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  • 1. Ambort, D.
    et al.
    Johansson, M.E.V.
    Gustafsson, J. K.
    Nilsson, Harriet
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Structural Biotechnology.
    Ermund, A.
    Johansson, B.R.
    Koeck, Philip J. B.
    KTH, School of Technology and Health (STH), Structural Biotechnology (Closed 20130701).
    Hebert, Hans
    KTH, School of Technology and Health (STH), Structural Biotechnology (Closed 20130701).
    Hansson, G.C.
    Calcium and pH-dependent packing and release of the gel-forming MUC2 mucin2012In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 109, no 15, p. 5645-5650Article in journal (Refereed)
    Abstract [en]

    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 Ca2+ 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. TheMUC2-N aggregates were dissolved by removing Ca2+ 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.

  • 2. Gustafsson, JK
    et al.
    Ermund, Anna
    Ambort, Daniel
    Johansson, MEV
    Nilsson, Harriet
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Structural Biotechnology.
    Thorell, K
    Hebert, Hans
    Karolinska Institutet, Sweden .
    Sjövall, H
    Hansson, Gunnar
    Bicarbonate and functional CFTR channel are required for proper mucin secretion and link cystic fibrosis with its mucus phenotype2012In: Journal of Experimental Medicine, ISSN 0022-1007, E-ISSN 1540-9538, Vol. 209, no 7, p. 1263-1272Article in journal (Refereed)
    Abstract [en]

    Cystic fibrosis (CF) is caused by a nonfunctional chloride and bicarbonate ion channel (CF transmembrane regulator [CFTR]), but the link to the phenomenon of stagnant mucus is not well understood. Mice lacking functional CFTR (CftrΔ508) have no lung phenotype but show similar ileal problems to humans. We show that the ileal mucosa in CF have a mucus that adhered to the epithelium, was denser, and was less penetrable than that of wild-type mice. The properties of the ileal mucus of CF mice were normalized by secretion into a high concentration sodium bicarbonate buffer (~100 mM). In addition, bicarbonate added to already formed CF mucus almost completely restored the mucus properties. This knowledge may provide novel therapeutic options for CF.

  • 3.
    Jang, Seongmin
    et al.
    Korea Adv Inst Sci & Technol, Dept Biol Sci, Daejeon 34141, South Korea..
    Kang, Chanshin
    Seoul Natl Univ, Dept Phys & Astron, Seoul 08826, South Korea..
    Yang, Han-Sol
    Sungkyunkwan Univ, Sch Pharm, Suwon 16419, South Korea..
    Jung, Taeyang
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Structural Biotechnology. Karolinska Inst, Dept Biosci & Nutr, S-14152 Huddinge, Sweden..
    Hebert, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Structural Biotechnology. Karolinska Inst, Dept Biosci & Nutr, S-14152 Huddinge, Sweden..
    Chung, Ka Young
    Sungkyunkwan Univ, Sch Pharm, Suwon 16419, South Korea..
    Kim, Seung Joong
    Korea Adv Inst Sci & Technol, Dept Phys, Daejeon 34141, South Korea..
    Hohng, Sungchul
    Seoul Natl Univ, Dept Phys & Astron, Seoul 08826, South Korea..
    Song, Ji-Joon
    Korea Adv Inst Sci & Technol, Dept Biol Sci, Daejeon 34141, South Korea..
    Structural basis of recognition and destabilization of the histone H2B ubiquitinated nucleosome by the DOT1L histone H3 Lys79 methyltransferase2019In: Genes & Development, ISSN 0890-9369, E-ISSN 1549-5477, Vol. 33, no 11-12, p. 620-625Article in journal (Refereed)
    Abstract [en]

    DOT1L is a histone H3 Lys79 methyltransferase whose activity is stimulated by histone H2B Lys120 ubiquitination, suggesting cross-talk between histone H3 methylation and H2B ubiquitination. Here, we present cryo-EM structures of DOT1L complexes with unmodified or H2B ubiquitinated nucleosomes, showing that DOT1L recognizes H2B ubiquitin and the H2A/H2B acidic patch through a C-terminal hydrophobic helix and an arginine anchor in DOT1L, respectively. Furthermore, the structures combined with single-molecule FRET experiments show that H2B ubiquitination enhances a noncatalytic function of the DOT1L-destabilizing nucleosome. These results establish the molecular basis of the cross-talk between H2B ubiquitination and H3 Lys79 methylation as well as nucleosome destabilization by DOT1L.

  • 4. Kozlova, Inna
    et al.
    Nilsson, Harriet
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Structural Biotechnology.
    Henriksnäs, Johanna
    Roomans, Godfried M
    X-ray microanalysis of apical fluid in cystic fibrosis airway epithelial cell lines.2006In: Cellular Physiology and Biochemistry, ISSN 1015-8987, E-ISSN 1421-9778, Vol. 17, no 1-2, p. 13-20Article in journal (Refereed)
    Abstract [en]

    The ionic composition of the fluid lining the airways (airway surface liquid, ASL) in healthy subjects and patients with cystic fibrosis (CF) has been a matter of controversy. It has been attempted to resolve conflicting theories by using cell cultures, but published results show a wide variety of values for the ionic concentrations in the apical fluid in these cultures. To investigate CFTR-mediated HCO(3)(-) conductance and the role of HCO(3)(-) in regulating ASL pH we determined the pH of the fluid covering the apical surface of airway epithelial cells. A normal (16HBE14o (-)) and a CF (CFBE41o (-)) bronchial epithelial cell line were grown on membrane inserts in both a liquid-liquid interface culture system for 7 days, and in an air-liquid interface culture system for one month. The elemental composition of the fluid covering the apical surface was determined by X-ray microanalysis of frozen-hydrated specimens, or by X-ray microanalysis of Sephadex beads that had been equilibrated with the apical fluid. Analysis showed that the apical fluid had a Na(+) and Cl(-) concentration of about 80-100 mM and thus was slightly hypotonic. The ionic concentrations were somewhat higher in air-liquid interface than in liquid-liquid interface cultures. The apical fluid in CF cells had significantly higher concentrations of Na and Cl than that in control cultures. In control cultures, the concentrations of Na and Cl in the apical fluid increased if glibenclamide, an inhibitor of the cystic fibrosis transmembrane conductance regulator (CFTR) was added to the apical medium. Exposing the cells to the metabolic inhibitor NaCN also resulted in a significant increase of the Na and Cl concentrations in the apical fluid. The results agree with the notion that these cell cultures are mainly absorptive cells, and that ion absorption by the CF cells is reduced compared to that in normal cells. The pH measurements of the fluid covering the apical part of cell cultures support the notion that bicarbonate ions may be transported by CFTR, and that this can be inhibited by specific CFTR inhibitors.

  • 5. Kozlova, Inna
    et al.
    Nilsson, Harriet
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Structural Biotechnology.
    Phillipson, Mia
    Riederer, Brigitte
    Seidler, Ursula
    Colledge, William H
    Roomans, Godfried M
    X-ray microanalysis of airway surface liquid in the mouse.2005In: American Journal of Physiology - Lung cellular and Molecular Physiology, ISSN 1040-0605, E-ISSN 1522-1504, Vol. 288, no 5, p. L874-8Article in journal (Refereed)
    Abstract [en]

    The ionic composition of airway surface liquid (ASL) has been debated, and, in particular for the mouse, a wide range of values has been published. Two techniques were developed to measure the elemental composition of the ASL. X-ray microanalysis of ASL was carried out at low temperature on trachea removed from isoflurane-anesthetized animals and shock-frozen. In the second technique, dextran beads were placed on top of the epithelium of the trachea removed from pentobarbital-anesthetized animals, left to equilibrate with the ASL, dried, and subjected to X-ray microanalysis. Both techniques showed that mouse tracheal ASL has significantly lower concentrations of Na and Cl (approximately 60-80 mM) than serum. Differences between the two techniques were due to different sampling of mucus. CFTR(-/-) mice had significantly higher concentrations of Na and Cl in their ASL than age-matched controls. Pilocarpine or isoproterenol stimulation significantly reduced the ion concentrations in tracheal ASL. ASL was also collected with the dextran bead method from the nasal cavity in situ in pentobarbital-anesthetized animals. In control animals, the elemental composition of nasal fluid was similar to that of tracheal ASL. Pilocarpine stimulation caused a significant increase in Na, Cl, and K; stimulation with isoproterenol or phenylephrine caused a significant increase only in K. It is concluded that mouse ASL under unstimulated conditions is hypotonic, which may be related to the relative paucity of submucosal glands in the mouse trachea.

  • 6.
    Nilsson, Harriet
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Structural Biotechnology.
    Dragomir, Anca
    Ahlander, Anders
    Johannesson, Marie
    Roomans, Godfried M
    Effects of hyperosmotic stress on cultured airway epithelial cells.2007In: Cell and Tissue Research, ISSN 0302-766X, E-ISSN 1432-0878, Vol. 330, no 2, p. 257-69Article in journal (Refereed)
    Abstract [en]

    Inhalation of hyperosmotic solutions (salt, mannitol) has been used in the treatment of patients with cystic fibrosis or asthma, but the mechanism behind the effect of hyperosmotic solutions is unclear. The relation between osmolarity and permeability changes was examined in an airway cell line by the addition of NaCl, NaBr, LiCl, mannitol, or xylitol (295-700 mOsm). Transepithelial resistance was measured as an indicator of the tightness of the cultures. Cell-cell contacts and morphology were investigated by immunofluorescence and by transmission electron microscopy, with lanthanum nitrate added to the luminal side of the epithelium to investigate tight junction permeability. The electrolyte solutions caused a significant decrease in transepithelial resistance from 450 mOsm upwards, when the hyperosmolar exposure was gradually increased from 295 to 700 mOsm; whereas the nonelectrolyte solutions caused a decrease in transepithelial resistance from 700 mOsm upwards. Old cultures reacted in a more rigid way compared to young cultures. Immuno-fluorescence pictures showed weaker staining for the proteins ZO-1, claudin-4, and plakoglobin in treated samples compared to the control. The ultrastructure revealed an increased number of open tight junctions as well as a disturbed morphology with increasing osmolarity, and electrolyte solutions opened a larger proportion of tight junctions than nonelectrolyte solutions. This study shows that hyperosmotic solutions cause the opening of tight junctions, which may increase the permeability of the paracellular pathway and result in increased transepithelial water transport.

  • 7.
    von Holst, Hans
    et al.
    Section of Neurosurgery, Karolinska University Hospital and Section of Research, MIPS Company.
    Purhonen, Pasi
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Structural Biotechnology. Department of Biosciences and Nutrition, Karolinska Institute and School of Engineering Sciences in Chemistry, Biotechnology and Health.
    Lanner, Daniel
    Section of Research, MIPS Company.
    Balakrishnan Kumar, Ramakrishnan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH). Department of Biosciences and Nutrition, Karolinska Institute and School of Engineering Sciences in Chemistry, Biotechnology and Health.
    Hebert, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Structural Biotechnology. Department of Biosciences and Nutrition, Karolinska Institute and School of Engineering Sciences in Chemistry, Biotechnology and Health.
    White Shark Protein Metabolism may be a Model to Improve the Outcome of Cytotoxic Brain Tissue Edema and Cognitive Deficiency after Traumatic Brain Injury and Stroke2018In: Journal of Neurology and Neurobiology, ISSN 2379-7150, Vol. 4, no 2Article in journal (Refereed)
    Abstract [en]

    Increased intracellular water content defined as cytotoxic brain tissue edema is a serious secondary clinical complication to traumatic brain injury (TBI) and stroke and without knowledge to the etiology. Recently a hypothesis to the nervous tissue edema was presented suggesting that external dynamic and internal mechanical static impact forces caused protein unfolding resulting in an increased brain tissue water content. The hypothesis was confirmed by computer simulation tests. In this laboratory study we further evaluated the hypothesis by using the mature protein laminin LN521 upon the effects of both dynamic as well as static impact forces, respectively. Laminin was chosen as a representative protein due to it´s general and abundance presence in the cells. The treated laminin solutions were then analyzed with denatured electrophoresis and Electron Microscopy showing aggregation and fragmentation of the laminin structures. The present results confirm earlier hypothesis and computer simulation suggesting for the first time that dynamic impact force in an accident and increased mechanical static force in stroke unfold mature proteins having the potential to increase the intracellular water content defined as cytotoxic brain tissue edema. The clinical condition resembles the phenomenon when elasmobranchs including white sharks prevent their cells from too high hydrostatic pressure in the deep sea. Thus, the present laboratory study results and knowledge from marine physics may be considered to improve the clinical treatment and outcome of TBI and stroke patients.

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