Tyrosine Phosphorylation Of S1pr1 Leads To Chaperone Bip-Mediated Import To The Endoplasmic Reticulum

Cell surface G protein-coupled receptors (GPCRs), upon agonist binding, undergo serine-threonine phosphorylation, leading to either receptor recycling or degradation. Here, we show a new fate of GPCRs, exemplified by ER retention of sphingosine-1-phosphate receptor 1 (S1PR1). We show that S1P phosphorylates S1PR1 on tyrosine residue Y-143, which is associated with recruitment of activated BiP from the ER into the cytosol. BiP then interacts with endocytosed Y-143-S1PR1 and delivers it into the ER. In contrast to WT-S1PR1, which is recycled and stabilizes the endothelial barrier, phosphomimicking S1PR1 ((YD)-D-143-S1PR1) is retained by BiP in the ER and increases cytosolic Ca2+ and disrupts barrier function. Intriguingly, a proinflammatory, but non-GPCR agonist, TNF-alpha, also triggered barrier-disruptive signaling by promoting S1PR1 phosphorylation on Y-143 and its import into ER via BiP. BiP depletion restored (YD)-D-143-S1PR1 expression on the endothelial cell surface and rescued canonical receptor functions. Findings identify Y-143-phosphorylated S1PR1 as a potential target for prevention of endothelial barrier breakdown under inflammatory conditions.G protein-coupled receptors (GPCRs), upon serine-threonine phosphorylation, undergo recycling or degradation. Anwar et al. demonstrate a new fate of GPCRs, exemplified by tyrosine phosphorylated sphingosine-1-phosphate receptor 1 (Y(143)S1PR1), which through its interaction with BiP, is routed to the endoplasmic reticulum where it dysregulates S1P-induced Ca2+ signaling and barrier function.