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

Project C2

Priv.-Doz. Dr. Susanne M. Krug    &   Prof. Dr. Michael Fromm

Institute of Clinical Physiology, Campus Benjamin Franklin,
Charité - Universitätsmedizin Berlin

Role of the tricellular tight junction in inflammatory bowel diseases

The tricellular TJ (tTJ) is considered to form a structural weak point of the barrier-forming TJ network (13). Passage of medium-sized and large molecules might be facilitated in this region in diseased states. Tricellulin plays a critical role for barrier formation against macromolecule passage but the general processes and concepts behind are widely unknown. In first studies with human colon biopsies we have shown that tricellulin is downregulated in the inflammatory bowel disease (IBD) ulcerative colitis and the tTJ is opened (3). We hypothesize that this causes luminal pathogens to pass which then support the inflammatory process (5, 10). A role of other proteins, which are located at the tTJ, e.g. angulins (LSR, ILDR1, ILDR2) (1), as well as for occludin might be assumed.

Our thesis topics comprise characterizing the tTJ proteins regarding their distinct function in IBD development and their regulation, as well as analyzing pathways of large-molecule passage across the bicellular and the tricellular TJ. The projects will cover regulation of macromolecule passage via the tricellular tight junction and functional characterization of tricellular tight junction proteins involved in IBD.

Besides standard molecular biological techniques to analyze expression and localization changes of tTJ proteins in IBD compared to control patients, overexpression and knockdown clones of the respective tTJ proteins are going to be generated and analyzed (13). Methods are Ussing chamber techniques including flux measurements and two-path impedance spectroscopy (14), confocal microscopic methods and visualization of macromolecule passage (9) as well as ultrastructural analysis using freeze fracture electron microscopy (7). Analysis of regulatory pathways include cytokine and inhibitor treatments of intestinal epithelial cell lines, followed by protein and RNA level evaluation as well as promotor analysis.

In summary, our specific thesis projects for two doctoral students (1 PhD and 1 MD) are:

-  Regulation of macromolecule passage via the tricellular tight junction.

-  Functional characterization of tricellular tight junction proteins involved in IBD.

PhD doctoral student

MD doctoral student

  • Thesis project for one Charité MD student, starting anytime.
    For financing the necessary study interception, the DFG provides a one-year student grant.

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. 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]