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Annual Review of Biochemistry Jun 2020Generating the barriers that protect our inner surfaces from bacteria and other challenges requires large glycoproteins called mucins. These come in two types,... (Review)
Review
Generating the barriers that protect our inner surfaces from bacteria and other challenges requires large glycoproteins called mucins. These come in two types, gel-forming and transmembrane, all characterized by large, highly -glycosylated mucin domains that are diversely decorated by Golgi glycosyltransferases to become extended rodlike structures. The general functions of mucins on internal epithelial surfaces are to wash away microorganisms and, even more importantly, to build protective barriers. The latter function is most evident in the large intestine, where the inner mucus layer separates the numerous commensal bacteria from the epithelial cells. The host's conversion of MUC2 to the outer mucus layer allows bacteria to degrade the mucin glycans and recover the energy content that is then shared with the host. The molecular nature of the mucins is complex, and how they construct the extracellular complex glycocalyx and mucus is poorly understood and a future biochemical challenge.
Topics: Animals; Carbohydrate Conformation; Carbohydrate Sequence; Gastrointestinal Microbiome; Gene Expression; Glycocalyx; Glycosylation; Glycosyltransferases; Goblet Cells; Humans; Mucins; Mucus; Symbiosis
PubMed: 32243763
DOI: 10.1146/annurev-biochem-011520-105053 -
Cell Host & Microbe Jul 2023The colon mucus layer is organized with an inner colon mucus layer that is impenetrable to bacteria and an outer mucus layer that is expanded to allow microbiota... (Review)
Review
The colon mucus layer is organized with an inner colon mucus layer that is impenetrable to bacteria and an outer mucus layer that is expanded to allow microbiota colonization. A major component of mucus is MUC2, a glycoprotein that is extensively decorated, especially with O-glycans. In the intestine, goblet cells are specialized in controlling glycosylation and making mucus. Some microbiota members are known to encode multiple proteins that are predicted to bind and/or cleave mucin glycans. The interactions between commensal microbiota and host mucins drive intestinal colonization, while at the same time, the microbiota can utilize the glycans on mucins and affect the colonic mucus properties. This review will examine this interaction between commensal microbes and intestinal mucins and discuss how this interplay affects health and disease.
Topics: Intestinal Mucosa; Mucin-2; Intestines; Mucus; Mucins; Microbiota; Polysaccharides
PubMed: 37442097
DOI: 10.1016/j.chom.2023.05.026 -
American Journal of Respiratory and... Mar 2019MUC5AC and MUC5B are the predominant gel-forming mucins in the mucus layer of human airways. Each mucin has distinct functions and site-specific expression. However, the...
RATIONALE
MUC5AC and MUC5B are the predominant gel-forming mucins in the mucus layer of human airways. Each mucin has distinct functions and site-specific expression. However, the regional distribution of expression and cell types that secrete each mucin in normal/healthy human airways are not fully understood.
OBJECTIVES
To characterize the regional distribution of MUC5B and MUC5AC in normal/healthy human airways and assess which cell types produce these mucins, referenced to the club cell secretory protein (CCSP).
METHODS
Multiple airway regions from 16 nonsmoker lungs without a history of lung disease were studied. MUC5AC, MUC5B, and CCSP expression/colocalization were assessed by RNA in situ hybridization and immunohistochemistry in five lungs with histologically healthy airways. Droplet digital PCR and cell cultures were performed for absolute quantification of MUC5AC/5B ratios and protein secretion, respectively.
MEASUREMENTS AND MAIN RESULTS
Submucosal glands expressed MUC5B, but not MUC5AC. However, MUC5B was also extensively expressed in superficial epithelia throughout the airways except for the terminal bronchioles. Morphometric calculations revealed that the distal airway superficial epithelium was the predominant site for MUC5B expression, whereas MUC5AC expression was concentrated in proximal, cartilaginous airways. RNA in situ hybridization revealed MUC5AC and MUC5B were colocalized with CCSP-positive secretory cells in proximal superficial epithelia, whereas MUC5B and CCSP-copositive cells dominated distal regions.
CONCLUSIONS
In normal/healthy human airways, MUC5B is the dominant secretory mucin in the superficial epithelium and glands, with distal airways being a major site of expression. MUC5B and MUC5AC expression is a property of CCSP-positive secretory cells in superficial airway epithelia.
Topics: Humans; Lung; Mucin 5AC; Mucin-5B; Protein Transport; Respiratory Physiological Phenomena
PubMed: 30352166
DOI: 10.1164/rccm.201804-0734OC -
Current Opinion in Structural Biology Jun 2019The study of mucin O-glycan recognition by glycan-binding proteins has been a challenging area of research at the interface of chemistry and biology. Compared with... (Review)
Review
The study of mucin O-glycan recognition by glycan-binding proteins has been a challenging area of research at the interface of chemistry and biology. Compared with N-glycans, the development of methods for mucin O-glycans has lagged behind and underrepresentation of O-glycans in any of the current microarray libraries have hampered their application in O-glycan recognition studies. A major reason is that, thus far, there has not been a universal O-glycanase for enzymatic release of O-glycans from mucins. Methods of chemical release result in degradation or modification of the core regions. Therefore, isolated O-glycans have been very limited while chemical/enzymatic synthesis has been slow. As for other types of glycans, a variety of approaches have been developed for construction of arrays using different strategies to overcome the limitation of direct immobilization of glycans onto solid matrices. In this presentation, we overview the current state of play in the construction of O-glycan libraries obtained after their release from mucin glycoproteins and from chemical and chemoenzymatic synthesis for microarray construction using non-covalent and covalent immobilization, and highlight their applications.
Topics: Animals; Humans; Mucins; Polysaccharides; Protein Array Analysis
PubMed: 31063936
DOI: 10.1016/j.sbi.2019.03.032 -
American Journal of Respiratory and... Feb 2024Non-cystic fibrosis bronchiectasis (NCFB) may originate in bronchiolar regions of the lung. Accordingly, there is a need to characterize the morphology and molecular...
Non-cystic fibrosis bronchiectasis (NCFB) may originate in bronchiolar regions of the lung. Accordingly, there is a need to characterize the morphology and molecular characteristics of NCFB bronchioles. Test the hypothesis that NCFB exhibits a major component of bronchiolar disease manifest by mucus plugging and ectasia. Morphologic criteria and region-specific epithelial gene expression, measured histologically and by RNA hybridization and immunohistochemistry, identified proximal and distal bronchioles in excised NCFB lungs. RNA hybridization and immunohistochemistry assessed bronchiolar mucus accumulation and mucin gene expression. CRISPR-Cas9-mediated IL-1R1 knockout in human bronchial epithelial cultures tested IL-1α and IL-1β contributions to mucin production. Spatial transcriptional profiling characterized NCFB distal bronchiolar gene expression. Bronchiolar perimeters and lumen areas per section area were increased in proximal, but not distal, bronchioles in NCFB versus control lungs, suggesting proximal bronchiolectasis. In NCFB, mucus plugging was observed in ectatic proximal bronchioles and associated nonectatic distal bronchioles in sections with disease. MUC5AC and MUC5B mucins were upregulated in NCFB proximal bronchioles, whereas MUC5B was selectively upregulated in distal bronchioles. Bronchiolar mucus plugs were populated by IL-1β-expressing macrophages. NCFB sterile sputum supernatants induced human bronchial epithelial MUC5B and MUC5AC expression that was >80% blocked by IL-1R1 ablation. Spatial transcriptional profiling identified upregulation of genes associated with secretory cells, hypoxia, interleukin pathways, and IL-1β-producing macrophages in mucus plugs and downregulation of epithelial ciliogenesis genes. NCFB exhibits distinctive proximal and distal bronchiolar disease. Both bronchiolar regions exhibit bronchiolar secretory cell features and mucus plugging but differ in mucin gene regulation and ectasia.
Topics: Humans; Bronchioles; Dilatation, Pathologic; Bronchiectasis; Cystic Fibrosis; Mucins; Interleukin-1beta; Fibrosis; RNA; Mucin 5AC
PubMed: 38016030
DOI: 10.1164/rccm.202306-1093OC -
Nature Biotechnology Apr 2024Targeted protein degradation is an emerging strategy for the elimination of classically undruggable proteins. Here, to expand the landscape of targetable substrates, we...
Targeted protein degradation is an emerging strategy for the elimination of classically undruggable proteins. Here, to expand the landscape of targetable substrates, we designed degraders that achieve substrate selectivity via recognition of a discrete peptide and glycan motif and achieve cell-type selectivity via antigen-driven cell-surface binding. We applied this approach to mucins, O-glycosylated proteins that drive cancer progression through biophysical and immunological mechanisms. Engineering of a bacterial mucin-selective protease yielded a variant for fusion to a cancer antigen-binding nanobody. The resulting conjugate selectively degraded mucins on cancer cells, promoted cell death in culture models of mucin-driven growth and survival, and reduced tumor growth in mouse models of breast cancer progression. This work establishes a blueprint for the development of biologics that degrade specific protein glycoforms on target cells.
Topics: Animals; Mice; Mucins; Peptide Hydrolases; Neoplasms; Proteolysis
PubMed: 37537499
DOI: 10.1038/s41587-023-01840-6 -
Advanced Drug Delivery Reviews Feb 2023Mucins represent a largely untapped class of polymeric building block for biomaterials, therapeutics, and other biotechnology. Because the mucin polymer backbone is... (Review)
Review
Mucins represent a largely untapped class of polymeric building block for biomaterials, therapeutics, and other biotechnology. Because the mucin polymer backbone is genetically encoded, sequence-specific mucins with defined physical and biochemical properties can be fabricated using recombinant technologies. The pendent O-glycans of mucins are increasingly implicated in immunomodulation, suppression of pathogen virulence, and other biochemical activities. Recent advances in engineered cell production systems are enabling the scalable synthesis of recombinant mucins with precisely tuned glycan side chains, offering exciting possibilities to tune the biological functionality of mucin-based products. New metabolic and chemoenzymatic strategies enable further tuning and functionalization of mucin O-glycans, opening new possibilities to expand the chemical diversity and functionality of mucin building blocks. In this review, we discuss these advances, and the opportunities for engineered mucins in biomedical applications ranging from in vitro models to therapeutics.
Topics: Humans; Mucins; Polysaccharides; Biotechnology
PubMed: 36375719
DOI: 10.1016/j.addr.2022.114618 -
Current Opinion in Supportive and... Jun 2019Alimentary mucositis is a severe dose limiting side effect of chemotherapy and radiotherapy. Mucin expression and secretion are associated with mucositis. This article... (Review)
Review
PURPOSE OF REVIEW
Alimentary mucositis is a severe dose limiting side effect of chemotherapy and radiotherapy. Mucin expression and secretion are associated with mucositis. This article aims to review current studies involving mucin and mucositis.
RECENT FINDINGS
Mucins have been shown to alter mucositis severity and key targets associated with mucositis. First, interventions increasing mucin content has been associated with reduce damage associated with mucositis. Second, mucins have also been shown to protect microbiota from radiation-induced damage. Finally, mucins have also been shown to be involved in lumen epithelial barrier interactions altering signalling for cell proliferation, motility, and the inhibition of apoptosis.
SUMMARY
The current studies suggest that mucin expression prior to and during mucositis may be very important in reducing the severity of mucositis and further research into the area is warranted.
Topics: Animals; Antineoplastic Agents; Diet Therapy; Gastrointestinal Microbiome; Histamine H2 Antagonists; Humans; Intestinal Mucosa; Mucins; Mucositis; Radiotherapy; Signal Transduction
PubMed: 30893104
DOI: 10.1097/SPC.0000000000000423 -
ChemPlusChem Dec 2020Mucins are bottlebrush biopolymers that are glycoproteins on the surfaces of cells and as hydrogels secreted inside and outside the body. Mucin function in biology... (Review)
Review
Mucins are bottlebrush biopolymers that are glycoproteins on the surfaces of cells and as hydrogels secreted inside and outside the body. Mucin function in biology includes cell-cell recognition, signaling, protection, adhesion, and lubrication. Because of their attractive and diverse properties, mucins have recently become the focus of synthetic efforts by researchers who hope to understand and emulate these biomaterials. This review is focused on the development of methodologies for preparing mucin-inspired synthetic oligomers and glycopolymers, including solid-phase synthesis, polymerization of glycosylated monomers, and post-polymerization grafting of glycans to polymer chains. How these synthetic mucins have been used in health applications is discussed. Natural mucins are formed from a conserved set of monomers that are combined into chains of different sequences and lengths to achieve materials with widely diverse properties. Adopting this design paradigm from natural mucins could lead to next-generation bioinspired synthetic materials.
Topics: Humans; Mucins; Polymers
PubMed: 33346954
DOI: 10.1002/cplu.202000637 -
Methods in Molecular Biology (Clifton,... 2022Mucin glycosylation is the key facilitator of microbial attachment and nutrition and it varies according to biological location, health and disease status, microbiome...
Mucin glycosylation is the key facilitator of microbial attachment and nutrition and it varies according to biological location, health and disease status, microbiome composition, infection, and multiple other factors. Mucin glycans have also been reported to attenuate pathogen virulence and mediate biofilm dispersal. With the labor intensive and time-consuming purification required for natural mucins and their low quantitative yield from biological sources, natural mucin microarrays provide a convenient and multiplexed platform to study mucin glycosylation and interactions. In this chapter we describe the purification of natural mucins, using sputum as an example biological source, and the printing of natural mucin microarrays.
Topics: Glycosylation; Microarray Analysis; Mucins; Polysaccharides; Virulence
PubMed: 34972934
DOI: 10.1007/978-1-0716-2148-6_8