Abstract
Purpose :
Retinal degenerations are caused by mutations in an unusually large number of genes making them difficult to study and treat. This is further complicated by multiple studies showing that different mutations in the same genes often lead to dissimilar progression of retinal degeneration. In our previous work we demonstrated that proteasomal overload is a common stress factor observed in several mouse models of retinal degeneration in which photoreceptors experience problems with protein folding/trafficking and outer segment formation. The goal of this work is to develop gene therapy based tools to manipulate proteasomal activity in retinal cells and assess their therapeutic potential to delay or halt retinal degenerations in mutation independent manner.
Methods :
Proteasomes are multi-subunit complexes assembled upon association of two principal components: the 20 core and the regulatory caps. The 20S core is responsible for the entire proteolytic process; however, its basal activity is very low in the absence of regulatory caps. The most common caps are 19S and 11S, which facilitate protein degradation in ubiquitin-dependent and -independent manners, respectively.
In this work we tested three approaches to modulate proteasomal activity: (1) by increasing the amounts of 11S regulators, (2) potentiation of 20S-19S complex interaction and (3) by increasing the basal proteasomal activity of 20S core.
The components of proteasomes were delivered to photoreceptors and RPE of wild type mice using AAV5 under the control of CAG promoter. Several months following intraocular delivery, mouse visual function was studied using two noninvasive technics: (i) electroretinography (ERG), a physiological method used to evaluate the visual function of retina and (ii) optical coherence tomography (OCT), a method that allow to monitor retinal morphology. At every time point a cohort of animals was humanely euthanized, their ocular tissue was collected and analyzed using morphometric analysis and proteolytic assays.
Results :
All tested approaches lead to an increase in proteasomal activity in retinal cells in the range from 15 to 60%. Furthermore, this increase in proteolytic capacity is well-tolerated and does not have any adverse effects on the health of photoreceptors or retinal pigment epithelium.
Conclusions :
Gene therapy could be used as efficient and non-toxic tool to manipulate proteasomal activity of photoreceptors and RPE.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.