High impact information on GLRX2

• Slow degradation under aerobic conditions was prevented by the presence of glutathione, whereas glutathione disulfide as well as one-electron oxidants or reductants promoted monomerization of Grx2 [1].
• We propose that the iron-sulfur cluster serves as a redox sensor for the activation of Grx2 during conditions of oxidative stress when free radicals are formed and the glutathione pool becomes oxidized [1].
• Mossbauer spectroscopy revealed the presence of a four cysteine-coordinated nonoxidizable [2Fe-2S]2+ cluster that bridges two Grx2 molecules via two structural Cys residues to form dimeric holo Grx2 [1].
• Here, we have characterized Grx2 as an iron-sulfur center-containing member of the thioredoxin fold protein family [1].
• Human mitochondrial glutaredoxin 2 (Grx2) is a glutathione-dependent oxidoreductase (active site: Cys-Ser-Tyr-Cys) that facilitates the maintenance of mitochondrial redox homeostasis upon induction of apoptosis by oxidative stress [2].
• Short interfering RNA-mediated silencing of glutaredoxin 2 increases the sensitivity of HeLa cells toward doxorubicin and phenylarsine oxide [2].

Biological context of GLRX2

• The properties that permit GLRX2, and not other glutaredoxins, to form an iron-sulfur-containing dimer are likely due to the proline-to-serine substitution in the active site motif, allowing the main chain more flexibility in this area and providing polar interaction with the stabilizing glutathione [3].
• Human mitochondrial glutaredoxin 2 (GLRX2), which controls intracellular redox balance and apoptosis, exists in a dynamic equilibrium of enzymatically active monomers and quiescent dimers [3].
• These results indicate a crucial role of Grx2 in the regulation of the mitochondrial redox status and regulation of cell death at the mitochondrial checkpoint [2].
• Alternative splicing forms of mammalian Grx2 mRNAs were identified that differed in sequences upstream of exon 2 [4].
• Grx2 was encoded in the genomes of mammals and birds and expressed in a variety of cell types [4].
• Alternative isoforms of Grx2, derived from alternative transcription initiation and splicing, have been demonstrated in human and mouse [5] [6].

Anatomical context of GLRX2

• Here, we have successfully established a method to silence the expression of Grx2 in HeLa cells by using short interfering RNA to study its role in the cell [2].
• The mitochondrial leader sequence was also present in mouse and rat Grx2 sequences and was shown to direct either Grx2 or green fluorescent protein to mitochondria [4].
• In this study we investigate Grx2 function by examining its potential peroxidase activity using lens epithelial cells (LEC). cDNA for human and mouse Grx2 was cloned into pET21d(+) vector and used to produce respective recombinant Grx2 for kinetic studies. cDNA for human Grx2 was transfected into human LEC and used for in vivo studies [7].
• Coimmunoprecipitation of radiolabeled iron with Grx2 from human cell lines indicated the presence of the cluster in vivo [1].
• Both Grx1 and Grx2 could be detected at the mRNA and protein level in cultured human lung cells, but only Grx1 was prominently expressed in lung homogenates and alveolar macrophages [8].

Associations of GLRX2 with chemical compounds

• Crystal structures of both monomeric and dimeric forms of human GLRX2 reveal a distinct glutathione binding mode and show a 2Fe-2S-bridged dimer [3].
• Short interfering RNA-mediated silencing of glutaredoxin 2 increases the sensitivity of HeLa cells toward doxorubicin and phenylarsine oxide [2].
• The human Grx2 sequence contains three characteristic regions of the glutaredoxin family: the dithiol/disulfide active site, CSYC, the GSH binding site, and a hydrophobic surface area [9].
• Grx1 and Grx2 were sensitive to inactivation by iodoacetamide and H(2)O(2) and exhibited similar pH dependence of catalytic activity [4].
• Using this novel electron donor pathway, Grx2 reduced low molecular weight disulfides such as CoA but with particular high efficiency glutathionylated substrates including GSSG [10].

Other interactions of GLRX2

• Mitochondrial thioltransferase (glutaredoxin 2) has GSH-dependent and thioredoxin reductase-dependent peroxidase activities in vitro and in lens epithelial cells [7].
• The high-resolution solution structure of E. coli Grx2 shows a two-domain protein, with residues 1 to 72 forming a classical "thioredoxin-fold" glutaredoxin domain, connected by an 11 residue linker to the highly helical C-terminal domain, residues 84 to 215 [11].

Analytical, diagnostic and therapeutic context of GLRX2

• Flow cytometry (FACS) analysis and confocal microscopy revealed that cells preloaded with pure Grx2 detoxified peroxides more efficiently [7].
• Grx2 is a glutathione binding protein and we have shown in the present study that the protein can be purified from crude bacterial extracts by a one-step affinity chromatography on glutathione-Sepharose [12].
• Two testis/cancer cell-specific non-mitochondrial isoforms.of Grx2 have been demonstrated in human [5].

References