Abstract
Sphingosine-1-phosphate receptor 1 (S1P1) is a G protein-coupled receptor that is activated by the sphingolipid ligand sphingosine-1-phosphate (S1P). S1P1 is widely expressed across tissues and, when activated, has broad functions in the immune, vascular and nervous systems. In several diseases in which inflammation plays a critical role, S1P1 activation has been found to be involved in pathogenesis. However, the details of S1P1 activation in vivo under different physiologic conditions are not well understood. Here we describe how a new in vivo methodology to identify S1P1 activation has helped increase understanding of the manner in which this signaling molecule functions both in homeostasis and during inflammation.