Mucin Molecules Research Articles

Research progress of T cell immunoglobulin mucin molecule 1 in the pathogenesis of sepsis

Sepsis 3.0 is defined as a life-threatening organ dysfunction caused by the host' uncontrol response to infection, with poor prognosis, high morbidity and fatality. Sepsis is one of the main causes of death in severe patients. As lack of comprehensive recognition of its pathogenesis, there were not specific treatment on it. It is reported that the T-cell immunoglobulin and mucin-domain-containing molecule (Tim) of Tim-1 play critical role in sepsis inflammation, immune tolerance and apoptosis, which is relative specific factor in assessment of sepsis prognostic and treatment efficiency, indicating that it could be a novel target in sepsis as well as provide a novel direction. This article mainly stated the discovery, structure, distribution and immune effect of Tim-1 as well as the possible role of TIM-1 in immunosuppression, lymphocyte proliferation and apoptosis, in order to provide reference for further research the treatment of sepsis.

Mucoadhesive Drug Delivery Systems: A Review of Recent Developments

Purpose: The aim of this article is to present a review of mucoadhesion drug delivery systems. The review covers the mucoadhesive concepts, polymers used, theories and mechanisms of mucoadhesion, and factors affecting the mucoadhesive dosage forms. Study Design: An extensive review was carried out on mucoadhesion formulations, applications, mechanisms, theories, and polymers used in these dosage forms. Results: Mucoadhesive drug delivery system can interact with the mucus membrane, which covers the mucin molecules and mucosal epithelial surface. This interaction leads to an increment of the dosage form residence time at the site of absorption and hence increasing the bioavailability, efficacy of drugs, and improving therapeutic outcomes. Polymers are used to provide muco-adhesion of the dosage form, enhancing drug release pattern, solubility and dissolution of inadequately soluble drugs. Conclusion: Mucoadhesive drug delivery systems were found to be the best alternative approaches for the traditional dosage forms to enhance bioavailability of poorly soluble drugs and to avoid GIT degradation and first pass metabolism of some drugs.

Structural evidence for a proline-specific glycopeptide recognition domain in an O-glycopeptidase

The glycosylation of proteins is typically considered as a stabilizing modification, including resistance to proteolysis. A class of peptidases, referred to as glycopeptidases or O-glycopeptidases, circumvent the protective effect of glycans against proteolysis by accommodating the glycans in their active sites as specific features of substrate recognition. IMPa from Pseudomonas aeruginosa is such an O-glycopeptidase that cleaves the peptide bond immediately preceding a site of O-glycosylation, and through this glycoprotein-degrading function contributes to the host-pathogen interaction. IMPa, however, is a relatively large multidomain protein and how its additional domains may contribute to its function remains unknown. Here, through the determination of a crystal structure of IMPa in complex with an O-glycopeptide, we reveal that the N-terminal domain of IMPa, which is classified in Pfam as IMPa_N_2, is a proline recognition domain that also shows the properties of recognizing an O-linked glycan on the serine/threonine residue following the proline. The proline is bound in the center of a bowl formed by four functionally conserved aromatic amino acid side chains while the glycan wraps around one of the tyrosine residues in the bowl to make classic aromatic ring-carbohydrate CH-π interactions. This structural evidence provides unprecedented insight into how the ancillary domains in glycoprotein-specific peptidases can noncatalytically recognize specific glycosylated motifs that are common in mucin and mucin-like molecules.

Thermodynamic equilibrium dose-response models for MERS-CoV infection reveal a potential protective role of human lung mucus but not for SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and Middle East respiratory syndrome coronavirus (MERS-CoV) infect the human respiratory tract. A prototype thermodynamic equilibrium model is presented here for the probability of the virions getting through the mucus barrier and infecting epithelial cells based on the binding affinity (Kmucin) of the virions to mucin molecules in the mucus and parameters for binding and infection of the epithelial cell. Both MERS-CoV and SARS-CoV-2 bind strongly to their cellular receptors, DDP4 and ACE2, respectively, and infect very efficiently both bronchus and lung ex vivo cell cultures which are not protected by a mucus barrier. According to the model, mucin binding could reduce the infectivity for MERS-CoV compared to SARS-CoV-2 by at least 100-fold depending on the magnitude of Kmucin. Specifically Kmucin values up to 106 M−1 have little protective effect and thus the mucus barrier would not remove SARS-CoV-2 which does not bind to sialic acids (SA) and hence would have a very low Kmucin. Depending on the viability of individual virions, the ID50 for SARS-CoV-2 is estimated to be ~500 virions (viral RNA genomic copies) representing 1 to 2 pfu. In contrast MERS-CoV binds both SA and human mucin and a Kmucin of 5 × 109 M−1 as reported for lectins would mop up 99.83% of the virus according to the model with the ID50 for MERS-CoV estimated to be ~295,000 virions (viral RNA genomic copies) representing 819 pfu. This could in part explain why MERS-CoV is poorly transmitted from human to human compared to SARS-CoV-2. Some coronaviruses use an esterase to escape the mucin, although MERS-CoV does not. Instead, it is shown here that “clustering” of virions into single aerosol particles as recently reported for rotavirus in extracellular vesicles could provide a co-operative mechanism whereby MERS-CoV could theoretically overcome the mucin barrier locally and a small proportion of 10 μm diameter aerosol particles could contain ~70 virions based on reported maximum levels in saliva. Although recent evidence suggests SARS-CoV-2 initiates infection in the nasal epithelium, the thermodynamic equilibrium models presented here could complement published approaches for modelling the physical entry of pathogens to the lung based on the fate and transport of the pathogen particles (as for anthrax spores) to develop a dose-response model for aerosol exposure to respiratory viruses. This would enable the infectivity through aerosols to be defined based on molecular parameters as well as physical parameters. The role of the spike proteins of MERS-CoV and SARS-CoV-2 binding to SA and heparan sulphate, respectively, may be to aid non-specific attachment to the host cell. It is proposed that a high Kmucin is the cost for subsequent binding of MERS-CoV to SAs on the cell surface to partially overcome the unfavourable entropy of immobilisation as the virus adopts the correct orientation for spike protein interactions with its protein cellular receptor DPP4.

A Mini Review on Mucoadhesion

The concept of mucoadhesion was started in early 1980’s with the aim of controlled delivery of drugs. Mucoadhesion is simply defined as the adhesion between two materials, in which one is the mucosal surface and the another one is the mucoadhesive dosage form. In the recent decades, mucoadhesive drug delivery system draw the attention in the gastroretentive delivery system. Mucoadhesive drug delivery systems interact with the mucus layer covering the mucosal epithelial surface, and mucin molecules and increase the residence time. Mucoadhesive dosage forms are designed to increase the retention of the drug/dosage form at the application site, to provide a controlled release of drug for increased curative consequence. The medications which have local action or those which have maximum absorption in gastrointestinal tract require increased duration of stay in GIT. Mucoadhesive drug delivery systems were prepared by using either natural or synthetic polymers, which is interacting with the mucous layer and used to prevail over the physiological barriers for extended drug delivery. The mucoadhesive ability of a dosage form is depending upon variety of factors, such as the nature of the mucosal tissue and the physicochemical properties of the polymeric formulation. This review article aims to provide an overview of the various theories of mucoadhesion, properties of mucoadhesive materials, methods to study the mucoadhesion, and finally various mucoadhesive dosage forms.

Expression and significance of T-cell immunoglobulin mucin molecule 3 and its ligand galectin-9 in patients with adenomyosis

The T cell immunoglobulin mucin molecule 3 (TIM-3), as a negative regulatory immune checkpoint, plays an important role in cellular immunity by binding to its ligand galectin-9 (Gal-9). Under abnormal conditions, this pathway can regulate the depletion of T cells and suppress the immune response. Abnormal expression of TIM-3 and Gal-9 has been confirmed in a variety of cancers, recurrent miscarriages, chronic infectious diseases and autoimmune diseases. More and more studies have shown that immune factors play an important role in the pathogenesis of adenomyosis. However, few studies have attempted to explore their expression in adenomyosis. The ectopic and eutopic endometrium were collected from 15 women with adenomyosis and 13 women without adenomyosis. TIM-3/Gal-9 expression in endometrial tissue was detected using immunohistochemistry, western blot analysis and real-time PCR. We observed TIM-3/Gal-9 expression in both eutopic and ectopic endometria, with elevated expression in adenomyosis. These data suggest that TIM-3/Gal-9 may be involved in the development and progression of adenomyosis.

Intraductal papillary neoplasms of the bile duct consist of two distinct types specifically associated with clinicopathological features and molecular phenotypes.

Intraductal papillary neoplasm of the bile duct (IPNB) is a grossly visible papillary biliary neoplasm with morphological variations and occasional invasion. Recently a new classification of IPNB into type 1 and type 2 was proposed in which the type 1 IPNBs consist of fine papillary neoplastic glands and the type 2 IPNBs consist of complex branching glands, seldom with foci of solid-tubular components. However, clinicopathological and molecular characteristics of these types of IPNBs are yet to be identified. We aimed to uncover clinicopathological and molecular characteristics of the types of IPNBs. Thirty-six IPNBs were studied retrospectively. Clinicopathological features as well as molecular alterations of 31 genes were evaluated by means of targeted next-generation sequencing and immunohistochemical examination of expression of mucin and cancer-associated molecules. The 36 IPNBs were classified into 22 of type 1 and 14 of type 2. The type 1 IPNBs were associated with a non-invasive phenotype, intestinal and oncocytic subtypes, development in the intrahepatic bile duct, overt mucin production, and a relatively good prognosis. The type 2 IPNBs were associated with an invasive phenotype, the pancreatobiliary subtype, development within the extrahepatic bile duct, and worse prognosis compared with the type 1 IPNBs. In the molecular analysis, recurrent mutations were found in TP53 (34.3%), KRAS (31.4%), STK11 (25.7%), CTNNB1 (17.1%), APC (14.3%), SMAD4 (14.3%), GNAS (11.4%), PBRM1 (11.4%), ELF3 (8.6%), KMT2C (8.6%), NF1 (8.6%), PIK3CA (8.6%), ARID1A (5.7%), ARID2 (5.7%), BAP1 (5.7%), BRAF (5.7%), EPHA6 (5.7%), ERBB2 (5.7%), ERBB3 (5.7%), KMT2D (5.7%), and RNF43 (5.7%). Mutations in KRAS and GNAS were enriched in the type 1 IPNBs, whereas mutations in TP53, SMAD4, and KMT2C were enriched in the type 2 IPNBs. These results indicate that IPNBs consist of two distinct types of neoplasms specifically associated with clinicopathological features and molecular phenotypes. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

α-Synuclein Penetrates Mucin Hydrogels Despite Its Mucoadhesive Properties.

Recent research indicates that the progression of Parkinson's disease can start from neurons of the enteric nervous system, which are in close contact with the gastrointestinal epithelium: α-synuclein molecules can be transferred from these epithelial cells in a prion-like fashion to enteric neurons. Thin mucus layers constitute a defense line against the exposure of noninfected cells to potentially harmful α-synuclein species. We show that-despite its mucoadhesive properties-α-synuclein can translocate across mucin hydrogels, and this process is accompanied by structural rearrangements of the mucin molecules within the gel. Penetration experiments with different α-synuclein variants and synthetic peptides suggest that two binding sites on α-synuclein are required to accomplish this rearrangement of the mucin matrix. Our results support the notion that the translocation of α-synuclein across mucus barriers observed here might be a critical step in the infection of the gastrointestinal epithelium and the development of Parkinson's disease.

Impact of bacteria motility in the encounter rates with bacteriophage in mucus

Bacteriophages—or phages—are viruses that infect bacteria and are present in large concentrations in the mucosa that cover the internal organs of animals. Immunoglobulin (Ig) domains on the phage surface interact with mucin molecules, and this has been attributed to an increase in the encounter rates of phage with bacteria in mucus. However, the physical mechanism behind this phenomenon remains unclear. A continuous time random walk (CTRW) model simulating the diffusion due to mucin-T4 phage interactions was developed and calibrated to empirical data. A Langevin stochastic method for Escherichia coli (E. coli) run-and-tumble motility was combined with the phage CTRW model to describe phage-bacteria encounter rates in mucus for different mucus concentrations. Contrary to previous theoretical analyses, the emergent subdiffusion of T4 in mucus did not enhance the encounter rate of T4 against bacteria. Instead, for static E. coli, the diffusive T4 mutant lacking Ig domains outperformed the subdiffusive T4 wild type. E. coli’s motility dominated the encounter rates with both phage types in mucus. It is proposed, that the local fluid-flow generated by E. coli’s motility combined with T4 interacting with mucins may be the mechanism for increasing the encounter rates between the T4 phage and E. coli bacteria.

Mucin 21 is a key molecule involved in the incohesive growth pattern in lung adenocarcinoma

Decreased cell adhesion has been reported as a significant negative prognostic factor of lung cancer. However, the molecular mechanisms responsible for the cell incohesiveness in lung cancer have not yet been elucidated in detail. We herein describe a rare histological variant of lung adenocarcinoma consisting almost entirely of individual cancer cells spreading in alveolar spaces in an incohesive pattern. A whole exome analysis of this case showed no genomic abnormalities in CDH1 or other genes encoding cell adhesion molecules. However, whole mRNA sequencing revealed that this case had an extremely high expression level of mucin 21 (MUC21), a mucin molecule that was previously shown to inhibit cell‐cell and cell‐matrix adhesion. The strong membranous expression of MUC21 was found on cancer cells using mAbs recognizing different O‐glycosylated forms of MUC21. An immunohistochemical analysis of an unselected series of lung adenocarcinoma confirmed that the strong membranous expression of MUC21 correlated with incohesiveness. Thus, MUC21 could be a promising biomarker with potential diagnostic and therapeutic applications for lung adenocarcinoma showing cell incohesiveness.

Pharmacology of Airway Goblet Cell Mucin Release

Airway mucus hypersecretion is one of the major clinical manifestations of patients suffering from various pulmonary diseases. However, no drugs are yet available to control airway mucus hypersecretion. For the past 15 years, a plethora of information has amassed with regard to the pharmacology of airway goblet cell mucin secretion using various primary cell culture systems. The recent discovery of various MUC genes has also greatly stimulated research in this field. Nevertheless, the heterogeneity of the oligosaccharide structure of mucin molecules makes it extremely difficult to assess the significance of the information derived from the pharmacological studies. Therefore, it seems crucially important to understand the roles of individual mucins in conjunction with normal airway physiology and pathology, which should be the future research directions necessary for studying airway goblet cell mucin pharmacology.

Study of mucin interaction with model phospholipid membrane at the air–water interface

The aim of the present study was to determine the interfacial behavior of model biomembrane in the presence of mucin. The Langmuir monolayer technique was used to form a mixed protein–phospholipid film at the air–water interface. Using the surface pressure-area isotherms, the relaxation curves and adsorption experiment, the nature of interactions between mucin and dipalmitoylphosphatidylcholine (DPPC) components of the monolayers under physiological conditions, (characteristic of the vagina and oral cavity), was investigated. It has been shown that at pH 4.2 mucin molecules reveal a strong affinity to the model biomembrane, composed of zwitterionic DPPC, and probably interact with it through the hydrophobic interactions. At pH 6.8 very weak electrostatic interactions are possible between the positively charged quaternary ammonium groups present in the DPPC molecules and the negatively charged mucin molecules. Moreover, from the relaxation experiment we concluded that beneath the DPPC layer there is a layer made of mucin particles due to electrostatic attraction. This layer of mucin beneath the DPPC particles stabilizes the entire system, especially at physiologically significant surface pressure, i.e. at π = 30 mN/m.

Tight junction, mucin, and inflammasome-related molecules are differentially expressed in eosinophilic, mixed, and neutrophilic experimental asthma in mice.

Asthma is a chronic respiratory disease with marked clinical and pathophysiological heterogeneity. Specific pathways are thought to be involved in the pathomechanisms of different inflammatory phenotypes of asthma; however, direct invivo comparison has not been performed. We developed mouse models representing three different phenotypes of allergic airway inflammation-eosinophilic, mixed, and neutrophilic asthma via different methods of house dust mite sensitization and challenge. Transcriptomic analysis of the lungs, followed by the RT-PCR, western blot, and confocal microscopy, was performed. Primary human bronchial epithelial cells cultured in air-liquid interface were used to study the mechanisms revealed in the invivo models. By whole-genome transcriptome profiling of the lung, we found that airway tight junction (TJ), mucin, and inflammasome-related genes are differentially expressed in these distinct phenotypes. Further analysis of proteins from these families revealed that Zo-1 and Cldn18 were downregulated in all phenotypes, while increased Cldn4 expression was characteristic for neutrophilic airway inflammation. Mucins Clca1 (Gob5) and Muc5ac were upregulated in eosinophilic and even more in neutrophilic phenotype. Increased expression of inflammasome-related molecules such as Nlrp3, Nlrc4, Casp-1, and IL-1β was characteristic for neutrophilic asthma. In addition, we showed that inflammasome/Th17/neutrophilic axis cytokine-IL-1β-may transiently impair epithelial barrier function, while IL-1β and IL-17 increase mucin expressions in primary human bronchial epithelial cells. Our findings suggest that differential expression of TJ, mucin, and inflammasome-related molecules in distinct inflammatory phenotypes of asthma may be linked to pathophysiology and might reflect the differences observed in the clinic.

Glycomic Profiling Highlights Increased Fucosylation in Pseudomyxoma Peritonei

Pseudomyxoma peritonei (PMP) is a subtype of mucinous adenocarcinoma that most often originates from the appendix, and grows in the peritoneal cavity filling it with mucinous ascites. KRAS and GNAS mutations are frequently found in PMP, but other common driver mutations are infrequent. As altered glycosylation can promote carcinogenesis, we compared N-linked glycan profiles of PMP tissues to those of normal appendix. Glycan profiles of eight normal appendix samples and eight low-grade and eight high-grade PMP specimens were analyzed by mass spectrometry. Our results show differences in glycan profiles between PMP and the controls, especially in those of neutral glycans, and the most prominent alteration was increased fucosylation. We further demonstrate up-regulated mRNA expression of four fucosylation-related enzymes, the core fucosylation performing fucosyltransferase 8 and three GDP-fucose biosynthetic enzymes in PMP tissues when compared with the controls. Up-regulated protein expression of the latter three enzymes was further observed in PMP cells by immunohistochemistry. We also demonstrate that restoration of fucosylation either by salvage pathway or by introduction of an expression of intact GDP-mannose 4,6-dehydratase enhance expression of MUC2, which is the predominant mucin molecule secreted by the PMP cells, in an intestinal-derived adenocarcinoma cell line with defective fucosylation because of deletion in the GDP-mannose 4,6-dehydratase gene. Thus, altered glycosylation especially in the form of fucosylation is linked to the characteristic mucin production of PMP. Glycomic data are available via ProteomeXchange with identifier PXD010086.

Reversible Condensation of Mucins into Nanoparticles.

Mucins are high molar mass glycoproteins that assume an extended conformation and can assemble into mucus hydrogels that protect our mucosal epithelium. In nature, the challenging task of generating a mucus layer, several hundreds of micrometers in thickness, from micrometer-sized cells is elegantly solved by the condensation of mucins inside vesicles and their on-demand release from the cells where they suddenly expand to form the extracellular mucus hydrogel. We aimed to recreate and control the process of compaction for mucins, the first step toward a better understanding of the process and creating biomimetic in vivo delivery strategies of macromolecules. We found that by adding glycerol to the aqueous solvent, we could induce drastic condensation of purified mucin molecules, reducing their size by an order of magnitude down to tens of nanometers in diameter. The condensation effect of glycerol was fully reversible and could be further enhanced and partially stabilized by cationic cross-linkers such as calcium and polylysine. The change of structure of mucins from extended molecules to nano-sized particles in the presence of glycerol translated into macroscopic rheological changes, as illustrated by a dampened shear-thinning effect with increasing glycerol concentration. This work provides new insight into mucin condensation, which could lead to new delivery strategies mimicking cell release of macromolecules condensed in vesicles such as mucins and heparin.

In Vitro Studies on Zinc Binding and Buffering by Intestinal Mucins.

The investigation of luminal factors influencing zinc availability and accessibility in the intestine is of great interest when analyzing parameters regulating intestinal zinc resorption. Of note, intestinal mucins were suggested to play a beneficial role in the luminal availability of zinc. Their exact zinc binding properties, however, remain unknown and the impact of these glycoproteins on human intestinal zinc resorption has not been investigated in detail. Thus, the aim of this study is to elucidate the impact of intestinal mucins on luminal uptake of zinc into enterocytes and its transfer into the blood. In the present study, in vitro zinc binding properties of mucins were analyzed using commercially available porcine mucins and secreted mucins of the goblet cell line HT-29-MTX. The molecular zinc binding capacity and average zinc binding affinity of these glycoproteins demonstrates that mucins contain multiple zinc-binding sites with biologically relevant affinity within one mucin molecule. Zinc uptake into the enterocyte cell line Caco-2 was impaired by zinc-depleted mucins. Yet this does not represent their form in the intestinal lumen in vivo under zinc adequate conditions. In fact, zinc-uptake studies into enterocytes in the presence of mucins with differing degree of zinc saturation revealed zinc buffering by these glycoproteins, indicating that mucin-bound zinc is still available for the cells. Finally, the impact of mucins on zinc resorption using three-dimensional cultures was studied comparing the zinc transfer of a Caco-2/HT-29-MTX co-culture and conventional Caco-2 monoculture. Here, the mucin secreting co-cultures yielded higher fractional zinc resorption and elevated zinc transport rates, suggesting that intestinal mucins facilitate the zinc uptake into enterocytes and act as a zinc delivery system for the intestinal epithelium.

Slippery When Wet: Airway Surface Liquid Homeostasis and Mucus Hydration.

The ability to regulate cell volume is crucial for normal physiology; equally the regulation of extracellular fluid homeostasis is of great importance. Alteration of normal extracellular fluid homeostasis contributes to the development of several diseases including cystic fibrosis. With regard to the airway surface liquid (ASL), which lies apically on top of airway epithelia, ion content, pH, mucin and protein abundance must be tightly regulated. Furthermore, airway epithelia must be able to switch from an absorptive to a secretory state as required. A heterogeneous population of airway epithelial cells regulate ASL solute and solvent composition, and directly secrete large mucin molecules, antimicrobials, proteases and soluble mediators into the airway lumen. This review focuses on how epithelial ion transport influences ASL hydration and ASL pH, with a specific focus on the roles of anion and cation channels and exchangers. The role of ions and pH in mucin expansion is also addressed. With regard to fluid volume regulation, we discuss the roles of nucleotides, adenosine and the short palate lung and nasal epithelial clone 1 (SPLUNC1) as soluble ASL mediators. Together, these mechanisms directly influence ciliary beating and in turn mucociliary clearance to maintain sterility and to detoxify the airways. Whilst all of these components are regulated in normal airways, defective ion transport and/or mucin secretion proves detrimental to lung homeostasis as such we address how defective ion and fluid transport, and a loss of homeostatic mechanisms, contributes to the development of pathophysiologies associated with cystic fibrosis.

Generation of mucin gel particles with self-degradable and -releasable properties.

Herein, we focused on mucin, which is a large viscous glycoprotein in terms of materials science, and reported preparation of mucin gel particles and incorporation of enzymes to provide the particle with self-degradable and releasable properties. To expose the hydrophobic peptide cores, trimming of sugar moieties was carried out by β-elimination reaction under alkaline conditions (tMucin). Nano-sized tMucin particles were prepared by the assembly of tMucin with the aid of a cationic surfactant. Then, cross-linking of tMucin particles was carried out via heat treatment (annealing) to induce thermal aggregation of the polypeptide chains. The hydrodynamic diameter of tMucin particles reversibly changed in response to calcium ions. Next, in an attempt to render the particle degradable, lysozyme was incorporated into the tMucin particles for the hydrolysis of oligosaccharide chains. These particles were gradually degraded upon enzymatic cleavage of the mucin molecules, facilitating the release of their incorporated substances. Also, the degradation of the mucin particles and the release of lysozyme were tunable by environmental conditions, such as temperature and calcium ions, in addition to the degree of cross-linking of the particles.

Mucins as multifunctional building blocks of biomaterials.

Mucins are large glycoproteins that are ubiquitous in the animal kingdom. Mucins coat the surfaces of many cell types and can be secreted to form mucus gels that assume important physiological roles in many animals. Our growing understanding of the structure and function of mucin molecules and their functionalities has sparked interest in investigating the use of mucins as building blocks for innovative functional biomaterials. These pioneering studies have explored how new biomaterials can benefit from the barrier properties, hydration and lubrication properties, unique chemical diversity, and bioactivities of mucins. Owing to their multifunctionality, mucins have been used in a wide variety of applications, including as antifouling coatings, as selective filters, and artificial tears and saliva, as basis for cosmetics, as drug delivery materials, and as natural detergents. In this review, we summarize the current knowledge regarding key mucin properties and survey how they have been put to use. We offer a vision for how mucins could be used in the near future and what challenges await the field before biomaterials made of mucins and mucin-mimics can be translated into commercial products.

Expression of fibronectin-binding protein of L. acidophilus NCFM and in vitro refolding to adhesion capable native-like protein from inclusion bodies

The ability of Lactobacilli to adhere to host epithelial surface and intestinal tracts is important for colonization and persistence of bacteria in the host gut. Extracellular matrix components like fibronectin, mucin, collagen and other adhesion molecules serve as substratum for attachment of bacteria. However, the precise structure, function and mechanism of binding of microbial surface adhesion proteins such as Fibronectin-binding protein (FBP) with host molecules remains unclear. This is primarily due to limitations in high expression of these proteins in biologically active form. To study adhesion of its FBP (64 kDa), the fbp gene of L. acidophilus NCFM was cloned and expressed in E. coli.However, the fibronectin-binding protein expressed in soluble form could not be purified by Ni-NTA affinity chromatography possibly because of partially buried Histidine tag in the recombinant fusion protein. Therefore, the protein was expressed as inclusion bodies (IBs) at 37 °C and solubilized in urea followed by purification in denatured form by Ni-NTA affinity chromatography. The purified denatured protein was refolded in vitro to structurally stable and biologically active form. The conformational properties of the refolded protein were studied by circular dichroism, which showed prominence of α+ β structural element. The refolded FBP also showed significant binding to human intestinal tissue sections. Our optimized refolding protocol from IBs of this recombinant probiotic FBP led into high amounts of biologically active protein. Our results help in increasing understanding of structure-function relation of surface adhesion proteins and host-microbial interactions.