Regulation of Mucin Exocytosis by Munc18

描述(申请人提供)：分泌到呼吸道的凝胶粘蛋白被认为通过清除吸入的病原体和微粒来保护肺部。然而，粘蛋白过度分泌会导致气流阻塞和呼吸道损伤。因此，严格控制粘蛋白的分泌是维持呼吸道内环境稳定的关键。Munc18蛋白是真核细胞受调节的分泌机制的重要组成部分，因此它们的缺失会导致分泌的完全失败。我们发现Munc18b在呼吸道分泌细胞的顶膜上表达，Munc18b杂合子缺失的小鼠在呼吸道粘蛋白分泌方面存在缺陷。由于纯合子Munc18b缺失小鼠不能存活，我们产生了仅在呼吸道分泌细胞中功能丧失的条件性Munc18b缺失小鼠。我们还产生了在呼吸道分泌细胞中过度表达功能获得突变Munc18b的转基因小鼠。我们假设，在呼吸道分泌细胞中缺失Munc18b的小鼠将完全不能在基线或刺激下分泌呼吸道粘蛋白，而转基因小鼠将分泌高水平的呼吸道粘蛋白。这些假说将在以下特定目标中得到检验：1)评估Munc18b缺失和转基因突变小鼠呼吸道结构的变化。2)测定Munc18b基因缺失和转基因突变小鼠的基线和刺激分泌功能。这些研究将促进对呼吸道分泌机制的结构和功能的了解，并为未来的研究提供必要的试剂，以测试粘蛋白分泌在肺部疾病中可能的保护和病理作用。公共卫生相关性：呼吸道中的粘液是保护肺部免受吸入颗粒物和感染的必要物质。另一方面，在囊性纤维化和哮喘中，过多的粘液会阻塞呼吸道。我们将研究粘液是如何分泌到呼吸道中的，以确定如何将其优化用于肺部疾病的治疗。

DESCRIPTION (provided by applicant): Gel-forming mucins secreted into the airways are thought to protect the lungs by clearance of inhaled pathogens and particulates. However, mucin hypersecretion can cause airflow obstruction and airway injury. Therefore, tight control of mucin secretion is critical for airway homeostasis. Munc18 proteins are essential components of the regulated secretory machinery of eukaryotic cells, such that their absence causes complete failure of secretion. We find that Munc18b is expressed at the apical membrane of airway secretory cells, and that heterozygous Munc18b null mice have a defect in airway mucin secretion. Since homozygous Munc18b null mice are not viable, we have generated conditional Munc18b deletant mice with a loss-of-function only in airway secretory cells. We have also generated transgenic mice overexpressing a gain-of-function Munc18b mutant in airway secretory cells. We hypothesize that the mice with Munc18b deleted in their airway secretory cells will completely fail to secrete airway mucins at baseline or with stimulation, and that the transgenic mice will hypersecrete airway mucins. These hypotheses will be tested in the following Specific Aims: 1) Assess changes in the structure of the airways of Munc18b null and transgenic mutant mice. 2) Determine baseline and stimulated secretory function in Munc18b null and transgenic mutant mice. The proposed studies will advance understanding of the structure and function of the airway secretory mechanism, and provide essential reagents for future studies to test the putative protective and pathologic roles of mucin secretion in lung diseases. PUBLIC HEALTH RELEVANCE: Mucus in the airways is needed to protect the lungs against inhaled particles and infections. On the other hand, too much mucus blocks the airways in cystic fibrosis and asthma. We will study how mucus is secreted into the airways to determine how this can be optimized for treatment of lung diseases.