Gap Junction - Properties of Connexon Channel Pairs

Properties of Connexon Channel Pairs

1. Allows for direct electrical communication between cells, although different connexin subunits can impart different single channel conductances, from about 30 pS to 500 pS.
2. Allows for chemical communication between cells, through the transmission of small second messengers, such as inositol triphosphate (IP₃) and calcium (Ca2+), although different connexin subunits can impart different selectivity for particular small molecules.
3. Generally allows molecules smaller than 1,111 Daltons to pass through, although different connexin subunits can impart different pore sizes and different charge selectivity. Large biomolecules, for example, nucleic acid and protein, are precluded from cytoplasmic transfer between cells through gap junction connexin channels.
4. Ensures that molecules and current passing through the gap junction do not leak into the intercellular space.

To date, five different functions have been ascribed to gap junction protein: a) electrical and metabolic coupling between cells b) Electrical and metabolic exchange through hemichannels c) Tumor suppressor genes (Cx43, Cx32 and Cx36) d) Adhesive function independent of conductive gap junction channel (neural migration in neocortex) e) Role of carboxyl-terminal in signaling cytoplasmic pathways (Cx43)