E-CADHERIN EXPRESSION CAN ALTER THE SPECIFICITY OF GAP JUNCTION FORMATION

Specificity of gap junction formation produces communication compartme nts, groups of cells joined to each other by gap junctions (homologous communication) but more rarely to cells in adjacent compartments (het erologous communication). Specificity of junction formation can be stu died in mixed cultures of different cell types. In these model systems , compartmentation is often associated with sorting out, a process tha t produces separate domains of the different cells. The borders of the physically distinct domains correlate with the functional boundaries of the communication compartments. Compartments have also been observe d in vivo where they are believed to play a role in separating groups of cells following different differentiation pathways. Two classes of cell surface molecule, connexins and cell adhesion molecules, are cand idates for a role in the control of specificity. A representative of e ach class appears to be necessary for gap junction formation and both are expressed in a tissue specific manner. We have shown that mixed cu ltures of rat epithelial (BRL) cells and rat (BICR) fibroblasts show s pecificity, form communication compartments and sort out. Both cell ty pes express the same connexin (connexin 43) but different cell adhesio n molecules (BRL, P-cadherin and 125-kDa N-cadherin; BICR, 140-kDa N-c adherin). Transfection of both cell types with E-cadherin results in a 10-fold increase in heterologous communication. These data suggest th at E-cadherin plays a role in the control of specificity of gap juncti on formation. (C) 1997 Academic Press.