Which proteins are central to tight junction strands?

• A. Claudins and occludins
• B. E-cadherin and integrins
• C. Desmoglein and desmocollin
• D. Cadherin and catenin

Answer: (A)

Tight junction strands are built primarily by claudins, which form the sealing mesh that blocks paracellular diffusion, and occludin, which supports the strand structure and helps regulate barrier properties. Claudins determine how permeable the seal is and even the charge selectivity of what can pass between cells, while occludin participates in maintaining junction integrity and can influence signaling pathways that affect barrier function. These proteins connect to scaffolding proteins like ZO-1 and ZO-2 and anchor the junction to the actin cytoskeleton, shaping the overall tight junction architecture.

Proteins such as E-cadherin with catenins belong to adherens junctions, desmoglein and desmocollin to desmosomes, and integrins mediate cell-matrix adhesions, so they are not the central components of tight junction strands.