Figure 7. OTC is an agonist for GPR109A. A: Bioluminescence resonance energy transfer (BRET) analysis of L-2-oxothiazolidine-4-carboxylic acid (OTC)-induced GPR109A activation in the presence or absence of pertussis toxin (PTX, 0.5 μg/ml). NA served as a positive control. B: Radiolabeled competition binding assay was used to evaluate the binding of [³H]nicotinate to MDA-MB-231 cells overexpressing human GPR109A in the presence or absence of increasing concentrations of unlabeled OTC or NA (positive control). C: Analysis of the effects of OTC or nicotinic acid (NA; positive control) on forskolin (FSK)-induced elevations in cAMP. *p<0.01 compared to control cells; #p<0.01 compared to FSK-treated cells.