Assessment of sphingosine-1-phosphate activity in biological samples by receptor internalization and adherens junction formation.

Sphingosine-1-phosphate (S1P) is a bioactive lipid mediator involved in many biological actions, including vascular homeostasis and immune cell trafficking. S1P activity is mediated by specific G protein-coupled receptors, leading to multiple physiological responses including adherens junction formation in endothelial cells. Here, we describe bioassays for rapidly assessing S1P activity in biological fluids based on ligand-induced receptor internalization in transfected HEK293 cells and consequent adherens junction formation of vascular endothelial cells.