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David Castillejos, Carlos Carvajal, Julia Grandjean, Edith Aguilar, Ayumi Ouchi, Wei-Chieh Jerry Chiang, Luke Wiseman, Jonathan H Lin; Intravitreal injection of novel small molecule proteostasis regulators activates the Unfolded Protein Response in murine retina. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4877.
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© ARVO (1962-2015); The Authors (2016-present)
Disruption of protein homeostasis has been observed in multiple retinal degeneration disease models. The Unfolded Protein Response (UPR) is a conserved signal transduction pathway in the cells that maintains cellular homeostasis by increasing ER protein folding capacity or degradation. Nontoxic small molecule proteostasis regulators have been identified that can activate different UPR signaling pathways in cell culture models. These small molecules, if they are effective in the eyes, maybe a potential therapeutic strategy to treat retinal diseases arising from the loss of ER proteostasis. Here we performed intravitreal injections of proteostasis regulators that activate IRE1 branch of UPR signaling pathways into mouse eyes and assessed the activation of the UPR in the retina, via qPCR and RNA-Seq analysis.
31 Female C57BL/6J mice (P90) were used for intravitreal injections. Control injections of PBS were administered intravitreally to the left eye of each mouse. The right eye was intravitreally injected with IRE1 activating small molecule proteostasis regulators (10uM). Six hours after injection, we isolated the retinas and extracted the retinal mRNA for qPCR and RNA-Seq analysis to assess the activation of IRE1, ATF6, and PERK pathways.
Retinas injected with IRE1 activating small molecule proteostasis regulators, when compared to retinas injected with PBS, showed a statistically significant increase in Xbp1 mRNA splicing (1.5 fold), demonstrating increased activation of the IRE1 pathway (p-value 0.0037). There were no statistically significant changes in the mRNA levels of Chop and Grp78, suggesting that PERK and ATF6 pathways were not activated by IRE1 activating small molecule.
We showed that intravitreal injections of an IRE1 activating small molecule proteostasis regulator is effective in selectively activating IRE1 branch of UPR signaling pathways. These results suggest that intravitreal injections of these molecules may have therapeutic benefits for protein misfolding disorders, while diminishing the risk of retinal detachments more common in subretinal injections. This small molecule proteostasis regulator’s effectiveness shows promise as a therapeutic strategy moving forward.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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