title: Membrane association of glutathione S-transferase mGSTA4-4, an enzyme that metabolizes lipid peroxidation products.
abstract: Lipid peroxidation products have signaling functions and at higher concentrations are toxic and may trigger cell death. The compounds are metabolized predominantly by glutathione S-transferases exemplified by mGSTA4-4, an enzyme highly efficient in glutathione conjugation of 4-hydroxyalkenals, and possessing glutathione peroxidase activity toward phospholipid hydroperoxides. mGSTA4-4 belongs to the predominant group of "canonical" glutathione S-transferases that are soluble and generally localized in the cytoplasm. The intracellular localization of mGSTA4-4 was examined in hepatocytes of normal mouse liver and in transfected HepG2 cells by fluorescence microscopy and digital deconvolution. mGSTA4-4 was found to be predominantly localized at or near the plasma membrane in transfected HepG2 cells, as well as in hepatocytes endogenously expressing the protein. In vitro, mGSTA4-4 associated with liposomes, and this interaction was potentiated when the liposomes contained negatively charged phospholipids. Mutating lysine 115 to glutamic acid resulted in a loss of the plasma membrane targeting of mGSTA4-4 as well as in a significant reduction of its binding to liposomes in vitro. These data suggest preferential targeting of mGSTA4-4 to the plasma membrane that may contain the major substrate(s) for this enzyme. Lysine 115 is critically important for the membrane association of mGSTA4-4, most likely by entering into an electrostatic interaction with negatively charged phospholipid headgroups.
authors.affiliation: Department of Internal Medicine, University of Arkansas for Medical Sciences, and Central Arkansas Veterans Healthcare System, Little Rock, Arkansas 72205, USA.
authors.forename: Sharda P
authors.initials: SP
authors.lastname: Singh
authors.forename: Andrzej J
authors.initials: AJ
authors.lastname: Janecki
authors.forename: Sanjay K
authors.initials: SK
authors.lastname: Srivastava
authors.forename: Sanjay
authors.initials: S
authors.lastname: Awasthi
authors.forename: Yogesh C
authors.initials: YC
authors.lastname: Awasthi
authors.forename: Shujuan J
authors.initials: SJ
authors.lastname: Xia
authors.forename: Piotr
authors.initials: P
authors.lastname: Zimniak
mesh_terms: D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D005982:Glutathione Transferase / Q000378:metabolism*; D022781:Hepatocytes / Q000201:enzymology; D015227:Lipid Peroxidation; D008081:Liposomes; D051379:Mice; D016297:Mutagenesis, Site-Directed; D010713:Phosphatidylcholines; D010743:Phospholipids / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology; D014162:Transfection
chemical_list: D008081:Liposomes; D010713:Phosphatidylcholines; D010743:Phospholipids; C024990:asolectin; D005982:Glutathione Transferase; C041116:leukotriene-C4 synthase