GLRX

GLRX (glutaredoxin 1) is a thiol-disulfide oxidoreductase that catalyzes protein deglutathionylation, thereby serving as a central regulator of redox-sensitive signaling, inflammatory responses, and cell survival under oxidative stress. GLRX removes glutathione mixed disulfides from specific substrates including AKT, maintaining its phosphorylation and pro-survival signaling (PMID:25788646), and HIF-1α, whose glutathionylation-dependent stabilization drives VEGF-A production and pulmonary angiogenesis in GLRX-deficient mice (PMID:36640422). GLRX loss increases global protein S-glutathionylation in vivo, attenuating NF-κB-dependent inflammatory signaling as demonstrated by reduced cigarette smoke-induced lung inflammation in Grx1 knockout mice (PMID:22723915), and sensitizes cells to oxidative stress through excessive mitochondrial ROS accumulation, cytochrome c release, and apoptosis (PMID:32892658). GLRX mRNA stability is regulated by the NRF1–METTL3 axis via m6A modification in an IGF2BP2-dependent manner, linking transcriptional and epitranscriptomic control to neuronal redox protection (PMID:37735974).

1. 1996 Medium

   Chromosomal localization of the human GLRX gene to 5q14 established its genomic identity, enabling subsequent functional studies.

   Evidence FISH and somatic cell hybrid analysis

   PMID:8838810

   Open questions at the time

   • No functional characterization at this stage
   • No regulatory elements identified
2. 2007 Medium

   Determining that GRX1 localizes exclusively to the mitochondrial intermembrane space (while GRX2 resides in the matrix) established compartment-specific roles for glutaredoxin isoforms in mitochondrial redox regulation.

   Evidence Subcellular fractionation of mitochondria with Western blotting

   PMID:17845131

   Open questions at the time

   • Single fractionation approach without immunofluorescence confirmation
   • Cytosolic pool not addressed in this study
   • No functional consequences of compartmentalization tested
3. 2012 Medium

   Grx1 knockout mice showed that endogenous Grx1 is required for NF-κB-dependent inflammatory signaling in vivo, as its absence increased global protein S-glutathionylation and reduced cigarette smoke-induced lung inflammation.

   Evidence Grx1 KO mouse, cigarette smoke exposure, BALF cytokine/cell counting, PSSG immunoblotting

   PMID:22723915

   Open questions at the time

   • Specific NF-κB subunit glutathionylation sites not identified
   • No reconstitution with catalytically dead Grx1 to confirm enzymatic requirement
4. 2015 Medium

   Identification of AKT as a direct deglutathionylation substrate of Grx1 established a mechanistic link between Grx1 activity and pro-survival signaling through maintenance of AKT phosphorylation.

   Evidence Overexpression/siRNA knockdown in retinal pigment epithelial cells, immunoprecipitation with anti-PSSG antibody, phospho-AKT Western blot, apoptosis assay

   PMID:25788646

   Open questions at the time

   • Specific glutathionylated cysteine residue on AKT not mapped
   • In vivo validation of AKT deglutathionylation not performed
5. 2019 Medium

   GLRX inhibition sensitized EGFR-TKI-resistant NSCLC cells to gefitinib through ROS-mediated apoptosis and cell cycle arrest, placing GLRX in the EGFR/FoxM1 signaling axis relevant to drug resistance.

   Evidence siRNA knockdown, proliferation/apoptosis/cell cycle assays, mouse xenograft

   PMID:30061098

   Open questions at the time

   • Direct deglutathionylation target in EGFR/FoxM1 pathway not identified
   • No catalytic-dead rescue to confirm enzymatic mechanism
6. 2020 Medium

   CRISPR-generated Grx1-null cells demonstrated that Grx1 is essential for mitochondrial redox homeostasis, as its loss caused excessive mitochondrial ROS, cytochrome c release, and apoptosis sensitivity to multiple oxidative stressors.

   Evidence CRISPR/Cas9 KO in HeLaS3, MitoSox Red, DCFDA, Western blot for oxidized proteins, annexin V apoptosis assay

   PMID:32892658

   Open questions at the time

   • Specific mitochondrial substrates responsible for phenotype not identified
   • Rescue with IMS-targeted versus cytosolic Grx1 not tested
7. 2023 Medium

   HIF-1α was identified as a deglutathionylation target of Grx1, establishing that Grx1 controls pulmonary angiogenesis by preventing glutathionylation-dependent HIF-1α stabilization and VEGF-A induction.

   Evidence Grx1 KO mouse, GSH-protein adduct measurement, VEGF-A quantification, YC-1 pharmacological rescue

   PMID:36640422

   Open questions at the time

   • Specific glutathionylated cysteine on HIF-1α not mapped
   • Whether Grx1 acts on HIF-1α directly or through an intermediary not resolved
8. 2023 Medium

   The NRF1–METTL3–IGF2BP2 axis was shown to regulate GLRX mRNA stability via m6A modification, revealing an epitranscriptomic layer of Grx1 regulation with neuroprotective consequences.

   Evidence ChIP, RIP, MeRIP, dual luciferase assay, MPTP mouse model of Parkinson's disease

   PMID:37735974

   Open questions at the time

   • Specific m6A sites on GLRX mRNA not mapped at nucleotide resolution
   • Whether this regulatory axis operates in tissues beyond dopaminergic neurons is unknown

• A comprehensive substrate map for Grx1 deglutathionylation activity — including identification of specific cysteine residues on substrates like AKT and HIF-1α — and the structural basis for substrate selectivity remain unresolved.
• No proteome-wide identification of Grx1-dependent deglutathionylation sites
• No crystal structure of Grx1 bound to a glutathionylated substrate
• Relative contributions of cytosolic versus IMS pools to specific phenotypes not delineated