Hepatocyte Proliferation During Development: Role of p38

描述：（由申请人提供）我们实验室以前的工作 特征性肝细胞周期调节在围产期和 大鼠的产后期。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核心作用。我们 发现细胞周期蛋白D1的丰度是转录后调节的， p38丝裂原活化蛋白激酶通路作为一种负性的 肝细胞增殖和细胞周期蛋白D1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.这些结果构成了本提案的基础。我们将测试 以下假设：1）肝脏p38活性受代谢变化调节 发生在围产期和新生儿到成年期 过渡2)p38通过以下两种途径之一或两者调节细胞周期蛋白D1的丰度 细胞周期蛋白D1翻译的控制和/或细胞周期蛋白D1的控制 通过泛素/蛋白酶体途径降解。3)这种生理 p38的调节至少部分地解释了肝细胞的调节 在完整的动物中增殖。基于这些假设，我们有 具体目标如下：1）研究生理刺激 解释了正常围产期期间p38调节的个体发生， 出生后肝脏发育2)确定p38的机制 控制细胞周期蛋白D1丰度。3)将我们的发现应用于动物模型， 调节肝细胞增殖，包括围产期发育、肝脏 肝部分切除术后再生，以及外源性 生长因子对肝细胞周期活化的影响。目标1将采用 在原代胎肝细胞培养物中操纵代谢环境， 与体内肝脏代谢环境的相关性。目标2将是 在胎肝细胞的原代培养物中使用瞬时 转染或腺病毒介导的p38活化激酶的引入， MKK 6.目标3将把我们的研究结果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节的新见解 发育和成熟大鼠。

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.