Cloning of mouse prostaglandin transporter PGT cDNA: species-specific substrate affinities

Abstract

We recently identified and/or cloned the PG transporter PGT in the rat (rPGT) (Kanai, N., R. Lu, J. A. Satriano, Y. Bao, A. W. Wolkoff, and V. L. Schuster, Science 268: 866–869, 1995) and the human (hPGT) (Lu, R., and V. L. Schuster, J. Clin. Invest. 98: 1142–1149, 1996). Here we have cloned and expressed the mouse PGT (mPGT) cDNA. The tissue distribution of mPGT mRNA expression is significantly more restricted than that of rPGT and hPGT mRNA. Although the deduced amino acid sequence of mPGT is similar to the rat (91% identity) and human (82% identity) homologues, it has three regions of dissimilarity: amino acids 128–163 and 283–298, and valine 610 and isoleucine 611 (predicted to lie within putative transmembrane span 12). Affinities of hPGT, rPGT, and mPGT for several PG substrates differed, with hPGT having the highest [low Michaelis constant ( K m)] and mPGT the lowest affinity. A chimeric protein, linking the N-terminal domain of mPGT with the C-terminal domain of hPGT, had affinity for PGE2 indistinguishable from that of hPGT, indicating that the C-terminal domain dictates K m. We mutagenized mouse valine 610 and isoleucine 611 to their corresponding human residues (methionine and glycine, respectively); however, these changes did not convert the inhibition constant of mPGT to that of hPGT. The mouse gene was localized to chromosome 9 in a region syntenic with the region of human chromosome 3 containing the hPGT gene. These studies highlight the species-dependence of tissue expression and function of PGT and lay the groundwork for the use of the mouse as a model system for the study of PGT function.

Involvement of Multidrug Resistance-Associated Protein 4 in Efflux Transport of Prostaglandin E2 across Mouse Blood-Brain Barrier and Its Inhibition by Intravenous Administration of Cephalosporins

“…PGE 2 is a substrate of MRP4, Oat3, and Pgt, which were reported to be expressed at the BBB (Pucci et al, 1999;Reid et al, 2003;Nilwarangkoon et al, 2007). We recently found that the protein expression level of MRP4 in mouse brain capillaries is 10.3 to 12.5% of that of P-glycoprotein, 33.1 to 39.6% of that of breast cancer resistance protein, and similar to that of Oat3 protein (Kamiie et al, 2008).…”

Prostaglandins in non-insectan invertebrates: recent insights and unsolved problems

“…They can also be carried across membranes by a PG transporter (PGT; Kanai et al, 1995;Pucci et al, 1999). The finding that PGT is expressed in cell types that synthesize and release PGs may suggest that the transporter is involved in the re-uptake of PGs, either as a way of negating their leakage and/or facilitating the transport of such molecules to target nuclear receptors (Bao et al, 2002).…”

The Two-Step Model of Prostaglandin Signal Termination: In Vitro Reconstitution with the Prostaglandin Transporter and Prostaglandin 15 Dehydrogenase

“…PGT is broadly expressed in many cell types (Kanai et al, 1995;Lu et al, 1996;Pucci et al, 1999a). The strong expression of PGT in the lung suggests that PGT may play a role in the single-pass metabolic clearance of PGs through that vascular bed.…”