Figure 1.

(A) Signal molecules, such as ATP, PGE2, glutamate, aspartate, and ions, transmit from cell to cell via GJs. Hemichannels (HCs) facilitate exchanges between intra- and extracellular compartments. Secondary messengers, small metabolites, and ions are involved in HC transmission. Thus, the diffusion of inflammatory signals can be carried out through GJs. (B) An HC is a tetraspan transmembrane (TM) protein with intracellular N- and C-terminals. HC has two extracellular loops and one cytoplasmic loop, which is the target of mimic peptide. In Cx43 HC, peptide 5 (red) and Gap27 (purple) target the extracellular loop. Meanwhile, L2 (green) and Gap19 (orange) target the cytoplasmic loop. These mimic peptides could regulate the activity of Cx43.