Regulation of Lens Gap Junctions

Gap junctions are membrane specializations that contain groups of intercellular channels. These channels are permeable to ions and small molecules up to 1,000 Da. They communicate the cytoplasm of adjacent cells, thereby providing a direct pathway for the passage of ions, nutrients, metabolites and second messengers between coupled cells. Gap junctional channels are made of oligomeric assemblies of members of a family of related proteins called connexins (Cx). These proteins cross the plasma membrane four times leaving the amino and carboxyl termini on the cytoplasmic side (reviewed by Beyer)1.