Glutaredoxin 1 protects lens epithelial cells from epithelial-mesenchymal transition by preventing casein kinase 1? S-glutathionylation during posterior capsular opacification

Oxidative stress drives protein S-glutathionylation, which regulates the structure and function of target proteins and is implicated in the pathogenesis of many diseases. Glutaredoxin 1 (Grx1), a cytoplasmic deglutathionylating enzyme, maintains a reducing environment within the cell under various conditions by reversing S-gluta-thionylation. Grx1 performs a wide range of antioxidant activities in the lens and prevents protein-thiol mixed disulfide accumulation, reducing protein-protein aggregation, insolubilization, and apoptosis of lens epithelial cells. Oxidative stress is related to epithelial-mesenchymal transition (EMT) during posterior capsular opacifi-cation (PCO). However, whether Grx1-regulated protein S-glutathionylation plays an essential role in PCO re-mains unclear. In this study, we revealed that Grx1 expression was decreased in mice following cataract surgery. Furthermore, the absence of Grx1 elevated oxidative stress and protein S-glutathionylation and aggravated EMT in both in vitro and in vivo models. Concurrently, these results could be reversed by Grx1 overexpression. Notably, liquid chromatography-tandem mass spectrometry results showed that casein kinase 1 alpha (CK1 alpha) was susceptible to S-glutathionylation under oxidative stress, and CK1 alpha S-glutathionylation (CK1 alpha-SSG) was mediated at Cys249. The absence of Grx1 upregulated CK1 alpha-SSG, subsequently decreasing the CK1 alpha-induced phosphorylation of beta-catenin at Ser45. The consequential downregulation of degradative beta-catenin and upregulation of its nuclear translocation activated the Wnt/beta-catenin signaling pathway and aggravated EMT. In conclusion, the down -regulated expression of Grx1 in mice following cataract surgery aggravated EMT by upregulating the extent of CK1 alpha-SSG. To the best of our knowledge, our study is the first to report how S-glutathionylation regulates CK1 alpha activity under oxidative stress.

Automated summary

Oxidative stress induces protein S-glutathionylation, which regulates the structure and function of target proteins and is involved in the pathogenesis of various diseases. The cytoplasmic deglutathionylating enzyme, Grx1, plays a crucial role in maintaining cellular redox state and preventing protein-thiol mixed disulfide accumulation. Our study demonstrates that the downregulation of Grx1 exacerbates oxidative stress, protein S-glutathionylation, and EMT in the context of cataract surgery. Additionally, we identify CK1 alpha as a target of S-glutathionylation, which further activates the Wnt/β-catenin signaling pathway and aggravates EMT.