INTERKERATINOCYTE ADHERENS JUNCTIONS - IMMUNOCYTOCHEMICAL VISUALIZATION OF CELL-CELL JUNCTIONAL STRUCTURES, DISTINCT FROM DESMOSOMES, IN HUMAN EPIDERMIS

Vinculin and beta-catenin are intracellular attachment proteins linkin g transmembrane adhesion molecules (E-cadherin) to the actin microfila ment cytoskeleton, thus participating in formation of cell-cell adhere ns junctions, or zonulae adherentes, This type of junction was only re cently described in human epidermis due to the imprecise morphological criteria for its recognition, In this study, we investigated the rela tionship between the expression of the zonula adherens-associated prot eins vinculin, beta-catenin, E-cadherin, and actin, on the one hand, a nd the presence of electron microscopically discernable structures in normal human epidermis on the other, Mouse jejunal epithelium with its orderly arrangement of various junctional structures served as a posi tive control. Simple and dual post-embedding immunogold labeling was p erformed on ultrathin sections of Lowicryl K4M and Lowicryl K11M embed ded tissues, The overall distribution of the antigens in human epiderm is was evaluated on frozen tissue sections using immunofluorescence an d laser confocal scanning microscopy, Antibodies against proteins asso ciated with desmosomes (i.e., keratins, desmoglein 1, and plakoglobin) were used as controls. Vinculin and beta-catenin were localized to ju nctional structures distinct from desmosomes, thus defining the presen ce of zonulae adherentes. Labeling of actin and E-cadherin was less cl early restricted to the junctions, but these two proteins were also co -expressed at zonulae adherentes and not at desmosomes. In human epide rmis, zonula adherens-associated labeling was consistently detected ne ar desmosomes, indicating the possibility of a functional relationship between the two types of junctions.