NTPDase2 expression and function in the liver

描述（由申请人提供）： 这项研究的目的是确定外核苷酸酶NTPDase2在肝脏中的表达和功能。该项目将把最初K08应用的发现扩展到PI的一个新领域，这最终将导致该领域的持续研究。K08最初申请的目的是确定胆管上皮细胞（BDE）中表达的P2Y受体亚型，确定BDE中这些受体的极化表达，并确定这些受体是否与胆管分泌有关。正如假设的那样，发现BDE表达多种P2 Y亚型，在基底外侧和顶端质膜结构域表达这些亚型，并与胆管分泌有关。然而，一个意想不到的发现是通过核苷酸水解的基底外侧P2Y受体的选择性失活。 为了进一步研究这一发现，研究了被称为三磷酸核苷二磷酸水解酶（NTPDases）的外核苷酸酶在肝脏中的表达。外核苷酸酶NTPDase2被发现在肝内胆管周围的门静脉成纤维细胞（PF）中表达，这为BDE基底外侧的核苷酸选择性水解提供了可能的解释。新的数据表明，NTPDase2的功能，以调节BDE的增殖，通过抑制基底外侧胆管P2Y受体。 我们现在建议通过以下三个具体目的研究NTPD酶2在肝脏中的生理功能： (1)测定PF是否抑制胆管上皮细胞增殖 (2)确定通过NTPDase2 siRNA阻断PF中NTPDase2表达是否恢复胆管上皮细胞增殖 (3)确定通过胆总管结扎阻断PF中NTPDase2表达是否恢复胆管上皮细胞的增殖。 在这些特定目标中提出的实验将为几种新的肝病研究提供基础，并应为胆汁淤积性和纤维化肝病的治疗提供新的治疗靶点。

DESCRIPTION (provided by applicant): The goal of this proposed research is to define the expression and function of the ecto-nucleotidase NTPDase2 in the liver. This project will extend the findings of the intial K08 application into a novel area for the PI, which should ultimately lead to an ongoing stream of research in this area. The aims of the initial K08 application were to define the P2Y receptor subtypes expressed in bile duct epithelia (BDE), to define the polarized expression of these receptors in BDE, and to determine whether these receptors link to bile ductular secretion. As hypothesized, BDE were found to express multiple P2Y subtypes, to express these subtypes at both basolateral and apical plasma membrane domains, and to link to bile ductular secretion. However, an unexpected finding was the selective inactivation of basolateral P2Y receptors by nucleotide hydrolysis. To investigate this finding further, the expression of ecto-nucleotidases known as nucleoside triphosphate diphosphohydrolases (NTPDases) in the liver was investigated. The ectonucleotidase NTPDase2 was found to be expressed in portal fibroblasts (PF) surrounding intrahepatic bile ducts, which provides a likely explanation for the selective hydrolysis of nucleotides at the basolateral aspect of BDE. New data suggest that NTPDase2 functions to regulate the proliferation of BDE through inhibition of basolateral bile ductular P2Y receptors. We now propose to investigate the physiologic function of NTPDase2 in the liver through the three following Specific Aims: (1) Determine whether PF suppress the proliferation of bile duct epithelia (2) Determine whether blockade of NTPDase2 expression in PF via NTPDase2 siRNA restores proliferation of bile duct epithelia (3) Determine whether blockade of NTPDase2 expression in PF via common bile duct ligation restores proliferation of bile duct epithelia. The experiments proposed in these specific aims will provide the basis of several new lines of liver disease research and should provide novel therapeutic targets for treatment of cholestatic and fibrotic liver disease.