Abstract 11115: Platelet Endothelial Aggregation Receptor-1 is a Critical Determinant of Endothelial Cell Function
BACKGROUND: Platelet Endothelial Aggregation Receptor-1 (PEAR1), a type I transmembrane receptor, is expressed on platelets and endothelial cells (ECs) but its contribution to EC behavior is unknown.
METHODS AND RESULTS: We studied the expression of PEAR1 in cultured human endothelial progenitors (blood outgrowth endothelial cells or BOECs), ECs from human umbilical cord and ECs freshly isolated from multiple vascular beds and evaluated the role of PEAR1 in proliferation and migration of the endothelial hybrid cell line EA.hy926. PEAR1 mRNA expression in different ECs was heterogeneous with the lowest expression in BOECs and the highest expression in macrovascular ECs and microvascular ECs from brain, heart and liver tissue. ECs from umbilical cord had intermediate expression levels. Lowering PEAR1 expression by lentiviral transduction with a short-hairpin anti-PEAR1 construct (shPEAR1) doubled the EA.hy926 EC proliferation rate. This was associated with significantly increased baseline Akt-P levels in shPEAR1 cells compared to control ECs. The expression of the proliferation suppressor p21/CIP1 was reduced by 60±2% (mean±SEM, RT-PCR) whereas the CDC2-protein band intensity was significantly elevated (western blot), consistent with enhanced mitosis. In addition, PEAR1 knockdown in EA.hy926 cells resulted in a 30±5% faster migration in in vitro wound healing assays. Anti-PEAR1 antibodies behaved as a pseudo-ligand in EA.hy926 ECs and triggered PI3-kinase activation, resulting in PEAR1- and Akt-phosphorylation. In turn, this resulted in PEAR1-mediated phosphorylation of eNOS (activating site P1177 on western blot) through the Akt-pathway (Figure).
CONCLUSIONS: Our study provides the first evidence that PEAR1 is expressed in ECs from multiple vascular beds and that PEAR1 plays a role in proliferation, migration and eNOS activation through regulation of the PI3K/Akt pathway in ECs. The physiological ligand remains to be elucidated.
- © 2012 by American Heart Association, Inc.