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Suraj Bhat, Rajendra Gangalum, Ishanee Dighe, Ivo Atanasov, Z Hong Zhou, Larry David; The Small Heat Shock Protein αB-crystallin is required for Exosome Biogenesis in Adult Human Retinal Pigment Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1202.
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The expression of the small heat shock protein αB-crystallin is developmentally controlled and is known to be associated with a myriad of neuro-degenerations including Alzheimer’s disease, multiple sclerosis and age-related macular degeneration (AMD). We have previously shown that αB-crystallin is a Golgi membrane-associated protein, which is secreted from adult human retinal pigment epithelial cell (ARPE19) via exosomes (Gangalum et al., J Biol Chem. 286:3261-9, 2011). In this investigation we have probed the relevance of αB-crystallin to RPE function and intercellular communication via exosomes.
Employing shRNA technologies to inhibit specific gene expression we have generated stably transfected ARPE19 cells lines in which αB-crystallin expression is variably inhibited. We have used Fluorescence activated Cell sorting analyses, immunofluorescence, electron microscopy and biochemical characterizations and polarized cell cultures.
Analyses of various cell lines expressing differential amounts of αB-crystallin protein show that absence of αB-crystallin protein has a significant impact on exosome biogenesis in human RPE cells in culture. Examination of various exosome markers and their status reveals that specific stages of exosome biogenesis are interfered with in the absence of this small heat shock protein.
Based on known cell-type-specificity of the molecular cargo of the exosomes these data indicate that cell-type specific proteins such as αB-crystallin may control intercellular communication in a cell-type specific fashion (and therefore, RPE physiology) by regulating exosome biogenesis.
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