CONTRIBUTIONS OF EXTRACELLULAR AND INTRACELLULAR DOMAINS OF FULL-LENGTH AND CHIMERIC CADHERIN MOLECULES TO JUNCTION ASSEMBLY IN EPITHELIAL-CELLS

The integrity of cell-cell junctions in epithelial cells depends on fu nctional interactions of both extracellular and intracellular domains of cadherins with other junction proteins. To examine the roles of the different domains of E-cadherin and desmoglein in epithelial junction s, we stably expressed full length desmoglein 1 and chimeras of E-cadh erin and desmoglein 1 in A431 epithelial cells. Full length desmoglein 1 was able to incorporate into or disrupt endogenous desmosomes depen ding on expression level. Each oi the chimeric cadherin molecules exhi bited distinct localization patterns at the cell surface. A chimera of the desmoglein 1 extracellular domain and the E-cadherin intracellula r domain was distributed diffusely at the cell surface while the rever se chimera, comprising the E-cadherin extracellular domain and the des moglein 1 intracellular domain, localized in large, sometimes contiguo us patches at cell-cell interfaces. Nevertheless, both constructs disr upted desmosome assembly. Expression of constructs containing the desm oglein 1 cytoplasmic domain resulted in approximately a 3-fold decreas e in E-cadherin bound to plakoglobin and a 5- to 10-fold reduction in the steady-state levels of the endogenous desmosomal cadherins, desmog lein 2 and desmocollin 2, possibly contributing to the dominant negati ve effect of the desmoglein 1 tail, In addition, biochemical analysis of protein complexes in the stable lines revealed novel in vivo protei n interactions. Complexes containing beta-catenin and desmoglein 1 wer e identified in cells expressing constructs containing the desmoglein 1 tail. Furthermore, interactions were identified between endogenous E -cadherin and the chimera containing the E-cadherin extracellular doma in and the desmoglein 1 intracellular domain providing in vivo evidenc e for previously predicted lateral interactions of E-cadherin extracel lular domains.