| 1. |
- Ambort, Daniel, 1978, et al.
(författare)
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Calcium and pH-dependent packing and release of the gel-forming MUC2 mucin.
- 2012
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 109:15, s. 5645-50
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Tidskriftsartikel (refereegranskat)abstract
- MUC2, the major colonic mucin, forms large polymers by N-terminal trimerization and C-terminal dimerization. Although the assembly process for MUC2 is established, it is not known how MUC2 is packed in the regulated secretory granulae of the goblet cell. When the N-terminal VWD1-D2-D'D3 domains (MUC2-N) were expressed in a goblet-like cell line, the protein was stored together with full-length MUC2. By mimicking the pH and calcium conditions of the secretory pathway we analyzed purified MUC2-N by gel filtration, density gradient centrifugation, and transmission electron microscopy. At pH 7.4 the MUC2-N trimer eluted as a single peak by gel filtration. At pH 6.2 with Ca(2+) it formed large aggregates that did not enter the gel filtration column but were made visible after density gradient centrifugation. Electron microscopy studies revealed that the aggregates were composed of rings also observed in secretory granulae of colon tissue sections. The MUC2-N aggregates were dissolved by removing Ca(2+) and raising pH. After release from goblet cells, the unfolded full-length MUC2 formed stratified layers. These findings suggest a model for mucin packing in the granulae and the mechanism for mucin release, unfolding, and expansion.
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| 2. |
- Ambort, Daniel, 1978, et al.
(författare)
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Perspectives on mucus properties and formation--lessons from the biochemical world.
- 2012
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Ingår i: Cold Spring Harbor perspectives in medicine. - : Cold Spring Harbor Laboratory. - 2157-1422. ; 2:11
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Forskningsöversikt (refereegranskat)abstract
- Our model of the MUC2 mucin shows a well-organized netlike gel that is cross-linked by six different covalent and noncovalent bonds. When the MUC2 mucin is packed in the mucin granule it is organized by an amino-terminal concatenated ring platform formed at high calcium and low pH. This packing allows an ordered release and a normal mucin expansion when calcium is removed and pH increased by bicarbonate. This process is defective in the absence of cystic fibrosis transmembrane conductance regulator (CFTR)-dependent bicarbonate transport. The expanded secreted mucin is suggested to be self-organizing by properties inherited in the MUC2 mucin and by proteolytic processes.
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| 3. |
- Arike, Liisa, et al.
(författare)
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Protein Turnover in Epithelial Cells and Mucus along the Gastrointestinal Tract Is Coordinated by the Spatial Location and Microbiota
- 2020
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Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 30:4, s. 1077-1087
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Tidskriftsartikel (refereegranskat)abstract
- The gastrointestinal tract is covered by a single layer of epithelial cells that, together with the mucus layers, protect the underlying tissue from microbial invasion. The epithelium has one of the highest turnover rates in the body. Using stable isotope labeling, high-resolution mass spectrometry, and computational analysis, we report a comprehensive dataset of the turnover of more than 3,000 and the expression of more than 5,000 intestinal epithelial cell proteins, analyzed under conventional and germ-free conditions across five different segments in mouse intestine. The median protein half-life is shorter in the small intestine than in the colon. Differences in protein turnover rates along the intestinal tract can be explained by distinct physiological and immune-related functions between the small and large intestine. An absence of microbiota results in an approximately 1 day longer protein half-life in germ-free animals.
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| 4. |
- Bos, Meike F., et al.
(författare)
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Goblet cell interactions reorient bundled mucus strands for efficient airway clearance
- 2023
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Ingår i: PNAS Nexus. - 2752-6542. ; 2:11
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Tidskriftsartikel (refereegranskat)abstract
- The respiratory tract of larger animals is cleared by sweeping bundled strands along the airway surface. These bundled strands can be millimetric in length and consist of MUC5B mucin. They are produced by submucosal glands, and upon emerging from these glands, the long axis of the bundled strands is oriented along the cilia-mediated flow toward the oral cavity. However, after release, the bundled strands are found to have turned orthogonal to the flow, which maximizes their clearance potential. How this unexpected reorientation is accomplished is presently not well understood. Recent experiments suggest that the reorientation process involves bundled strands sticking to MUC5AC mucus threads, which are tethered to the goblet cells. Such goblet cells are present in small numbers throughout the airway epithelium. Here, we develop a minimal model for reorientation of bundled mucus strands through adhesive interactions with surface goblet cells. Our simulations reveal that goblet cell interactions can reorient the bundled strands within 10 mm of release-making reorientation on the length scale of the tracheal tube feasible-and can stabilize the orthogonal orientation. Our model also reproduces other experimental observations such as strong velocity fluctuations and significant slow-down of the bundled strand with respect to the cilia-mediated flow. We further provide insight into the strand turning mechanism by examining the effect of strand shape on the impulse exerted by a single goblet cell. We conclude that goblet cell-mediated reorientation is a viable route for bundled strand reorientation, which should be further validated in future experiment.
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| 5. |
- Dolan, Brendan, et al.
(författare)
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Clearance of small intestinal crypts involves goblet cell mucus secretion by intracellular granule rupture and enterocyte ion transport
- 2022
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Ingår i: Science Signaling. - : American Association for the Advancement of Science (AAAS). - 1945-0877 .- 1937-9145. ; 15:752
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Tidskriftsartikel (refereegranskat)abstract
- Goblet cells in the small intestinal crypts contain large numbers of mucin granules that are rapidly discharged to clean bacteria from the crypt. Because acetylcholine released by neuronal and nonneuronal cells controls many aspects of intestinal epithelial function, we used tissue explants and organoids to investigate the response of the small intestinal crypt to cholinergic stimulation. The activation of muscarinic acetylcholine receptors initiated a coordinated and rapid emptying of crypt goblet cells that flushed the crypt contents into the intestinal lumen. Cholinergic stimulation induced an expansion of the granule contents followed by intracellular rupture of the mucin granules. The mucus expanded intracellularly before the rupture of the goblet cell apical membrane and continued to expand after its release into the crypt lumen. The goblet cells recovered from membrane rupture and replenished their stores of mucin granules. Mucus secretion from the goblet cells depended on Ca2+ signaling and the expansion of the mucus in the crypt depended on gap junctions and on ion and water transport by enterocytes adjacent to the goblet cells. This distinctive mode of mucus secretion, which we refer to as “expanding secretion,” efficiently cleans the small intestine crypt through coordinated mucus, ion, and fluid secretion by goblet cells and enterocytes.
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| 6. |
- El Hachmane, Michael, et al.
(författare)
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Extracellular ATP activates store-operated Ca2+ entry in white adipocytes: functional evidence for STIM1 and ORAI1
- 2018
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Ingår i: Biochemical Journal. - : Portland Press Ltd.. - 0264-6021 .- 1470-8728. ; 475, s. 691-704
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, we have applied ratiometric measurements of intracellular Ca2+ concentrations ([Ca2+](i)) to show that extracellularly applied ATP (adenosine triphosphate) (100 mM) stimulates store-operated Ca2+ entry (SOCE) in 3T3-L1 adipocytes. ATP produced a rapid increase in [Ca2+](i) consisting of an initial transient elevation followed by a sustained elevated phase that could be observed only in the presence of extracellular Ca2+. Gene expression data and [Ca2+](i) recordings with uridine-50-triphosphate or with the phospholipase C (PLC) inhibitor U73122 demonstrated the involvement of purinergic P2Y2 receptors and the PLC/inositol trisphosphate pathway. The [Ca2+](i) elevation produced by reintroduction of a Ca2+-containing intracellular solution to adipocytes exposed to ATP in the absence of Ca2+ was diminished by known SOCE antagonists. The chief molecular components of SOCE, the stromal interaction molecule 1 (STIM1) and the calcium release-activated calcium channel protein 1 (ORAI1), were detected at the mRNA and protein level. Moreover, SOCE was largely diminished in cells where STIM1 and/or ORAI1 had been silenced by small interfering (si) RNA. We conclude that extracellular ATP activates SOCE in white adipocytes, an effect predominantly mediated by STIM1 and ORAI1.
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| 7. |
- Ermund, Anna, et al.
(författare)
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Assembly, Release, and Transport of Airway Mucins in Pigs and Humans
- 2018
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Ingår i: Annals of the American Thoracic Society. - 1546-3222. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- The respiratory system is protected from inhaled particles and microbes by the mucociliary system. This system differs between animal species, where pigs and humans have numerous submucosal glands. The polymer-forming mucin, MUC5B, is packed in a highly organized way in granules of the mucus-secreting cells in the glands. Upon secretion, the packed MUC5B is flushed out by a chloride-and bicarbonate-rich fluid from the cystic fibrosis transmembrane conductance regulator-expressing serosal cells located at the most distal part of the gland. The bicarbonate raises the pH and removes calcium from the N terminus of MUC5B, allowing the mucin to be pulled out into a linear polymer. Thousands of such polymers gather in bundles in the submucosal gland duct, and these bundles appear at the opening of the glands. They are moved by the beating cilia, and sweep over the airway surface and are patchily coated with the MUC5AC mucin from the surface goblet cells. The movement of these bundles is controlled by the MUC5AC mucin attachment/detachment to the goblet cells. Thus, higher animals with submucosal glands and large diameters of the proximal airways are efficiently cleaned by the thick mucus bundles sweeping the airway surface and moving particles and bacteria toward the larynx.
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| 8. |
- Ermund, Anna
(författare)
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Bioactive Lipids in Nociception
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on bioactive lipids as (1) metabolites of the widely used antipyretic and analgesic drug acetaminophen and (2) activators of the ion channel TRPV1, an important downstream target for inflammatory mediators, in the phospholipase C (PLC)/TRPV1 signaling pathway. Evidence is presented for a fatty acid amide hydrolase (FAAH)-dependent fatty acid conjugation of p-aminophenol, a known acetaminophen metabolite, to form the potent TRPV1 activator AM404 in the central nervous system. We show that acetaminophen is able to reduce the content of prostanoids in brain and kidney, but this effect is independent of FAAH. While ibuprofen produces a similar reduction as acetaminophen of the PGE2 level in brain, only acetaminophen displays antinociceptive activity in animal tests of acute non-inflammatory pain, indicating that other mechanisms than central cyclooxygenase inhibition must be sought to explain the analgesic effect of acetaminophen in these tests. Knowledge of the mechanisms of action of acetaminophen may help to develop analogs with improved analgesic activity. Many TRP ion channels, including TRPV1, are regulated by PLC-coupled surface receptors. After PLC-dependent cleavage of phosphatidylinositol bisphosphate into diacylglycerol (DAG) and inositoltrisphosphate, diacylglycerol may be further metabolized to monoacyl-glycerols, such as 2-arachidonoylglycerol (2-AG) and 2-oleoylglycerol by the action of DAG lipase. 2-Arachidonoylglycerol and 1-AG activate both native TRPV1 on sensory nerve fibers in rodent mesenteric arteries and heterologously expressed rat and human TRPV1. The effects of 2-AG and the metabolically stable analog noladin ether were almost absent in TRPV1 gene-deficient mice. Stimulation of isolated rat dorsal root ganglia with the inflammatory mediators bradykinin and ATP led to an increase in the level of 2-AG, whereas the levels of anandamide and 2-oleoylglycerol were unaffected. Extensive metabolism of d8-2-AG and d5-1-AG, in contrast to d8-anandamide, was demonstrated in homogenates of rat mesenteric arteries. The monoacylglycerol lipase inhibitor MAFP prevented the metabolism of these lipids and enhanced the TRPV1-mediated vascular effects of 2-AG and 1-AG, but not anandamide. The existence of a regulated biosynthesis and enzymatic degradation of 2-AG and 1-AG in TRPV1-containing tissues is compatible with a physiological role for these monoacylglycerols as messengers in the PLC/TRPV1 signaling cascade. Bioactive lipids, with TRPV1 activity, can be formed via drug metabolism and after stimulation of PLC-coupled surface receptors.
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| 9. |
- Ermund, Anna, et al.
(författare)
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Hyper-osmolarity and calcium chelation: Effects on cystic fibrosis mucus
- 2015
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Ingår i: European Journal of Pharmacology. - : Elsevier BV. - 0014-2999. ; 764, s. 109-117
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Tidskriftsartikel (refereegranskat)abstract
- A non-functional Cystic Fibrosis Transmembrane conductance Regulator (CFTR) leads to the disease cystic fibrosis (CF). Although the CFTR is expressed in multiple organs, pulmonary disease is the major cause of illness and death in patients with CF. Stagnant mucus, causing airway obstruction, bacterial overgrowth, persistent inflammation and tissue destruction characterizes the disease, but how the defect in CFTR function is coupled to the mucus phenotype is still controversial. We have recently shown that bicarbonate ions passing through CFTR are necessary for proper unfolding of the MUC2 mucin, thus highlighting the importance of bicarbonate ion transport via the CFTR and the ability of these ions to raise the pH and chelate calcium bound to the mucin as the important steps in forming normal mucus. In order to find potential CF treatments and expand our knowledge about the usefulness of bicarbonate as an active ingredient in formulations to alleviate mucus plugging, we used an Ussing-type chamber and explants from the F508del-CFTR mutant mouse ileum to test the effect of calcium chelators on mucus attachment, either in isolation or in combination with osmolytes such as mannitol or hypertonic saline. We found that increasing the concentration of bicarbonate, both alone or in combination with increased osmolarity of the solution, detached the otherwise attached CF mucus. (C) 2015 Elsevier B.V. All rights reserved.
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| 10. |
- Ermund, Anna, et al.
(författare)
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Hypertonic saline releases the attached small intestinal cystic fibrosis mucus.
- 2015
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Ingår i: Clinical and experimental pharmacology & physiology. - : Wiley. - 1440-1681 .- 0305-1870. ; 42:1, s. 69-75
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Tidskriftsartikel (refereegranskat)abstract
- Hypertonic saline inhalation has become a cornerstone in the treatment of cystic fibrosis (CF), but its effect on CF mucus is still not understood. In CF, mucus stagnates in the airways, causing mucus plugging, and forming a substrate for bacterial invasion. Using horizontal Ussing-type chambers to allow easy access to the tissue, we have recently shown that the small intestinal mucus of CF mice is attached to the epithelium and not freely movable as opposed to normal mucus, thus pointing to a similarity between the CF mucus in the ileum and airways. In the same type of system, we investigated how hypertonic saline affects mucus thickness, attachment and penetrability to fluorescent beads the size of bacteria in ileal explants from the cystic fibrosis transmembrane conductance regulator mutant (ΔF508) mouse, in order to characterize how this common therapy affects mucus properties. Hypertonic saline (1.75-5%) detached the mucus from the epithelium, but the mucus remained impenetrable to beads the size of bacteria. This approach might be used to test other mucolytic interventions in CF.
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