Occludin proteolysis and increased permeability in endothelial cells through tyrosine phosphatase inhibition

Regulation of epithelial and endothelial permeability is essential for prop er function of compartmentalized organisms, and tyrosine phosphorylation pl ays an important role in this process. We analyzed the impact of protein ty rosine phosphatase (PTP) inhibition on the structure of endothelial junctio nal proteins. In human umbilical vein endothelial cells (HUVECs) the PTP in hibitors phenylarsine oxide (PAO) and pervanadate induced proteolysis of th e tight junction protein occludin. Occludin proteolysis was inhibited by th e metalloproteinase inhibitor 1,10-phenanthroline (PHEN), but not by inhibi tors against other types of proteases. The junctional proteins ZO-1, cadher in and beta-catenin were not cleaved. Under conditions of occludin proteoly sis, PAO cleaved. Under conditions of occludin proteolysis, PAO treatment e levated permeability for FITC-dextran. Simultaneous incubation of HUVECs wi th PAO and PHEN inhibited the rise in permeability by more than 60%, PAO tr eatment lead to progressive disappearance of occludin from the cell periphe ry. In contrast, ZO-1, cadherin and beta-catenin retained their positions a t the sites of intercellular contact. Simultaneous administration of PAO an d PHEN greatly prevented the redistribution of occludin, These results demo nstrate a selective cleavage of occludin by a metalloproteinase and suggest that this process can contribute to the control of paracellular permeabili ty in endothelial cells.