REGULATION OF CHLORIDE ION CONDUCTANCE IN PANCREAS DUCT

囊性纤维化（CE）是由囊性纤维化跨膜传导调节因子（CFTR）蛋白突变引起的多系统疾病。 正常情况下，该蛋白在顶端质膜中作为cAMP调节的C1通道发挥作用。 缺陷性CFTR和CF的病理生理学之间的确切联系尚不清楚。 通常认为CF是由受影响上皮细胞中的异常离子和水运动引起的;然而，归因于CFTR的其他调节功能可能有助于疾病。 CF上皮细胞顶膜C1渗透性的遗传和药理学恢复通常被认为是一种可行的治疗策略。 一种这样的方法是激活“交替”顶膜，非CFTR Cl-通道。这种方法的基本原理基于以下观察结果：人CF气道上皮细胞中保留了Ca 2+激活的C1-电导（CACC），CF敲除小鼠中器官特异性疾病的严重程度与CACC的活性呈负相关。胰腺导管上皮细胞表达至少4种类型的质膜C1-传导：cAMP激活的（CFTR）、cAMP激活的（非CFTR）、CACC和肿胀激活的（SACC）。至少有两个，也许多达四个，不同的质膜阴离子通道的基础这四个传导途径。只有一个（CFTR）的分子身份是已知的。 CACC、cAMP激活的（非CFTR）和SACC电导的调节在胰管细胞中很少受到关注。 我们以前的研究表明，Ca 2+激活和cAMP激活（非CFTR）的电导存在于胰管细胞的顶端细胞膜，从而代表潜在的途径，以规避功能CFTR的损失。 本提案中描述的工作的目标是确定这两个电导的单通道基础，并确定控制通道活性的调节途径。 将使用响应于信号转导通路的操纵的通道功能的电生理学测量。 这项工作的长期目标是开发控制盐和水转运的药理学方法，以补偿受囊性纤维化影响的上皮细胞中CFTR功能的丧失。

Cystic Fibrosis (CE) is a multi-system disease caused by mutations in the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) protein. Normally the protein functions as a cAMP-regulated C1-channel in the apical plasma membrane. The precise link between defective CFTR and the pathophysiology of CF is not known. It is generally assumed that CF results from abnormal ion and water movement across affected epithelia; however, other regulatory functions ascribed to CFTR may contribute to the disease. Genetic and pharmacologic restoration of apical membrane C1-permeability in CF epithelia are often cited as a viable therapeutic strategies. One such approach is to activate "alternate" apical membrane, non-CFTR C1-channels. The rationale for this approach rests upon the observation that Ca2+-activated C1-conductance (CACC) is preserved in human CF airway epithelia and that organ-specific disease severity in the CF knockout mouse is inversely related to the activity of CACC. Pancreatic duct epithelial cells express at least 4 types of plasma membrane C1-conductances: cAMP-activated (CFTR), cAMP-activated (non-CFTR), CACC, and swelling activated (SACC). At least two, and perhaps as many as four, different plasma membrane anion channels underlie these four conductance pathways. The molecular identity of only one (CFTR) is known. Regulation of the CACC, cAMP-activated (non-CFTR), and SACC conductances has received little attention in pancreatic duct cells. Our previous studies revealed that the Ca2+-activated and the cAMP-activated (non-CFTR) conductances are present in the apical cell membrane of pancreatic duct cells and thereby represent potential pathways to circumvent the loss of functional CFTR. The goal of the work described in this proposal is to identify the single channel basis for these two conductances and to determine the regulatory pathways that control channel activity. Electrophysiological measurements of channel function in response to manipulation of signal transduction pathways will be used. The long term objective of the work is to develop pharmacologic approaches to control salt and water transport so as to compensate for loss of CFTR function in epithelia affected by cystic fibrosis.