Unique ligand selectivity of the GPR92/LPA5 lysophosphatidate receptor indicates role in human platelet activation.
Lysophosphatidic acid (LPA) is a ligand for LPA(1-3) of the endothelial differentiation gene family G-protein-coupled receptors, and LPA(4-8) is related to the purinergic family G-protein-coupled receptor. Because the structure-activity relationship (SAR) of GPR92/LPA(5) is limited and whether LPA is its preferred endogenous ligand has been questioned in the literature, in this study we applied a combination of computational and experimental site-directed mutagenesis of LPA(5) residues predicted to interact with the headgroup of LPA. Four residues involved in ligand recognition in LPA(5) were identified as follows: R2.60N mutant abolished receptor activation, whereas H4.64E, R6.62A, and R7.32A greatly reduced receptor activation. We also investigated the SAR of LPA(5) using LPA analogs and other non-lysophospholipid ligands. SAR revealed that the rank order of agonists is alkyl glycerol phosphate > LPA > farnesyl phosphates >> N-arachidonoylglycine. These results confirm LPA(5) to be a bona fide lysophospholipid receptor. We also evaluated several compounds with previously established selectivity for the endothelial differentiation gene receptors and found several that are LPA(5) agonists. A pharmacophore model of LPA(5) binding requirements was developed for in silico screening, which identified two non-lipid LPA(5) antagonists. Because LPA(5) transcripts are abundant in human platelets, we tested its antagonists on platelet activation and found that these non-lipid LPA(5) antagonists inhibit platelet activation. The present results suggest that selective inhibition of LPA(5) may provide a basis for future anti-thrombotic therapies.
From the Department of Chemistry and Computational Research on Materials Institute, University of Memphis, Memphis, Tennessee 38152.
Jesica R
JR
Williams
Institute for Prevention of Cardiovascular Diseases, Medical Faculty, University of Munich, 80336 Munich, Germany.
Anna L
AL
Khandoga
Institute for Prevention of Cardiovascular Diseases, Medical Faculty, University of Munich, 80336 Munich, Germany.
Pankaj
P
Goyal
From the Department of Chemistry and Computational Research on Materials Institute, University of Memphis, Memphis, Tennessee 38152.
James I
JI
Fells
From the Department of Chemistry and Computational Research on Materials Institute, University of Memphis, Memphis, Tennessee 38152.
Donna H
DH
Perygin
Institute for Prevention of Cardiovascular Diseases, Medical Faculty, University of Munich, 80336 Munich, Germany.
Wolfgang
W
Siess
From the Department of Chemistry and Computational Research on Materials Institute, University of Memphis, Memphis, Tennessee 38152.
Abby L
AL
Parrill
Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163.
Gabor
G
Tigyi
Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163. Electronic address: yuko@physio1.utmem.edu.
Yuko
Y
Fujiwara
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001665:Binding Sites / Q000235:genetics; D020013:Calcium Signaling; D006801:Humans; D066298:In Vitro Techniques; D008024:Ligands; D008246:Lysophospholipids / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015539:Platelet Activation / Q000187:drug effects / Q000502:physiology*; D049368:Receptors, Lysophosphatidic Acid / Q000819:agonists / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship
C512992:LPAR5 protein, human; D008024:Ligands; D008246:Lysophospholipids; D049368:Receptors, Lysophosphatidic Acid; D011994:Recombinant Proteins