Project Details
Projekt
Role of Dsg2-dependent adhesion and signalling in Crohn s disease
Subject Area
Cell Biology
Term
from 2015 to 2023
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 273724278
Crohn’s disease (CD) is an inflammatory bowel disease (IBD) with complex pathogenesis which is characterized by impaired intestinal epithelial barrier integrity. We had previously shown that the desmosomal adhesion molecule desmoglein 2 (Dsg2) is crucial for barrier function. We found that in patients’ intestinal biopsies with CD Dsg2 is reduced and displays altered localization. Electron microscopy revealed that desmosome ultrastructure is altered in parallel to tight junctions (TJ) whereas adherens junctions appeared normal in CD. In cultured enterocytes, a Dsg2-linking tandem peptide (TP) stabilized cell adhesion and barrier function when challenged with tumor necrosis factor α indicating that impaired Dsg2 binding may contribute to CD pathogenesis. Because these data are supported by the cooperation project of Pavel Strnad in Dsg2-deficient mice, we started to stabilize Dsg2 binding via TP in vivo. We found extradesmosomal Dsg2 on the surface of enterocytes. Since Dsg2 binds to and modulates EGFR and PI3-kinase, which are involved in barrier regulation we identified Dsg2 as a signaling hub in enterocytes. Therefore we will study how EGFR and PI3-kinase control cell cohesion and TJ function in the second funding period. In cooperation with Mechthild Hatzfeld we will study the role of desmosomal plaque proteins such as plakophilins and plakoglobin for intestinal barrier regulation in enterocytes deficient for these proteins because we found that they modify molecular binding properties of different Dsg isoforms. For desmoplakin, we will reconstitute enterocytes with the new desmoplakin tension sensor of Carsten Grashoff for which we have shown that it is sufficient to induce desmosome formation. Homophilic binding of Dsg2 in comparison to heterophilic interaction with both desmocollin 2 or EGFR will be characterized with Rudolf Leube. In the translational part of the project, we observed that glial cell line-derived neurotrophic factor (GDNF), which enhanced intestinal barrier maturation in vitro, was reduced in CD biopsies. In Dsg2-deficient cells, we found that the barrier-protective effects of GDNF are mediated via stabilisation of Dsg2-mediated adhesion and signalling. GDNF administration in vivo in a model of DSS-induced colitis attenuated inflammation-induced loss of Dsg2. GDNF also abolished p38MAPK-mediated phosphorylation of keratins 8 and 18 as well as keratin filament reorganization in vitro and in vivo, both of which paralleled barrier breakdown in CD patients. In cooperation with Thomas Magin, we observed that keratin filaments in keratinocytes regulate p38MAPK activity. We will establish enterocyte cell lines deficient for keratin 8 and 18 and will reconstitute them with phospho-mimetic and –deficient keratin mutants to investigate the effects on barrier function. Based on new insights gathered during the first funding period, we will further elucidate the interplay between Dsg2 adhesion properties and signalling pathways.
DFG Programme
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