Regulation of cholangiocytes by InsP3 receptor isoforms

胆汁分泌是肝脏的主要功能之一。为了保持胆汁流动，不仅必须 肝细胞分泌胆汁，但这必须由胆管上皮进一步修饰和调节。 细胞，或胆管细胞。胆管细胞功能异常导致胆汁淤积，胆汁淤积是胆汁淤积的主要原因 肝病的表现。胆汁淤积性肝病占全国肝移植的20%。 在美国，是儿科移植患者中最常见的肝病原因。此外, 胆管细胞功能异常是囊性纤维化肝脏表现的原因之一。 最常见的遗传性疾病。 胆管细胞的胆汁分泌在一定程度上受细胞内钙离子的调节。一般而言，细胞是受调控的 通过钙信号随时间的模式和通过细胞中出现钙信号的区域。 然而，对胆管细胞内钙信号的时间或空间方面知之甚少。 关于这些钙信号是如何调节的，我们一无所知。肌醇1，4，5-三磷酸受体 (InsP3R)介导上皮细胞内的钙信号，胆管细胞表达这三种亚型 受体。这一建议的假设是胆管细胞内的钙信号受 InsP3R亚型的亚细胞分布。这一假设将通过以下方式进行调查 具体目标： 1.在单通道水平上比较InsP3Rs的功能和调节。 2.研究各受体在胆管细胞钙信号转导中的作用 在经过修饰以表达这些受体中的一个或其组合的胆管细胞系中。 3.这些发现可能与天然钙信号的组织和分泌功能有关。 胆管细胞，如在分离的微灌流胆管节段中测定的。 这项工作不仅应该确定负责钙信号转导的分子机制。 胆管细胞，但作为一个模型，如何分子组织的信号通路 负责胆管分泌的调节。

Bile secretion is one of the principal functions of the liver. In order to maintain bile flow, not only must hepatocytes secrete bile, but this must then be modified and conditioned further by bile duct epithelial cells, or cholangiocytes. Abnormal cholangiocytes function results in cholestasis, which is a cardinal manifestation of liver disease. Cholestatic liver diseases are responsible for 20% of liver transplants in the US, and are the most common cause of liver disease among pediatric transplant patients. In addition, abnormal cholangiocyte function is responsible for the hepatic manifestations of cystic fibrosis, one of the most common inherited diseases. Bile secretion in cholangiocytes is regulated in part by cytosolic Ca2+. In general, cells are regulated both by the pattern of Ca2+ signals over time and by the regions of the cells in which Ca2+ signals occur. However, little is known about temporal or spatial aspects of Ca2+ signaling in cholangiocytes, and nothing is known about how these Ca2+ signals are regulated. Inositol 1,4,5-trisphosphate receptors (InsP3R) mediate Ca2+ signaling in epithelia, and cholangiocytes express all three isoforms of this receptor. The hypothesis of this proposal is that Ca2+ signals in the cholangiocyte are regulated by the subcellular distribution of the InsP3R isoforms. This hypothesis will be investigated through the following specific aims: 1. The function and regulation of the InsP3Rs will be compared at the single channel level. 2. The contribution that each of the receptors plays to Ca2+ signaling in cholangiocytes will be examined in a bile duct cell line modified to express either one or a combination of these receptors. 3. These findings will be related to the organization of Ca2+ signals and secretory function in native cholangiocytes, as determined in isolated microperfused bile duct segments. This work should not only identify the molecular mechanisms responsible for Ca2+ signaling in cholangiocytes, but serve as a model for how the molecular organization of signaling pathways is responsible for regulation of ductular secretion.