Phospholipase C? Modulates Rap1 Activity and the Endothelial Barrier.

ABSTRACT: The phosphoinositide-specific phospholipase C, PLC?, is a unique signaling protein with known roles in regulating cardiac myocyte growth, astrocyte inflammatory signaling, and tumor formation. PLC? is also expressed in endothelial cells, however its role in endothelial regulation is not fully established. We show that endothelial cells of multiple origins, including human pulmonary artery (HPAEC), human umbilical vein (HUVEC), and immortalized brain microvascular (hCMEC/D3) endothelial cells, express PLC?. Knockdown of PLC? in arterial endothelial monolayers decreased the effectiveness of the endothelial barrier. Concomitantly, RhoA activity and stress fiber formation were increased. PLC?-deficient arterial endothelial cells also exhibited decreased Rap1-GTP levels, which could be restored by activation of the Rap1 GEF, Epac, to rescue the increase in monolayer leak. Reintroduction of PLC? rescued monolayer leak with both the CDC25 GEF domain and the lipase domain of PLC? required to fully activate Rap1 and to rescue endothelial barrier function. Finally, we demonstrate that the barrier promoting effects PLC? are dependent on Rap1 signaling through the Rap1 effector, KRIT1, which we have previously shown is vital for maintaining endothelial barrier stability. Thus we have described a novel role for PLC? PIP2 hydrolytic and Rap GEF activities in arterial endothelial cells, where PLC?-dependent activation of Rap1/KRIT1 signaling promotes endothelial barrier stability.

SUBMITTER: DiStefano PV 

PROVIDER: S-EPMC5017709 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature