Disruption of cAMP and Prostaglandin E₂Transport by Multidrug Resistance Protein 4 Deficiency Alters cAMP-Mediated Signaling and Nociceptive Response

Abstract

Multidrug resistance protein 4 (MRP4; ABCC4) is a member of the MRP/ATP-binding cassette family serving as a transmembrane transporter involved in energy-dependent efflux of anticancer/antiviral nucleotide agents and of physiological substrates, including cyclic nucleotides and prostaglandins (PGs). Phenotypic consequences of mrp4 deficiency were investigated using mrp4-knockout mice and derived immortalized mouse embryonic fibroblast (MEF) cells. Mrp4 deficiency caused decreased extracellular and increased intracellular levels of cAMP in MEF cells under normal and forskolin-stimulated conditions. Mrp4 deficiency and RNA interference-mediated mrp4 knockdown led to a pronounced reduction in extracellular PGE 2 but with no accumulation of intracellular PGE 2 in MEF cells. This result was consistent with attenuated cAMP-dependent protein kinase activity and reduced cyclooxygenase-2 (Cox-2) expression in mrp4-deficient MEF cells, suggesting that PG synthesis is restrained along with a lack of PG transport caused by mrp4 deficiency. Mice lacking mrp4 exhibited no outward phenotypes but had a decrease in plasma PGE metabolites and an increase in inflammatory pain threshold compared with wild-type mice. Collectively, these findings imply that mrp4 mediates the efflux of PGE 2 and concomitantly modulates cAMP mediated signaling for balanced PG synthesis in MEF cells. Abrogation of mrp4 affects the regulation of peripheral PG levels and consequently alters inflammatory nociceptive responses in vivo.MRP4 (ABCC4) is a member of the multidrug resistance proteins (MRPs) belonging to the C group of the ATP-binding cassette (ABC) protein superfamily. To date, nine total MRP members, MRP1

Xenobiotic, Bile Acid, and Cholesterol Transporters: Function and Regulation

“…In addition, Mrp4/MRP4 transports endogenous molecules such as leukotrienes, prostaglandins, folate, bile acids, urate, and cyclic nucleotides Lai and Tan, 2002;Reid et al, 2003b;Zelcer et al, 2003a;Jedlitschky et al, 2004;Van Aubel et al, 2005;Rius et al, 2006Rius et al, , 2008Bataille et al, 2008;Lin et al, 2008). Mrp5/MRP5 transports endogenous (cAMP, cGMP, folate, hyaluronan) and exogenous chemicals [methotrexate, 6-mercaptopurine, 6-thioguanine, 9-(2-phosphonylmethoxyethyl)adenine, 5-fluorouracil] (McAleer et al, 1999;Jedlitschky et al, 2000;Wijnholds et al, 2000b;Wielinga et al, 2002Wielinga et al, , 2003Wielinga et al, , 2005Pratt et al, 2005;Schulz et al, 2007).…”

Mammalian Cyclic Nucleotide Phosphodiesterases: Molecular Mechanisms and Physiological Functions

“…However, the cN-binding properties of GAFs (named for cGMP-binding PDEs, Anabaena adenylyl cyclase, and Escherichia coli FhlA) in some PDEs can sequester cN (129,198). Although cNs are extruded from some cells by certain multianion transporters, the impact of this process on lowering cN levels is suggested to be small (21,64,211). Other processes may lower cN levels in particular cells.…”

Cysteinyl Leukotriene Receptor 1/2 Antagonists Nonselectively Modulate Organic Anion Transport by Multidrug Resistance Proteins (MRP1-4)

“…The seven LTMs were also tested for their ability to modulate uptake of [ 3 H]PGE 2 by MRP4, a physiologic substrate of this short MRP that is not transported by MRP1, 2, or 3 Lin et al, 2008). Thus PGE 2 uptake into MRP4-enriched membrane vesicles was measured in the presence of the LTMs at six concentrations (range 0.1-100 mM) and IC 50 s determined as before.…”

“…Thus MRP4 is involved in the tissue distribution and elimination of antimetabolites used to treat viral and neoplastic diseases (Schuetz et al, 1999;Slot et al, 2011;Park et al, 2014). It is also distinct in its ability to efflux prostanoids [e.g., prostaglandin E 2 (PGE 2 )] and cyclic nucleotides Lin et al, 2008;Jin et al, 2014). However, like MRP1-3, MRP4 can transport E 2 17bG.…”