Molecular organization of the mucins and glycocalyx underlying mucus transport over mucosal surfaces of the airways.
Molecular organization of the mucins and glycocalyx underlying mucus transport over mucosal surfaces of the airways.
复制标题
作者：
黏液携带着吸入的颗粒物和病原体，通过纤毛在纤毛周围层（PCL）内的摆动从气道黏膜表面清除。人们认为PCL是“水样的”，并且由于纤毛摆动产生的类触变力而没有黏液。然而，由于旋转半径约为250纳米，聚合黏蛋白应该很容易进入PCL，所以我们评估了糖萼的屏障功能。PCL对MUC5AC和MUC5B染色呈阴性，但对硫酸角质素呈阳性，硫酸角质素是一种通常与糖缀合物相关的糖胺聚糖。鸟枪法蛋白质组学显示，来自黏液的富含硫酸角质素的组分含有大量的系留黏蛋白MUC1、MUC4和MUC16，但没有蛋白聚糖。通过光学和电子显微镜进行的免疫组织学研究将MUC1定位在微绒毛上，MUC4和MUC20定位在纤毛上，MUC16定位在杯状细胞上。电子显微镜和原子力显微镜显示系留黏蛋白的分子长度为190 - 1500纳米，以及一个填充纤毛间空间的质地精细的糖萼基质。腺病毒颗粒被排除在微绒毛的糖萼之外，而较小的腺相关病毒（AAV）能够穿透，但被困在其中。因此，组织成填充空间的糖萼的系留黏蛋白作为PCL的选择性屏障发挥作用，拓宽了它们在先天性肺部防御中的作用，并为常规治疗和基因治疗提供了新的分子靶点。
Mucus, with its burden of inspired particulates, and pathogens, is cleared from mucosal surfaces of the airways by cilia beating within the periciliary layer (PCL). The PCL is held to be ‘watery’ and free of mucus by thixotropic-like forces arising from beating cilia. With radii of gyration ~250 nm, however, polymeric mucins should reptate readily into the PCL, so we assessed the glycocalyx for barrier functions. The PCL stained negative for MUC5AC and MUC5B, but it was positive for keratan sulfate, a glycosaminoglycan commonly associated with glycoconjugates. Shotgun proteomics showed keratan sulfate-rich fractions from mucus containing abundant tethered mucins, MUC1, MUC4, and MUC16, but no proteoglycans. Immuno-histology by light and electron microscopy localized MUC1 to microvilli, MUC4 and MUC20 to cilia, and MUC16 to goblet cells. Electron and atomic force microscopy revealed molecular lengths of 190–1,500 nm for tethered mucins, and a finely textured glycocalyx matrix filling interciliary spaces. Adenoviral particles were excluded from glycocalyx of the microvilli, while the smaller AAV penetrated, but were trapped within. Hence, tethered mucins organized as a space-filling glycocalyx function as a selective barrier for the PCL, broadening their role in innate lung defense and offering new molecular targets for conventional and gene therapies.