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Nadezda A. Stepicheva, Joseph Weiss, Peng Shang, Meysam Yazdankhah, Sayan Ghosh, Imran Ahmed Bhutto, Stacey L Hose, J Samuel Zigler, Jr, Debasish Sinha; Lysosomal distribution and function may be affected by the cell type and spatial localization of the cell within the tissue. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5981.
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© ARVO (1962-2015); The Authors (2016-present)
For a long time, lysosomes were considered to be just “trash cans” of the cells; however, recently it has become apparent that they also play a critical role in cell signaling. Highly efficient and perfectly timed lysosomal activity in the retinal pigmented epithelium (RPE) cells is critical for coping with the immense load of phagosomes needed to clear the shedding outer segments of photoreceptors to maintain retinal health. We hypothesize that lysosomal distribution and function may differ between cell types and might be unique in the RPE.
For this study, three cell types were selected: 1) polarized and highly phagocytic RPE, 2) non-polarized and highly phagocytic macrophages and microglia and 3) polarized, but not phagocytic gut epithelial cells. For the initial analysis, live cell imaging was performed in primary mouse RPE or microglia cultures, human ARPE-19 cell line and freshly obtained mouse peritoneal macrophages using Lyso-tracker (to label acidic organelles) and pHrodo labeled dextran (to label newly formed phagosomes). Immunostaining against lysosomal LAMP1 was performed on cryopreserved sections of mouse gut epithelium. The identity of the cells was confirmed by cell-specific markers: CD68 (macrophages), Iba1 (microglia) and EpCAM (gut epithelial cells).
Preliminary observations indicated that lysosomes mostly co-localized with phagosomes in macrophages or microglia, but not in the RPE. Interestingly, lysosomal distribution in the gut villi was found to vary during development: at P5 the gut epithelial cells located near the tip of the villi were significantly enriched in lysosomes as compared to those located closer to the crypt. Two days later this difference was less profound reaching an even distribution of lysosomes along the villi by P14.
Preliminary data indicate that lysosomal distribution may be affected not only by the cell type but also by the spatial localization of the cell within the tissue, which is consistent with the proposed hypothesis. Further experiments will be aimed at testing whether lysosomal function varies among different cell types, with emphasis on understanding the molecular mechanisms and consequences of the observed differences. This work will contribute to a novel in-depth understanding of cell-specific lysosomal functions.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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