Experimental manipulation of desmosome structure

A systematic investigation of the effects of proteolytic enzymes, chelators and detergents on desmosomes originating in a variety of tissues was undertaken. Although junctions from different tissues are morphologically similar, we found great differences in their sensitivity to various reagents, indicating dissimilarities in biochemical composition. In general, desmosomes from stratified squamous and glandular epithelia were insensitive to ethylenediaminetetraacetic acid (EDTA), but readily dissociable with trypsin. Enzymatic digestion caused disruption of material within the junctional extracellular space, and dislocation of paired desmosomal plaques. In contrast, the extracellular components of desmosomes from simple columnar epithelia were usually EDTA‐sensitive but trypsin‐resistant. There were, however, exceptions to the general pattern. Desmosomes from rat pancreas were affected only by the detergent sodium desoxycholate (DOC). DOC also solubilized the intermediate dense line of desmosomes from the frog skin. We have divided desmosomes into two broad categories based upon the differential effects of these reagents. One group, sensitive to trypsin or DOC, may be functionally “stable” in maintaining cell‐to‐cell associations for long periods. Such junctions occur in stratified squamous and many glandular epithelia. Another group of desmosomes, affected by chelating agents, may be physiologically “labile” or plastic. These junctions, occurring in simple columnar epithelia such as the gut, may respond to physiological stimuli by opening or closing, thus allowing intercellular migration of cells and substances passing through the epithelial sheet.