Rb,p53, Bcl-2 Proteins in Apoptosis

细胞凋亡中的 Rb、p53、Bcl-2 蛋白

• 批准号: 6943011
• 负责人: Steven Jay Weintraub
• 金额: $ 30.64万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-06-01 至 2008-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6943011
• 关键词: BCL2 gene /protein; acidity /alkalinity; amination; antineoplastics; apoptosis; biological signal transduction; cis platinum compound; drug interactions; human tissue; laboratory mouse; mass spectrometry; matrix assisted laser desorption ionization; neoplasm /cancer chemotherapy; neoplastic cell; p53 gene /protein; polymerase chain reaction; protein structure function; retinoblastoma protein; site directed mutagenesis; western blottings

DESCRIPTION (provided by applicant): The therapeutic value of DNA-damaging antineoplastic agents is dependent upon their ability to induce tumor cell apoptosis while sparing most normal tissues. We recently found that a component of the apoptotic response to these agents in several different types of tumor cells is the deamidation of two asparagines in the unstructured loop of Bcl-xL, and we found that deamidation of these asparagines imparts susceptibility to apoptosis by disrupting the ability of Bcl-xL to block the proapoptotic activity of BH3 domain-only proteins. Conversely, we found that Bcl-xL deamidation is actively suppressed in fibroblasts, and that suppression of deamidation is an essential component of their resistance to DNA damage-induced apoptosis. Finally, we found that at least in some cells, the retinoblastoma protein mediates the suppression of Bcl-xL deamidation. We have begun to define the mechanism by which deamidation of Bcl-XL is regulated. Our data provides evidence that deamidation of Bcl-xL is induced by an upward shift in the cytosolic pH that is induced by cisplatin treatment and that the retinoblastoma protein suppresses Bcl-xL deamidation because it suppresses the increase in pH. Importantly, our data strongly suggests that the increase in pH does not directly cause deamidation of Bcl-xL. Instead, our findings support a mechanism in which the cytosolic pH increase induces deamidation of Bcl-xL by activating an autocatalytic "deamidase" function of Bcl-xL. We propose that this mechanism affords the cell tighter control of Bcl-xL deamidation and allows deamidation to occur at a lower pH and more rapidly than if deamidation were regulated directly by pH. We speculate that a similar mechanism has an important role in the regulation of other proteins. We now propose to (1) characterize the autocatalytic deamidase activity by performing a structure-function analysis of Bcl-xL with respect to this activity; (2) delineate signal transduction pathways that mediate cisplatin-induced cytosolic alkalinization; and (3) examine the potential role of dysregulation of cisplatin-induced cytosolic alkalinization and Bcl-xL deamidation in tumor cell resistance to cisplatin. These studies may lead to the identification of cellular targets that allow for the development of more efficacious and less toxic antineoplastic therapies.

描述（由申请人提供）：DNA损伤性抗肿瘤药物的治疗价值取决于它们诱导肿瘤细胞凋亡同时不伤害大多数正常组织的能力。我们最近发现，在几种不同类型的肿瘤细胞中，对这些药物的凋亡反应的一个组成部分是 Bcl-xL 非结构化环中两个天冬酰胺的脱酰胺作用，并且我们发现这些天冬酰胺的脱酰胺作用通过破坏Bcl-xL 阻断仅 BH3 结构域蛋白的促凋亡活性的能力。相反，我们发现 Bcl-xL 脱酰胺作用在成纤维细胞中受到积极抑制，并且脱酰胺作用的抑制是其抵抗 DNA 损伤诱导的细胞凋亡的重要组成部分。最后，我们发现至少在某些细胞中，视网膜母细胞瘤蛋白介导 Bcl-xL 脱酰胺化的抑制。我们已经开始定义 Bcl-XL 脱酰胺的调节机制。我们的数据提供的证据表明，Bcl-xL 的脱酰胺作用是由顺铂治疗诱导的胞质 pH 值上升引起的，并且视网膜母细胞瘤蛋白抑制 Bcl-xL 脱酰胺作用，因为它抑制 pH 值的增加。重要的是，我们的数据强烈表明 pH 值的增加不会直接导致 Bcl-xL 的脱酰胺化。相反，我们的研究结果支持了一种机制，即胞质 pH 值升高通过激活 Bcl-xL 的自催化“脱酰胺酶”功能来诱导 Bcl-xL 脱酰胺。我们认为，这种机制使细胞能够更严格地控​​制 Bcl-xL 脱酰胺作用，并允许脱酰胺作用在较低 pH 下发生，并且比直接通过 pH 调节脱酰胺作用更快。我们推测类似的机制在其他蛋白质的调节中具有重要作用。我们现在建议 (1) 通过对 Bcl-xL 的自催化脱酰胺酶活性进行结构功能分析来表征该活性； (2) 描绘介导顺铂诱导的胞质碱化的信号转导途径； (3) 检查顺铂诱导的胞质碱化和 Bcl-xL 脱酰胺调节失调在肿瘤细胞对顺铂耐药中的潜在作用。这些研究可能有助于识别细胞靶点，从而开发出更有效、毒性更小的抗肿瘤疗法。