Stabilization of Cardiomyocyte cohesion via adrenergic Stimulation

• Applicant: Professor Dr. Jens Waschke
• Subject Area: Nuclear Medicine, Radiotherapy, Radiobiology ; Cell Biology
• Term: from 2018 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 397804678

Cardiomyocytes are mechanically and electrically coupled via intercalated discs containing desmosomes, adherens junctions (AJ) and gap junctions (GJ). Desmosomal components are Crucial for intercalated disc integrity and functions because mutations affecting these proteins cause arrhythmogenic cardiomyopathy (AC). Typically, mutations are detectable in adhesion molecules desmoglein 2 (Dsg3), desmocollin 2 (Dsc2) as well as plaque proteins plakophillin2 (Pkp2), plakoglobin (Pg) and desmoplakin (Dp), which anchor cell contacts to the cytoskeleton. Little is known about regulation of cardiomyocyte cohesion and especially the mechanisms by which desmosomal adhesion controls GJ junctions are unclear. We characterized a first signaling pathway regulation cardiomyocyte adhesion and found that adrenergic stimulation via cAMP and PKA causes Pg phosphorylation at S665, which appears to be necessary for enhanced cohesion, which we referred to as positive adhesiotropy. In the recent project we plan to characterize other signaling pathways known to regulate desmosomal adhesion in keratinocytes such as PKC, p38MAPK and GSK-3. We will use single-molecule atomic force microscopy adhesion measurements on cultured and primary cardiomyocytes. Similar to cAMP, for relevant pathways we will investigate ultrastructural changes using STED microscopy and TEM to understand the underlying mechanisms. For relevant pathways the significance of intercalated disc components will be determined by siRNA-mediated depletion in cultured cardiomyocytes as well as using primary cells derived from a Pg-deficient AC-mouse model. In the second part of the project, GJ regulation via desmosomal adhesion will be studied. Using multielectrode arrays, in cultured cardiomyocytes adhesion-stabilizing signaling pathways as well as peptide-mediated Dsg2-crosslinking will be used to modulate GJ-mediated excitation propagation. Dsg2-crosslinking will also performed in intact Langendorff-perfused hearts since our preliminary data show that this approach is effective to ameliorate arrhythmia in Pg-deficient mouse hearts. Afterwards, hearts will be subjected to ultrastructural analysis. In our project, we expect to achieve new insight into the regulation of cell cohesion and GJ function in cardiomyocytes.

• DFG Programme: Research Grants