Autophagy-mediated mucin degradation is necessary for resolution of mucous metaplasia

粘膜阻塞性气道疾病包括哮喘、COPD、囊性纤维化和非CF支气管扩张， 不同的遗传和环境起源，但有一些共同的特点，包括病理上皮细胞， 这种变化被称为粘膜化生。气道分泌细胞分化为杯状粘液细胞 细胞形态学上充满了含有MUC5AC和MUC5B的粘蛋白颗粒。这些气道 疾病的特征是由于粘液分泌过多和粘膜的阻塞而频繁恶化。 导致肺功能丧失、住院和死亡风险的气道。虽然许多因素， 因为粘液化生已经被确认，但关于它是如何解决的知之甚少。自噬是一个关键 细胞蛋白质再循环系统，在营养缺乏、炎症和 感染过去几年，我们一直在使用模型研究自噬在气道疾病中的作用 一个关键的自噬调控基因的基因缺失。在本申请中，我们提出了一种新的范例， 该粘蛋白颗粒降解通过以下作用有助于粘液化生的消退 自噬我们的初步数据中有三个关键发现支持了这一假设：第一，自噬缺陷小鼠 并且细胞培养模型在粘液化生期间积累更多的细胞质粘蛋白颗粒， 尤其是在解决问题期间。其次，粘膜化生与mTOR激活相关，并且增加了mTOR的表达。 然后在消退过程中下调上皮代谢。我们认为，这种新陈代谢的转变是 在消退期间启动粘蛋白降解的关键触发因素。第三，模仿新陈代谢的这种变化， mTOR抑制剂导致人气道上皮分泌细胞自噬激活和粘蛋白降解 细胞 为了验证我们的假设，即自噬导致粘蛋白颗粒的降解，我们提出了三项研究， 目的：首先，我们将确定mTOR信号传导如何促进分泌细胞的代谢变化， 最终导致自噬介导的粘蛋白降解。第二，我们将强调 通过检查囊泡运输，溶酶体，在粘液化生消退期间自体溶酶体-溶酶体融合 生物发生和溶酶体蛋白水解功能。第三，我们将探索粘蛋白降解作为一种治疗方法， 粘膜阻塞性气道疾病模型中的策略。这些发现可以为新的 治疗策略，以加速气道疾病恶化的解决。

Muco-obstructive airway diseases including asthma, COPD, cystic fibrosis, and non-CF bronchiectasis have diverse genetic and environmental origins, but have certain common features that includes pathologic epithelial changes referred to as mucous metaplasia. Airway secretory cells differentiate into mucous cells with a goblet cell morphology packed with mucin granules containing MUC5AC and, to lesser extent, MUC5B. These airway diseases are characterized by frequent exacerbations due to mucous hypersecretion and blockage of the airways that leads to loss of lung function, hospitalization, and risk of death. While many of the factors that cause mucous metaplasia have been identified, little is known about how it resolves. Autophagy is a key cellular protein recycling system that degrades proteins in response to nutrient deprivation, inflammation, and infection. We have spent the last several years studying the role of autophagy in airway disease using models with genetic deletions of a key autophagy regulatory genes. In this application, we propose a new paradigm in which mucin granule degradation contributes to resolution of mucous metaplasia through the action of autophagy. Three key findings in our preliminary data support this hypothesis: First, autophagy deficient mouse and cell culture models accumulate more cytoplasmic mucin granules during mucous metaplasia and particularly during resolution. Second, mucous metaplasia is associated with mTOR activation and increased epithelial metabolism which is then down-regulate during resolution. We propose that this shift in metabolism is the key trigger initiating mucin degradation during resolution. Third, mimicking this shift in metabolism with mTOR inhibitors leads to autophagy activation and mucin degradation in human airway epithelial secretory cells. To test our hypothesis that autophagy leads to degradation of mucin granules, we propose three research aims: First, we will determine how mTOR signaling contributes to metabolism change in the secretory cell and ultimately to autophagy-mediated mucin degradation. Second, we will characterize the importance of autolysosome-lysosome fusion during mucous metaplasia resolution by examinig vesicle trafficking, lysosome biogenesis, and lysosome proteolytic function. Third, we will explore mucin degradation as a therapeutic strategy in models of muco-obstructive airway diseases. These findings can provide the framework for a new therapeutic strategy to hasten the resolution of airway disease exacerbations.