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PKG-Mediated Phosphorylation of TOP2A Activates HDAC to Drive Photoreceptor Cell Death in rd1 Mouse Inherited Retinal
Yujie Dong1, Wandong Zuo1,2, Yan Li1
1Key Laboratory of Yunnan Province, Yunnan Eye Institute, Affiliated Hospital of Yunnan University, Yunnan University, Kunming, Yunnan, China.
Abstract:
Inherited retinal degeneration (IRD) is a debilitating condition characterized by progressive loss of photoreceptor cells. However, the underlying mechanisms remain largely unclear. This study investigated the role of DNA topoisomerase II alpha (TOP2A) and its interplay with protein kinase G (PKG) and histone deacetylase (HDAC) in the rd1 mouse model for IRD. Immunofluorescence and quantitative western blotting analyses were performed to evaluate the expression of TOP2A, PKG1, PKG2, HDAC1, and other related markers. TSC24 and suberoylanilide hydroxamic acid were used to specifically inhibit TOP2A and HDAC, respectively, in organotypic retinal explant cultures derived from wild-type or rd1 mice. Furthermore, we examined the effect of PKG activity on TOP2A phosphorylation using KT5823. Significant upregulation of TOP2A was observed in the rd1 mouse retina compared with wild-type controls, especially in the outer nuclear layer. Phosphorylation levels of TOP2A strongly correlated with photoreceptor cell death. Treatment with TSC24 significantly reduced TOP2A-positive and TUNEL-positive cells. TOP2A phosphorylation was accompanied by HDAC activation, which was mitigated by TSC24. PKG inhibition by KT5823 reduced TOP2A phosphorylation at specific residues and photoreceptor HDAC activity. Our findings position TOP2A in the PKG-TOP2A-HDAC photoreceptor degenerative pathway, offering new potential therapeutic targets for combating IRD-type diseases.
Insights
DNA topoisomerase II alpha (TOP2A) is upregulated in inherited retinal degeneration (IRD). Inhibiting TOP2A and its associated pathway (PKG-TOP2A-HDAC) shows promise for treating photoreceptor cell loss in IRD.
Area of Science:
- Ophthalmology
- Molecular Biology
- Genetics
Background:
- Inherited retinal degeneration (IRD) causes progressive photoreceptor cell loss.
- The molecular mechanisms driving IRD remain incompletely understood.
- This study focuses on the rd1 mouse model, a common model for IRD.
Purpose of the Study:
- Investigate the role of DNA topoisomerase II alpha (TOP2A) in IRD.
- Explore the interplay between TOP2A, protein kinase G (PKG), and histone deacetylase (HDAC) in photoreceptor degeneration.
- Identify potential therapeutic targets for IRD.
Main Methods:
- Utilized immunofluorescence and quantitative western blotting to assess protein expression in rd1 and wild-type mouse retinas.
- Employed specific inhibitors (TSC24 for TOP2A, suberoylanilide hydroxamic acid for HDAC) in retinal explant cultures.
- Examined the effect of PKG inhibition (KT5823) on TOP2A phosphorylation and HDAC activity.
Main Results:
- TOP2A was significantly upregulated in rd1 mouse retinas, particularly in the outer nuclear layer.
- TOP2A phosphorylation levels correlated strongly with photoreceptor cell death.
- Inhibition of TOP2A (TSC24) reduced TOP2A-positive and TUNEL-positive cells, mitigating HDAC activation.
- PKG inhibition (KT5823) decreased TOP2A phosphorylation and photoreceptor HDAC activity.
Conclusions:
- Established a novel PKG-TOP2A-HDAC pathway implicated in photoreceptor degeneration in IRD.
- TOP2A is a key player in the degenerative process.
- Targeting the PKG-TOP2A-HDAC pathway presents a potential therapeutic strategy for IRD.
