De novo formation of desmosomes in cultured cells upon transfection of genes encoding specific desmosomal components.

Desmosomes are cell junctions and cytoskeleton-anchoring structures of epithelia, the myocardium, and dendritic reticulum cells of lymphatic follicles whose major components are known. Using cultured HT-1080 SL-1 fibrosarcoma-derived cells and transfection of cDNAs encoding specific desmosomal components, we have determined a minimum ensemble of proteins sufficient to introduce de novo structures, which, by morphology and functional competence, are indistinguishable from authentic desmosomes. In a more refined analysis, the influence of the desmosomal proteins desmoplakin (Dp), plakoglobin (Pg), and plakophilin 2 (Pp2) on the lateral clustering of the desmosomal transmembrane-glycoprotein desmoglein 2 (Dsg) was examined. We found that for efficient clustering of desmoglein 2 and desmosome structure formation, all three major plaque proteins-desmoplakin, plakoglobin, and plakophilin 2- were necessary. Furthermore, in this cell model, plakophilin 2 was capable of directing desmoplakin to adhaerens junctions (AJ), whereas plakoglobin was crucial for the segregation of desmosomal and AJ components. These results are discussed with respect to the variability in cell junction composition observed in various nonepithelial tissues.