Fig. 5. Immuno-EM identifies colocalization of T-catenin and PKP2 at adhering junctions of the intercalated discs of cardiomyocytes. (A) Single labeling with silver amplification of T-catenin and PKP2 at fascia adhaerens-like junctions (left panel) and desmosome-like junctions (right panel). Whereas PKP2 is detected in both junction types, T-catenin is confined to the fascia adhaerens-like junction type, which we named `hybrid adhering junctions'. (B) Consecutive double labeling at the mixed-type junctional structure (area composita): detection of T-catenin by silver amplification (large dots) was followed by PKP2 labeling (10-nm gold particles, small dots, arrows). (C) Detection of intermediate filaments at the area composita by consecutive double labeling: T-catenin detection by silver amplification (big dots, indicated by arrowheads) was followed by desmin labeling (10-nm gold particles, small dots). (D) Schematic representation of the number of gold particles counted at the site of hybrid adhering junctions (left, black bars) and desmosome-like junctions (right, black bars) in comparison to the cytoplasmic background label (grey bars) after immunogold labeling of several cadherin/catenin-associated proteins (T-catenin, E-catenin and β-catenin) and several desmosomal proteins (PKP2, desmoglein and desmoplakin). The classic cadherin-catenin complex is found only at the hybrid adhering junctions, whereas desmosomal proteins are detected at both the desmosome-like and the hybrid adhering junctions of the intercalated disc.