Vol. 59, Issue 6, 1506-1513, June 2001

Prostaglandin F₂ Receptor-Dependent Regulation of Prostaglandin Transport

Roberta Vezza, Joshua Rokach, and Garret A. FitzGerald

Center for Experimental Therapeutics, University of Pennsylvania, Philadelphia, Pennsylvania (R.V., G.A.F.); and The Claude Pepper Institute and Department of Chemistry, Florida Institute of Technology, Melbourne, Florida (J.R.)

Prostaglandin (PG) F₂ may act on its G protein-coupled receptor (FP) or be imported intracellularly via a transporter, which has high affinity for PGF₂ and PGE₂, but not prostacyclin (PGI₂). In cells overexpressing the epitope-tagged FP together with the human prostaglandin transporter (hPGT), stimulation of the FP with PGF₂ (1 nM-1 µM), or the less potent FP agonist, the isoprostane 8,12-iso-iPF₂-III, inhibited prostaglandin uptake via the hPGT. This effect was abolished by pretreatment of the cells with cholera toxin, but not with pertussis toxin. Furthermore, two dominant negative constructs directed against G_s partially blocked FP-mediated regulation of hPGT function, also suggesting G_s involvement in this phenomenon. Surprisingly, neither an activator (dibutyryl cyclic AMP) nor an inhibitor (H89) of cyclic AMP-dependent protein kinase had any effect on FP-mediated inhibition of hPGT activity. Furthermore, although PGF₂ increases intracellular cyclic AMP via G_s activation, it does not induce phosphorylation of the transporter, excluding a role of cyclic AMP-dependent protein kinase in hPGT regulation. Activation of the PGI₂ receptor, which is also coupled to G_s, does not regulate hPGT activity, despite markedly augmenting adenylate cyclase activation. In conclusion, activation of the FP reduces intracellular import of prostaglandins for metabolic inactivation, increasing prostanoid availability for membrane receptor activation. This effect seems to be mediated via G_s, independent of adenylate cyclase and cyclic AMP-dependent protein kinase activation.