Unfolded Protein Response as a Therapeutic Target for ADRP Animal Models This project is focused on the elucidation of the role of the Unfolded Protein Response (UPR) in autosomal dominant retinitis pigmentosa (ADRP) pathogenesis and development of the gene therapy based on modulation of the UPR signaling markers. Retinitis pigmentosa (RP) is the most common inherited form of blindness, affecting about 1 in every 4000 people in all ethnic groups worldwide. RP can be transmitted either as an autosomal dominant (ADRP), autosomal recessive (ARRP), or X-linked trait. More than 100 mutations in rhodopsin account for approximately 30% of ADRP cases with varying severity of visual impairment. Misfolded opsin interferes with the trafficking of wild-type rhodopsin, accumulates in the endoplasmic reticulum (ER) and stimulates a signal transduction cascade known as the Unfolded Protein Response (UPR). If unchecked, this pathway triggers photoreceptor death, presumably through apoptosis. Although supplementation with vitamin A may be beneficial in some cases, currently, there is no effective pharmacological therapy for ADRP. Therefore, the major objective of this proposal is to determine whether the gene therapy based on the re-programming of the ER stress response caused by aberrant rhodopsin is a viable treatment, unlimited by different localizations of rhodopsin mutations (P23H and T17M). In two mouse models of ADRP, we plan to reprogram the ER stress signaling by viral delivery of the molecular chaperone GRP78/BiP and delivery of small interfering siRNAs targeting caspase-7, caspase-12 and pro-apoptotic CHOP/GADD153 mRNAs to diminish the level of apoptosis in ADRP photoreceptors. For each ADRP model, we plan to: (1) modulate the UPR in favor of activation of pro-survival pathway by over- expression of BiP protein;(2) suppress apoptosis by diminishing levels of activated caspase-7 and caspase-12 and (3) inhibit the CHOP-associated apoptosis by targeting CHOP mRNA. We will monitor survival of photoreceptors using electroretinography and morphometry and will measure the activation of the ER stress and apoptosis using specific antibodies and RT-PCR. We will also measure improvement in vision using Optometry, a technique that can evaluate both acuity and contrast sensitivity in mice. We anticipate that the success of this approach will also require the appropriate combination of AAV serotype, vector dosage, photoreceptor specific promoter and optimized expression for the chaperone BiP. While AAV mediated gene transfer is being developed for treatment of RP, the suppression of ER stress and of apoptosis using chaperones is novel. This approach may overcome the genetic diversity of this disease and reveal the pathways of cell death that lead from mutation to retinal degeneration.
Our goal is to design gene therapy for blinding disorder known as Autosomal Dominant Retinitis Pigmentosa (ADRP). We plan to study cellular mechanisms involved in photoreceptor death and develop a gene therapy based on the blockage of apoptosis in ADRP photoreceptors. Using a harmless virus, we plan to deliver molecular chaperon BiP and small RNA molecules to improve function and structure of photoreceptors and also intend to study the mechanism by which these therapeutic molecules provide therapy.
|Shinde, V; Kotla, P; Strang, C et al. (2016) Unfolded protein response-induced dysregulation of calcium homeostasis promotes retinal degeneration in rat models of autosomal dominant retinitis pigmentosa. Cell Death Dis 7:e2085|
|Chiang, Wei-Chieh; Joseph, Victory; Yasumura, Douglas et al. (2016) Ablation of Chop Transiently Enhances Photoreceptor Survival but Does Not Prevent Retinal Degeneration in Transgenic Mice Expressing Human P23H Rhodopsin. Adv Exp Med Biol 854:185-91|
|Gully, Joseph C; Sergeyev, Valeriy G; Bhootada, Yogesh et al. (2016) Up-regulation of activating transcription factor 4 induces severe loss of dopamine nigral neurons in a rat model of Parkinson's disease. Neurosci Lett 627:36-41|
|Bhootada, Yogesh; Kotla, Pravallika; Zolotukhin, Sergei et al. (2016) Limited ATF4 Expression in Degenerating Retinas with Ongoing ER Stress Promotes Photoreceptor Survival in a Mouse Model of Autosomal Dominant Retinitis Pigmentosa. PLoS One 11:e0154779|
|Shinde, Vishal; Pitale, Priyamvada M; Howse, Wayne et al. (2016) Neuronatin is a stress-responsive protein of rod photoreceptors. Neuroscience 328:1-8|
|Salganik, Maxim; Sergeyev, Valeriy G; Shinde, Vishal et al. (2015) The loss of glucose-regulated protein 78 (GRP78) during normal aging or from siRNA knockdown augments human alpha-synuclein (Î±-syn) toxicity to rat nigral neurons. Neurobiol Aging 36:2213-23|
|Bhootada, Yogesh; Choudhury, Shreyasi; Gully, Clark et al. (2015) Targeting Caspase-12 to Preserve Vision in Mice With Inherited Retinal Degeneration. Invest Ophthalmol Vis Sci 56:4725-33|
|Murray, Anne R; Vuong, Linda; Brobst, Daniel et al. (2015) Glycosylation of rhodopsin is necessary for its stability and incorporation into photoreceptor outer segment discs. Hum Mol Genet 24:2709-23|
|Lenox, Austin R; Bhootada, Yogesh; Gorbatyuk, Oleg et al. (2015) Unfolded protein response is activated in aged retinas. Neurosci Lett 609:30-5|
|Sizova, Olga S; Shinde, Vishal M; Lenox, Austin R et al. (2014) Modulation of cellular signaling pathways in P23H rhodopsin photoreceptors. Cell Signal 26:665-72|
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