Gclc influences eye development: possible link between protein glutathionylation and gene expression in the lens

Abstract

Purpose : Glutamate-cysteine ligase catalytic subunit (Gclc) is an essential enzyme in the biosynthesis of glutathione (GSH). We have previously demonstrated that gclc suppression in zebrafish and Gclc deletion from surface ectoderm-derived tissues in the mouse both induce microphthalmia. However, the mechanism by which this induces microphthalmia remains unknown. By impacting cellular redox signaling and the oxidation status of exposed thiols in proteins, decreased levels of GSH (subsequent to ablated Gclc activity) may promote microphthalmia by influencing the proteome or transcriptome of the developing lens.

Methods : Gclc-floxed mice were bred with Le-Cre transgenic (which utilize the Pax6 P0 gene promoter to drive CRE recombinase expression) mice to create KO mice in which Gclc was conditionally deleted from only the surface ectoderm-derived tissues within the developing eye. Gclc-floxed mice serve as the control. Changes in the redox status of the lens proteome was estimated by Western blot analysis of glutathionylated proteins in the lens of postnatal day (P) 21 mice. qRT-PCR was used to determine alterations in lens gene expression in P0 mice.

Results : At P21, KO lens display increased global protein glutathionylation compared with Gclc control (CON) mice. Notably, high molecular weight (>40 kDa) lens proteins were selectively glutathionylated in KO but not control mice. At P0, the KO lens transcriptome revealed marked changes in the expression of stress response genes (i.e., Hmox1, Cdkn1a), Foxe3 (essential lens epithelial transcription factor), and Cryaa (lens molecular chaperone).

Conclusions : Our results provide evidence that suppression of Gclc influences important lens transcription factors and results in the glutathionylation of select lens proteins. Investigations into the role of protein glutathionylation in causing gene expression changes that adversely affect eye development and cause microphthalmia are on-going.

This is a 2020 ARVO Annual Meeting abstract.