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Merideth Kamradt Krevosky, Jeffery Bowen; Looking into the Crystallin Ball: αB-crystallin is cleaved coincident with inflammasome activation in retinal epithelial cells. Invest. Ophthalmol. Vis. Sci. 2016;57(12):6538.
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© ARVO (1962-2015); The Authors (2016-present)
Inhibitors of apoptosis are upregulated in cancer, conferring cellular survival, while downregulated in degenerative diseases. αB-crystallin cleavage and inactivation is coincident with destructive endophthalmitis and loss of retinal function, supporting αB-crystallin’s protective role in the retina. αB-crystallin is expressed in retinal pigmented epithelial (RPE) cells and in drusen of patients with age-related macular-degeneration (AMD). While this protein has been suggested as a potential biomarker for AMD, the functionality of this protective protein has not been characterized. Research implicates inflammation in retinal destruction during AMD which involves the inflammasome, a complex which promotes cell death via pyroptosis. Studies herein address the hypothesis that αB-crystallin is cleaved during inflammasome activation in RPE cells.
RPE cells were activated with IL-1a (10ng/ml) for 18h, treated for 2h with the lysosomal disrupting agent, L-Leucyl-L-leucine methyl ester (LeuLeuOMe, 1mM) and collected for lysosomal, immunocytochemical or Western Blot analysis.
LeuLeuOMe treatment culminates in cell death and activation of the inflammasome, as evidenced by Caspase-1 activation. The number and size of lysosomes increase in response to LeuLeuOMe and αB-crystallin co-localizes in lysosomes, suggesting that this protein is trafficked to and destroyed in lysosomes, potentially preventing its protective role. Western blot analysis supports that αB-crystallin is cleaved in LeuLeuOMe-treated RPE cells suggesting that αB-crystallin is inactivated during inflammasome activation. Taken together, these results support that loss of αB-crystallin correlates with retinal cell destruction.
These studies support that cleavage of αB-crystallin may render it nonfunctional due to localization within cellular lysosomes. As such, cleavage of αB-crystallin likely abrogates its protective effects, which may underlie retinal cell destruction during inflammasome activation. Therefore, ongoing studies will determine whether the protein is exported from the cell, where it may accumulate in retinal spaces resulting in the hallmarks of AMD. Since few therapeutic interventions exist for AMD, modulation of αB-crystallin expression may promote retinal cell viability and prevent vision loss.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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