Structure of Tight Junctions and their Dynamic Functions in Health and Disease
Tight junction (TJ) discovery in the 1960s helped determine the nature of paracellular transport while the discovery of their constituting proteins subsequently improved understanding of TJs’ dynamic structure. Their role can be appreciated particularly in epithelial cells and when their formation is compromised; I aim to briefly explore the cause of Crohn’s disease to illustrate this. Furthermore, I will outline the key structural components of TJs which make them dynamic across different tissues using the blood-brain barrier as an example meanwhile discussing some ambiguities that require further research.
TJs play vital roles in paracellular transport (movement of substances via gaps between cells) (Anderson, Van Itallie 2007). They are localised at the most apical point of the intracellular cleft to separate the apical and basolateral compartments (see fig. 1 – FIG 19-2 BIG TEXTBOOK) so larger molecules (>15Å sometimes >60Å) are forced to pass through transporter proteins embedded in the epithelial cells using transcellular pathways (intracellular movement of substances) (Anderson, Van Itallie 2007). These transporter proteins must navigate to either the apical or basal regions of epithelia and TJs aid …show more content…
The maintenance of a chemical gradient is especially important in sustaining transepithelial resistance (high electrical resistance) which occurs because ions can move more freely in the apical or basal fluid compared with the epithelia (see fig. 2 – embryology) (Goodman 2007). This property is of further significance in the blood-brain barrier (BBB) where synaptic transmission is dependent on chemical signalling so the brain needs to be protected from chemical fluctuations in blood (Blumenfeld 2010). In fact, TJs are ‘tighter’ at the BBB for this reason (Abbott et al.
Tight junction (TJ) discovery in the 1960s helped determine the nature of paracellular transport while the discovery of their constituting proteins subsequently improved understanding of TJs’ dynamic structure. Their role can be appreciated particularly in epithelial cells and when their formation is compromised; I aim to briefly explore the cause of Crohn’s disease to illustrate this. Furthermore, I will outline the key structural components of TJs which make them dynamic across different tissues using the blood-brain barrier as an example meanwhile discussing some ambiguities that require further research.
TJs play vital roles in paracellular transport (movement of substances via gaps between cells) (Anderson, Van Itallie 2007). They are localised at the most apical point of the intracellular cleft to separate the apical and basolateral compartments (see fig. 1 – FIG 19-2 BIG TEXTBOOK) so larger molecules (>15Å sometimes >60Å) are forced to pass through transporter proteins embedded in the epithelial cells using transcellular pathways (intracellular movement of substances) (Anderson, Van Itallie 2007). These transporter proteins must navigate to either the apical or basal regions of epithelia and TJs aid …show more content…
The maintenance of a chemical gradient is especially important in sustaining transepithelial resistance (high electrical resistance) which occurs because ions can move more freely in the apical or basal fluid compared with the epithelia (see fig. 2 – embryology) (Goodman 2007). This property is of further significance in the blood-brain barrier (BBB) where synaptic transmission is dependent on chemical signalling so the brain needs to be protected from chemical fluctuations in blood (Blumenfeld 2010). In fact, TJs are ‘tighter’ at the BBB for this reason (Abbott et al.