Tight Junctions

Tight junctions are multiprotein complexes that act as rivets between cells and control transportation through the extra-cellular matrix.

Tight Junctions attach cells tightly to their neighbors, these junctions act as a barrier preventing molecules from diffusing between adjacent cells.

When a molecules need to transfer through the layer of cells the transport is a multi-step process involving signaling pathways, the regulation of junction proteins, and modifications in the cytoskeletal organization.

Barrier Role

• Tight junctions act as one type of specialized intercellular junctional complex that facilitates transference of molecules between cells.
• Tight junctions also help to distinguish the apical (inside the cell) and basolateral (outside the cell) domains of the cell by acting as intracellular barriers to macromolecules and proteins between these two regions.

Three main transmembrane protein types are found in tight junctions; members of the occludin, claudins, and junctional adhesion molecules (JAMs) families.

1: Occludin proteins consist of 4 domains – 2 intracellular and 2 extracellular and are involved with the regulation of signaling event.

2: Claudins proteins compose the major structural and functional elements of tight junctions. They also consist of 4 domains – 2 intracellular and 2 extracellular and mediate calcium-independent cell-cell adhesion.

3: JAMs have only a single transmembrane domain, unlike occludin and claudins. It is believed that JAM proteins regulate the paracellular barrier.

Some Diseases/Conditions Affecting TJ

• Edema
• Jaundice
• Diarrhea
• Chronic inflammatory diseases of the intestine
• Cancer (loss of cell polarity)

References

• Cell-Cell Interactions. (2006, November 23). Retrieved October 1, 2015.
• Image 1: http://scienceblogs.com/clock/2006/11/cellcell_interactions.php
• Image 2: http://ajpheart.physiology.org/content/282/4/H1485

References Cont.

• Image 3: http://openi.nlm.nih.gov/detailedresult.php?img=3404166_gnl-6-305-g002&req=...