Mechanism of prostaglandin E2 transport across the plasma membrane of HeLa cells and Xenopus oocytes expressing the prostaglandin transporter 'PGT'

Brenda S. Chan, Joe A. Satriano, Michael Pucci, Victor L. Schuster

Research output: Contribution to journalArticle

115 Scopus citations

Abstract

We recently identified a novel prostaglandin transporter called PGT (Kanai, N., Lu, R., Satriano, J. A., Bao, Y., Wolkoff, A. W., and Schuster, V. L. (1995) Science 268, 866-869). Based on initial functional studies, we have hypothesized that PGT might mediate the release of newly synthesized prostaglandins (PG), epithelial transport of PGs, or metabolic clearance of PGs. Here we examined the mechanism of PGT transport as expressed in HeLa cells and Xenopus oocytes, using isotopic PG influx and efflux studies. In both native HeLa cells and oocytes, cell membranes were poorly permeable to PGs. In contrast, in oocytes injected with PGT mRNA, the PG influx permeability coefficient was 90-157 times that of oocytes injected with water. The rank order substrate profile was PGF(2α) ≃ PGE2 > TXB2 >> 6 keto-PGF(1α). PG influx displayed an overshoot with rapid accumulation of tracer PGE2, followed by a gradual return to baseline. Based on estimated oocyte volumes, the PGT-mediated accumulation of PGE2 reached steady state at intraoocyte concentration 25-fold higher than the external media. The accumulation of PG was not due to intracellular binding or metabolism. PGT- mediated uptake was ATP- and temperature-dependent, but not sodium-dependent, and was inhibited by disulfonic stilbenes, niflumic acid, and the thiol reactive anion MTSES (Na(2-sulfonatoethyl)methanethiosulfonate). [3H]PGE2 efflux from PGT-transfected HeLa cells was stimulated by external (trans) PGE2 in a dose-dependent fashion and was inhibited by bromcresol green and 4,4'-diisothiocyanatostilbene-2,2'-disulfonate. Membrane depolarization inhibited uptake of [3H]PGE2, consistent with a model of net outward movement of negative charge during the translocation event. These findings suggest that PGT mediates [3H]PGE2, accumulation via obligatory, electrogenic anion exchange.

Original languageEnglish (US)
Pages (from-to)6689-6697
Number of pages9
JournalJournal of Biological Chemistry
Volume273
Issue number12
DOIs
StatePublished - Mar 20 1998

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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