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Digestive Diseases (Basel, Switzerland) 2021Mucus protects the epithelium against invaders and toxic materials. Sticky and thick mucus is characteristic of CF.
BACKGROUND
Mucus protects the epithelium against invaders and toxic materials. Sticky and thick mucus is characteristic of CF.
OBJECTIVE
The aim of this systematic review is to characterize the specific mucins secreted in the lung and intestinal tract of CF patients.
METHODS
A systematic literature search was conducted up to December 31, 2019. The following terms were used: "cystic fibrosis" AND "mucin." Case-control studies comparing mucin expression in CF patients to healthy controls were included.
RESULTS
We found 741 eligible studies, 694 studies were rejected because they were performed in animals and not in full text, and 32 studies were excluded being editorials, duplications, review articles, meta-analysis, or not in English. Fifteen studies were eligible for our study, including 150 CF patients compared to 82 healthy controls, all fulfilled the inclusion criteria. The main mucin types expressed in the sinus submucosal glands, sputum, tracheobronchial surface epithelium, and lung submucosal glands were MUC5AC and MUC5B. Increase in the number of sinusoidal submucosal glands and expression of MUC5B was found in CF patients, but no such difference from healthy controls was found for the number of goblet cells in the surface epithelium nor in the expression of -MUC5AC. The opposite was found in the tracheobronchial surface epithelium and in the lungs.
CONCLUSIONS
Increased expression of MUC5AC in the surface epithelium and of MUC5B in the subepithelial glands may be the result of higher secretion rate of mucin into the lumen of the respiratory tract, causing mucus plaque, infection, and inflammation.
Topics: Animals; Bodily Secretions; Case-Control Studies; Cystic Fibrosis; Gastrointestinal Tract; Humans; Lung; Mucin 5AC; Mucin-5B; Mucins
PubMed: 33049746
DOI: 10.1159/000512268 -
BMB Reports Jul 2021Mucins are high molecular-weight epithelial glycoproteins and are implicated in many physiological processes, including epithelial cell protection, signaling... (Review)
Review
Mucins are high molecular-weight epithelial glycoproteins and are implicated in many physiological processes, including epithelial cell protection, signaling transduction, and tissue homeostasis. Abnormality of mucus expression and structure contributes to biological properties related to human cancer progression. Tumor growth sites induce inhospitable conditions. Many kinds of research suggest that mucins provide a microenvironment to avoid hypoxia, acidic, and other biological conditions that promote cancer progression. Given that the mucus layer captures growth factors or cytokines, we propose that mucin helps to ameliorate inhospitable conditions in tumor-growing sites. Additionally, the composition and structure of mucins enable them to mimic the surface of normal epithelial cells, allowing tumor cells to escape from immune surveillance. Indeed, human cancers such as mucinous carcinoma, show a higher incidence of invasion to adjacent organs and lymph node metastasis than do non-mucinous carcinoma. In this minireview, we discuss how mucin provides a tumor-friendly environment and contributes to increased cancer malignancy in mucinous carcinoma. [BMB Reports 2021; 54(7): 344-355].
Topics: Biomarkers, Tumor; Humans; Mucin-1; Mucins; Neoplasms; Neoplastic Stem Cells; Tumor Microenvironment
PubMed: 34154702
DOI: 10.5483/BMBRep.2021.54.7.064 -
Colloids and Surfaces. B, Biointerfaces Jul 2023Mucus reduces friction between epithelial surfaces by providing lubrication in the boundary and mixed regime. Mucins, the main macromolecule, are heavily glycosylated...
Mucus reduces friction between epithelial surfaces by providing lubrication in the boundary and mixed regime. Mucins, the main macromolecule, are heavily glycosylated proteins that polymerise and retain water molecules, resulting in a hydrated biogel. It is assumed that positively charged ions can influence mucin film structure by screening the electrostatic repulsions between the negatively charged glycans on mucin moieties and draw in water molecules via hydration shells. The ionic concentration can vary significantly in different mucus systems and here we show that increasing the ionic concentration in mucin films leads to an increase in lubrication between two polydimethylsiloxane surfaces at sliding contact in a compliant oral mimic. Mucins were found to bind sodium ions in a concentration-dependent manner and increased ionic concentration appears to cause mucin films to swell when assessed by Quartz Crystal hiMicrobalance with Dissipation (QCM-D) analysis. Furthermore, we determined that the removal of negatively charged sialic acid moieties by sialidase digestion resulted in reduced adsorption to hydrophilic surfaces but did not affect the swelling of mucin films with increasing ionic concentrations. Moreover, the coefficient of friction was increased with sialic acid removal, but lubrication was still increased with increasing ionic concentrations. Taken together this suggests that sialic acids are important for lubrication and may exert this through the sacrificial layer mechanism. Ionic concentration appears to influence mucin films and their lubrication, and sialic acids, at least partly, may be important for ion binding.
Topics: Mucins; Lubrication; Sialic Acids; N-Acetylneuraminic Acid; Water
PubMed: 37172419
DOI: 10.1016/j.colsurfb.2023.113327 -
FASEB Journal : Official Publication of... Feb 2020Many members of the mucin family are evolutionarily conserved and are often aberrantly expressed and glycosylated in various benign and malignant pathologies leading to...
Many members of the mucin family are evolutionarily conserved and are often aberrantly expressed and glycosylated in various benign and malignant pathologies leading to tumor invasion, metastasis, and immune evasion. The large size and extensive glycosylation present challenges to study the mucin structure using traditional methods, including crystallography. We offer the hypothesis that the functional versatility of mucins may be attributed to the presence of intrinsically disordered regions (IDRs) that provide dynamism and flexibility and that the IDRs offer potential therapeutic targets. Herein, we examined the links between the mucin structure and function based on IDRs, posttranslational modifications (PTMs), and potential impact on their interactome. Using sequence-based bioinformatics tools, we observed that mucins are predicted to be moderately (20%-40%) to highly (>40%) disordered and many conserved mucin domains could be disordered. Phosphorylation sites overlap with IDRs throughout the mucin sequences. Additionally, the majority of predicted O- and N- glycosylation sites in the tandem repeat regions occur within IDRs and these IDRs contain a large number of functional motifs, that is, molecular recognition features (MoRFs), which directly influence protein-protein interactions (PPIs). This investigation provides a novel perspective and offers an insight into the complexity and dynamic nature of mucins.
Topics: Glycosylation; Humans; Models, Molecular; Mucins; Protein Domains; Sequence Analysis, Protein; Structure-Activity Relationship
PubMed: 31908009
DOI: 10.1096/fj.201901898RR -
Glycobiology Dec 2014Vascular endothelial cells, in addition to many other mammalian cell types, express proteins that are highly modified with mucin-type O-glycosylation, a specific type of... (Review)
Review
Vascular endothelial cells, in addition to many other mammalian cell types, express proteins that are highly modified with mucin-type O-glycosylation, a specific type of glycosylation that begins with the addition of an N-acetylgalactosamine moiety to serine or threonine residues within the peptide backbone. Recently, it has become evident that O-glycosylation governs the separation of blood and lymphatic vessels throughout life and plays a critical role in maintaining vascular integrity in specific tissues such as the brain and lymph node. This mini-review seeks to highlight some of these recent advances regarding in vivo functions of mucin-type O-glycans.
Topics: Animals; Endothelium, Vascular; Glycosylation; Humans; Mucins; Polysaccharides
PubMed: 24946788
DOI: 10.1093/glycob/cwu058 -
American Journal of Respiratory Cell... Feb 2007Mucus secretions have played a central role in the evolution of multicellular organisms, enabling adaptation to widely differing environments. In vertebrates, mucus... (Review)
Review
Mucus secretions have played a central role in the evolution of multicellular organisms, enabling adaptation to widely differing environments. In vertebrates, mucus covers and protects the epithelial cells in the respiratory, gastrointestinal, urogenital, visual, and auditory systems, amphibian's epidermis, and the gills in fishes. Deregulation of mucus production and/or composition has important consequences for human health. For example, mucus obstruction of small airways is observed in chronic airway diseases, including chronic obstructive pulmonary disease, asthma, and cystic fibrosis. The major protein component in the mucus is a family of large, disulfide-bonded glycoproteins known as gel-forming mucins. These proteins are accumulated in large, regulated secretory granules (the mucin granules) that occupy most of the apical cytoplasm of specialized cells known as mucous/goblet cells. Since mucin oligomers have contour dimensions larger than the mucin granule average diameter, the question arises how these highly hydrophilic macromolecules are organized within these organelles. I review here the intraluminal organization of the mucin granule in view of our knowledge on the structure, biosynthesis, and biophysical properties of gel-forming mucins, and novel imaging studies in living mucous/goblet cells. The emerging concept is that the mucin granule lumen comprises a partially condensed matrix meshwork embedded in a fluid phase where proteins slowly diffuse.
Topics: Animals; Cystic Fibrosis Transmembrane Conductance Regulator; Extracellular Matrix; Goblet Cells; Humans; Mucins; Protein Transport; Secretory Vesicles
PubMed: 16960124
DOI: 10.1165/rcmb.2006-0291TR -
International Journal of Medical... 2017Pseudomyxoma peritonei (PMP) is a rare disease with excess intraperitoneal mucin secretion. Treatment involves laparotomy, cytoreduction and chemotherapy that is very...
Pseudomyxoma peritonei (PMP) is a rare disease with excess intraperitoneal mucin secretion. Treatment involves laparotomy, cytoreduction and chemotherapy that is very invasive with patients often acquiring numerous compromises. Hence a mucolytic comprising of bromelain and N-acetyl cystein has been developed to solubilise mucin in situ for removal by catherization. Owing to differences in mucin appearance and hardness, dissolution varies. Therefore the current study investigates the inter-mucin physical and chemical characteristics, in order to reformulate an effective mucolytic for all mucin. PMP mucin, from the three categories (soft, semi hard and hard mucin) was solubilised and then various physical characteristics such as turbidity, density, kinematic viscosity were measured. The water content and the density of solid mucin were also determined. This was followed by the determination of sialic acid, glucose, lipid, Thiol (S-S and S-H) content of the samples. Lastly, the distribution of MUC2, MUC5B and MUC5AC was determined using western blot technique. Both turbidity and kinematic viscosity and sialic acid content increased linearly as the hardness of mucin increased. However, density, hydration, protein, glucose, lipid and sulfhydryl and disulphide content decreased linearly as hardness of mucin increased. The distribution ratio of mucins (MUC2:MUC5B:MUC5AC) in soft mucin is 2.25:1.5:1.0, semi hard mucin is 1:1:1 and hard mucin is 3:2:1. The difference in texture and hardness of mucin may be due to cellular content, hydration, glucose, protein, lipids, thiol and MUC distribution. Soft mucin is solely made of glycoprotein whilst the others contained cellular materials.
Topics: Glucose; Humans; Lipids; Mucin 5AC; Mucin-2; Mucin-5B; Mucins; Mucus; N-Acetylneuraminic Acid; Peritoneal Neoplasms; Pseudomyxoma Peritonei; Sulfhydryl Compounds; Viscosity
PubMed: 28138305
DOI: 10.7150/ijms.16422 -
Biochemical Society Transactions Jun 2018In humans and mice, the first line of innate defense against inhaled pathogens and particles in the respiratory tract is airway mucus. The primary solid components of... (Review)
Review
In humans and mice, the first line of innate defense against inhaled pathogens and particles in the respiratory tract is airway mucus. The primary solid components of the mucus layer are the mucins MUC5AC and MUC5B, polymeric glycoproteins whose changes in abundance and structure can dramatically affect airway defense. Accordingly, and are tightly regulated at a transcriptional level by tissue-specific transcription factors in homeostasis and in response to injurious and inflammatory triggers. In addition to modulated levels of mucin gene transcription, translational and post-translational biosynthetic processes also exert significant influence upon mucin function. Mucins are massive macromolecules with numerous functional domains that contribute to their structural composition and biophysical properties. Single MUC5AC and MUC5B apoproteins have molecular masses of >400 kDa, and von Willebrand factor D-like as well as other cysteine-rich domain segments contribute to mucin polymerization and flexibility, thus increasing apoprotein length and complexity. Additional domains serve as sites for O-glycosylation, which increase further mucin mass several-fold. Glycosylation is a defining process for mucins that is specific with respect to additions of glycans to mucin apoprotein backbones, and glycan additions influence the physical properties of the mucins via structural modifications as well as charge interactions. Ultimately, through their tight regulation and complex assembly, airway mucins follow the biological rule of 'form fits function' in that their structural organization influences their role in lung homeostatic mechanisms.
Topics: Animals; Gene Expression Regulation; Homeostasis; Humans; Inflammation; Lung; Mucins; Transcription, Genetic
PubMed: 29802217
DOI: 10.1042/BST20170455 -
Biochimie Jun 2013Mucins belong to a heterogeneous family of large O-glycoproteins composed of a long peptidic chain called apomucin on which are linked hundreds of oligosaccharidic... (Review)
Review
Mucins belong to a heterogeneous family of large O-glycoproteins composed of a long peptidic chain called apomucin on which are linked hundreds of oligosaccharidic chains. Among mucins, membrane-bound mucins are modular proteins and have a structural organization usually containing Pro/Thr/Ser-rich O-glycosylated domains (PTS), EGF-like and SEA domains. Via these modular domains, the membrane-bound mucins participate in cell signalling and cell interaction with their environment in normal and pathological conditions. Moreover, the recent knowledge of these domains and their biological activities led to the development of new therapeutic approaches involving mucins. In this review, we show 3D structures of EGF and SEA domains. We also describe the functional features of the evolutionary conserved domains of membrane-bound mucins and discuss consequences of splice events.
Topics: Animals; Biological Evolution; Humans; Mucins; Protein Structure, Tertiary
PubMed: 23178705
DOI: 10.1016/j.biochi.2012.11.005 -
The International Journal of... Jul 2014Our current understanding of cystic fibrosis (CF) has revealed that the biophysical properties of mucus play a considerable role in the pathogenesis of the disease in... (Review)
Review
Our current understanding of cystic fibrosis (CF) has revealed that the biophysical properties of mucus play a considerable role in the pathogenesis of the disease in view of the fact that most mucus-producing organs are affected in CF patients. In this review, we discuss the potential causal relationship between altered cystic fibrosis transmembrane conductance regulator (CFTR) function and the production of mucus with abnormal biophysical properties in the intestine and lungs, highlighting what has been learned from cell cultures and animal models that mimic CF pathogenesis. A similar cascade of events, including mucus obstruction, infection and inflammation, is common to all epithelia affected by impaired surface hydration. Hence, the main structural components of mucus, namely the polymeric, gel-forming mucins, are critical to the onset of the disease. Defective CFTR leads to epithelial surface dehydration, altered pH/electrolyte composition and mucin concentration. Further, it can influence mucin transition from the intracellular to extracellular environment, potentially resulting in aberrant mucus gel formation. While defective HCO3(-) production has long been identified as a feature of CF, it has only recently been considered as a key player in the transition phase of mucins. We conclude by examining the influence of mucins on the biophysical properties of CF sputum and discuss existing and novel therapies aimed at removing mucus from the lungs. This article is part of a Directed Issue entitled: Cystic Fibrosis: From o-mics to cell biology, physiology, and therapeutic advances.
Topics: Animals; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Humans; Mucins
PubMed: 24685676
DOI: 10.1016/j.biocel.2014.03.011