scholarly journals Structure and biosynthesis of human salivary mucins.

2000 ◽  
Vol 47 (4) ◽  
pp. 1067-1079 ◽  
Author(s):  
A Zalewska ◽  
K Zwierz ◽  
K Zółkowski ◽  
A Gindzieński
Keyword(s):  
Molecular Mass ◽  
Salivary Glands ◽  
Disulfide Bonds ◽  
Tandem Repeats ◽  
Mucous Cells ◽  
Central Domain

Human salivary glands secrete two types of mucins: oligomeric mucin (MG1) with molecular mass above 1 MDa and monomeric mucin (MG2) with molecular mass of 200-250 kDa. Monomers of MG1 and MG2 contain heavily O-glycosylated tandem repeats located at the central domain of the molecules. MG1 monomers are linked by disulfide bonds located at sparsely glycosylated N- and C-end. MG1 are synthesized by mucous cells and MG2 by the serous cells of human salivary glands.

scholarly journals Electron Microscopic Immunogold Localization of Salivary Mucins MG1 and MG2 in Human Submandibular and Sublingual Glands

2003 ◽  
Vol 51 (1) ◽  
pp. 69-79 ◽  
Author(s):  
Marco Piludu ◽  
Sean A. Rayment ◽  
Bing Liu ◽  
Gwynneth D. Offner ◽  
Frank G. Oppenheim ◽  
...  
Keyword(s):  
Salivary Glands ◽  
Expression Patterns ◽  
Cell Types ◽  
Mucous Cells ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Dense Cores ◽  
Duct Cells ◽  
Rabbit Igg ◽  
Lowicryl K4m

The human salivary mucins MG1 and MG2 are well characterized biochemically and functionally. However, there is disagreement regarding their cellular and glandular sources. The aim of this study was to define the localization and distribution of these two mucins in human salivary glands using a postembedding immunogold labeling method. Normal salivary glands obtained at surgery were fixed in 3% paraformaldehyde-0.1% glutaraldehyde and embedded in Lowicryl K4M or LR Gold resin. Thin sections were labeled with rabbit antibodies to MG1 or to an N-terminal synthetic peptide of MG2, followed by gold-labeled goat anti-rabbit IgG. The granules of all mucous cells of the submandibular and sublingual glands were intensely reactive with anti-MG1. No reaction was detected in serous cells. With anti-MG2, the granules of both mucous and serous cells showed reactivity. The labeling was variable in both cell types, with mucous cells exhibiting a stronger reaction in some glands and serous cells in others. In serous granules, the electron-lucent regions were more reactive than the dense cores. Intercalated duct cells near the acini displayed both MG1 and MG2 reactivity in their apical granules. In addition, the basal and lateral membranes of intercalated duct cells were labeled with anti-MG2. These results confirm those of earlier studies on MG1 localization in mucous cells and suggest that MG2 is produced by both mucous and serous cells. They also indicate differences in protein expression patterns among salivary serous cells.

scholarly journals Function of the CysD domain of the gel-forming MUC2 mucin

2011 ◽  
Vol 436 (1) ◽  
pp. 61-70 ◽  
Author(s):  
Daniel Ambort ◽  
Sjoerd van der Post ◽  
Malin E. V. Johansson ◽  
Jenny MacKenzie ◽  
Elisabeth Thomsson ◽  
...  
Keyword(s):  
Fusion Proteins ◽  
Disulfide Bonds ◽  
Tandem Repeats ◽  
Gel Filtration ◽  
Middle Part ◽  
Domain Of Unknown Function ◽  
Cross Links ◽  
Native Gel ◽  
The Individual ◽  
Covalent Nature

The colonic human MUC2 mucin forms a polymeric gel by covalent disulfide bonds in its N- and C-termini. The middle part of MUC2 is largely composed of two highly O-glycosylated mucin domains that are interrupted by a CysD domain of unknown function. We studied its function as recombinant proteins fused to a removable immunoglobulin Fc domain. Analysis of affinity-purified fusion proteins by native gel electrophoresis and gel filtration showed that they formed oligomeric complexes. Analysis of the individual isolated CysD parts showed that they formed dimers both when flanked by two MUC2 tandem repeats and without these. Cleavages of the two non-reduced CysD fusion proteins and analysis by MS revealed the localization of all five CysD disulfide bonds and that the predicted C-mannosylated site was not glycosylated. All disulfide bonds were within individual peptides showing that the domain was stabilized by intramolecular disulfide bonds and that CysD dimers were of non-covalent nature. These observations suggest that CysD domains act as non-covalent cross-links in the MUC2 gel, thereby determining the pore sizes of the mucus.

scholarly journals Mucus formation in goblet cells

1933 ◽  
Vol 113 (784) ◽  
pp. 459-463 ◽  
Keyword(s):  
Golgi Apparatus ◽  
Salivary Glands ◽  
Secretory Granules ◽  
Goblet Cells ◽  
Neutral Red ◽  
Basal Region ◽  
Mucous Cells ◽  
Cell Type ◽  
Golgi Network ◽  
Golgi Zone

The formation of mucus in goblet cells and its relation to the Golgi apparatus has been studied by various workers. Nassanow (1923) showed clearly that the mucin granules in the goblet cells of Triton originated in the Golgi apparatus, and so brought secretion in these cells into line with his theory of the bound secretion. More recently Clara (1926) has shown in the goblet cells of birds that the mucin first appears in the region next to the nucleus, between it and the gland lumen. Florey (1932, a, b ) has considered this more extensively in two recent papers, and for a number of mammals has shown that the mucin granules of goblet cells first form in the meshes of the Golgi network. In epithelial cells of the mouse vagina, undergoing conversion into mucous cells, he has found that the same process occurs. In a recent investigation of secretory formation in the salivary glands and pancreas it was found by the present author that in every cell type examined the young secretory granules first appeared in the basal region of the cell in relation to the mitochondria. Subsequent emigration occurred into the Golgi zone, where they underwent conversion into mature secretory granules. In the mucous cells of the salivary glands it was shown that these newly formed granules might be stained intravitam by Janus green or neutral red, and that in fixed preparations they stained selectively with acid fuchsin as described by Noll (1902), In the light of this work it appeared probable that while mucin formation might occur in the Golgi zone of the goblet cells as described by these authors, the origin of the granules might lie in the basal region of the cell.

scholarly journals The Mechanical Power of Protein Folding

2018 ◽  
Author(s):  
Edward C. Eckels ◽  
Shubhasis Haldar ◽  
Rafael Tapia-Rojo ◽  
Jaime Andres Rivas Pardo ◽  
Julio M. Fernández
Keyword(s):  
Protein Folding ◽  
Functional Significance ◽  
Disulfide Bonds ◽  
Tandem Repeats ◽  
Muscle Protein ◽  
Muscle Mechanics ◽  
Magnetic Tweezers ◽  
Mechanical Power ◽  
Ig Domain

AbstractThe delivery of mechanical power, a crucial component of animal motion, is constrained by the universal compromise between force and velocity of its constituent molecular systems. Here we demonstrate a switchable power amplifier in an Ig domain of the massive muscle protein titin. Titin is composed of many tandem repeats of individually foldable Ig domains, which unfold and extend during muscle stretch and readily refold when the force on titin is quenched during a contraction. Cryptic cysteine residues are common in elastic proteins like titin where they can oxidize to form intra-domain disulfide bonds, limiting the extensibility of an unfolding domain. However, the functional significance of disulfide-bonds in titin Ig domains remains unknown and may be fundamental to muscle mechanics. Here we use ultra-stable magnetic tweezers force spectroscopy to study the elasticity of a disulfide bonded modular titin protein operating in the physiological range, with the ability to control the oxidation state of the protein in real time using both organic reagents and oxidoreductase enzymes. We show that presence of an oxidized disulfide bond allows the parent Ig domain to fold at much higher forces, shifting the midpoint folding probability from 4.0 pN to 12.8 pN after formation. The presence of disulfide bonds in titin regulates the power output of protein folding in an all-or-none manner, providing for example at 6.0 pN, a boost from 0 to 6,000 zeptowatts upon oxidation. At this same force, single molecular motors such as myosin are typically stalled and perform little to no work. We further demonstrate that protein disulfide isomerase (PDI) readily reintroduces disulfide bonds into unfolded titin Ig domains, an important mechanism for titin which operates under a resting force of several pNin vivo. Our results demonstrate, for the first time, the functional significance of disulfide bonds as potent power amplifiers in titin and provide evidence that protein folding can generate substantial amounts of power to supplement the myosin motors during a contraction.

Structure, Function and Gene Expression of Epithelial Mucins

1997 ◽  
Vol 83 (3) ◽  
pp. 625-632 ◽  
Author(s):  
Ettore Seregni ◽  
Carlo Botti ◽  
Simonetta Massaron ◽  
Claudia Lombardo ◽  
Alba Capobianco ◽  
...  
Keyword(s):  
Gene Expression ◽  
Structure Function ◽  
Cdna Library ◽  
Tandem Repeats ◽  
Core Protein ◽  
Variable Number ◽  
Apical Surface ◽  
Central Domain ◽  
Intestinal Mucin ◽  
Bronchial Glands

In this review the main characteristics, i.e., structure, function and gene expression, of the different mucins are discussed. Mucin-type molecules consist of a core protein moiety (apomucin) where a number of carbohydrate chains are attached to serines and threonines by glycosidic bonds. O-linked carbohydrates form up to 80% of the molecule and the length of the glucidic side chains varies from one to more than 20 residues. At least eight mucin-like genes have been isolated so far, and the main characteristic is the presence of a central domain composed of a variable number of “tandem repeats”. The sequence homology of the central domain among the different members of the mucin-type family is limited, indicating that this internal domain is unique for each mucin. Thanks to the integrated results of genetic, immunological and biochemical studies, it is now possible to identify eight apomucin genes, namely MUC1, MUC2, MUC3, MUC4, MUC5AC, MUC5B, MUC6 and MUC7. MUC1 is the best characterized mucin and it is expressed on the apical surface of most polarized epithelial cells. The MUC1 gene has been cloned and sequenced. The MUC2 gene encodes a typical secretory gel-forming mucin which represents the predominant form in human intestinal and colon tissues. Another intestinal mucin is MUC3. The MUC4, MUC5AC and MUC5B genes have been isolated from a bronchial tissue cDNA library. The MUC4 and MUC5AC genes are mainly expressed in the respiratory tract, in gastric and reproductive mucosa, while MUC5B is highly detectable only in the bronchial glands. The MUC6 gene is expressed by gastric tissue and, recently, MUC7 has been cloned and sequenced using a salivary cDNA library.

scholarly journals The central domain of bovine submaxillary mucin consists of over 50 tandem repeats of 329 amino acids

2000 ◽  
Vol 267 (8) ◽  
pp. 2208-2217 ◽  
Author(s):  
Weiping Jiang ◽  
Dwijendra Gupta ◽  
Dan Gallagher ◽  
Scott Davis ◽  
Veer P. Bhavanandan
Keyword(s):  
Amino Acids ◽  
Tandem Repeats ◽  
Central Domain ◽  
Bovine Submaxillary Mucin

The histology of salivary glands in the colubrid snake Sibynomorphus mikanii (Schlegel, 1837)

1983 ◽  
Vol 61 (4) ◽  
pp. 936-941 ◽  
Author(s):  
M. G. D. Contrera ◽  
R. A. Lopes ◽  
J. R. V. Costa ◽  
S. O. Petenusci ◽  
J. S. Lima-Verde
Keyword(s):  
Salivary Glands ◽  
Nuclear Volume ◽  
Mucous Cells ◽  
Tubule Cells ◽  
Acid Mucosubstances

A study of the morphology of the salivary glands of the colubrid snake Sibynomorphus mikanii showed the following: (i) the acini of supralabial, infralabial, and premaxillary glands are formed by mucous cells, the tubules of lateral and median posterior sublingual glands are formed by mucoserous cells, and the Duvemoy's gland by seromucous cells; and (ii) mucous cells produce neutral and acid mucosubstances, mucoserous cells secrete neutral and acid mucosubstances and protein, and seromucous cells have neutral mucosubstance and protein secretions. The nuclear volume of acinar and tubule cells were evaluated morphometrically.

scholarly journals Ubiquitination of renal ENaC subunits in vivo

2020 ◽  
Vol 318 (5) ◽  
pp. F1113-F1121 ◽  
Author(s):  
Gustavo Frindt ◽  
Marko Bertog ◽  
Christoph Korbmacher ◽  
Lawrence G. Palmer
Keyword(s):  
Molecular Mass ◽  
Hormonal Regulation ◽  
Disulfide Bonds ◽  
Proteolytic Processing ◽  
Apparent Molecular Mass ◽  
Ubiquitinated Proteins ◽  
Tissue Homogenates ◽  
Putative Binding Site ◽  
Affinity Beads

Ubiquitination of the epithelial Na+ channel (ENaC) in epithelial cells may influence trafficking and hormonal regulation of the channels. We assessed ENaC ubiquitination (ub-ENaC) in mouse and rat kidneys using affinity beads to capture ubiquitinated proteins from tissue homogenates and Western blot analysis with anti-ENaC antibodies. Ub-αENaC was observed primarily as a series of proteins of apparent molecular mass of 40–70 kDa, consistent with the addition of variable numbers of ubiquitin molecules primarily to the NH2-terminal cleaved fragment (~30 kDa) of the subunit. No significant Ub-βENaC was detected, indicating that ubiquitination of this subunit is minimal. For γENaC, the protein eluted from the affinity beads had the same apparent molecular mass as the cleaved COOH-terminal fragment of the subunit (~65 kDa). This suggests that the ubiquitinated NH2 terminus remains attached to the COOH-terminal moiety during isolation through disulfide bonds. Consistent with this, under nonreducing conditions, eluates contained material with increased molecular mass (90–150 kDa). In mice with a Liddle syndrome mutation (β566X) deleting a putative binding site for the ubiquitin ligase neural precursor cell expressed developmentally downregulated 4-2, the amount of ub-γENaC was reduced as expected. To assess aldosterone dependence of ubiquitination, we fed rats either control or low-Na+ diets for 7 days before kidney harvest. Na+ depletion increased the amounts of ub-αENaC and ub-γENaC by three- to fivefold, probably reflecting increased amounts of fully cleaved ENaC. We conclude that ubiquitination occurs after complete proteolytic processing of the subunits, contributing to retrieval and/or disposal of channels expressed at the cell surface. Diminished ubiquitination does not appear to be a major factor in aldosterone-dependent ENaC upregulation.

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