All ETDs from UAB

Advisory Committee Chair

Marina Gorbatyuk

Advisory Committee Members

Alecia Gross

Mohammad Athar

Shu- Zhen Wang

Thomas Norton

Document Type

Dissertation

Date of Award

2015

Degree Name by School

Doctor of Philosophy (PhD) School of Optometry

Abstract

The photoreceptor cell death in autosomal dominant retinitis pigmentosa (ADRP) is associated with molecular changes that occur due to mutations in a specific gene. S334ter RHO and P23H RHO are two ADRP rat models expressing mutant rhodopsin. The unfolded protein response (UPR) is a cellular stress response involved in the pathophysiology of several retinal disorders including P23H RHO rats. Considering our previous findings, we started our investigation by examining the status of UPR in S334ter RHO rats. As UPR tightly regulates several signaling pathways, we further studied whether UPR activation in S334ter and P23H RHO retina is accompanied by the changes in other cellular pathways such as autophagy, inflammation, calcium signaling and mitochondria dependent and independent apoptosis. By gene and protein expression profiling in S334ter RHO retina, we demonstrated the activation of UPR at postnatal day (P) 15. We have also noticed that activated UPR in S334ter RHO is accompanied with alterations in the expression of BCL2 family genes, oxidative stress associated genes and caspases. In P23H RHO retina we examined the changes in autophagy, mTOR/AKT and BCL2 family proteins. Our data demonstrated that P23H RHO retina experiences significant decline in the expression of autophagy associated proteins whereas marked overproduction in mTOR, which is a negative regulator of autophagy. We have observed a delay in retinal degeneration in P23H rats upon the modulation of mTOR with rapamycin. The UPR and calcium dysregulation are tightly linked mechanisms, therefore we validated whether both the ADRP model retinas experience a dysregulation in calcium homeostasis. Through retinal calcium imaging we noticed an elevated cytoplasmic Ca2+ in both ADRP model retinas together with calpain activation. After examining the activity of several calcium sensing proteins and calcium channels, we validated that UPR induced ER Ca2+ depletion plays a significant role in the progression of retinal degeneration in S334ter and P23H RHO retinas. In a series of experiments in both ADRP model retinas, we have also found disrupted mitochondrial permeability, which can trigger apoptotic events. Our study has revealed several novel potential therapeutic targets from UPR, apoptotic and calcium regulatory pathways. Modulation of these molecular targets could potentially reduce the rate of retinal degeneration.

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