DFG Research Training Group "TJ-Train" (GRK 2318/2)
 Tight junctions and their proteins
Molecular features and actions in health and disease

Project C2     1st period   2nd period

Priv.-Doz. Dr. Susanne M. Krug

Clinical Physiology / Nutritional Medicine, Campus Benjamin Franklin,
Charité - Universitätsmedizin Berlin

Interaction of immune cells and TJ proteins in IBD

 

Background: In inflammatory bowel disease (IBD), the epithelial barrier is impaired, leading on one hand to loss of ions and water, on the other hand to enhanced luminal antigen uptake supporting the inflammatory process further (Krug et al., 2014, Martini et al., 2017). Expression of tight junction (TJ) proteins is linked to barrier disturbance and is regulated by pro-inflammatory cytokines released from various types of immune cells. While the bicellular TJ (bTJ) is located between two cells, the tricellular TJ (tTJ) is formed at the meeting points of three cells. The tTJ is distinct in molecular composition and serves as a regulating site for macromolecule passage. Tricellulin (Ikenouchi et al., 2005, Krug et al., 2009a) and the members of the angulin family (Higashi et al., 2013) are specialized TJ proteins located at the tTJ and are regulatory factors for the barrier properties of the tTJ.

Alterations of the tTJ protein expression and localization are crucially involved in IBD. While downregulation of tricellulin has direct effects on the paracellular macromolecule barrier in ulcerative colitis (Krug et al., 2018), angulins are mainly responsible for its tricellular localization (Higashi et al., 2013) and angulin-1 has been shown to be affected Crohn’s disease (Hu et al., 2020), where tricellulin is mislocated. Besides the main forms of angulins, a new variant has been recently found in intestinal tissues, which might be involved in the regulatory processes of the tTJ and is unknown in its functional properties.

Hypotheses: The newly discovered angulin isoform is involved in regulation of the intestinal tTJ. By this, it affects barrier properties as well as immune regulatory processes in both, normal intestinal function and in inflammatory diseases.

Aims: The new angulin isoform will be analyzed: (i) functionally: Effects on barrier properties, effects on tTJ proteins, (ii) structurally: E.g. specific differentiation from other isoforms, interaction with other tTJ proteins, (iii) regarding expression profiles in different tissues and sample types

Current Thesis project: Mechanistic characterization of a new angulin isoform.

For this, the angulin on one hand will be overexpressed on the other hand downregulated or knocked out in suitable cell culture or intestinal organoids. The resulting clones will be characterized in detail using electrophysiological techniques and functional assays as well as standard molecular biological techniques to clarify the role of this angulin isoform in context of the TJ barrier properties with special focus on the tTJ. Interaction with TJ proteins will be analysed to bring the observed properties and structural particularities in functional and mechanistic context. Besides this functional characterization on molecular level, the physiological and potential pathophysiological role will be elucidated for this angulin isoform. Expression profiles in different tissues apart from the intestine will be analysed and may be connected to the functional findings. In addition, different conditions of the intestine will be of further interest as inflammatory or other pathological conditions affecting the intestinal epithelium might be linked to expression changes of this angulin isoform, which might contribute essentially to the resulting barrier impairment.

3rd cohort PhD doctoral student

Amélie Moll (start 10.2024)
Kristian Koci (12.2023 - 06.2024)

2nd cohort PhD doctoral student

Lena Voges

  • Voges L, Weiß F, Branco AT, Fromm M, Krug SM (2024) Expression and localization profiles of tight junction proteins in immune cells depend on their activation status. Int. J. Mol. Sci. 25(9): 4861 (18 pages), doi: 10.3390/ijms25094861 (°IF 4.9)

  • Weiß F, Czichos C, Knobe L, Voges L, Bojarski C, Michel G, Fromm M, Krug SM (2022) MarvelD3 is upregulated in ulcerative colitis and has attenuating effects during colitis indirectly stabilizing the intestinal barrier. Cells 11: 1551 (16 pages) doi: 10.3390/cells11091541 (IF 6.0)

2nd cohort MD doctoral student

Seymanur Yildirim

1st cohort PhD doctoral student

Jia-Chen E. Hu
19.04.21: Doctoral examination passed,Dr. rer. nat. (PhD), Freie Universität Berlin, magna cum laude

  • Hu JCE, Weiß F, Bojarski C, Branchi F, Schulzke JD, Fromm M, Krug SM (2021) Expression of tricellular tight junction proteins and the paracellular macromolecule barrier are recovered in remission of ulcerative colitis. BMC Gastroenterology 21(1): 141, doi: 10.1186/s12876-021-01723-7 (IF 2.9) 

  • Hu JCE, Bojarski C, Branchi F, Fromm M, Krug SM (2020) Leptin downregulates angulin-1 in active Crohn's disease via STAT3. Int. J. Mol. Sci. 21(21): 7824 (17 pages) [PubMed] [WebPage] [PDF] [Supplement] (IF 5.9)

Project-related publications

If a paper is not accessible, please mail to .

  1. Krug SM, Hayaishi T, Iguchi D, Watari A, Takahashi A, Fromm M, Nagahama M, Takeda H, Okada Y, Sawasaki T, Doi T, Yagi K, Kondoh M (2017) Angubindin-1, a novel paracellular absorption enhancer acting at the tricellular tight junction. J. Contr. Release 260: 1-11 [PubMed] [WebPage] [PDF] [Supplement]

  2. Schütz A, Radusheva V, Krug SM*, Heinemann U* (*shared last authorship) (2017) Crystal structure of the tricellulin C-terminal coiled-coil domain reveals a unique mode of dimerization. Ann. N.Y. Acad. Sci. 1405: 147-159 [PubMed] [WebPage] [PDF] [Supplement]

  3. Krug SM, Bojarski C, Fromm A, Lee IM, Dames P, Richter JF, Turner JR, Fromm M*, Schulzke JD* (*shared last authorship) (2018) Tricellulin is regulated via interleukin-13-receptor α2, affects macromolecule uptake, and is decreased in ulcerative colitis. Mucosal Immunol. 11(2): 345-356 [PubMed] [WebPage] [PDF] [Supplement] [Supplementary Movie]

  4. Krug SM (2017) Contribution of the tricellular tight junction to paracellular permeability in leaky and tight epithelia. Ann. N.Y. Acad. Sci. 1317(1): 219-230 (°IF 4.7) [PubMed] [WebPage] [PDF]

  5. Martini E, Krug SM, Siegmund B, Neurath MF, Becker C (2017) Mend your fences: The epithelial barrier and its relationship with mucosal immunity in inflammatory bowel disease. Cell. Mol. Gastroent. Hepatol. 4(1): 33-46  [PubMed] [WebPage] [PDF] (Review)

  6. Conrad MP*, Piontek J* (*shared first authorship), Günzel D, Fromm M, Krug SM (2016) Molecular basis of claudin-17 anion selectivity. Cell. Mol. Life Sci. 73(1): 185-200 [PubMed] [WebPage] [PDF] [Supplement]

  7. Demehri FR*, Krug SM* (*shared first authorship), Feng Y, Lee IM, Schulzke JD, Teitelbaum DH (2016) Tight junction ultrastructure alterations in a mouse model of enteral nutrient deprivation. Dig. Dis. Sci. 61(6): 1524-1533  [PubMed] [WebPage] [PDF]

  8. Yang S*, Krug SM* (*shared first authorship), Heitmann J, Hu L, Reinhold AK, Sauer S, Bosten J, Sommer C, Fromm M, Brack A*, Rittner HL* (*shared last authorship) (2016) Analgesic drug delivery via recombinant tissue plasminogen activator and mRNA-183-triggered opening of the blood-nerve barrier. Biomaterials 82: 20-33 [PubMed] [WebPage] [PDF] [Supplement]  

    9.

  9. Richter JF, Schmauder R, Krug SM, Gebert A, Schumann M (2016) A novel method for imaging sites of paracellular passage of macromolecules in epithelial sheets. J. Contr. Release 229: 70-79 [PubMed] [WebPage] [PDF] [Supplement] [Movie S1] [Movie S2]

  10. Krug SM, Schulzke JD, Fromm M (2014) Tight junction, selective permeability, and related diseases. Semin. Cell Devel. Biol. 36: 166-176 [PubMed] [WebPage] [PDF] (Review)

  11. Krug SM, Amasheh M, Dittmann I, Christoffel I, Fromm M, Amasheh S (2013) Sodium caprate as an enhancer of macromolecule permeation across tricellular tight junctions of intestinal cells. Biomaterials 34(1): 275-282 [PubMed] [WebPage] [PDF]

  12. Westphal JK, Dörfel MJ, Krug SM, Cording JD, Piontek J, Blasig IE, Tauber R, Fromm M, Huber O (2010) Tricellulin forms homomeric and heteromeric tight junctional complexes. Cell. Mol. Life Sci. 67(12): 2057-2068 [PubMed] [WebPage] [PDF] [Supplement]

  13. Krug SM, Amasheh S, Richter JF, Milatz S, Günzel D, Westphal JK, Huber O, Schulzke JD, Fromm M (2009) Tricellulin forms a barrier to macromolecules in tricellular tight junctions without affecting ion permeability. Mol. Biol. Cell 20: 3713-3724 [PubMed] [WebPage] [PDF] [Supplement text] [Supplement video]

  14. Krug SM, Fromm M, Günzel D (2009) Two-path impedance spectroscopy for measuring paracellular and transcellular epithelial resistance. Biophys. J. 97(8): 2202-2211 [PubMed] [WebPage] [PDF] [Supplement]