Fluid Shear Stress Differentially Regulates gpr3, gpr6, and gpr12 Expression in Human Umbilical Vein Endothelial Cells

Fluid shear stress is a major factor involved in the control of gene expression in vascular endothelial cells. Sphingosine 1-phosphate has emerged as a multifaceted regulator of endothelial cell function and its high affinity S1P1 receptor is one among the many shear stress regulated genes. We recently identified the orphan G protein coupled receptors gpr3, gpr6 and gpr12 as additional S1P receptors. Here, we investigated their expression in various human endothelial and vascular smooth muscle cell lines via RT-PCR and western blot analysis. We next sought to determine the role of fluid shear stress in the regulation of expression of gpr3, gpr6 and gpr12 by using human umbilical vein endothelial cells (HUVECs). Laminar shear stress (12dyne/cm2) did not significantly increase gpr3, gpr6 and gpr12 mRNA after 1, 2, 4, 6, and 8 hrs of application of elevated pressure as determined by quantitative Taqman RT-PCR analysis. In contrast, gpr3 and gpr12 protein were increased after 12 hrs of shear stress by 95% and 40%, respectively. gpr6 mRNA and protein were absent in HUVECs as determined by Taqman and western blot techniques. Our results suggest that shear stress regulates gpr3 and gpr12 but not gpr6 expression and that regulation does not occur transcriptionally but posttranslationally. gpr3 and gpr12 may therefore add to the repertoire of S1P receptors, translating extracellular S1P effects into intracellular signals in human endothelial cells.