Regulation of Mucin Exocytosis by Munc18

描述（由申请人提供）：分泌到气道中的凝胶状粘蛋白被认为通过清除吸入的病原体和颗粒来保护肺部。然而，粘蛋白分泌过多可引起气流阻塞和气道损伤。因此，严格控制粘蛋白分泌对气道内稳态至关重要。Munc18蛋白是真核细胞调节分泌机制的重要组成部分，因此它们的缺失会导致分泌完全失败。我们发现Munc18b在气道分泌细胞的顶膜表达，杂合Munc18b缺失小鼠气道黏蛋白分泌存在缺陷。由于纯合子Munc18b缺失小鼠不能存活，我们产生了仅在气道分泌细胞中功能丧失的条件Munc18b缺失小鼠。我们还培养了在气道分泌细胞中过表达功能获得型Munc18b突变体的转基因小鼠。我们假设在小鼠的气道分泌细胞中缺失Munc18b的小鼠在基线或刺激下完全不能分泌气道粘蛋白，而转基因小鼠则会高分泌气道粘蛋白。这些假设将在以下具体目的中得到验证：1)评估Munc18b null和转基因突变小鼠气道结构的变化。2)测定Munc18b无基因和转基因突变小鼠的基线和刺激分泌功能。本研究将有助于进一步了解气道分泌机制的结构和功能，并为进一步研究黏蛋白分泌在肺部疾病中的保护性和病理学作用提供必要的试剂。公共卫生相关性：需要气道中的粘液来保护肺部免受吸入颗粒和感染。另一方面，过多的粘液阻塞了囊性纤维化和哮喘的气道。我们将研究粘液如何分泌到气道中，以确定如何优化治疗肺部疾病。

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.