Molecular cloning and characterization of a lysophosphatidic acid receptor, Edg-7, expressed in prostate.
Two G protein-coupled receptors (Edg-2) and (Edg-4) for the lysolipid phosphoric acid mediator lysophosphatidic acid have been described by molecular cloning. However, the calcium-mobilizing receptor Edg-4 is not expressed in some cell lines that exhibit robust calcium responses to this ligand, thus predicting the existence of additional receptor subtypes. We report here on the characterization of a third human lysophosphatidic acid receptor subtype, Edg-7, which mediates lysophosphatidic acid-evoked calcium mobilization. In a rat hepatoma Rh7777 cell line that lacks endogenous responses to lysophosphatidic acid, this lipid mediator, but not others, evokes calcium transients when the cells have been transfected with Edg-7 or Edg-4 DNAs. Furthermore, frog oocytes exhibit a calcium-mediated chloride conductance in response to mammalian-selective lysophosphatidic acid mimetics after injection of Edg-7 mRNA. Edg-7-expressing Rh7777 cells do not show inhibition of forskolin-driven rises in cAMP in response to lysophosphatidic acid. However, membranes from HEK293T cells cotransfected with Edg-7 and G(i2)alpha protein DNAs show lysophosphatidic acid dose-dependent increases in [gamma-(35)S]GTP binding with an EC(50) value of 195 nM. When we used this assay to compare various synthetic LPA analogs at Edg-2, Edg-4, and Edg-7 receptors, we found that ethanolamine-based compounds, which are full LPA mimetics at Edg-2 and Edg-4, exhibit little activity at the Edg-7 receptor. Edg-7 RNA was detected in extracts of several rat and human tissues including prostate. Together, our data indicate that Edg-7 is a third lysophosphatidic acid receptor that couples predominantly to G(q/11)alpha proteins.
Im
D S
DS
Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, Virginia, USA.
Heise
C E
CE
Harding
M A
MA
George
S R
SR
O'Dowd
B F
BF
Theodorescu
D
D
Lynch
K R
KR
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004247:DNA; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D011467:Prostate / Q000378:metabolism*; D051381:Rats; D011956:Receptors, Cell Surface / Q000096:biosynthesis / Q000235:genetics*; D043562:Receptors, G-Protein-Coupled; D049368:Receptors, Lysophosphatidic Acid; D017386:Sequence Homology, Amino Acid
D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D049368:Receptors, Lysophosphatidic Acid; D004247:DNA