Abstract
Purpose :
Multiple studies suggested that alterations in the ability to maintain a healthy proteome contribute to cell death. The Ubiquitin Proteasome System (UPS) is a complex fine-tuned cellular network that includes hundreds of proteins working in concert with chaperone and autophagy systems. A potentially efficient strategy to manipulate the complex cellular system is to target transcriptional factors or pathways controlling the expression levels of its key components. Here, we identified the Nuclear factor erythroid-2-like (Nfe2l1) transcriptional factor as a powerful master regulator controlling the expression of many genes involved in protein folding and degradation.
Methods :
To study the role of Nfe2l1 in the retina, we used mice overexpressing and lacking the Nfe2l1 gene. Transcriptional changes were assessed using bulk and single cell RNAseq. The changes in efficiency of protein degradation were studied in mouse models of photoreceptor degeneration expressing UPS reporter. The proteasomal activity was measured using fluorogenic peptidase assays. Retinal function was assessed with electroretinography (ERG), an impact on retinal structure was studied with Optical Coherence Tomography (OCT), morphometric analysis and immunolocalization studies.
Results :
We report the critical role of Nfe211 in the control of proteasomes in the retina: its overexpression increases, and knockout reduces the proteasome pool and activity. An overexpression of Nfe2l1 does not have adverse effects on retinal structure and function. Furthermore, Nfe2l1 overexpression improved clearance of in vivo UPS reporter in photoreceptors of two mouse models of retinal degeneration stressed by cytosolic and transmembrane misfolded proteins. Finally, we showed that Nfe2l1 overexpression delayed visual loss in a heterozygote RhoP23H/WT knock-in mouse model of human blindness. Transcriptional studies revealed that Nfe2l1 regulates a wide range of proteostasis related genes, including regulators of autophagy, ubiquitination/deubiquitination, chaperones, as well as genes controlling antioxidative stress response. Loss Nfe2l1 leads to progressive retinal thinning, with particularly prominent loss of ganglion and horizontal cells.
Conclusions :
The findings highlight Nfe2l1 as an emerging therapeutic target to treat neurodegenerative diseases linked to protein misfolding and emphasize critical role of tight proteostasis control in retinal viability.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.