Project 3: Membrane-bound mucins on the airway surface ensure efficient mucus clearance and lung health

健康的气道上皮粘膜屏障是强大的先天性免疫系统的中心，该系统保护气道上皮细胞， 肺部表面受到吸入的传染性和有毒物质的持续冲击。然而，在这方面， 粘液清除系统的异常是许多气道疾病的特征，包括囊性纤维化， 慢性阻塞性肺病和哮喘。这些疾病的发病机制是多因素的，但出现 包括一个常见的疾病引发步骤，减少粘液清除。我们已经开发出一种新颖 描述粘液运输系统的范例，称为“双凝胶”模型，其突出了 气道表面上的两个含粘蛋白层：1）粘液层，含有分泌的粘蛋白， 结合吸入的颗粒;和2）跨膜系留粘蛋白-称为纤毛周层的层- 糖萼（或PCL-G），其衬在气道表面。我们之前已经证明，如果不能对两者进行监管， 层与粘膜纤毛清除的减少有关。然而，目前尚不清楚纤毛和 PCL-G的组织有助于有效清除肺部粘液， 病原体本PPG项目3的总体目标是应用新的理论概念和实验 方法来回答关于PCL-G在粘液运输和免疫调节方面的多重作用的关键问题。 以及保护气道表面所需的宿主屏障防御活动。首先，我们试图了解 粘液层实际上被运输，即，动量是如何从纤毛转移到粘液层的在Aim中 1，我们将检验假设，即在远端气道中，粘蛋白太低而不能产生粘弹性凝胶， 水被“泵出”睫状体周围空间，提供足以输送稀释的水的水动力。 粘液层为此目的的研究旨在量化纤毛跳动产生的抽水力， 评估它们是否足以推动低粘度粘液穿过气道表面，并了解 重力的影响。在目标2中，我们将检验以下假设：在较大的气道中，粘蛋白浓度 足以形成粘弹性凝胶，需要纤毛-粘液动量转移的第二模式，以有效地 粘液运输。在这里，我们假设纤毛顶端的高度糖基化的粘蛋白 在纤毛动力冲程期间与粘液凝胶的微弱/短暂的相互作用， 性新本研究将评估调节系留粘蛋白对粘液凝胶转运功效的影响 以及它在疾病中的变化。目标3中的研究旨在了解密集堆积的 系留粘蛋白在气道保护中起作用。我们将检验这一假设，即气道内的粘蛋白 表面形成物理屏障，以防止吸入的病原体（包括病毒）穿透PCL-G 空间我们预计，这些研究的结果将导致我们对如何理解的范式转变。 粘液清除保持健康，并有助于发现治疗策略， 加速/恢复粘膜阻塞性肺病患者的清除。

The healthy airway epithelial mucosal barrier is the center of a powerful innate immune system that protects the pulmonary surfaces from the constant onslaught of inhaled infectious and noxious substances. However, abnormalities in the mucus clearance system characterize a number of airway diseases, including cystic fibrosis, chronic obstructive lung disease, and asthma. The pathogenesis of these diseases is multi-factorial, but appears to include a common disease-initiating step, a reduction of mucus clearance. We have developed a novel paradigm describing the mucus transport system, referred to as the “two-gel” model, which highlights the role of the two mucin-containing layers on the airway surface: 1) the mucus layer, containing secreted mucins which bind inhaled particles; and 2) membrane-spanning tethered mucins – a layer referred to as the periciliary layer- glycocalyx (or PCL-G) which lines the airway surface. We have previously shown that the failure to regulate both layers is associated with a reduction in mucociliary clearance. However, it is currently unknown how the cilia and PCL-G are organized to facilitate the efficient clearance of mucus out of the lungs and protect against inhaled pathogens. The overarching goal of Project 3 of this PPG is to apply novel theoretical concepts and experimental approaches to answer key questions about the multiple roles of the PCL-G with respect to both mucus transport and the host barrier defense activities required to protect the airway surfaces. First, we seek to understand how the mucus layer actually is transported, i.e., how momentum is transferred from cilia to the mucus layer. In Aim 1, we will test the hypothesis that in the distal airways, where mucins are too low to generate a viscoelastic gel, water is “pumped out” of the periciliary space, providing hydrodynamic force sufficient to transport the dilute mucus layer. Studies in this aim are directed at quantifying the water pumping forces generated by cilia beating, assess whether they are sufficient to propel a low-viscosity mucus across airway surfaces, and understand the impact of gravity. In Aim 2, we will test the hypothesis that in the larger airways, where mucin concentrations are sufficient to form a viscoelastic gel, a second mode of cilia-mucus momentum transfer is required for efficient mucus transport. Here, we hypothesize that the highly glycosylated tethered mucins on the tips of cilia form weak/transient interactions with the mucus gel during the cilia power stroke and physically “thrust” the mucus gel forward. Studies here will assess the impact of modulating tethered mucins on the efficacy of mucus gel transport and how it is altered in disease. Studies in Aim 3 are directed at understanding the role that the densely packed tethered mucins play in airway protection. We will test the hypothesis that tethered mucins lining the airway surface form a physical barrier to prevent inhaled pathogens, including viruses, from penetrating the PCL-G space. We anticipate that results from these studies will lead to paradigm shifts in our understanding of how mucus clearance is maintained in health and aid in the discovery of therapeutic strategies which can accelerate/restore clearance in persons with muco-obstructive lung diseases.