ADAM17 cleaves sphingosine 1 phosphate receptor 1 and regulates downstream signaling in endothelial cells (851.1)

Abstract

Sphingosine‐1‐ phosphate receptor 1 (S1PR1) is a high affinity seven‐membrane G protein coupled receptor for bioactive lipid sphingosine‐1‐ phosphate (S1P). S1PR1 plays a critical role in regulating several endothelial cell functions such as proliferation, migration and importantly enhances endothelial barrier function. However, mechanism regulating S1PR1 cell surface retention remains unclear. Members of the ADAM (a disntintegrin and metalloproteases) family of proteases are known for cleaving the ectodomain of a variety of cell surface receptors thereby regulating their activities. In our present study, we addressed the possibility that ADAM family of proteases target S1PR1 and thereby downregulate it’s signaling in endothelial cells. We found that treatment of human pulmonary arterial endothelial (HPAE) cells with phorbol‐12‐myristate 13‐acetate (PMA), an activator of ADAM proteases, induces cleavage of S1PR1 within 2 hrs, while treatment with a broad range MMP inhibitor (TAPI‐0), stabilized S1PR1 expression. Additionally, PMA‐cleaved S1PR1 failed to localize on the cell surface rendering it refractive to exogenous S1P ligation and in enhancing the endothelial barrier. Also, Transendothelial resistance after ADAM17 deletion clearly shows enhanced barrier function. Over expression or depletion of ADAM17, but not ADAM10, in HPAE cells altered S1PR1 cell surface expression and endothelial barrier function by S1P identifying a novel role of ADAM17 as the protease responsible for targeting S1PR1.