Structural Requirements for Functional Interaction of Glutathione Tripeptide Analogs with the Human Multidrug Resistance Protein 1 (MRP1) (original) (raw)

Research ArticleABSORPTION, DISTRIBUTION, METABOLISM, AND EXCRETION

Journal of Pharmacology and Experimental Therapeutics February 2003, 304 (2) 643-653; DOI: https://doi.org/10.1124/jpet.102.044073

Abstract

The human multidrug resistance protein 1 (MRP1) is a primary active transporter of reduced (GSH) and oxidized glutathione, as well as GSH-, glucuronate-, and sulfate-conjugated organic anions. In addition, the transport of certain MRP1 substrates is stimulated by the presence of GSH. To evaluate the structural features of GSH required for interaction with the protein, we investigated the ability of a series of GSH analogs to enhance GSH stimulatable transport of [3H]estrone 3-sulfate (E1SO4). We found that substitution of the γ-Glu residue with Gly, β-Asp, and α-Glu resulted in complete loss of transport stimulation. In contrast, substitution of Gly with Glu or β-Ala resulted in only a partial loss of stimulatory activity. E1SO4transport activity surpassed GSH-stimulated levels in the presence of tripeptides in which Cys was substituted with the hydrophobic amino acids Leu, Phe, and homo-Phe. Moreover, polar substitutions of Cys did not enhance transport to the same extent as nonpolar substitutions of comparable size. γ-Glu-Leu-Gly was 1.6-fold more effective than GSH in stimulating E1SO4 uptake, and kinetic analysis indicated this was due to an increased_V_max. In addition, this tripeptide was shown to be a competitive inhibitor of apigenin-stimulated GSH transport (_K_i value of 14 μM), confirming that it either interacts with the same site on MRP1 as GSH or that the binding of the two tripeptides is mutually exclusive. These data provide insight into the architecture of the GSH binding domain of MRP1.

Footnotes

• This work was supported by Grant MOP-10519 from the Canadian Institutes of Health Research. E.M.L. is the recipient of a Canadian Institutes of Health Research Doctoral Award. R.G.D. is the Stauffer Cancer Research Professor of Queen's University, and S.P.C.C. is a Canada Research Chair in Cancer Biology.

• DOI: 10.1124/jpet.102.044073

• Abbreviations:
  GSH
  glutathione
  GST
  glutathione_S_-transferase
  MRP1
  multidrug resistance protein 1
  E1SO4
  estrone 3-sulfate
  NNAL
  4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol
  Abu
  aminobutyrate
  DTT
  dithiothreitol

• • Received September 4, 2002.
  • Accepted October 16, 2002.

• The American Society for Pharmacology and Experimental Therapeutics

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