Abstract
Purpose :
Multiple studies suggested that alterations in the cellular ability to maintain healthy proteome contribute to vision loss. The majority of proteins in any cells are degraded by Ubiquitin-Protein System (UPS), a complex cellular network that includes hundreds of proteins working in concert with chaperone and autophagy systems. A potentially efficient strategy to manipulate such complex cellular system is to target transcriptional factor(s) or pathways controlling the expression levels of its key components. Previous studies established transcriptional factor Nfe2l1 (Nuclear factor erythroid-2-like 1) as an activator of proteasomal gene expression in response to lethal concentrations of proteasomal inhibitors in cancer cells lines. Other studies suggested that Nfe2l1 instead regulates genes related to redox and anti-inflammatory response, cell regeneration and protection from cholesterol toxicity. Here, we used mouse genetics to define regulatory gene networks of Nfe2l1 in the retina.
Methods :
To understand the role of Nfe2l1, we studied retinal phenotypes of mice overexpressing or lacking Nfe2l1. Levels of proteasomes and other proteins were assessed using RNA-seq, qRT-PCR and WB. The proteasomal activity was measured using fluorogenic peptidase assay. Health, function, and structural changes of the retina were evaluated with OCT, ERG, morphometric and microscopic analysis.
Results :
Nfe2l1 overexpression increases levels and activity of proteasomes in the retina without affecting retinal morphology or function. Whole retina knockout of Nfe2l1 reduces the pool of proteasomes and their activity. This leads to progressive thinning of the retina, loss of photoreceptors and other retinal neurons with particularly pronounced loss of ganglion and horizontal cells. Transcriptional studies uncovered that in addition to proteasomal subunits, Nfe2l1 regulates critical autophagy genes, ubiquitin ligases, deubiquitinating enzymes and chaperones.
Conclusions :
Nfe2l1 is a powerful master regulator of proteostasis in the retina and controls expression of proteasomal components, wide range of proteins involved in the degradation of ubiquitinated proteins, chaperones and autophagy. The basal activity of Nfe2l1 sets proteolytic capacity of retinal neurons and plays an important role in retinal health. These findings warrant further studies of Nfe2l1 in the retina and support exploring an enhancement of this pathway with therapeutic goals.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.