The antioxidant enzyme glutathione peroxidase 4 (GPx4) belongs to the family of glutathione peroxidases, which consists of 8 known mammalian isoenzymes (GPx1-8). Gpx4 catalyzes the reduction of hydrogen peroxide, organic hydroperoxides, and lipid peroxides at the expense of reduced glutathione and functions in the protection of cells against oxidative stress. The oxidized form of glutathione (glutathione disulfide), which is generated during the reduction of hydroperoxides by GPx4, is recycled by glutathione reductase and NADPH/H+. GPx4 differs from the other GPx family members in terms of its monomeric structure, a less restricted dependence on glutathione as reducing substrate, and the ability to reduce lipid-hydroperoxides inside biological membranes.
Mammalian GPx1, GPx2, GPx3, and GPx4 (this protein) have been shown to be selenium-containing enzymes, whereas GPx6 is a selenoprotein in humans with cysteine-containing homologues in rodents. In selenoproteins, the 21st amino acid selenocysteine is inserted in the nascent polypeptide chain during the process of translational recoding of the UGA stop codon. GPx4 shares the amino acid motif of selenocysteine, glutamine, and tryptophane (catalytic triad) with other glutathione peroxidases.
This reaction occurs at the selenocysteine within the catalytic center of GPx4. During the catalytic cycle of GPx4, the active selenol (-SeH) is oxidized by peroxides to selenenic acid (-SeOH), which is then reduced with glutathione (GSH) to an intermediate selenodisulfide (-Se-SG). GPx4 is eventually reactivated by a second glutathione molecule, releasing glutathione disulfide (GS-SG).
Subcellular distribution of isoforms
In mouse and rat, three distinct GPx4 isoforms with different subcellular localization are produced through alternative splicing and transcription initiation; cytosolic GPx4, mitochondrial GPx4 (mGPx4), and nuclear GPx4 (nGPx4). Cytosolic GPx4 has been identified as the only GPx4 isoform being essential for embryonic development and cell survival. The GPx4 isoforms mGPx4 and nGPx4 have been implicated in spermatogenesis and male fertility.[5] In humans, experimental evidence for alternative splicing exists; alternative transcription initiation and the cleavage sites of the mitochondrial and nuclear transit peptides need to be experimentally verified.[6]
Animal models
Knockout mice of GPX4 die at embryonic day 8[7][8]
and conditional inducible deletion in adult mice (neurons) results in degeneration and death in less than a month.[9] Targeted disruption of the mitochondrial GPx4 isoform (mGPx4) caused infertility in male mice and disruption of the nuclear GPx4 isoform (nGPx4) reduced the structural stability of sperm chromatin, yet both knockout mouse models (for mGPx4 and nGPx4) were fully viable. Surprisingly, knockout of GPX4 heterozygously in mice (GPX4+/−) increases their median life span.[10] Knockout studies with GPx1, GPx2, or GPx3 deficient mice showed that cytosolic GPx4 is so far the only glutathione peroxidase that is indispensable for embryonic development and cell survival. As mechanisms to dispose of both hydrogen peroxide and lipid hydroperoxides are essential to life, this indicates that in contrast to the multiple metabolic pathways that can be utilised to dispose of hydrogen peroxide, pathways for the disposal of lipid hydroperoxides are limited.
While mammals have only one copy of the GPX4 gene, fish have two copies, GPX4a and GPX4b.[11] The GPX4's appear to play a greater role in the fish GPX system than in mammals. For example, in fish GPX4 activity contributes to a greater extent to total GPX activity,[12] GPX4a is the most highly expressed selenoprotein mRNA (in contrast to mammals where it is GPX1 mRNA)[13] and GPX4a appears to be highly inducible to changes within the cellular environment, such as changes in methylmercury and selenium status.[14]
References
↑Esworthy RS, Doan K, Doroshow JH, Chu FF (July 1994). "Cloning and sequencing of the cDNA encoding a human testis phospholipid hydroperoxide glutathione peroxidase". Gene. 144 (2): 317–8. doi:10.1016/0378-1119(94)90400-6. PMID8039723.
↑Friedmann Angeli, Jose Pedro; Schneider, Manuela; Proneth, Bettina; Tyurina, Yulia Y.; Tyurin, Vladimir A.; Hammond, Victoria J.; Herbach, Nadja; Aichler, Michaela; Walch, Axel; Eggenhofer, Elke; Basavarajappa, Devaraj; Rådmark, Olof; Kobayashi, Sho; Seibt, Tobias; Beck, Heike; Neff, Frauke; Esposito, Irene; Wanke, Rüdiger; Förster, Heidi; Yefremova, Olena; Heinrichmeyer, Marc; Bornkamm, Georg W.; Geissler, Edward K.; Thomas, Stephen B.; Stockwell, Brent R.; O’Donnell, Valerie B.; Kagan, Valerian E.; Schick, Joel A.; Conrad, Marcus (17 November 2014). "Inactivation of the ferroptosis regulator Gpx4 triggers acute renal failure in mice". Nature Cell Biology. 16 (12): 1180–1191. doi:10.1038/ncb3064. PMC4894846.
↑Smith AC, Mears AJ, Bunker R, Ahmed A, MacKenzie M, Schwartzentruber JA, Beaulieu CL, Ferretti E, Majewski J, Bulman DE, Celik FC, Boycott KM, Graham GE (2014). "Mutations in the enzyme glutathione peroxidase 4 cause Sedaghatian-type spondylometaphyseal dysplasia". Journal of Medical Genetics. 51 (7): 470–4. doi:10.1136/jmedgenet-2013-102218. PMID24706940.
↑Schneider M, Förster H, Boersma A, Seiler A, Wehnes H, Sinowatz F, Neumüller C, Deutsch MJ, Walch A, Hrabé de Angelis M, Wurst W, Ursini F, Roveri A, Maleszewski M, Maiorino M, Conrad M (May 2009). "Mitochondrial glutathione peroxidase 4 disruption causes male infertility". FASEB J. 23 (9): 3233–42. doi:10.1096/fj.09-132795. PMID19417079.
↑Yant LJ, Ran Q, Rao L, Van Remmen H, Shibatani T, Belter JG, Motta L, Richardson A, Prolla TA (February 2003). "The selenoprotein GPX4 is essential for mouse development and protects from radiation and oxidative damage insults". Free Radic. Biol. Med. 34 (4): 496–502. doi:10.1016/S0891-5849(02)01360-6. PMID12566075.
↑Seiler A, Schneider M, Förster H, Roth S, Wirth EK, Culmsee C, Plesnila N, Kremmer E, Rådmark O, Wurst W, Bornkamm GW, Schweizer U, Conrad M (September 2008). "Glutathione peroxidase 4 senses and translates oxidative stress into 12/15-lipoxygenase dependent- and AIF-mediated cell death". Cell Metab. 8 (3): 237–48. doi:10.1016/j.cmet.2008.07.005. PMID18762024.
↑Ran Q, Liang H, Ikeno Y, Qi W, Prolla TA, Roberts LJ, Wolf N, Van Remmen H, VanRemmen H, Richardson A (2007). "Reduction in glutathione peroxidase 4 increases life span through increased sensitivity to apoptosis". J. Gerontol. A Biol. Sci. Med. Sci. 62 (9): 932–42. doi:10.1093/gerona/62.9.932. PMID17895430.
↑Penglase S, Hamre K, Ellingsen S (2014). "Selenium prevents downregulation of antioxidant selenoprotein genes by methylmercury". Free Radical Biology and Medicine. 75: 95–104. doi:10.1016/j.freeradbiomed.2014.07.019. PMID25064324.
Further reading
Nakagawa Y (2005). "Role of mitochondrial phospholipid hydroperoxide glutathione peroxidase (PHGPx) as an antiapoptotic factor". Biol. Pharm. Bull. 27 (7): 956–60. doi:10.1248/bpb.27.956. PMID15256721.
Esworthy RS, Doan K, Doroshow JH, Chu FF (1994). "Cloning and sequencing of the cDNA encoding a human testis phospholipid hydroperoxide glutathione peroxidase". Gene. 144 (2): 317–8. doi:10.1016/0378-1119(94)90400-6. PMID8039723.
Maruyama K, Sugano S (1994). "Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides". Gene. 138 (1–2): 171–4. doi:10.1016/0378-1119(94)90802-8. PMID8125298.
Chu FF (1994). "The human glutathione peroxidase genes GPX2, GPX3, and GPX4 map to chromosomes 14, 5, and 19, respectively". Cytogenet. Cell Genet. 66 (2): 96–8. doi:10.1159/000133675. PMID8287691.
Bonaldo MF, Lennon G, Soares MB (1997). "Normalization and subtraction: two approaches to facilitate gene discovery". Genome Res. 6 (9): 791–806. doi:10.1101/gr.6.9.791. PMID8889548.
Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K, Suyama A, Sugano S (1997). "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library". Gene. 200 (1–2): 149–56. doi:10.1016/S0378-1119(97)00411-3. PMID9373149.
Opalenik SR, Ding Q, Mallery SR, Thompson JA (1998). "Glutathione depletion associated with the HIV-1 TAT protein mediates the extracellular appearance of acidic fibroblast growth factor". Arch. Biochem. Biophys. 351 (1): 17–26. doi:10.1006/abbi.1997.0566. PMID9501919.
Kelner MJ, Montoya MA (1998). "Structural organization of the human selenium-dependent phospholipid hydroperoxide glutathione peroxidase gene (GPX4): chromosomal localization to 19p13.3". Biochem. Biophys. Res. Commun. 249 (1): 53–5. doi:10.1006/bbrc.1998.9086. PMID9705830.
Ursini F, Heim S, Kiess M, Maiorino M, Roveri A, Wissing J, Flohé L (1999). "Dual function of the selenoprotein PHGPx during sperm maturation". Science. 285 (5432): 1393–6. doi:10.1126/science.285.5432.1393. PMID10464096.
Choi J, Liu RM, Kundu RK, Sangiorgi F, Wu W, Maxson R, Forman HJ (2000). "Molecular mechanism of decreased glutathione content in human immunodeficiency virus type 1 Tat-transgenic mice". J. Biol. Chem. 275 (5): 3693–8. doi:10.1074/jbc.275.5.3693. PMID10652368.
Richard MJ, Guiraud P, Didier C, Seve M, Flores SC, Favier A (2001). "Human immunodeficiency virus type 1 Tat protein impairs selenoglutathione peroxidase expression and activity by a mechanism independent of cellular selenium uptake: consequences on cellular resistance to UV-A radiation". Arch. Biochem. Biophys. 386 (2): 213–20. doi:10.1006/abbi.2000.2197. PMID11368344.
Yagi K, Komura S, Ohishi N (2003). "Expression of human phospholipid hydroperoxide glutathione peroxidase. Expression of Human Phospholipid Hydroperoxide Glutathione Peroxidase". Methods Mol. Biol. 196: 195–9. doi:10.1385/1-59259-274-0:195. ISBN1-59259-274-0. PMID12152199.
Foresta C, Flohé L, Garolla A, Roveri A, Ursini F, Maiorino M (2003). "Male fertility is linked to the selenoprotein phospholipid hydroperoxide glutathione peroxidase". Biol. Reprod. 67 (3): 967–71. doi:10.1095/biolreprod.102.003822. PMID12193409.
Borchert A, Savaskan NE, Kuhn H (2003). "Regulation of expression of the phospholipid hydroperoxide/sperm nucleus glutathione peroxidase gene. Tissue-specific expression pattern and identification of functional cis- and trans-regulatory elements". J. Biol. Chem. 278 (4): 2571–80. doi:10.1074/jbc.M209064200. PMID12427732.
Villette S, Kyle JA, Brown KM, Pickard K, Milne JS, Nicol F, Arthur JR, Hesketh JE (2003). "A novel single nucleotide polymorphism in the 3' untranslated region of human glutathione peroxidase 4 influences lipoxygenase metabolism". Blood Cells Mol. Dis. 29 (2): 174–8. doi:10.1006/bcmd.2002.0556. PMID12490284.
Maiorino M, Bosello V, Ursini F, Foresta C, Garolla A, Scapin M, Sztajer H, Flohe L (2004). "Genetic variations of gpx-4 and male infertility in humans". Biol. Reprod. 68 (4): 1134–41. doi:10.1095/biolreprod.102.007500. PMID12606444.
Wang HP, Schafer FQ, Goswami PC, Oberley LW, Buettner GR (2003). "Phospholipid hydroperoxide glutathione peroxidase induces a delay in G1 of the cell cycle". Free Radic. Res. 37 (6): 621–30. doi:10.1080/1071576031000088283. PMID12868489.
Chen CJ, Huang HS, Chang WC (2003). "Depletion of phospholipid hydroperoxide glutathione peroxidase up-regulates arachidonate metabolism by 12S-lipoxygenase and cyclooxygenase 1 in human epidermoid carcinoma A431 cells". FASEB J. 17 (12): 1694–6. doi:10.1096/fj.02-0847fje. PMID12958179.
Sneddon AA, Wu HC, Farquharson A, Grant I, Arthur JR, Rotondo D, Choe SN, Wahle KW (2004). "Regulation of selenoprotein GPx4 expression and activity in human endothelial cells by fatty acids, cytokines and antioxidants". Atherosclerosis. 171 (1): 57–65. doi:10.1016/j.atherosclerosis.2003.08.008. PMID14642406.