Interaction of Omega, Sigma, and Theta glutathione transferases with p38b mitogen-activated protein kinase from the fruit fly, Drosophila melanogaster.

J Wongtrakul,K Janphen,C Saisawang,A.J Ketterman,David Schooley

doi:10.1093/jis/14.1.60

Abstract

Glutathione S-transferases (GSTs) are a diverse family of phase II detoxification enzymes found in almost all organisms. Besides playing a major role in the detoxification of xenobiotic and toxic compounds, GSTs are also involved in the regulation of mitogen activated protein (MAP) kinase signal transduction by interaction with proteins in the pathway. An in vitro study was performed for Theta, Omega, Sigma GSTs and their interaction with MAP kinase p38b protein from the fruit fly Drosophila melanogaster Meigen (Diptera: Drosophilidae). The study included the effects of all five Omega class GSTs (DmGSTO1, DmGSTO2a, DmGSTO2b, DmGSTO3, DmGSTO4), all five Theta class GSTs (DmGSTT1, DmGSTT2, DmGSTT3a, DmGSTT3b, DmGSTT4), and one Sigma class glutathione transferase on the activity of Drosophila p38b, including the reciprocal effect of this kinase protein on glutathione transferase activity. It was found that DmGSTT2, DmGSTT3b, DmGSTO1, and DmGSTO3 activated p38b significantly. Substrate specificities of GSTs were also altered after co-incubation with p38b. Although p38b activated DmGSTO1, DmGSTO2a, and DmGSTT2, it inhibited DmGSTT3b and DmGSTO3 activity toward xenobiotic and physiological substrates tested. These results suggest a novel link between Omega and Theta GSTs with the p38b MAP kinase pathway.

Highlights

Glutathione S-transferases (GSTs, EC 2.5.1.18) are multifunctional enzymes involved in detoxification and excretion of physiological and toxic substances (Hayes et al 2005)
DmGSTT3a had the greatest activity toward p-nitrophenethyl bromide (PNPB), which is the substrate preference of Theta class, compared to DmGSTT3b and DmGSTT1, which had 2.48-fold and 10.8fold less activity than DmGSTT3a, respectively
DmGSTT1 had the lowest activity toward PNPB compared to DmGSTT3a and DmGSTT3b, it demonstrated the greatest activity for DCNB, as well as activity for CDNB

Summary

Introduction

Glutathione S-transferases (GSTs, EC 2.5.1.18) are multifunctional enzymes involved in detoxification and excretion of physiological and toxic substances (Hayes et al 2005). Several studies indicated that in addition to the enzymatic functions, GSTs have roles such as regulation of mitogenactivated protein kinase (MAPK) pathways. A number of reports have shown that GST enzymes can interact and modulate several proteins in MAPK pathways, e.g. JNK, TRAF2, and ASK1 (Adler et al 1999; Cho et al 2001; Wang et al 2001; Wu et al 2006; Laborde 2010). By extending the mammalian nomenclature, insect GSTs have been grouped into six classes: Delta, Epsilon, Omega, Sigma, Theta, and Zeta (Enayati et al 2005). Studies on the insect GSTs have mainly focused on their roles in conferring insecticide resistance, e.g., Delta and Epsilon GSTs (Hemingway 2000; Enayati et al 2005). There is accumulating evidence that suggests GSTs in Omega, Sigma, and Theta classes have important roles in oxidative stress (Singh et al 2001; Burmeister et al 2008; JaramilloGutierrez et al 2009; Piaggi et al 2010; Nair and Choi 2011; Kim et al 2012), which suggests additional roles in cell signaling in response to oxidative stress

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