Protein phosphatase 2A activity is required for functional adherent junctions in endothelial cells.

Microvascular research

PubMedID: 23721711

Kása A, Czikora I, Verin AD, Gergely P, Csortos C. Protein phosphatase 2A activity is required for functional adherent junctions in endothelial cells. Microvasc Res. 2013;8986-94.
Reversible Ser/Thr phosphorylation of cytoskeletal and adherent junction (AJ) proteins has a critical role in the regulation of endothelial cell (EC) barrier function. We have demonstrated earlier that protein phosphatase 2A (PP2A) activity is important in EC barrier integrity. In the present work, macro- and microvascular EC were examined and we provided further evidence on the significance of PP2A in the maintenance of EC cytoskeleton and barrier function with special focus on the Ba (regulatory) subunit of PP2A. Immunofluorescent staining revealed that the inhibition of PP2A results in changes in the organization of EC cytoskeleton as microtubule dissolution and actin re-arrangement were detected. Depletion of Ba regulatory subunit of PP2A had similar effect on the cytoskeleton structure of the cells. Furthermore, transendothelial electric resistance measurements demonstrated significantly slower barrier recovery of Ba depleted EC after thrombin treatment. AJ proteins, VE-cadherin and ß-catenin, were detected along with Ba in pull-down assay. Also, the inhibition of PP2A (by okadaic acid or fostriecin) or depletion of Ba caused ß-catenin translocation from the membrane to the cytoplasm in parallel with its phosphorylation on Ser552. In conclusion, our data suggest that the A/Ba/C holoenzyme form of PP2A is essential in EC barrier integrity both in micro- and macrovascular EC.