Expression of full-length desmosomal glycoproteins (desmocollins) is not sufficient to confer strong adhesion on transfected L929 cells

Desmocollins are cadherin-like glycoproteins that are localized in desmosomes. They are thought to play a role in cell adhesion but direct evidence for this is currently unavailable. For this reason we have expressed cDNAs encoding full-length bovine desmocollin type la and type Ib in mouse fibroblast (L929) cells. This system has Previously been used to demonstrate the adhesive properties of E-cadherin. F-cadherin-mediated cell-cell adhesion is thought to require interaction of the cytoplasmic domain with the catenins that are expressed in L-cells. Because L929 cells do not express cytoplasmic desmosomal components that may be required for desmocollin-mediated adhesion, we constructed a chimeric cDNA encoding the bovine type 1 extracellular domain linked to the mouse E-cadherin transmembrane and cytoplasmic domains. cDNAs were transfected: into cells and clones that expressed heterologous protein at the cell surface were isolated. The full-length desmocollins apparently did not interact with any other molecules, but the chimeric protein did bind to endogenous mouse alpha- and beta-catenin. Surprisingly none of the desmocollin-transfected cell lines showed significant adhesive properties under conditions where cells transfected with F-cadherin exhibited strong adhesiveness. We conclude that desmocollin expression alone is not sufficient to confer adhesion on transfected cells and more than one desmosomal component may be required.