GPX1

Glutathione peroxidase 1
PDB rendering based on 2f8a.
Available structures PDB Ortholog search: PDBe, RCSB List of PDB id codes 2F8A
Identifiers
Symbols	GPX1 ; GPXD; GSHPX1
External IDs	OMIM: 138320 MGI: 104887 HomoloGene: 20155 GeneCards: GPX1 Gene
EC number	1.11.1.9
Gene ontology Molecular function • glutathione peroxidase activity • selenium binding • SH3 domain binding • glutathione binding • phospholipid-hydroperoxide glutathione peroxidase activity Cellular component • nucleus • cytoplasm • mitochondrion • mitochondrial matrix • cytosol • extracellular vesicular exosome Biological process • temperature homeostasis • endothelial cell development • negative regulation of inflammatory response to antigenic stimulus • purine nucleobase metabolic process • purine nucleotide catabolic process • triglyceride metabolic process • glutathione metabolic process • response to lipid hydroperoxide • aging • sensory perception of sound • intrinsic apoptotic signaling pathway in response to oxidative stress • response to xenobiotic stimulus • response to symbiotic bacterium • response to toxic substance • UV protection • response to glucose • response to selenium ion • response to gamma radiation • protein oxidation • arachidonic acid metabolic process • lipoxygenase pathway • response to estradiol • regulation of mammary gland epithelial cell proliferation • response to nicotine • regulation of gene expression, epigenetic • vasodilation • response to hydrogen peroxide • hydrogen peroxide catabolic process • negative regulation of apoptotic process • negative regulation of cysteine-type endopeptidase activity involved in apoptotic process • skeletal muscle tissue regeneration • regulation of neuron apoptotic process • blood vessel endothelial cell migration • small molecule metabolic process • fat cell differentiation • cell redox homeostasis • skeletal muscle fiber development • myoblast proliferation • response to folic acid • interaction with symbiont • positive regulation of protein kinase B signaling • nucleobase-containing small molecule metabolic process • heart contraction • angiogenesis involved in wound healing • regulation of proteasomal protein catabolic process • negative regulation of release of cytochrome c from mitochondria • negative regulation of extrinsic apoptotic signaling pathway via death domain receptors • negative regulation of oxidative stress-induced intrinsic apoptotic signaling pathway Sources: Amigo / QuickGO
Orthologs
Species	Human	Mouse
Entrez	2876	14775
Ensembl	ENSG00000233276	ENSMUSG00000063856
UniProt	P07203	P11352
RefSeq (mRNA)	NM_000581	NM_008160
RefSeq (protein)	NP_000572	NP_032186
Location (UCSC)	Chr 3: 49.39 – 49.4 Mb	Chr 9: 108.34 – 108.34 Mb
PubMed search

Glutathione peroxidase 1 also known as GPx-1 is an enzyme that in humans is encoded by the GPX1 gene.^[1] Two alternatively spliced transcript variants encoding distinct isoforms have been found for this gene.^[2]

Function

This gene encodes a member of the glutathione peroxidase family, consisting of eight known glutathione peroxidases (Gpx1-8) in humans. Mammalian Gpx1 (this gene), Gpx2, Gpx3, and Gpx4 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.

Glutathione peroxidase functions in the detoxification of hydrogen peroxide, and is one of the most important antioxidant enzymes in humans. It has been reported that the protein encoded by this gene protects from CD95-induced apoptosis in cultured breast cancer cells and inhibits 5-lipoxygenase in blood cells, and its overexpression delays endothelial cell growth and increases resistance to toxic challenges. This protein is one of only a few proteins known in higher vertebrates to contain selenocysteine, which occurs at the active site of glutathione peroxidase and is coded by the nonsense (stop) codon TGA.

After many decades of speculation, it was found that GPX1 forms a highly reactive selenenic acid intermediate, providing insight into the way that the protein environment stabilizes these intermediates and paving the way for new therapeutics. Analysis of the structure shows that selenenic acid is protected by the protein environment from reactive groups within the protein. The mechanism of action is based on selenenic acid reacting with the amid or amine bond of another protein, forming a senyladmide bond, suggesting a role for this bond new bond in protecting the reactivity of GPX1.^[3]

Clinical signficance

Glutathione peroxidase 1 is characterized in a polyalanine sequence polymorphism in the N-terminal region, which includes three alleles with five, six or seven alanine (Ala) repeats in this sequence. The allele with five Ala repeats is significantly associated with breast cancer risk.^[2]

GPX1 helps to prevent cardiac dysfunction after ischemia-reperfusion injuries. Han and colleagues analyzed the effects of reoxygenation on cardiac protein in GPX1 knockout mouse hearts. Mitochondrial ROS production and oxidative mtDNA damage were increased during reoxygenation in the GPX1 knockout mice, in addition to structural abnormalities in cardiac mitochondria and myocytes, suggesting GPX1 may play an important role in protecting cardiac mitochondria from reoxygenation damage in vivo.^[4]

Kocabasoglu, et al., sought to investigate connections between oxidative stress genes, including GPX1, and Panic Disorder, an anxiety disorder characterized by random and unexpected attacks of intense fear. Although the GPX1 Pro198Leu polymorphism, in general, did not significantly correlate with panic disorder risk, the study found a plausible association of the C allele of the GPX1 Pro198Leu polymorphism, found to be more frequent in the female cohort, with PD development.^[5]

Ergen and colleagues analyzed gene expression of oxidative stress genes, specifically GPX1, in colorectal tumors in comparison to healthy colorectal tissues. ELISA was utilized to quantify GPX1 protein expression levels in both tissue types, highlighting a 2-fold decrease in tumor tissue (p<0.05).^[6]

In esophageal cancer, Chen and colleagues found that vitamin D, a known suppressor of GPX1 expression via the NF-kB signaling pathway, could help to decrease the proliferative, migratory, and invasive capabilities of esophageal cancer cells. Unlike in colorectal cancer, GPX1 expression in esophageal cancer cells is thought to drive aggressive growth and metastasis, but Vitamin D-mediated decrease in GPX1 prevents such growth.^[7]

In a study looking at gene polymorphisms of GPX1 and other oxidative stress genes in relation to prevalence of Type 2 diabetes mellitus, Banerjee, et al, found that while no association was found in expression of most GPX1 polymorphisms and risk of Type 2 diabetes mellitus, having the C allele of GPX1 led to a 1.362 times higher risk of the disease, highlighting the importance of finding individuals in the population with this gene variant to help treat them early on.^[8]

Recent work by Diamond and colleagues has shown that allelic variations of GPX1, like the codon 198 polymorphism that results in leucine or proline and an increase in alanine repeat codons, can result in different localization levels in MCF-7 human breast carcinoma cells. For instance, the allele expressing the leucine-198 polymorphism and 7 alanine repeats generates GPX-1 localization that is disproportionately in the cytoplasm as compared to other allelic variants. To further understand the effects of these variants on GPX-1 function, mutant GPX-1 with mitochondrial localization sequences were generated and the GPX-1 infused cells were analyzed for their response to oxidative stress, energy metabolism and cancer-associated signaling molecules. Ultimately, GPX-1 variants heavily influenced cellular biology, suggesting that different GPX-1 variants affect cancer risk differently.^[9]

An analysis of GPX1 expression in oligodendrocytes from patients with major depressive disorder and control patients showed that GPX1 levels were significantly decreased in patients with the disorder, but not in their astrocytes. Shortening of telomeres and decreased expression of telomerase were also evident in these oligodendrocytes, but not in the astrocytes in these patients. This suggests that decreased oxidative stress protection, as observed by decreased GPX1 levels, and decreased telomerase expression may help give rise to telomere shortening in patients suffering from MDD.^[10]

In a study observing the effects of age-related vascular dysfunction in GPX1 (-/-) mice, oxidant formation increased, endothelial NO synthase was deregulated, and adhesion of leukocytes to cultured endothelial cells was increased. This data suggests that GPX1 amplifies certain aspects of aging, namely endothelial dysfunction, vascular remodeling, and invasion of leukocytes in cardiovascular tissue.^[11]

Interactions

GPX1 has been shown to interact with Abl gene.^[12]

A recently discovered suppressor for GPX1 is S-adenosylhomocysteine, which when accumulated in endothelial cells can cause tRNA(Sec) hypomethylation, reducing the expression of GPX1 and other selenoproteins. The decreased GPX-1 expression can then lead to inflammatory activating of endothelial cells, helping give rise to a proatherogenic endothelial phenotype.^[13]

References

Further reading

PDB gallery 2f8a: Crystal structure of the selenocysteine to glycine mutant of human glutathione peroxidase 1