Glutathione S-transferases (GSTs) inhibit transcriptional activation by the peroxisomal proliferator-activated receptor gamma (PPAR gamma) ligand, 15-deoxy-delta 12,14prostaglandin J2 (15-d-PGJ2).

Abstract

15-Deoxy-Delta(12,14)prostaglandin J(2) (15-d-PGJ(2)), a terminal metabolite of the J-series cyclopentenone prostaglandins, influences a variety of cellular processes including gene expression, differentiation, growth, and apoptosis. As a ligand of peroxisomal proliferator-activated receptor gamma (PPAR gamma), 15-d-PGJ(2) can transactivate PPAR gamma-responsive promoters. Previously, we showed that multidrug resistance proteins MRP1 and MRP3 attenuate cytotoxic and transactivating activities of 15-d-PGJ(2) in MCF7 breast cancer cells. Attenuation was glutathione-dependent and was associated with formation of the glutathione conjugate of 15-d-PGJ(2), 15-d-PGJ(2)-SG, and its active efflux by MRP. Here we have investigated whether the glutathione S-transferases (GST) can influence biological activities of 15-d-PGJ(2). MCF7 cells were stably transduced with human cytosolic GST isozymes M1a, A1, or P1a. These GSTs had no effect on 15-d-PGJ(2) cytotoxicity when expressed either alone or in combination with MRP1. However, expression of any of the three GSTs significantly inhibited 15-d-PGJ(2)-dependent transactivation of a PPAR gamma-responsive reporter gene. The degree of inhibition correlated with the level of GST expressed. Under physiologic conditions, the nonenzymatic rate of 15-d-PGJ(2) conjugation with glutathione was significant. Of the three GST isozymes, only GSTM1a-1a further stimulated the rate of 15-d-PGJ(2)-SG formation. Moreover, GSTM1a-1a rate enhancement was only a transient burst that was complete within 15 s. Hence, catalysis plays little, if any, role in GST inhibition of 15-d-PGJ(2)-dependent transactivation. In contrast, inhibition of transactivation was associated with strong GST/15-d-PGJ(2) interactions. Potent inhibition by 15-d-PGJ(2) and 15-d-PGJ(2)-SG of GST activity was observed with K(i) in the 0.15-2.0 microM range for the three GST isozymes, results suggesting avid associations between GST and 15-d-PGJ(2) or 15-d-PGJ(2)-SG. Electrospray ionization mass spectrometry (ESI/MS) studies revealed no stable adducts of GST and 15-d-PGJ(2) indicating that GST/15-d-PGJ(2) interactions are primarily noncovalent. These results are consistent with a mechanism of GST-mediated inhibition of transactivation in which GST binds 15-d-PGJ(2) and 15-d-PGJ(2)-SG thereby sequestering the ligands in the cytosol away from their nuclear target, PPAR gamma.

• Authors: Christian M Paumi, Pamela K Smitherman, Alan J Townsend, Charles S Morrow
• Journal: Biochemistry (Biochemistry) Vol. 43 Issue 8 Pg. 2345-52 (Mar 02 2004) ISSN: 0006-2960 [Print] United States
• PMID: 14979731 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• 15-deoxy-delta(12,14)-prostaglandin J2
• Growth Inhibitors
• Isoenzymes
• Receptors, Cytoplasmic and Nuclear
• Trans-Activators
• Transcription Factors
• Glutathione Transferase
• Glutathione
• Prostaglandin D2

Topics

• Catalysis
• Cell Death (drug effects)
• Cell Line, Tumor
• Genetic Vectors
• Glutathione (chemistry, metabolism)
• Glutathione Transferase (chemistry, genetics, metabolism)
• Growth Inhibitors (antagonists & inhibitors, chemistry, metabolism, toxicity)
• Humans
• Isoenzymes (chemistry, genetics, metabolism)
• Prostaglandin D2 (analogs & derivatives, antagonists & inhibitors, chemistry, metabolism, toxicity)
• Receptors, Cytoplasmic and Nuclear (antagonists & inhibitors, chemistry, metabolism)
• Trans-Activators (antagonists & inhibitors, chemistry, metabolism, toxicity)
• Transcription Factors (antagonists & inhibitors, chemistry, metabolism)
• Transcriptional Activation
• Transduction, Genetic