title: Peptide-bond modified glutathione conjugate analogs modulate GSTpi function in GSH-conjugation, drug sensitivity and JNK signaling.
abstract: Glutathione S-transferase pi (GST, E.C.2.5.1.18) overexpression contributes to resistance of cancer cells towards cytostatic drugs. Furthermore, GSTpi is involved in the cellular stress response through inhibition of Jun N-terminal-kinase (JNK), a process that can be modulated by GST inhibitors. GSH conjugates are potent GST inhibitors, but are sensitive towards gamma-glutamyltranspeptidase (gammaGT)-mediated breakdown. In search for new peptidase stable GST inhibitors we employed the following strategy: (1) selection of a suitable (GST inhibiting) peptide-bond isostere from a series of previously synthesized gammaGT stabilized GSH-analogs. (2) The use of this peptidomimetic strategy to prepare a GSTpi selective inhibitor. Two gammaGT stable GSH conjugate analogs inhibited human GSTs, although non-selectively. One of these, a urethane-type peptide-bond is well accepted by GSTs and we selected this modification for the development of a gammaGT stable, GSTpi selective inhibitor, UrPhg-Et(2). This compound displayed selectivity for GSTpi compared to alpha and mu class enzymes. Furthermore, the inhibitor reversed GSTpi-mediated drug resistance (MDR) in breast tumor cells. In addition, short-term exposure of cells to UrPhg-Et(2) led to GSTpi oligomerization and JNK activation, suggesting that it activates the JNK-cJun signaling module through GSTpi dissociation. Altogether, we show the successful use of peptidomimetic glutathione conjugate analogs as GST inhibitors and MDR-modifiers. As many MDR related enzymes, such as MRP1, glyoxalase 1 and DNA-pk are also inhibited by GSH conjugates, these peptidomimetic compounds can be used as scaffolds for the development of multi-target MDR drugs.
authors.affiliation: Division of Toxicology, Leiden/Amsterdam Center for Drug Research, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
authors.forename: Danny
authors.initials: D
authors.lastname: Burg
authors.forename: Joey
authors.initials: J
authors.lastname: Riepsaame
authors.forename: Chantal
authors.initials: C
authors.lastname: Pont
authors.forename: Gerard
authors.initials: G
authors.lastname: Mulder
authors.forename: Bob
authors.initials: B
authors.lastname: van de Water
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004976:Ethacrynic Acid / Q000494:pharmacology; D005978:Glutathione / Q000031:analogs & derivatives* / Q000494:pharmacology*; D051549:Glutathione S-Transferase pi / Q000037:antagonists & inhibitors*; D006801:Humans; D020128:Inhibitory Concentration 50; D007527:Isoenzymes; D048670:MAP Kinase Kinase 4 / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D010455:Peptides; D011994:Recombinant Proteins; D051549:Glutathione S-Transferase pi; D048670:MAP Kinase Kinase 4; D005978:Glutathione; D004976:Ethacrynic Acid