Biophysical Approaches to Salivary Mucin Structure, Conformation and Dynamics

Gerken, Thomas A.

doi:10.1177/10454411930040030201

Cited by 30 publications

(18 citation statements)

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“…Although the organization of intracellular mucins is virtually unknown, a reasonable picture can be proposed in view of the information reviewed in the preceding sections, results from early biochemical investigations, and recent live cell imaging investigations (see next section below). Studies with purified, de-glycosylated native mucins support the view that in the endoplasmic reticulum the largely uncharged and non-O-glycosylated mucin precursors (monomers and dimers) likely form globular but highly flexible random coils (16,21,22), which is consistent with the fact that the large central domains comprise repetitive sequences rich in Ser and Thr, and often Gly and Pro residues. Highly flexible chains can form more compact structures and consequently facilitate the transport of mucin precursors out of the endoplasmic reticulum.…”

Section: Gel-forming Mucins: Structural Changes During Biosynthesis Asupporting

confidence: 58%

“…Third, extensive sulfation and sialylation of N-and O-linked oligosaccharide chains in mucins (1), and eventually the conversion of mucins to polyanionic macromolecules, occurs. High negative charge density contributes to the stiffness of the mucin oligomers by increasing the repulsion between adjacent negatively charged rests (21,22). Altogether, these changes create appropriate conditions for novel interchain interactions beyond topological entanglements.…”

Section: Gel-forming Mucins: Structural Changes During Biosynthesis Amentioning

confidence: 99%

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Mucin Granule Intraluminal Organization

Pérez-Vilar

2007

Am J Respir Cell Mol Biol

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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.Keywords: granule matrix; mucin granules; mucins; secretory granules; secretion GEL-FORMING MUCINS: STRUCTURE AND BIOSYNTHESISFive gel-forming mucins (MUC2, MUC5AC, MUC5B, MUC6, and MUC19) have been found in humans. These mucins share a similar structural organization ( Figure 1A) characterized by (1, 2): (i ) multi-domain polypeptide chains with thousands of amino acid residues; (ii) a large, centrally located region mainly consisting of threonine and/or serine-rich tandemly repeated sequences to which O-linked oligosaccharides are covalently bound; (iii) the presence of several under-glycosylated, Cys-rich domains that are conserved among different mucins; (iv) the formation of disulfide-linked species ranging from dimers to more than 16 oligomers (3); and (v ) molecular polydispersity because of genetic polymorphism (e.g., multiple alleles encoding

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Section: Gel-forming Mucins: Structural Changes During Biosynthesis Asupporting

confidence: 58%

Section: Gel-forming Mucins: Structural Changes During Biosynthesis Amentioning

confidence: 99%

Mucin Granule Intraluminal Organization

Pérez-Vilar

2007

Am J Respir Cell Mol Biol

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“…Intermolecular disulphide bridges in conjunction with hydrophobic interaction give mucin its gel-like property. 3 The size of mucin, its gel-like property, and its heavy glycosylation make it a formidable physical barrier to pathogens attempting to colonise the underlying epithelium. Thus, the outcome of the interaction of trichomonads with the host mucous layer will determine whether T vaginalis will be successful in colonising a new host.…”

Section: Introductionmentioning

confidence: 99%

Trichomonad invasion of the mucous layer requires adhesins, mucinases, and motility

Lehker

Sweeney

1999

Sexually Transmitted Infections

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Background/objective: Trichomonas vaginalis, the causal agent of trichomonosis, is a flagellated parasitic protozoan that colonises the epithelial cells of the human urogenital tract. The ability of T vaginalis to colonise this site is in part a function of its ability to circumvent a series of non-specific host defences including the mucous layer covering epithelial cells at the site of infection. Mucin, the framework molecule of mucus, forms a lattice structure that serves as a formidable physical barrier to microbial invasion. The mechanism by which trichomonads traverse the mucous covering is unknown. Proteolytic degradation of mucin, however, may provide for a mechanism to penetrate this layer. The goal, therefore, was to determine how trichomonads cross through a mucous layer. Methods: Secreted trichomonad proteinases were analysed for mucinase activity by mucin substrate-sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The importance of trichomonad mucinases for traversing the mucous layer was examined on an artificial mucin layer in invasion chambers. Adherence to mucin and tissue culture cells was measured using a microtitre plate assay. Results: Trichomonad isolate 24402 secreted five proteinases when incubated in PBS. All five proteinases were shown to possess mucinase activity. These mucinases were able to degrade bovine submaxillary mucin and to a lesser extent porcine stomach mucin. These enzymes were active over a pH range of 4.5-7.0 and were inhibited with cysteine proteinase inhibitors. Furthermore, T vaginalis was shown to bind to mucin possibly via a lectin-like adhesin. Adherence to mucin was increased threefold when parasites were grown in iron deficient medium. Adherence to soluble mucin prevented attachment to HeLa cells. Proteinase activity, adherence, and motility were required for trichomonads to traverse a mucin layer in vitro. Conclusions: These results show that trichomonads can traverse the mucous barrier first by binding mucin followed by its proteolytic degradation. The data further underscore the importance of trichomonad proteinases in the pathogenesis of trichomonosis. Finally, this study suggests that interference with trichomonad mucin receptors and proteinases may be a strategy to prevent colonisation by this parasite. (Sex Transm Inf 1999;75:231-238)

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“…In the oral cavity, MUC5B is produced by goblet cells in the submandibular and sublingual glands (2). The peptide backbone is composed of a variable number of tandem repeats (VNTR) section that has repeating sequences rich in serine, threonine, and proline, which participate in O-glycosylation (1,2,21). Because of the extended VNTR region, MUC5B is composed of approximately 80% carbohydrate in the form of O-linked glycan chains and 20% protein, consisting of the peptide backbone (22,23).…”

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confidence: 99%

Salivary Mucins Protect Surfaces from Colonization by Cariogenic Bacteria

Frenkel

Ribbeck

2015

Appl Environ Microbiol

108

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bUnderstanding how the body's natural defenses function to protect the oral cavity from the myriad of bacteria that colonize its surfaces is an ongoing topic of research that can lead to breakthroughs in treatment and prevention. One key defense mechanism on all moist epithelial linings, such as the mouth, gastrointestinal tract, and lungs, is a layer of thick, well-hydrated mucus. The main gel-forming components of mucus are mucins, large glycoproteins that play a key role in host defense. This study focuses on elucidating the connection between MUC5B salivary mucins and dental caries, one of the most common oral diseases. Dental caries is predominantly caused by Streptococcus mutans attachment and biofilm formation on the tooth surface. Once S. mutans attaches to the tooth, it produces organic acids as metabolic by-products that dissolve tooth enamel, leading to cavity formation. We utilize CFU counts and fluorescence microscopy to quantitatively show that S. mutans attachment and biofilm formation are most robust in the presence of sucrose and that aqueous solutions of purified human MUC5B protect surfaces by acting as an antibiofouling agent in the presence of sucrose. In addition, we find that MUC5B does not alter S. mutans growth and decreases surface attachment and biofilm formation by maintaining S. mutans in the planktonic form. These insights point to the importance of salivary mucins in oral health and lead to a better understanding of how MUC5B could play a role in cavity prevention or diagnosis. One of the body's key defense mechanisms on wet epithelial linings, such as the mouth, gastrointestinal tract, and lungs, is a layer of thick, well-hydrated mucus. The viscoelastic properties of mucus are attributed to mucins, large glycoproteins that play a key role in host defense and maintaining a healthy microbial environment (1-3). Defects in mucin production can lead to diseases such as ulcerative colitis when mucins are underproduced or cystic fibrosis and asthma when mucins are overproduced (4-6). In addition, studies have shown that mucins can interact with microbes, such as Helicobacter pylori, Haemophilus parainfluenzae, and human immunodeficiency virus (7-10). These diseases and microbial interactions highlight the necessity of mucins as one of the body's key natural defenses; however, few studies have focused specifically on the connection between MUC5B salivary mucins and oral diseases. This study fills this gap in understanding by exploring the connection between purified human MUC5B and the virulence of Streptococcus mutans, one of the main cavitycausing bacteria naturally found in the oral cavity (11). MUC7 is another salivary mucin, but MUC5B is the primary mucin component of the dental pellicle coating the soft and hard tissues in the oral cavity (12, 13). Importantly, the effects of MUC5B are characterized in a clinically relevant three-dimensional model that mimics the natural environment in the oral cavity; mucins are secreted into an aqueous phase as opposed to a two-dimensional surfac...

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Biophysical Approaches to Salivary Mucin Structure, Conformation and Dynamics

Cited by 30 publications

References 37 publications

Mucin Granule Intraluminal Organization

Mucin Granule Intraluminal Organization

Trichomonad invasion of the mucous layer requires adhesins, mucinases, and motility

Salivary Mucins Protect Surfaces from Colonization by Cariogenic Bacteria

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