Gap junction modulation describes the functional manipulation of gap junctions, specialized channels that allow direct electrical and chemical communication between cells without exporting material from the cytoplasm. Gap junctions play an important regulatory role in various physiological processes including signal propagation in cardiac muscles and tissue homeostasis of the liver. Modulation is required, since gap junctions must respond to their environment, whether through an increased expression or permeability. Impaired or altered modulation can have significant health implications and are associated with the pathogenesis of the liver, heart and intestines.
Modulation is achieved by endogenous chemicals, growth factors, hormones and proteins that affect gap junction expression, structure, degradation and permeability. Natural forms of modulation include voltage gating and chemical modulation. Voltage-gating is a relatively fast modulation categorized into Vj gating and slow voltage gating, which are further influenced by calcium ions (Ca2+), pH and calmodulin. Chemical modulation entails the addition or removal of a functional group or protein from the connexin subunits of gap junctions; this can alter gap junction expression and structure.