Breaking the connection: displacement of the desmosomal plaque protein desmoplakin from cell-cell interfaces disrupts anchorage of intermediate filament bundles and alters intercellular junction assembly.

Abstract

Abstract. The desmosomal plaque protein desmoplakin (DP), located at the juncture between the intermediate filament (IF) network and the cytoplasmic tails of the transmembrane desmosomal cadherins, has been proposed to link IF to the desmosomal plaque. Consistent with this hypothesis, previous studies of individual DP domains indicated that the DP COOH terminus associates with IF networks whereas NH2-terminal sequences govern the association of DP with the desmosomal plaque. Nevertheless, it had not yet been demonstrated that DP is required for attaching IF to the desmosome. To test this proposal directly, we generated A431 cell lines stably expressing DP NH2-terminal polypeptides, which were expected to compete with endogenous DP during desmosome assembly. As these polypeptides lacked the COOH-terminal IF-binding domain, this competition should result in the loss of IF anchorage if DP is required for linking IF to the desmosomal plaque.In such cells, a 70-kD DP NH2-terminal polypeptide (DP-NTP) colocalized at cell-cell interfaces with desmosomal proteins. As predicted, the distribution of endogenous DP was severely perturbed. At cell-cell borders where endogenous DP was undetectable by immunofluorescence, there was a striking absence of attached tonofibrils (IF bundles). Furthermore, DP-NTP assembled into ultrastructurally identifiable junctional structures lacking associated IF bundles. Surprisingly, immunofluorescence and immunogold electron microscopy indicated that adherens junction components were coassembled into these structures along with desmosomal components and DP-NTP. These results indicate that DP is required for anchoring IF networks to desmosomes and furthermore suggest that the DP-IF complex is important for governing the normal spatial segregation of adhesive junction components during their assembly into distinct structures.

Identification of differentially expressed genes in pulmonary adenocarcinoma by using cDNA array

“…Table 1 presents these genes, their function and chromosomal location. Figure 1 shows all Bornslaeger et al, 1996, 4 Caligo et al, 1995 Lee et al, 1997, 6 Pines and Hunter, 1992, 7 Toyoshima-Morimoto et al, 2001, 8 Everett et al, 2001, 9 Nhung et al, 1999, 10 Smith, 1991, 11 Fassina et al, 2000 Laronga et al, 2000, 13 Nakanishi et al, 1997, 14 Smith et al, 1997, 15 Yu andRohan, 2000, 16 Jaques et al, 1997, 17 Nishihira, 1998 Sethi et al, 1999, 19 Zhou et al, 1998, 20 Ratziu et al, 1998, 21 Kojima et al, 2000, 22 Diviani and Scott, 2001, 23 Feliciello et al, 2001 Wilson et al, 2000, 25 Engelman et al, 1998 Razani andLisanti, 2001, 27 Tuder et al, 2001, 28 Hefferan et al, 2000, 29 Boot et al, 1998, 30 Dohr et al, 1997, 31 Matikainen et al, 2001, 32 Chu et al, 1995. a Clontech array gene-specification number Figure 1 The gene expression profile of the 25 most over-and under-expressed genes in 14 patients calculated with either PCA analysis or permutation test. Names of the genes appear on the right-hand side and the samples studied are listed at the top.…”

Arrhythmogenic Right Ventricular Cardiomyopathy Plakophilin-2 Mutations Disrupt Desmosome Assembly and Stability

“…In this study, we generated a retroviral expression system to express selected plakophilin-2 mutants in epithelial cells that assemble robust desmosomes to examine the subcellular localization of the mutant protein and the possibility that mutant plakophilin-2 may act in a dominant manner to disrupt endogenous desmosomal structures. The A431 cell line is a cervical squamous cell carcinoma cell line used extensively to examine desmosome assembly and stability (Bornslaeger et al 1996;Palka and Green 1997;Wahl et al 2000). Because epithelial cells have been used extensively to study desmosome assembly and stability, we chose to use this system to examine the effect of plakophilin-2 mutations on junction assembly and stability.…”

“…Up to 40% of ARVC patients display mutations in the desmosomal plaque protein plakophilin-2, suggesting disruption of plakophilin-2 function in cardiomyocytes is a critical event in the pathogenesis of ARVC (van Tintelen et al 2006). In the present study, we examined the molecular mechanisms of desmosome disruption in response to mutant plakophilin-2 expression using a well-characterized epithelial cell culture system (Bornslaeger et al 1996;Wahl 2005;Sobolik-Delmaire et al 2006). For these studies, we utilized a retroviral expression system to stably express selected plakophilin-2 mutants previously identified in ARVC patient samples.…”

Anchoring Junctions As Drug Targets: Role in Contraceptive Development

“…2), but it also has additional roles in desmosome assembly and the maintenance of desmosome stability (Gallicano et al, 1998). Similar to plakoglobin, desmoplakin seems to function in the segregation of desmosome and adherens junction proteins (Bornslaeger et al, 1996). This is because expression of dominant-negative desmoplakin resulted in the formation of adhesive contacts that contained components of both cell junction types (Bornslaeger et al, 1996).…”

“…Two isoforms of desmoplakin exist, desmoplakin I and desmoplakin II, and both are abundant in all types of epithelia (Ruhrberg and Watt, 1997;Jefferson et al, 2004;Sonnenberg and Liem, 2007). Desmoplakin's function is to link intermediate filaments to the plasma membrane (Bornslaeger et al, 1996) (Fig. 2), but it also has additional roles in desmosome assembly and the maintenance of desmosome stability (Gallicano et al, 1998).…”