Article

Molecular organization of the mucins and glycocalyx underlying mucus transport over mucosal surfaces of the airways.

1] Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina, USA [2] Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina, USA.
Mucosal Immunology (Impact Factor: 7.54). 08/2012; DOI: 10.1038/mi.2012.81
Source: PubMed

ABSTRACT 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 (KS), a glycosaminoglycan commonly associated with glycoconjugates. Shotgun proteomics showed KS-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, whereas the smaller adenoassociated virus 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.Mucosal Immunology advance online publication 29 August 2012; doi:10.1038/mi.2012.81.

0 Bookmarks
 · 
59 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: MUC16 is a high-molecular-weight glycoprotein that is expressed by the various epithelial cell surfaces of the human body to protect the cell layer from a myriad of insults. It is the largest mucin known to date, with an ∼22,152 aa sequence. Structurally, MUC16 is characterized into 3 distinct domains: the amino terminal, the tandem repeat, and the carboxyl terminal domain, with each domain having unique attributes. The extracellular portion of MUC16 is shed into the bloodstream and serves as a biomarker for diagnosing and monitoring patients with cancer; however, its functional role in cancer is yet to be elucidated. Several factors contribute to this challenge, which include the large protein size; the extensive glycosylation that the protein undergoes, which confers functional heterogeneity; lack of specific antibodies that detect the unique domains of MUC16; and the existence of splicing variants. Despite these limitations, MUC16 has been established as a molecule of significant application in cancer. Hence, in this review, we discuss the various aspects of MUC16, which include its discovery, structure, and biological significance both in benign and malignant conditions with an attempt to dissect its functional relevance.-Haridas, D., Ponnusamy, M. P., Chugh, S., Lakshmanan, I., Seshacharyulu, P., and Batra, S. K. MUC16: molecular analysis and its functional implications in benign and malignant conditions.
    The FASEB Journal 07/2014; 28(10). DOI:10.1096/fj.14-257352 · 5.48 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Basal cells play a critical role in the response of the airway epithelium to injury and are recently recognized to also contribute to epithelial immunity. Antimicrobial proteins and peptides are essential effector molecules in this airway epithelial innate immunity. However, little is known about the specific role of basal cells in antimicrobial protein and peptide production and about the regulation of the ubiquitous antimicrobial protein RNase 7. In this study, we report that basal cells are the principal cell type producing RNase 7 in cultured primary bronchial epithelial cells (PBEC). Exposure of submerged cultured PBEC (primarily consisting of basal cells) to the respiratory pathogen nontypeable Haemophilus influenzae resulted in a marked increase in expression of RNase 7, although this was not observed in differentiated air-liquid interface cultured PBEC. However, transient epithelial injury in air-liquid interface-cultured PBEC induced by cigarette smoke exposure led to epidermal growth factor receptor-mediated expression of RNase 7 in remaining basal cells. The selective induction of RNase 7 in basal cells by cigarette smoke was demonstrated using confocal microscopy and by examining isolated luminal and basal cell fractions. Taken together, these findings demonstrate a phenotype-specific innate immune activity of airway epithelial basal cells, which serves as a second line of airway epithelial defense that is induced by airway epithelial injury. Copyright © 2015 by The American Association of Immunologists, Inc.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Hypertonic saline inhalation has become a cornerstone in the treatment of cystic fibrosis (CF), but its effect on CF mucus is still not understood. In CF, mucus stagnates in the airways, causing mucus plugging and forming a substrate for bacterial invasion. Using horizontal Ussing-type chambers to allow easy access to the tissue, we have recently shown that the small intestinal mucus of CF mice is attached to the epithelium and not freely movable as opposed to normal mucus, thus pointing to a similarity between the CF mucus in the ileum and airways. In the same type of system, we investigated how hypertonic saline affects mucus thickness, attachment and penetrability to fluorescent beads the size of bacteria in ileal explants from the CFTR mutant (ΔF508) mouse, in order to characterize how this common therapy affects mucus properties. Hypertonic saline (1.75-5%) detached the mucus from the epithelium but the mucus remained impenetrable to beads the size of bacteria. This approach may be used to test other mucolytic interventions in CF.This article is protected by copyright. All rights reserved.
    Clinical and Experimental Pharmacology and Physiology 10/2014; DOI:10.1111/1440-1681.12322 · 2.41 Impact Factor

Full-text

Download
22 Downloads
Available from
May 19, 2014