DESMOSOMES AND CYTOSKELETAL ARCHITECTURE IN EPITHELIAL DIFFERENTIATION - CELL-TYPE-SPECIFIC PLAQUE COMPONENTS AND INTERMEDIATE FILAMENT ANCHORAGE

Among the diverse kinds of intercellular, plaque bearing, cadherin con taining junctions, desmosomes (maculae adhaerentes) represent a major type characterized by the presence of specific transmembrane glycoprot eins, i.e. desmosomal cadherins of the desmoglein and desmocollin cate gories, and the cytoplasmic plaque proteins, desmoplakin I and plakogl obin. Recent studies, however, have shown that the composition of desm osomes is not identical in the various normal and tumorous desmosome-f orming tissues and cell cultures, including diverse forms of epithelia and carcinomas, meningothelia and meningiomas, myocardium and the lym ph node follicle reticulum. Desmosomes can differ in their specific co mplement of desmogleins, Dsg1-3, and desmocollins, Dsc1a-3b, as well a s in the additional presence and in their relative amounts of certain accessory plaque proteins such as desmoplakin II and plakophilin 1, a basic member of the larger plakoglobin family of proteins (''band 6 pr otein''). Assembly and function of desmosomes are effected by the inte raction of the specific complement of desmosomal cadherins with certai n cytoplasmic proteins. In particular, the cytoplasmic portions (''tai ls'') of the desmosomal cadherins contain certain domains and amino ac id sequence moths, identified by mutagenesis and transfection assays, that are essential elements in desmosome formation, notably the assemb ly of plaque proteins, and in the site-specific anchorage of intermedi ate-sized filaments (IFs) of the cytoskeleton, thereby contributing to the specific intracellular as well as supracellular, i.e. tissue, arc hitecture.