Hepatocyte Proliferation During Development: Role of p38

描述：(申请人提供)我们实验室以前的工作 围产期及围产期肝细胞周期调控特点 大鼠出生后的月经。我们的研究表明，细胞周期调节因子， 细胞周期蛋白D1在控制肝细胞增殖中起着核心作用。我们 发现细胞周期蛋白D1的丰度是在转录后调节的，并且 P38丝裂原活化蛋白激酶途径的作用是阴性的 肝细胞增殖和细胞周期蛋白Dl丰度的调节剂。最后，我们 已经证明了肝细胞生长停滞与 足月胎儿、围产期p38通路的激活和细胞周期蛋白的丢失 D1。这些结果构成了当前提案的基础。我们将测试 以下假设：1)肝脏p38活性受代谢变化的调节 发生在围产期和新生儿到成人期间 过渡。2)p38通过其中一种或两种方式调节细胞周期蛋白D1的丰度 细胞周期蛋白D1翻译的机制、调控和/或调控细胞周期蛋白D1 通过泛素/蛋白酶体途径降解。3)这是生理上的 调节p38账户，至少部分是为了调节肝细胞 完整动物体内的增殖。基于这些假设，我们有 制定了以下具体目标：1)调查生理刺激 这解释了p38调控在正常围产期和 出生后肝脏发育。2)确定p38的作用机制(S) 控制细胞周期蛋白D1的丰度。3)将我们的发现应用于以下动物模型 肝细胞增殖受到调节，包括围产期发育、肝脏 肝部分切除后再生及外源性激素的体内效应 生长因子对肝细胞周期激活的影响。AIM 1将聘用 原代胎肝细胞培养及代谢环境的调控 与体内肝脏代谢环境的相关性。目标2将是 在胎肝细胞原代培养中应用瞬变 转染腺病毒介导的p38激活激酶的导入， MKK6。Aim 3将把我们的发现扩展到成熟的啮齿动物模型 肝细胞生长调节。我们预计这些研究将提供 对正常肝细胞增殖调控的新认识 在发育和成熟大鼠中。

DESCRIPTION: (Provided By Applicant) Previous work in our laboratory has characterized hepatocyte cell cycle regulation during the perinatal and postnatal periods in the rat. Our studies showed that the cell cycle regulator, cyclin D1, plays a central role in controlling hepatocyte proliferation. We found that the abundance of cyclin D1 is regulated posttranscriptionally, and that the p38 mitogen-activated protein kinase pathway acts as a negative regulator of both hepatocyte proliferation and cyclin Dl abundance. Finally, we have demonstrated a functional relationship between hepatocyte growth arrest in the term fetus, the perinatal activation of the p38 pathway and loss of cyclin D1. These results form the basis for the current proposal. We will test the following hypotheses: 1) Hepatic p38 activity is regulated by metabolic changes that occur during the perinatal period and during the newborn-to-adult transition. 2) p38 regulates cyclin D1 abundance through one or both of two mechanisms, control of cyclin D1 translation and/or control of cyclin D1 degradation via theubiquitin/proteasome pathway. 3) This physiological regulation of p38 accounts, at least in part, for regulation of hepatocyte proliferation in the intact animal. Based on these hypotheses, we have developed the following specific aims: 1) Investigate the physiological stimuli that account for the ontogeny of p38 regulation during normal perinatal and postnatal liver development. 2) Determine the mechanism(s) by which p38 controls cyclin D1 abundance. 3) Apply our findings to animal models in which hepatocyte proliferation is modulated, including perinatal development, liver regeneration after partial hepatectomy, and the in vivo effect of exogenous growth factors on hepatocyte cell cycle activation. Aim 1 will employ manipulation of the metabolic milieu in primary fetal hepatocyte cultures and correlation with the in vivo hepatic metabolic environment. Aim 2 will be carried out in primary cultures of fetal hepatocytes using transient transfection or adenovirus-mediated introduction of the p38-activating kinase, MKK6. Aim 3 will extend our findings to well-established rodent models of hepatocyte growth regulation. We anticipate that these studies will provide novel insights into the regulation of hepatocyte proliferation during normal development and in the mature rat.