Cytosolic glutaredoxin 1 is upregulated in AMD and controls retinal pigment epithelial cells proliferation via ß-catenin.

Thioredoxin (Trx) family proteins are key players in redox signaling. Here, we have analyzed glutaredoxin (Grx) 1 and Grx2 in age-related macular degeneration (AMD) and in retinal pigment epithelial (ARPE-19) cells. We hypothesized that these redoxins regulate cellular functions and signaling circuits such as cell proliferation, Wnt signaling and VEGF release that have been correlated to the pathophysiology of AMD. ARPE-19 cells were transfected with specific siRNAs to silence the expression of Grx1 and Grx2 and were analyzed for proliferation/viability, migration capacity, ß-catenin activation, and VEGF release. An active site-mutated C-X-X-S Grx1 was utilized to trap interacting proteins present in ARPE-19 cell extracts. In both, AMD retinas and in ARPE-19 cells incubated under hypoxia/reoxygenation conditions, Grx1 showed an increased nuclear localization. Grx1-silenced ARPE-19 cells showed a significantly reduced proliferation and migration rate. Our trapping approach showed that Grx1 interacts with ß-catenin in a dithiol-disulfide exchange reaction. Knock-down of Grx1 led to a reduction in both total and active ß-catenin levels. These findings add redox control to the regulatory mechanisms of ß-catenin signaling in the retinal pigment epithelium and open the door to novel therapeutic approaches in AMD that is currently treated with VEGF-inhibitors.

Vertebrate-specific glutaredoxin is essential for brain development.

Cellular functions and survival are dependent on a tightly controlled redox potential. Currently, an increasing amount of data supports the concept of local changes in the redox environment and specific redox signaling events controlling cell function. Specific protein thiol groups are the major targets of redox signaling and regulation. Thioredoxins and glutaredoxins catalyze reversible thiol-disulfide exchange reactions and are primary regulators of the protein thiol redox state. Here, we demonstrate that embryonic brain development depends on the enzymatic activity of glutaredoxin 2. Zebrafish with silenced expression of glutaredoxin 2 lost virtually all types of neurons by apoptotic cell death and the ability to develop an axonal scaffold. As demonstrated in zebrafish and in a human cellular model for neuronal differentiation, glutaredoxin 2 controls axonal outgrowth via thiol redox regulation of collapsin response mediator protein 2, a central component of the semaphorin pathway. This study provides an example of a specific thiol redox regulation essential for vertebrate embryonic development.

Redox atlas of the mouse. Immunohistochemical detection of glutaredoxin-, peroxiredoxin-, and thioredoxin-family proteins in various tissues of the laboratory mouse.

BACKGROUND: Oxidoreductases of the thioredoxin family of proteins have been thoroughly studied in numerous cellular and animal models mimicking human diseases. Despite of their well documented role in various disease conditions, no systematic information on the presence of these proteins is available. METHODS: Here, we have systematically analyzed the presence of some of the major constituents of the glutaredoxin (Grx)-, peroxiredoxin (Prx)-, and thioredoxin (Trx)-systems, i.e. Grx1, Grx2, Grx3 (TXNL-2/PICOT), Grx5, nucleoredoxin (Nrx), Prx1, Prx2, Prx3, Prx4, Prx5, Prx6, Trx1, thioredoxin reductase 1 (TrxR1), Trx2, TrxR2, and γ-glutamyl cysteine synthetase (γ-GCS) in various tissues of the mouse using immunohistochemistry. RESULTS: The identification of the Trx family proteins in the central nervous system, sensory organs, digestive system, lymphatic system, reproductive system, urinary system, respiratory system, endocrine system, skin, heart, and muscle revealed a number of significant differences between these proteins with respect to their distribution in these tissues. CONCLUSION: Our results imply more specific functions and interactions between the proteins of this family than previously assumed. GENERAL SIGNIFICANCE: Crucial functions of Trx family proteins have been demonstrated in various disease conditions. A detailed overview on their distribution in various tissues will be helpful to fully comprehend their potential role and the interactions of these proteins in the most thoroughly studied model for human diseases-the laboratory mouse. This article is part of a Special Issue entitled Human and Murine Redox Protein Atlases.