Role of autoantibodies in arrhythmogenic cardiomyopathy

• Applicant: Professor Dr. Jens Waschke
• Subject Area: Nuclear Medicine, Radiotherapy, Radiobiology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 503029846

Arrhythmogenic cardiomyopathy (AC) is a rare genetic heart disease causing sudden cardiac deaths in young people. In 50% mutations can be detected in desmosomal components of cardiomyocyte intercalated discs including desmoglein (Dsg) 2, desmocollin (Dsc) 2, plakophilin (Pkp) 2, plakoglobin (Pg) and desmoplakin (Dp). Intercalated discs are composed of adhesive contacts such as desmosomes and adherens junctions together with gap junctions (GJ) and sodium channels important for electric coupling. However, pathogenesis of AC is partly understood and the mechanisms without genetic cause remain elusive. Recently autoantibodies targeting Dsg2 in AC have been reported which may contribute to pathogenesis similar to the blistering skin disease pemphigus. The aim is to characterize the underlying mechanisms by which autoantibodies contribute to pathogenesis of AC. The mechanisms can be separated into inhibition of Dsg2 interaction and induction of signalling pathways regulating cardiomyocyte cohesion and excitation propagation. Similar to our studies on pemphigus, we will purify IgG fractions from AC patients (AC-IgG) compared to healthy individuals and first test pathogenic effects on cell adhesion. With cell dissociation assays we will measure cardiomyocyte adhesion. In preliminary experiments, we found that two different AC-IgG reduce cell adhesion and using Dsg2 atomic force microscopy under cell-free conditions, we observed that AC-IgG directly interfere with Dsg2 interaction. The effects on Dsg2- and N-cadherin-mediated adhesion will then be correlated with analyses of autoantibodies targeting intercalated discs and Dsg2 by immunostaining, Western blot and ELISA. In a third set of experiments, ultrastructural alterations of intercalated discs will be investigated by transmission electron microscopy and STED-microscopy, effects on excitation propagation will be monitored using multi-electrode assays (MEA) and ex-vivo Langendorff heart perfusion and signalling mechanisms induced by AC-IgG will be characterized. We found that cAMP, p38MAPK, PKC and ERK regulate cardiomyocyte adhesion and GSK3β and NFκB are involved in AC pathogenesis. Therefore, we will test whether these signalling pathways are altered by AC-IgG and whether they contribute to loss of cardiomyocyte adhesion, ultrastructural alterations and impaired excitation propagation. Dissociation assays and MEA will be performed both in cultured cardiomyocytes and murine cardiac slice cultures. Because aDsg2 autoantibodies AC were found in different genetic backgrounds, we will test whether AC-IgG induce different mechanisms in slice cultures from wild-type and a cardiomyocyte-specific Pg-deficient mouse model for AC. Finally, we will study whether effects of autoantibodies on cardiomyocyte adhesion and excitation propagation in the different assays can be rescued by a peptide designed to crosslink Dsg molecules. The study will give new insights in the role of autoantibodies in AC pathogenesis.

• DFG Programme: Research Grants