Transcriptional Control in Hepatocyte Proliferation

描述（由申请人提供）：成人肝脏具有显著的能力 以恢复其质量，以应对部分肝切除术，肝移植， 或毒性或炎性损伤。肝部分切除后的再生是 在CCAAT增强子结合蛋白β（C/EBP-β）-/-小鼠中受损， 与肝细胞DNA合成减少、长期低血糖和 生长相关和细胞周期相关基因的表达降低， 包括细胞周期蛋白E。C/EBP-β对Fas介导的凋亡损伤的抵抗 -/-肝脏还将C/EBP-β与初始肝损伤的调节联系起来 反应C/EBP-α和β之间的生理关联和 视网膜母细胞瘤蛋白在其他细胞类型和发现， 部分肝切除术后C/EBP-β-/-肝的磷酸化水平降低 将C/EBP-β与pRb磷酸化、细胞周期蛋白E激活和肝细胞连接起来 细胞周期进程C/EBP-β中特定结构域的磷酸化 蛋白质克服了与诱导相关的细胞周期进展的阻滞 未修饰的C/EBP-β在细胞模型中，这表明翻译后 C/EBP-β的修饰对于肝细胞周期也是必需的 肝脏再生的进展。这项建议的具体目标是 (1)鉴定凋亡途径中异常表达的组分 在Fas抗体处理的C/EBP-β-/-肝脏中调节，并确定 C/EBP-β还参与调节TNF-α介导的凋亡。 肝损伤(2)为了确定C/EBP-β和/或C/EBP-α是否 与pRb的相互作用对pRb磷酸化、细胞周期蛋白E 活化和肝细胞周期进展。(3)定义C/EBP-β 肝细胞增殖所需的功能结构域。C/EBP-β 在对应于连接的磷酸受体位点的残基处修饰的蛋白质 再生肝脏中的信号通路将被引入到 CIEBP-β-/-原代肝细胞，并评估其促进 肝细胞周期进展。这些研究将提供 重要的机械见解的基础上的反应， 肝损伤和生长刺激后肝细胞增殖。 这些知识将有助于开发治疗方法， 在各种肝病中肝脏的再生能力。

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.