Mucins in protozoan parasites (original) (raw)
Expression of conserved mucin domains by epithelial tissues in various mammalian species
Research in Veterinary Science, 2009
Mucins are related to infectious and non-infectious diseases in Veterinary and Human Medicine. MUC1 mucin is a transmembrane glycoprotein expressed on the apical surface of human epithelia while MUC5AC is the predominant secreted mucin expressed in human gastric epithelium and goblet cells of lung and eyes. MUC5AC C-terminus cysteine rich regions and the cytoplasmic tail of MUC1 domains are conserved among several mammalian species. Objective: to compare the expression of MUC1 and MUC5AC mucins in mammalian epithelia. CT33 anti-MUC1 cytoplasmic tail (MUC1CT) polyclonal antibody and 45M1 anti-MUC5AC monoclonal antibody were employed. By immunohistochemistry, MUC1CT was expressed in most tissues while MUC5AC was restricted to gastric surface epithelium and goblet cells from trachea and lung. By western blot, MUC1CT showed a band at approximately 35 kDa in most tissues; MUC5AC revealed bands at >180 kDa in stomach and lung secretions from rat, cat, pig and cow. When rat MUC5AC was immunoprecipitated, a band at about 180 kDa was obtained.
Structure and function of epithelial mucins
Biopolymers and Cell, 1998
Mucins are the structural components of the epithelial mucose that protects the respiratory, gastrointestinal and reproductive tracts from the hostile environments, including microorganisms, toxim and abrasives. Mucins constitute a group of high molecular weight (> 200 kDa), polydisperse and highly glycosylated proteins which are present on the surface of most epithelial tissues. Our understanding of the structure and function of mucins has advanced significantly in the last decade. This progress was mainly associated with the isolation of the cDNA clones, encoding a family of epithelial mucins. To date, this family includes eight mucin genes (MUCJ-MUC8) and more await to be discovered. Based on sequence analysis and studies of subcellular localisation, epithelial mucins could be divided into two classes: membrane-associated (MUC1) and secretory (MUC2-8). This review is focused on our current knowledge of the structure of products of mucin genes and their function in normal tissues and in disease. The regulation of the expression of mucin genes, posttranslational modifications and alterations in secretion and processing will also be discussed.
Microbiology, 2008
Naegleria fowleri is the aetiological agent of primary amoebic meningoencephalitis (PAM). This parasite invades its host by penetrating the olfactory mucosa. During the initial stages of infection, the host response is initiated by the secretion of mucus that traps the trophozoites. Despite this response, some trophozoites are able to reach, adhere to and penetrate the epithelium. In the present work, we evaluated the effect of mucins on amoebic adherence and cytotoxicity to Madin-Darby canine kidney (MDCK) cells and the MUC5AC-inducing cell line NCI-H292. We showed that mucins inhibited the adhesion of amoebae to both cell lines; however, this inhibition was overcome in a time-dependent manner. N. fowleri re-established the capacity to adhere faster than N. gruberi. Moreover, mucins reduced the cytotoxicity to target cells and the progression of the illness in mice. In addition, we demonstrated mucinolytic activity in both Naegleria strains and identified a 37 kDa protein with mucinolytic activity. The activity of this protein was inhibited by cysteine protease inhibitors. Based on these results, we suggest that mucus, including its major mucin component, may act as an effective protective barrier that prevents most cases of PAM; however, when the number of amoebae is sufficient to overwhelm the innate immune response, the parasites may evade the mucus by degrading mucins via a proteolytic mechanism.
Soft Matter, 2013
In this highlight, we discuss the multifaceted biology of mucins, where molecular architecture meets function, and especially the collective properties of mucin networks and gels that select adherent bacteria and restrict penetration.
Journal of Biological Chemistry, 2000
Infective larvae of the parasitic nematode Toxocara canis secrete a family of mucin-like glycoproteins, which are implicated in parasite immune evasion. Analysis of T. canis expressed sequence tags identified a family of four mRNAs encoding distinct apomucins (Tcmuc-1-4), one of which had been previously identified in the TES-120 family of glycoproteins secreted by this parasite. The protein products of all four cDNAs contain signal peptides, a repetitive serine/threonine-rich tract, and varying numbers of 36-amino acid six-cysteine (SXC) domains. SXC domains are found in many nematode proteins and show similarity to cnidarian (sea anemone) toxins. Antibodies to the SXC domains of Tc-MUC-1 and Tc-MUC-3 recognize differently migrating members of TES-120. TES-120 proteins separated by chromatographic methods showed distinct amino acid composition, mass, and sequence information by both Edman degradation and matrix-assisted laser desorption ionization/time of flight mass spectrometry on peptide fragments. Tc-MUC-1, -2, and -3 were shown to be secreted mucins with real masses of 39.7, 47.8, and 45.0 kDa in contrast to their predicted peptide masses of 15.7, 16.2, and 26.0 kDa, respectively. The presence of SXC domains in all mucin products supports the suggestion that the SXC motif is required for mucin assembly or export. Homology modeling indicates that the sixcysteine domains of the T. canis mucins adopt a similar fold to the sea anemone potassium channel-blocking toxin BgK, forming three disulfide bonds within each subunit.
Strategic Biochemical Analysis of Mucins
Analytical Biochemistry, 1998
MUC-type mucins comprise a family of structurally related molecules, which are expressed in epithelia of the body that are in close contact with the milieu. Because of their large sizes and very complex structures, containing very extensive O-glycosylation, MUC-type mucins are difficult to study by conventional techniques. Many see MUC-type mucins as protective molecules; however, functional studies on the individual MUC-type mucins are very scarce. At present, essential steps in MUC research are to characterize the specific expression patterns of each MUCtype mucin in the body and to find methods to reliably quantify these MUC-type mucins. These aims can only be met at the level of the primary sequences of the MUC-type mucins, as the O-glycosylation even within one species of MUC-type mucin is not only very complex, but may also vary among individuals, organs, and cell types. We will discuss some recent advances in mucin research, particularly the identification of MUC precursor molecules in metabolic labeling experiments. We will try to define some strategic considerations in the study of the expression patterns of MUC-type mucins, which circumvent the complications caused by the very complex and heterogeneous O-glycosylation of the molecules.
Glycoconjugate Journal, 2015
Mucins are major glycoprotein components of the mucus that coats the surfaces of cells lining the respiratory, digestive, gastrointestinal and urogenital tracts. They function to protect epithelial cells from infection, dehydration and physical or chemical injury, as well as to aid the passage of materials through a tract i.e., lubrication. They are also implicated in the pathogenesis of benign and malignant diseases of secretory epithelial cells. In Human there are two types of mucins, membrane-bound and secreted that are originated from mucous producing goblet cells localized in the epithelial cell layer or in mucous producing glands and encoded by MUC gene. Mucins belong to a heterogeneous family of high molecular weight proteins composed of a long peptidic chain with a large number of tandem repeats that form the so-called mucin domain. The molecular weight is generally high, ranging between 0.2 and 10 million Dalton and all mucins contain one or more domains which are highly glycosylated. The size and number of repeats vary between mucins and the genetic polymorphism represents number of repeats (VNTR polymorphisms), which means the size of individual mucins can differ substantially between individuals which can be used as markers. In human it is only MUC1 and MUC7 that have mucin domains with less than 40 % serine and threonine which in turn could reduce number of PTS domains. Mucins can be considered as powerful two-edged sword, as its normal function protects from unwanted substances and organisms at an arm's length while, malfunction of mucus may be an important factor in human diseases. In this review we have unearthed the current status of different mucin proteins in understanding its role and function in various noncommunicable diseases in human with special reference to its organ specific locations. The findings described in this review may be of direct relevance to the major research area in biomedicine with reference to mucin and mucin associated diseases.
Molecular signaling in the regulation of mucins
Journal of Cellular Biochemistry, 2007
Mucins are large, highly glycosylated proteins involved in the protection of epithelia. The 20 different mucins show a diverse and highly regulated distribution among different epithelia. Most of the studies on mucin regulation done to date have been on the membrane mucins MUC1 and MUC4 and the gel-forming mucins. Multiple mechanisms have been implicated in that regulation, including examples at the transcriptional, transcript stabilization and posttranslational levels. Several signaling pathways have been demonstrated to be involved, most frequently the canonical Erk MAP kinase pathway, but also the cytokine-JAK-STAT pathway and TGFb-SMAD pathways. Diversity in Erk signaling is achieved through multiple activation mechanisms and multiple downstream transcriptional factors that are affected. Given the still limited amount of information available on regulation of most of the mucins, other mechanisms and pathways are likely to be uncovered in the future.
American Journal of Respiratory Cell and Molecular Biology, 2004
Mucin glycans are the major determinant of mucin functions. Mucin glycan branch structures, which increase structural heterogeneity and thus functional potential, are extended from 6 N-acetylglucosaminides formed by 6 N-acetylglucosaminyltransferases (6GnT). Core 2 6GnT-M (C2GnT-M) is the only branching enzyme that can synthesize all known mucin 6 N-acetylglucosaminides. We report the cloning of four different bovine (b) C2GnT-M transcripts that are different only at 5-untranslated regions. Two bC2GnT-M transcripts are found exclusively in tracheal epithelium and testis, whereas the other two are found in all other mucus-secreting tissues. The bC2GnT-M gene contains four exons spanning 5.3 kb, and the entire open reading frame is in one exon. The bC2GnT-M ORF has 95, 83, and 75% sequence identity to those of bovine herpes virus type 4 (BHV-4), human, and rat C2GnT-Ms, respectively. The homology between bovine and BHV-4 C2GnT-M genes is in the region between 170 nucleotides upstream from ATG start codon and 114 nucleotides downstream from TGA stop codon of the viral gene. Localized at the nonconserved region of the viral genome, the BHV-4 C2GnT-M gene is the only known viral C2GnT-M gene. The results suggest that BHV-4 acquired its C2GnT-M gene from the bovine gene. The mechanism of the viral acquisition of bC2GnT-M gene and the roles of the C2GnT-M gene in the survival and pathogenesis of this virus remain to be elucidated. There are two types of mucins, secreted and membrane-bound (1). The secreted mucins are found in the mucus that covers the epithelial tissues, such as airways, gastrointestinal tract, cervix, etc. The primary function of these mucins, such as MUC2, MU-C5AC, and MUC5B, is to maintain the viscoelastic property of the mucus, and in the case of airway mucins also serve as a trap for airborne pathogens because many bacteria contain lectins, which can bind to mucin carbohydrates (2, 3). To perform this important function, the peptide backbone of the secreted mucins is decorated with oligosaccharides of heterogeneous structures. For example, more than 100 different oligosaccharides were detected in the tracheobronchial mucins of a single individual (3, 4). The membrane-bound mucins also can serve as ligands for many cell adhesion molecules involved in cell-cell interactions,