Molecular cloning and characterization of a novel human G-protein-coupled receptor, EDG7, for lysophosphatidic acid

Lysophosphatidic acid (LPA), together with sphingosine l-phosphate, is a bi oactive lipid mediator that acts on G-protein-coupled receptors to evoke mu ltiple cellular responses, including Ca2+ mobilization, modulation of adeny lyl cyclase, and mitogen-activated protein (MAP) kinase activation. In this study, we isolated a human cDNA encoding a novel G-protein-coupled recepto r, designated EDG7, and characterized it as a cellular receptor for LPA. Th e amino acid sequence of the EDG7 protein is 53.7 and 48.8% identical to th ose of the human functional LPA receptors EDGE and EDG4, respectively, prev iously identified. LPA (oleoyl) but not other lysophospholipids induced an increase in the [Ca2+](i) of EDG7-overexpressing Sf9 cells. Other LPA recep tors, EDG4 but not EDG2, transduced the Ca2+ response by LPA when expressed in Sf9 cells. LPAs with an unsaturated fatty acid but not with a saturated fatty acid induced an increase in the [Ca2+](i) of EDG7-expressing Sf9 cel ls, whereas LPAs with both saturated and unsaturated fatty acids elicited a Ca2+ response in Sf9 cells expressing EDG4. In EDG7- or EDG4-expressing Sf 9 cells, LPA stimulated forskolin-induced increase in intracellular cAMP le vels, which was not observed in EDG2-expressing cells. In PC12 cells, EDG4 but not EDG2 or EDG7 mediated the activation of MAP kinase by LPA. Neither the EDG7- nor EDG4-transduced Ca2+ response or cAMP accumulation was inhibi ted by pertussis toxin. In conclusion, the present study demonstrates that EDG7, a new member of the EDG family of G-protein-coupled receptors, is a s pecific LPA receptor that shows distinct properties from known cloned LPA r eceptors in ligand specificities, Ca2+ response, modulation of adenylyl cyc lase, and MAP kinase activation.