Identification of functional platelet-activating factor receptors in Raji lymphoblasts.
The binding and metabolism of platelet-activating factor (PAF) were characterized in Raji, a human Burkitt's lymphoma-derived cell line. Raji lymphoblasts readily metabolized PAF by deacetylation-reacylation at 37 degrees C, but not at 4 degrees C. Binding studies conducted at 4 degrees C demonstrated specific binding that reached saturation within 80 min. This binding was only partially reversible. Scatchard analysis of PAF binding data revealed a single class of PAF binding sites (17,800 +/- 3,600/cell) with a K of 2.3 +/- 0.3 nM. These high-affinity PAF binding sites were shown to be functional receptors, as 100 pM to 1 microM PAF increased free intracellular calcium in a dose-dependent manner. The dose of PAF necessary to achieve half maximal calcium mobilization response was 6.3 nM, which was in the range of the K for the receptor calculated from the binding studies. The structurally dissimilar PAF receptor antagonists CV-3988 and BN52021 inhibited the PAF-induced calcium changes at doses that competed with PAF binding. These studies provide the first evidence for a functional PAF receptor expressed on a lymphocyte cell line.
Travers
J B
JB
Department of Pharmacology, Ohio State University College of Medicine, Columbus 43210.
Li
Q
Q
Kniss
D A
DA
Fertel
R H
RH
D001402:B-Lymphocytes / Q000378:metabolism*; D001667:Binding, Competitive; D002051:Burkitt Lymphoma / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D010972:Platelet Activating Factor / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface / Q000032:analysis*; D043562:Receptors, G-Protein-Coupled; D014407:Tumor Cells, Cultured / Q000378:metabolism
D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; C039351:platelet activating factor receptor; D002118:Calcium