Ginkgolic Acid Rescues Lens Epithelial Cells from Injury Caused by Redox Regulated-Aberrant Sumoylation Signaling by Reviving Prdx6 and Sp1 Expression and Activities.

Bhavana Chhunchha,Dhirendra Singh,Prerna Singh,Eri Kubo

doi:10.3390/ijms19113520

Bhavana Chhunchha, Dhirendra Singh + Show 2 more

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https://doi.org/10.3390/ijms19113520

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Abstract

Sumoylation is a downstream effector of aging/oxidative stress; excess oxidative stress leads to dysregulation of a specificity protein1 (Sp1) and its target genes, such as Peroxiredoxin 6 (Prdx6), resulting in cellular damage. To cope with oxidative stress, cells rely on a signaling pathway involving redox-sensitive genes. Herein, we examined the therapeutic efficacy of the small molecule Ginkgolic acid (GA), a Sumoylation antagonist, to disrupt aberrant Sumoylation signaling in human and mouse lens epithelial cells (LECs) facing oxidative stress or aberrantly expressing Sumo1 (small ubiquitin-like modifier). We found that GA globally reduced aberrant Sumoylation of proteins. In contrast, Betulinic acid (BA), a Sumoylation agonist, augmented the process. GA increased Sp1 and Prdx6 expression by disrupting the Sumoylation signaling, while BA repressed the expression of both molecules. In vitro DNA binding, transactivation, Sumoylation and expression assays revealed that GA enhanced Sp1 binding to GC-boxes in the Prdx6 promoter and upregulated its transcription. Cell viability and intracellular redox status assays showed that LECs pretreated with GA gained resistance against oxidative stress-driven aberrant Sumoylation signaling. Overall, our study revealed an unprecedented role for GA in LECs and provided new mechanistic insights into the use of GA in rescuing LECs from aging/oxidative stress-evoked dysregulation of Sp1/Prdx6 protective molecules.

Highlights

The posttranslational modification Sumoylation of proteins to a specific lysine (K) residue in target protein by the small ubiquitin-related modifier (SUMO) protein family regulates diverse cellular processes, including protein stabilization, gene transcription, regulation of protein function, protein-protein and protein-DNA interaction and so forth
After 6 h, we found that Ginkgolic acid (GA) significantly promoted the expression of specificity protein1 (Sp1) and Peroxiredoxin 6 (Prdx6) mRNA in concentration-dependent fashion (Figure 1A, left panel Sp1 mRNA and right panel Prdx6 mRNA; gray vs. black bars)
In another set of GA-treated mouse LECs (mLECs) (Figure 1C), cellular extract immunoblotted with anti-Sp1 or anti-Prdx6 antibodies revealed a significant increase in expression of both the proteins, with maximum expression levels observed at 80 μM and 100 μM of GA concentration, which was consistent with increased expression of mRNA (Figure 1A)

Summary

Introduction

The posttranslational modification Sumoylation of proteins to a specific lysine (K) residue in target protein by the small ubiquitin-related modifier (SUMO) protein family regulates diverse cellular processes, including protein stabilization, gene transcription, regulation of protein function, protein-protein and protein-DNA interaction and so forth. The Sumoylation process can be disturbed by various physiological and environmental stressors Among these are oxidative stress caused by overproduction of intracellular reactive oxygen species (ROS) in response to external stimuli and loss of antioxidant proteins in aging [12,13,14,15]. Recent evidence reveals that a disturbance in the Sumoylation process results in the onset and progression of several disorders [22,23,24,25,26] Based on these facts, we hypothesized that blocking aberrant Sumoylation by means of Sumoylation inhibitors should be a logical strategy to reverse aberrant Sumoylation-mediated pathobiology of cells/tissues by restoring the cellular proteins responsible for maintaining cell homeostasis

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