Mechanisms and function of intercellular calcium signaling

Intercellular Ca²⁺ waves initiated by mechanical or chemical stimuli propagate between cells via gap junctions. The ability of a wide diversity of cells to display intercellular Ca²⁺ waves suggests that these Ca²⁺ waves may represent a general mechanism by which cells communicate. Although Ca²⁺ may permeate gap junctions, the intercellular movement of Ca²⁺ is not essential for the propagation of Ca²⁺ waves. The messenger that moves from one cell to the next through gap junctions appears to be IP₃ and a regenerative mechanism for IP₃ may be required to effect multicellular communication. Extracellularly mediated Ca²⁺ signaling also exists and this could be employed to supplement or replace gap junctional communication. The function of intercellular Ca²⁺ waves may be the coordination of cooperative cellular responses to local stimuli.