Adrenergic signaling‐induced ultrastructural strengthening of intercalated discs via PG is crucial for positive adhesiotropy in murine cardiomyocytes.

Abstract

Intercalated discs (ICD), which connect adjacent cardiomyocytes, are composed of desmosomes, adherens junctions (AJ) and gap junctions (GJ). Previous data demonstrated that adrenergic signaling enhances cardiac myocyte cohesion, referred to as positive adhesiotropy, via PKA‐mediated phosphorylation of plakoglobin (PG). Here, we further investigated the role of PG in adrenergic signaling‐mediated ultrastructural changes in ICD of cardiomyocytes. Quantitative transmission electron microscopy analysis of ICD demonstrated that cAMP elevation caused significant elongation of area composita and thickening of the ICD plaque, paralleled by enhanced cardiomyocyte cohesion, in WT but not PG‐deficient cardiomyocytes. STED microscopy analysis supported that cAMP elevation ex vivo enhanced Dsg2 and N‐cadherin (N‐cad) staining in ICDs of WT but not PG‐deficient cardiomyocytes. For dynamic analyses we utilized HL‐1 cardiomyocytes, in which cAMP elevation induced translocation of desmoglein‐2 (Dsg2) and PG but not of N‐cad to cell junctions. Nevertheless, depletion of N‐cad but not of Dsg2 resulted in a decrease in basal cell cohesion whereas positive adhesiotropy was abrogated in monolayers depleted for either Dsg2 or N‐cad. Moreover, AFM experiments showed that the cAMP elevation‐induced increase in Dsg2 binding events close to cell junctions was abolished by depletion of either Dsg2 or N‐cad. Our data demonstrate that in murine cardiomyocytes, adrenergic signaling via PG enhances N‐cad and Dsg2 in the ICD leading to strengthening of ICDs and thereby positive adhesiotropy.Support or Funding InformationThis work was supported by the Ludwig‐Maximilians‐Universität Munich with the Föfole program; and the Deutsche Forschungsgemeinschaft DFG grant number WA2474/11‐1 to Jens Waschke