Structure-function analysis of tight junction-directed permeation enhancer PIP250.

The intestinal paracellular route of absorption is modulated via tight junction (TJ) structures located at the apical neck of polarized intestinal epithelial cells to restrict solute movement through the intercellular space between them. Tight junctions open or close in response to changes in the phosphorylation status of light chain (MLC) at position Ser-19. This phosphorylation event is primarily controlled by MLC kinase (MLCK) and MLC phosphatase (MLCP), the latter being a holoenzyme that involves interaction between protein phosphatase 1 (PP1) and myosin targeting protein 1 (MYPT1).