The molecular structure of the tight junction.

The maintenance of a barrier with controlled permeability is an important characteristic for multi-cellular organisms. In mammalian cells, the tight junction functions in that role allowing compartments with different solute composition to be separate, but not absolutely unconnected. The permeability of this paracellular zone needs to be controlled by both internal and external factors allowing for modulation of the permeability under certain circumstances. The purpose of this chapter is to introduce the reader to the molecular components of the mammalian tight junction. Also provided, is a brief description of how these junctional components interact with other members of the tight junction plaque and components of both the cytoskelton and signaling cascade.