Fig. 3. Ability of DP to become codistributed with both the desmin network and keratin intermediate filaments in a transfected human keratinocyte cell line, that stably expresses desmin (A-F) as well as with the desmin network in transfected primary rat cardiomyocytes (G-I). The cells were transiently transfected with cDNA encoding DP BC^S2849G, GFP-tagged at its N-terminus (A-I). Transfected cells were double-stained with an anti-GFP antiserum (A,D) and either a monoclonal antibody directed against desmin (B) or a monoclonal anti-keratin 14 antibody (E), and subsequently examined by laser confocal microscopy. Overlays are shown in C and F. Primary rat cardiomyocytes were transiently transfected with cDNA encoding GFP-tagged DP-BC^S2849G (G-I). The GFP is localized in the fluorescein channel. Cells were also stained with a monoclonal anti-desmin antibody (overlays in G and F) or with both the rabbit NW161 anti-DP antiserum and a monoclonal anti-desmin antibody (overlays in I). DP-BC^S2849G is found colocalized with desmin filaments that are either still longitudinal (overlay in G) or already rearranged into a cross-striated pattern (overlay in H). At intercalated discs, DP-BC^S2849G colocalizes with endogenous DP and desmin (white color in I, arrows). Notably, in cells in which the GFP-DP-BC^S2849G construct strongly stained the region of intercalated discs, the staining pattern of endogenous desmin extending from the junctional region into the cytoplasm appeared disorganized (arrowhead) and reduced (I) suggesting that the DP-tail acted in a dominant negative fashion by competing with the endogenous DP for sites of IF attachment at intercalated discs. Bars, 10 µm.