Catalytic and non-catalytic mechanisms involved in glutathione S-transferase Pi mediated cytoprotection

• Main Author: McGarry, David
• Other Authors: Henderson, Colin ; Wolf, C
• Published: University of Dundee 2012
• Subjects: 610
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578887

Glutathione S-transferases (GSTs) are a multi-gene family of enzymes involved in the detoxification of a wide range of electrophilic compounds and are an integral component to antioxidant defence in the mammalian cell. Among GST, the Pi class (GSTP1) is the most prominent extrahepatic isoform in humans, and it is well documented that increased expression of this enzyme is present in human tumours and can contribute to anticancer drug resistance, involving many compounds which are not known substrates for GSTP1. In addition to xenobiotic metabolism, GSTP1 has a key and varied role in cell regulation, showing to be a modulator of a stress response pathway and has been implicated in mediating sulfhydryl homeostasis. The present study aims to address functions of GSTP1 which are independent of its catalytic activity. Initial in vivo studies have identified that targeting a Tyr7Phe substitution in the murine Gstp1 gene results in a GSTP1 protein which is devoid of catalytic activity. When challenged with a toxic dose of acetaminophen, these mice show a high degree of resistance to the hepatotoxic effects of this compound compared to their wild-type counterparts, in part, due to a partial recovery of hepatic glutathione levels. The ability of GSTP1 to mediate glutathione homeostasis was demonstrated in vitro, where silencing of GSTP1 in a colon carcinoma cell line demonstrated increased levels of glutathione disulphide and protein S-glutathionylation, a reversible post-translational modification involved in thiol protection. Subsequent analysis of GSTP1 silencing in this cell line led to the identification of potential novel pathways which may be mediated by GSTP1.This study examines the regulatory processes mediated by GSTP1 and aims to further our understanding of this protein in the aetiology of disease and toxicity.