Chapter 94 - Cell–Cell Communication Through Gap Junctions

Abstract

A swarm of fish displays a collective behavior (“swarm behavior”) and moves en masse despite the huge number of individual animals. In analogy, organ function is supported by a huge number of cells that act in an orchestrated fashion. It is obvious that communication is required to achieve this vital goal. The communication channel is indeed a true channel that interlinks the cytosol of adjacent cells by a pore sealed against the extracellular space. Many channels that cluster in a specific region of intimate cell contact bridge the remaining gap to form a low-resistance connection (gap junction) allowing exchange of ions and other small molecules. The modular bricks of these channels are connexins. Because charge (and membrane potential) is transferred, gap junctions convert many individual smooth muscle cells into a synchronously contracting or relaxing unit of smooth muscle. This chapter will outline assembly and physiology of gap junctions and provide ample evidence for their importance in smooth muscle function.