration of normal gene transcription in cancer cells where the RIIbeta cAMP receptor plays an important role. By the use of site-directed mutagenesis technique, the structure-function analysis of RI and Rll is currently underway. The RI and Rll are distinguished by their autophorylation and nuclear translocation properties. RII has an autophosphorylation site at a proteolytically sensitive hinge region around the R and C interaction site while RI has a pseudo-phosphorylation site. The Rll but not the RI contains a nuclear location signal, K K R K. The autophosphorylation and nuclear location sequences are either point-mutated in RIIbeta of introduced into RIalpha to specifically assess the role of these sequences in the growth regulatory function. These studies contribute to understanding the mechanism of cAMP control cell growth and differentiation and provide new approaches to the treatment of cancer.

8-CL-cAMP的显着生长抑制作用与其 蛋白激酶同工酶的选择性结合和激活：它与 RII对站点B具有高亲和力，但对站点A的亲和力较低， 将类型的IL蛋白激酶保持在全酶形式中，同时与 对站点A和网站B的适度高亲和力对RI，促进 RI亚基的解离和I型蛋白的下调 激酶。由8-CL训练引起的生长抑制作用带来了不同的 测试细胞系的影响，包括抑制 癌基因和转化生长因子A（TGFALPHA）和形态学 变化，差异和反向转换。尽管有 成熟表型和确定生长停滞的标记的出现， 8-CL-cAMP处理的白血病细胞在细胞周期没有变化 阶段。因此，8-CL-cAMP会产生增长抑制，同时允许 细胞通过其正常细胞周期发展，尽管在较慢 速率，这可能导致最终恢复细胞之间的平衡 癌细胞的增殖和分化。因此，与细胞毒性不同 药物，8-CL-cAMP不作用防止有丝分裂，而是作用于改变 生长比，通过恢复细胞出生与细胞死亡的比率 癌细胞中的RI/RII平衡。生长的细胞事件 8-CL训练诱导的癌细胞的抑制和分化 包括Riibeta的快速核易位和此类易位 riibeta进入核与n转录的增加相关 癌细胞专门结合cAMP反应元件的因素 （CRE）。因此，8-CL训练在抑制中的作用机理 恶性肿可能涉及恢复正常基因转录 riibeta cAMP受体的癌细胞起着重要作用。经过 使用位置定向诱变技术，结构功能 RI和RLL的分析目前正在进行中。 RI和RLL是 以它们的自噬和核易位为特殊 特性。 RII在蛋白水解上具有一个自磷酸化位点 RI的敏感铰链区域周围的敏感铰链区域，而RI具有 伪磷酸化位点。 RLL但不包含RI的核 位置信号，K k r K.自磷酸化和核位置 序列要么在引入rialpha的riibeta中点数 专门评估这些序列在生长中的作用 调节功能。这些研究有助于理解 营地控制细胞生长和分化的机制，并提供新的 癌症治疗的方法。