What is the Origin of Tight Junctions?

The term is descriptive, referring to the close, "tight" adherence between adjacent cells. This cellular structure was first visualized using electron microscopy in the 1960s, revealing the precise anatomical point of contact. The understanding of their physiological role in barrier function and disease pathology has grown significantly in gastroenterology and neurobiology.

What is the Mechanism of Tight Junctions?

These junctions are composed of transmembrane proteins, primarily claudins and occludin, which link the cytoskeletons of neighboring cells. The mechanism involves the homotypic and heterotypic binding of these proteins across the intercellular space, effectively fusing the outer leaflets of the plasma membranes. Hormonal signals and inflammatory mediators can modulate the phosphorylation of these proteins, causing the junctions to temporarily open or "leak," a process often implicated in increased intestinal permeability.

Tight Junctions

Meaning

Tight junctions, also known as zonula occludens, are multi-protein complexes that form a continuous, circumferential seal around the apical end of epithelial and endothelial cells. Their primary function is to regulate paracellular permeability, controlling the selective passage of ions and solutes between cells. Maintaining the integrity of these junctions is crucial for establishing and preserving essential tissue barriers, such as the intestinal and blood-brain barriers. Disruption is often referred to as “leaky” barrier function.