Regulation of Liver by Nuclear Ca2+ Signaling

Ca2+在肝脏中起着重要作用。在细胞质中，它调节胆汁分泌、葡萄糖代谢和细胞骨架组织等活动。我们假设肿瘤中的Ca2+反而调节肝脏生长和再生以及基因转录等过程。核质Ca2+被调控的机制具有重要的潜在意义。有人认为，核Ca2+被动地跟随细胞质Ca2+，但我们的初步数据表明，有核机制允许核质Ca2+被控制独立于细胞质中的Ca2+浓度。这种机制反过来又允许独立调节Ca2+介导的核事件。由于肌醇1,4,5，-三磷酸（InsP3）受体调节肝细胞中的Ca2+信号，我们的假设将通过以下项目系统地定义肝脏中核Ca2+信号的机制和作用来验证：项目A将在完整的肝细胞和肝细胞系中确定核Ca2+储存的组织和调节Ca2+从这些储存中释放的因素。在单通道水平上研究肝细胞天然和克隆核InsP3受体的功能和调控。将研究丝裂原活化蛋白激酶（MAPK）磷酸酶-1 （MAPK-1）在核Ca2+信号响应中控制MAPK介导的肝脏特异性基因转录事件中的作用。核Ca2+信号对肝脏基因转录的重要性将通过确定Ca2+和Ca2+动员胆汁酸如何调节肝脏特异性功能的基因来研究。为了帮助实施这些项目，将建立细胞和分子生物学、细胞成像和管理的核心设施。

Ca2+ plays an important role in the liver. In the cytosol, it regulates activities such as bile secretion, glucose metabolism and cytoskeletal organization. We hypothesize that Ca2+ in the neoplasm instead regulates processes such as hepatic growth and regeneration and gene transcription. The mechanism by which nucleoplasmic Ca2+ is regulated thus is of great potential importance. It has been suggested that nuclear Ca2+ passively follows cytosolic Ca2+, but our preliminary data instead suggest that there is nuclear machinery that allows nucleoplasmic Ca2+ to be controlled independent of the Ca2+ concentration in the cytosol. Such machinery would in turn allow independent regulation of Ca2+- mediated events in the nucleus. Since the inositol 1,4,5,-triphosphate (InsP3) receptor regulates Ca2+ signaling in hepatocytes, our hypothesis will be tested by systematically defining the mechanisms and effects of nuclear Ca2+ signaling in liver through the following projects: Project A The organization of nuclear Ca2+ stores and the factors that regulate release of Ca2+ from these stores will be determined in intact hepatocytes and in liver cell lines. Project B The function and regulation of both native and cloned nuclear InsP3 receptors of hepatocytes will be characterized at the single channel level. Project C The role of the mitogen-activated protein kinase (MAPK) phosphatase-1 (MAPK-1) in controlling MAPK-mediated liver-specific gene transcription events in response to nuclear Ca2+ signals will be examined. Project D The significance of nuclear Ca2+ signals for gene transcription in liver will be examined by determining how genes integral to liver- specific functions are regulated by Ca2+ and by Ca2+-mobilizing bile acids. To help carry out these projects, core facilities will be established for cell and molecular biology, cell imaging, and administration.