Salivary gland hypofunction & genetic defects

约20%的口干症病例病因不明。这些特发性“口干”疾病中的许多很可能是由于液体运输机制的遗传缺陷造成的。为后一类患者开发治疗方法的第一步是确定液体分泌过程中涉及的关键运输蛋白。分泌是由K+和C1-通道激活驱动的。已在唾液腺泡细胞中鉴定出几种不同类型的K+和Cl-通道，但只有少数被鉴定为特定的基因产物。这些蛋白质的一些性质已经确定，但对这些通道对液体分泌过程的具体贡献知之甚少。因此，这个子项目的长期目标是确定人类和小鼠腮腺产生唾液所必需的K+和Cl-通道蛋白。作为子项目3的一部分，我们将尝试证实我们在特发性口干患者中的发现。目标1将通过表征通道的生物物理学特征来区分不同的K+和Cl-通道中的哪一个对唾液的产生具有重要的功能。我们将与子项目1协调工作，以确定激动剂诱导的信号对K+和Cl-通道激活的生理相关影响。在目标2中，将通过克隆编码相应的K+和Cl-通道蛋白的cDNA来确定在人和小鼠腮腺腺泡细胞中表达的通道的分子同一性。目标1和目标2以及子项目1的结果将为预测单个通道在分泌过程中的作用提供必要的信息。然而，由于缺乏针对许多通道的不同药理作用，在测试某一特定蛋白的重要性时，最容易通过研究该通道表达缺陷的动物来获得。在目标3中，将通过检测基因中断的影响来确定特定通道蛋白的功能意义。缺乏两种不同氯通道表达的小鼠目前可用于研究(CFTR和C1C3)。其他被发现在分泌中起关键作用的通道，不能被抑制剂选择性地阻断，将通过定向重组在老鼠身上消除。这些研究的结果有望揭示某些形式的特发性唾液腺功能低下的遗传基础，并为开发针对这些人以及那些患有其他形式的唾液腺功能障碍的患者的治疗方法提供基础。

Approximately 20% of xerostomia cases are of unknown etiology. Many of these idiopathic "dry mouth" disorders are likely due to genetic defects in the fluid transport mechanism. An initial step in the development of treatments for these latter individuals is to identify the key transport proteins involved in the fluid secretion process. Secretion is driven by the activation of K+ and C1-channels. Several distinct types of K+ and Cl- channels have been functionally identified in salivary acinar cells, but only a few of these have been identified as specific gene products. Some of the properties of these proteins have been determined but little is known about the specific contribution these channels make to the fluid secretion process. Thus, the long-term objective of this Subproject is to identify the K+ and Cl-channel proteins essential for saliva production in human and mouse parotid glands. We will attempt to corroborate our findings in humans identified as suffering from idiopathic dry mouth as part of Subproject 3. Aim 1 will distinguish which of the different K+ and Cl-channels are functionally important to the production of saliva by characterizing channel different K+ and Cl-channels are functionally important in the production of saliva by characterizing channel biophysics. We will coordinate our efforts with Subproject 1 in order to determine the physiologically relevant effects of agonist-induced signals on the activation of K+ and Cl-channels. In Aim 2, the molecular identity of the channels expressed in human and mouse parotid acinar cells will be determined by cloning cDNAs that encode the corresponding K+ and Cl- channel proteins. The results from Aims 1 and 2, as well as those from Subproject 1, will provide essential information for predicting the role of individual channels in the secretion process. However, owing to the lack of different pharmacology for many channels in the test of the importance of a given protein can be obtained most easily by studying an animal defective in the expression of the channel. In Aim 3 the functional significance of specific channel proteins will be determined by examining the effects of gene disruption. Mice lacking expression of two different Cl-channels are currently available for study (CFTR and C1C3). Additional channels found to play critical roles in secretion that can not be selectively blocked with inhibitors will be eliminated in mice by targeted recombination. The results of these studies are expected to uncover the genetic basis for some forms of idiopathic salivary gland hypofunction and to provide a foundation for the development of treatments for these individuals as well as those patients suffering from other forms of salivary gland dysfunction.