Differential activation mechanisms of lipid GPCRs by lysophosphatidic acid and sphingosine 1-phosphate

Abstract

Lysophospholipids are bioactive lipids and can signal through G-protein-coupled receptors (GPCRs). The best studied lysophospholipids are lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P). The mechanisms of lysophospholipid recognition by an active GPCR, and the activations of lysophospholipid GPCR–G-protein complexes remain unclear. Here we report single-particle cryo-EM structures of human S1P receptor 1 (S1P₁) and heterotrimeric G_i complexes formed with bound S1P or the multiple sclerosis (MS) treatment drug Siponimod, as well as human LPA receptor 1 (LPA₁) and G_i complexes in the presence of LPA. Our structural and functional data provide insights into how LPA and S1P adopt different conformations to interact with their cognate GPCRs, the selectivity of the homologous lipid GPCRs for S1P versus LPA, and the different activation mechanisms of these GPCRs by LPA and S1P. Our studies also reveal specific optimization strategies to improve the MS-treating S1P₁-targeting drugs.

Liu et al. report structures of human sphingosine 1-phosphate (S1P) receptor 1 (S1P₁) in complex with Gi and S1P or the multiple sclerosis (MS) drug Siponimod, as well as human lysophosphatidic acid (LPA) receptor 1 (LPA₁) in complex with Gi and LPA, revealing distinct conformations of the lysophospholipids interacting with their cognate GPCRs.