Transcriptional Control in Hepatocyte Proliferation

描述(申请人提供)：成人肝脏具有显著的恢复其质量的能力，以响应部分肝切除，肝移植， 或毒性或炎症性损伤。肝部分切除后再生是 CCAAT增强子结合蛋白β(C/EBP-β)-/-小鼠和IS受损 与肝细胞DNA合成减少，长期低血糖和 生长相关基因和细胞周期相关基因表达减少， 包括细胞周期蛋白E对Fas介导的细胞凋亡损伤的抵抗作用 -/-肝脏还将C/EBP-β与初始肝损伤的调节联系起来 回应。C/EBP-α和β与高血压的生理学联系 视网膜母细胞瘤蛋白在其他细胞类型中的表达和pRb的发现 肝部分切除后C/EBP-β/-肝的磷酸化水平降低 C/EBP-β与pRb磷酸化、细胞周期蛋白E活化及肝细胞的关系 细胞周期进程。C/EBP-β中特定结构域的磷酸化 蛋白质可抑制与诱导相关的细胞周期进程 未修饰的C/EBP-β在细胞模型中的表达，表明翻译后 C/EBP-β的修饰对肝细胞周期也是必要的 再生肝脏的进展。这项提议的具体目的是 (1)鉴定异常的细胞凋亡途径成分(S) 在Fas抗体处理的C/EBP-β/-肝中的调节，并确定 C/EBP-β也参与了肿瘤坏死因子-α介导的细胞凋亡的调节 肝脏损伤。(2)确定C/EBP-β和/或C/EBP-α 与pRb的相互作用对pRb的磷酸化很重要，细胞周期蛋白E 活化与肝细胞周期进程。(3)定义C/EBP-BETA 肝细胞增殖所需的功能结构域。C/EBP-测试版 与所连接的磷受体位点对应的残基上修饰的蛋白质 再生肝脏中的信号通路将被引入 CIEBP-β/-原代肝细胞及其促进 肝细胞周期进程。这些研究将共同提供 关于反应的基础的重要的机制见解 肝损伤和生长刺激后肝细胞的增殖。 这一知识将有助于发展治疗学以增强 肝脏在各种肝病中的再生能力。

DESCRIPTION (provided by applicant): The adult liver has a remarkable capacity to restore its mass in response to partial hepatectomy, liver transplantation, or toxic or inflammatory injury. Regeneration after partial hepatectomy is impaired in CCAAT enhancer binding protein beta(C/EBP-beta) -/- mice and is associated with decreased hepatocyte DNA synthesis, prolonged hypoglycemia and reduced expression of growth-associated and cell cycle-associated genes, including cyclin E. Resistance to Fas-mediated apoptotic injury in C/EBP-beta -/- livers also links C/EBP-beta to the regulation of the initial liver injury response. Physiologic associations between C/EBP-alpha and beta and the retinoblastoma protein in other cell types and the finding that pRb phosphorylation is decreased in C/EBP-beta -/- livers after partial hepatectomy link C/EBP-beta with pRb phosphorylation, cyclin E activation and hepatocyte cell cycle progression. Phosphorylation of specific domains in the C/EBP-beta protein overrides the block to cell cycle progression associated with induction of unmodified C/EBP-beta in cell models, suggesting that posttranslational modifications of C/EBP-beta are also necessary for hepatocyte cell cycle progression in the regenerating liver. The Specific Aims of this proposal are (1) To identify the component(s) of the apoptotic pathway that are abnormally regulated in Fas-antibody treated C/EBP-beta -/- livers and to determine if C/EBP-beta is also involved in the regulation of TNF-alpha mediated apoptotic liver injury. (2) To determine whether C/EBP-beta and/or C/EBP-alpha interactions with pRb are important for pRb phosphorylation, cyclin E activation and hepatocyte cell cycle progression. (3) To define the C/EBP-beta functional domains that are required for hepatocyte proliferation. C/EBP-beta proteins modified at residues that correspond to phosphoacceptor sites linked to signaling pathways in the regenerating liver will be introduced into CIEBP-beta -/- primary hepatocytes and assessed for their ability to facilitate hepatocyte cell cycle progression. Together these studies will provide important mechanistic insights regarding the basis for the response of the liver to injury and for hepatocyte proliferation following growth stimulation. This knowledge will be useful for the development of therapeutics to augment the regenerative capacity of the liver in a variety of liver diseases.