De novo construction of cell-to-cell channels.

Nexus (gap junctions), which are considered to contain cell-to-cell channels, are newly formed in uterine smooth muscle during parturition or in response to estrogen treatment of virginal animals. A mRNA preparation was isolated from estrogen-dominated rat myometria and was encapsulated into liposomes. Subsequently the liposomes were fused with cultured cells of a mouse cell line CL-1D. It is established that these tumor cells normally are neither electrically coupled nor do they contain nexus. The cells, however, become electrically coupled a few hours after being loaded with the mRNA preparation. This de novo expression of cell coupling persisted for a litte more than 24 hr after a single loading procedure. Freeze-fracture electron microscopy revealed small nexus-like particle aggregates at the time coupling was present. In control experiments the cells remained noncoupling when the RNA preparation was pretreated with ribonuclease, when cycloheximide was applied to the cells, or when liposomes filled with buffer solution only were used. These data suggest that the de novo expression of cell-to-cell coupling is accomplished by mRNA-induced protein biosynthesis resulting in the formation of cell-to-cell channels.