Salivary gland hypofunction & genetic defects

大约20%的口干症病例病因不明。许多这些特发性“口干”疾病可能是由于遗传缺陷的液体运输机制。为后者开发治疗方法的第一步是确定参与液体分泌过程的关键转运蛋白。分泌由K+和C1-通道的激活驱动。几种不同类型的K+和Cl-通道已被确定在唾液腺泡细胞的功能，但只有少数这些已被确定为特定的基因产物。这些蛋白质的一些性质已经确定，但很少有人知道这些通道的具体贡献的液体分泌过程。因此，该子项目的长期目标是鉴定人类和小鼠腮腺中唾液产生所必需的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。目的1将通过表征通道来区分不同的K+和Cl-通道中的哪些对唾液的产生在功能上重要。通过表征通道生物物理学，不同的K+和Cl-通道在唾液的产生中在功能上重要。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作用。在目标2中，将通过克隆编码相应K+和Cl-通道蛋白的cDNA来确定人和小鼠腮腺腺泡细胞中表达的通道的分子身份。目标1和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重要信息。然而，由于缺乏不同的药理学的许多渠道在测试的重要性，一个给定的蛋白质可以最容易地获得通过研究动物有缺陷的表达的通道。在目标3中，将通过检查基因破坏的影响来确定特定通道蛋白的功能意义。缺乏两种不同Cl-通道表达的小鼠目前可用于研究（CFTR和C1 C3）。发现在分泌中起关键作用的不能被抑制剂选择性阻断的额外通道将通过靶向重组在小鼠中被消除。这些研究的结果有望揭示某些形式的特发性唾液腺功能减退的遗传基础，并为这些个体以及患有其他形式唾液腺功能障碍的患者的治疗方法的开发提供基础。

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.