Tight junctions serve several critical functions in tissues:
1. Barrier Function: They prevent the passage of molecules and ions through the space between cells, maintaining distinct compositions of extracellular fluids on either side of the epithelial layer. 2. Selective Permeability: They regulate the selective movement of ions and small molecules, allowing certain substances to pass while blocking others. 3. Cell Polarity: They help maintain cell polarity by preventing the diffusion of membrane proteins and lipids between the apical and basolateral surfaces of the cell. 4. Signal Transduction: Tight junction proteins are involved in various intracellular signaling pathways that influence cell proliferation, differentiation, and survival.
