Analysis of Desmosomal Cadherin–Adhesive Function and Stoichiometry of Desmosomal Cadherin-Plakoglobin Complexes

Abstract

Desmosomes are intercellular adhesive junctions that associate with the intermediate filament cytoskeleton. The two major classes of transmembrane desmosomal glycoproteins, desmogleins and desmocollins, are widely considered to function as adhesion molecules. This assumption is based in part on their homology to the cadherin family of calcium-dependent homophilic adhesion molecules. In addition, autoantibodies from pemphigus patients bind directly to desmoglein family members and are thought to cause epidermal blistering by inhibiting the function of these cadherins. To directly test the ability of the desmosomal cadherins to mediate adhesion, desmoglein-1 (Dsg1), desmocollin-2 (Dsc2a) and plakoglobin were expressed in mouse L cell fibroblasts. Similar to catenin:classical cadherin complexes, plakoglobin:Dsc2a complexes exhibited an approximately 1:1 stoichiometry; however, plakoglobin:Dsg1 complexes exhibited a 6:1 stoichiometry. When L cells expressing the desmosomal cadherins were tested for the ability to aggregate in suspension, L cells expressing E-cadherin exhibited extensive aggregation, but L cells expressing Dsg1 or Dsc2a did not aggregate. In addition, L cells co-expressing Dsg1, Dsc2a, and plakoglobin failed to aggregate. The cytoplasmic domain of E-cadherin is thought to play a central role in the adhesive function of E-cadherin by providing a link to the actin cytoskeleton. Therefore, two chimeric cadherins comprising the cytoplasmic domain of E-cadherin and the extracellular domain of either Dsg1 or Dsc2a were expressed in L cells. Both chimeras formed a complex with alpha- and beta-catenin. Nevertheless, neither of these chimeras supported aggregation of L cells when expressed individually or when co-expressed. These data suggest that the extracellular domains of the desmosomal cadherins exhibit functional properties distinct from those of the classical cadherins, such as E-cadherin.

Modulating the strength of cadherin adhesion: evidence for a novel adhesion complex

“…In addition, all three catenins, ␣-catenin, ␤-catenin and p120 ctn , were detected in the LNER cells, and no significant difference was seen in the levels or molecular weights of these catenins when comparing the LNER cells treated or not with 4OHT. Plakoglobin was not detected (data not shown), consistent with its reported absence in L cells (Kowalczyk et al, 1996). Together, our data indicated that the cellular level of NcadER and catenins in LNER cells was not altered by 4OHT.…”

Structural and Functional Diversity of Desmosomes

“…Biochemical data confi rmed these predictions. Specifi cally, desmoplakin anchored intermediate fi laments Kouklis et al, 1994;Bornslaeger et al, 1996;Meng et al, 1997); plakophilins, plakoglobin, and desmoplakin bound each other to form a plaque (Chen et Kowalczyk et al, 1997;Bornslaeger et al, 2001), and interactions mediated by plakoglobin and plakophilin linked the plaque-fi lament complex to transmembrane, desmogleins, and desmocollins (Smith & Fuchs, 1998;Chen et al, 2002;Bonne et al, 2003;Hatzfeld et al, 2000;Kami et al, 2009;Troyanovsky et al, 1994a, 1994b, Kowalczyk et al, 1996Witcher et al, 1996;Choi et al, 2009;Mathur et al, 1994;Roh & Stanley, 1995;Kowalczyk et al, 1999;Andl & Stanley, 2001;Bornslaeger et al, 2001;Gaudry et al, 2001). The ability of desmosomal cadherins to establish trans interactions between cells, in turn, accounted for the actual adhesive bond formed between two cells (Waschke et al, 2007;Nie et al, 2011;Chitaev & Troyanovsky, 1997;Aoyama et al, 2009).…”

Defining a Molecular Atlas of the Hippocampus Using DNA Microarrays and High-ThroughputIn SituHybridization

“…org). At the extreme, desmoplakin, a component of desmosomal tight junctions in peripheral tissues (Kowalczyk et al, 1996), is completely restricted to granule cells of the dentate gyrus, both within the hippocampus ( Fig. 2A,F) and throughout the entire brain (supplemental Fig.…”

“…These characteristics are presumably attributable to expression of cytoskeletal proteins and ion channels, a number of which display striking region-specific expression. For example, desmoplakin, known as a component of desmosomal plaques (Kowalczyk et al, 1996), is expressed solely in the dentate gyrus. Granule cell axons, the so-called "mossy fibers," have a very distinctive morphology with extremely large terminal endings characterized by rows of puncta adherens (Claiborne et al, 1986;Acsady et al, 1998).…”