CHARACTERIZATION OF A SCINTILLATION PROXIMITY ASSAY TO DETECT MODULATORS OF TRANSFORMING GROWTH FACTOR-ALPHA (TGF-ALPHA) BINDING

A scintillation proximity assay (SPA) for transforming growth factor α (TGFα) using SPA beads coated with A431 membranes has been studied. Binding of TGFα to the beads was characteristic of a receptor interaction. A class of high-affinity receptors for [125I]-TGFα (Kd = 0.10-0.26 nm) was detected by competition studies between [125I]TGFα and cold TGFα and by analysis of association and dissociation rate constants. An antibody to the epidermal growth factor receptor (clone 528) inhibited binding of [125I]TGFα (IC50 = 0.20 μg/ml), but an anti-TGFα antibody (clone 134A-2B3) (〈25 μg/ml) did not block binding. Suramin inhibited [125I]-TGFα binding (IC50 = 0.20 mm). The ether lipids 1-O-hexadecyl-2-O-methyl-sn-glycero-3-phosphocholine, 1-O-octadecyl-2-O-methyl-sn-glycero-3-phosphocholine, and rac-lyso-platelet activating factor inhibited TGFα binding (IC50 values of 49, 69, and 57 μm, respectively). SPA is a convenient method for identifying agents that may act by interfering with TGFα binding. © 1992.