PKP2 is required for proper assembly of DP into desmosomes. (A and B) Impaired DP border localization in PKP2-deficient cultures. SCC9 cells (A, wide-field microscopy) or A431 cells (B, confocal microscopy) expressing pooled siRNAs against human PKP2 or nontargeting (NT) control, immunostained for endogenous DP and PKP2. Immunoblot analysis of SCC9 (A, right) or A431 (B, right) from NT or PKP2 siRNA-transfected cells to detect total levels of PKP2, PKP1, PKP3, DP, DSC2, DSG2, DSG3, and α-tubulin. PG protein levels were unaffected (not depicted). Arrows indicate the cell–cell border. (C) DP particles colocalize with keratin IF during PKP2 knockdown. Confocal images of SCC9 cells expressing PKP2 or NT siRNA immunostained for DP (green) and keratin (red). Panels b′ and d′ show magnified views of the boxed areas in a′ and c′, respectively. (D) DP assembly is impaired during PKP2 knockdown. Calcium switch of SCC9 cells transfected with siRNA against PKP2 or NT + siGlo, endogenous PKP2, or DP staining. DP border fluorescence intensity was measured, normalized to background, and plotted in D (right). Arrows indicate siGLO particles. Error bars represent SEM. (E) DP accumulates in a filamentous cytoplasmic pattern during PKP2 knockdown. Shown are stills from Videos 1 and 2 (available at http://www.jcb.org/cgi/content/full/jcb.200712133/DC1) depicting PKP2 or NT siRNA-transfected A431 DP-GFP cells. Arrows indicate where new borders are being formed. Red arrowheads show DP accumulation on IF. Time points indicate time lapsed from beginning of video. Bars, 10 μm.