Expression and activity of multidrug resistance protein 1 in a murine thymoma cell line

Abstract

SummaryMultidrug resistance proteins [MRPs and P-glycoprotein (Pgp)] are members of the family of ATP-binding cassette (ABC) transport proteins, originally described as being involved in the resistance against anti-cancer agents in tumour cells. These proteins act as ATP-dependent efflux pumps and have now been described in normal cells where they exert physiological roles. The aim of this work was to investigate the expression and activity of MRP and Pgp in the thymoma cell line, EL4. It was observed that EL4 cells expressed mRNA for MRP1, but not for MRP2, MRP3 or Pgp. The activity of ABC transport proteins was evaluated by using the efflux of the fluorescent probes carboxy-2 0 -7 0 -dichlorofluorescein diacetate (CFDA) and rhodamine 123 (Rho 123). EL4 cells did not retain CFDA intracellularly, and MRP inhibitors (probenecid, indomethacin and MK 571) decreased MRP1 activity in a concentration-dependent manner. As expected, EL4 cells accumulated Rho 123, and the presence of cyclosporin A and verapamil did not modify this accumulation. Most importantly, when EL4 cells were incubated in the presence of the MRP1 inhibitors indomethacin and MK 571 for 6 days, they started to express CD4 and CD8 molecules on their surface, producing double-positive cells and CD8 single-positive cells. Our results suggest that MRP activity is important for the maintenance of the undifferentiated state in this cell type. This finding might have implications in the physiological process of normal thymocyte maturation.

SLCO/OATP-like Transport of Glutathione in FasL-induced Apoptosis

“…The CF release assay is widely used to study the activity of ABCC/MRP proteins (32). Multidrug resistance protein-mediated transport of organic substrates, like CF, has been reported to be coupled to the extrusion of GSH, and both are inhibited by a wide variety of drug reversal agents (15,(27)(28)(29)(32)(33)(34). We observed that preloaded Jurkat cells actively extrude CF (Fig.…”

“…Glutathione transport mediated by ABCC/MRP has been shown to be involved in the detoxification of the intracellular environment of the cell, and it is coupled to the extrusion of a wide variety of structurally unrelated organic molecules. Drug reversal agents of ABCC/MRP transport inhibit ABCC/MRP transport of organic molecules as well as GSH extrusion (15,(27)(28)(29)(32)(33)(34). We report that Jurkat cells functionally express ABCC/MRP proteins from which we detect mRNA for several members, particularly ABCC1/MRP-1, ABCC2/MRP-2, ABCC4/MRP-4, and ABCC5/MRP-5.…”

ATP-binding-cassette transporters in hematopoietic stem cells and their utility as therapeutical targets in acute and chronic myeloid leukemia

“…37 Similarly, ABCC1 was implicated in the differentiation of a thymoma cell line into CD4 þ CD8 þ cells. 38 Although these studies failed to identify the involved substrates and ABCC1 was not targeted by more specific molecular means, in both these reports it is hypothesized that ABCC1 is important to keep cells in an undifferentiated state, reiterating the possibility that ABC transporters may play a role in the differentiation of mature bone marrow cell types. Whether ABCC1 has such a role in HSC remains to be determined.…”

Multidrug Resistance Protein Transporter and Ins(1,4,5)P3-Sensitive Ca2+-Signaling Involved in Adenosine Triphosphate Export via Gq Protein–Coupled NK2-Receptor Stimulation With Neurokinin A

“…We have shown here that the neurokinin A-inducible ATP export was suppressed by the MRP-transporter inhibitors benzbromarone (23,24), indomethacin (25,26), and MK-571 (24,27) , but not by CFTR-inh 172, a CFTRCl − channel inhibitor, and α-GA, a gap junction hemichannel blocker. At present, there is no report regarding the blockade of Ca 2+ -signaling and Ca 2+ channels via these MRP-transporter inhibitors.…”