Molecular architecture of tight junctions.
The tight junction creates a regulated barrier in the paracellular pathway and, together with the actin-rich adherens junction, forms a functional unit called the apical junction complex. A growing number of tight junction-associated proteins have been identified, but functions are defined for only a few. The intercellular barrier is formed by rows of the transmembrane protein occludin, which is bound on the cytoplasmic surface to ZO-1 and ZO-2. These proteins are members of the membrane-associated guanylate kinase (MAGUK) protein family and are likely to have both structural and signaling roles. Junctional plaque proteins without known functions include cingulin, p130, and 7H6; single reports describe ZA-1TJ and symplekin. Many cellular signaling pathways affect assembly and sealing of junctions. Transducing proteins, which localize within the junction, include both heterotrimeric and rho-related GTP-binding proteins, PKC-zeta and nonreceptor tyrosine kinases. Control of perijunctional actin may be the unifying mechanism for regulating paracellular permeability.
Mitic
L L
LL
Department of Cell Biology, Yale School of Medicine, New Haven, Connecticut 06520, USA. laura.mitic@yale.edu
Anderson
J M
JM
D000595:Amino Acid Sequence; D000818:Animals; D051528:Guanylate Kinases; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D009703:Nucleoside-Phosphate Kinase / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D019108:Tight Junctions / Q000737:chemistry* / Q000201:enzymology / Q000502:physiology
D008565:Membrane Proteins; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases