. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. INTERMEDIATE FILAMENTS, HEMIDESMOSOMES, AND DESMOSOMES Desmosome 375. Figure 1. Diagram comparing the major molecular constituents of the two intercellular adhesive junc- tions found m epithelial tissues. The adhesion molecules in both junctions are members of the larger cadherin family of calcium-dependent cell adhesion molecules. These are desmogleins and desmocollins in the desmosome (top), and classic cadherins, such as E-cadherin, in the adherens junction (bottom). Members of the armadillo gene family, plakoglobin and /
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. INTERMEDIATE FILAMENTS, HEMIDESMOSOMES, AND DESMOSOMES Desmosome 375. Figure 1. Diagram comparing the major molecular constituents of the two intercellular adhesive junc- tions found m epithelial tissues. The adhesion molecules in both junctions are members of the larger cadherin family of calcium-dependent cell adhesion molecules. These are desmogleins and desmocollins in the desmosome (top), and classic cadherins, such as E-cadherin, in the adherens junction (bottom). Members of the armadillo gene family, plakoglobin and /3-catenin, associate with the cytoplasmic tails of the cadherins and link the membrane molecules to the cytoskeleton through adapter proteins. In the desmosome, desmoplakin is an adapter protein that anchors the cadherin complex specifically to the intermediate filament cytoskeleton. and in the adherens junction a-catenin anchors the cadherin complex specifically to the microfilament cytoskeleton. the IF cytoskeleton is unknown, desmoplakin (DP) is a putative link. Our previous work demonstrated that the DP C-terminus associates with IF networks, whereas the DP N-terminus is required for incorporation into desmo- somes. To directly test whether DP is required to link IF to the desmosome, a dominant negative mutant compris- ing 70 kDa of the DP N-terminus (DP-NTP) was stably expressed in A-431 epithelial cells (Bohnslaeger et ai. 1996). DP-NTP dramatically perturbed endogenous DP. likely by competing for interaction with transmembrane adhesive complexes. Ultrastructural analysis revealed junctional structures that were largely lacking associated IF bundles. Adherens junction components, such as a- catenin and E-cadherin. coassembled into these structures, along with desmosomal components and DP-NTP. This observation suggests that sequences in full length DP, not present in DP-NTP, and perhaps anchorage to the IF cytoskeleton, are required for the normal segregation of desmosomal
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