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Ching-Hwa Sung, Kuo-Shun Hsu, Wataru Otsu, Jen-Zen Chuang; Endosome Trafficking and Matrix Degradation of MMP14 in RPE Cells. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3991.
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Dysregulated extracellular matrix (ECM) remodeling has been long implicated in the etiology and/or advancement of dry age-related macular degeneration (AMD). The mechanism underlying the ECM homeostasis in the retinas is not well understood. We tested the hypothesis that the membrane-type metalloproteinase matrix metalloproteinase 14 (MMP14 or MT1-MMP) plays an important role in the ECM degradation of retinal pigment epithelial (RPE) cells. Chloride intracellular channel 4 (CLIC4) is a novel MMP14 binding protein and has a role in endosomal trafficking and maintaining the structural integrity of the retina-RPE-choroidal complex. We investigated the hypothesis that CLIC4 regulates the targeting and ECM degradation of MMP14 in RPE cells.
We subjected ARPE19 cells to a previously established gelatin-degrading assay, in which the membrane localized MMP cleaved the fluorescein-gelatin matrix, leaving dark footprints underneath. We performed immunostaining and reporter assays to characterize the pericellular degradation loci, and the distribution of MMP14 and CLIC4 in RPE cells, both in vitro and in vivo. We characterize the mechanism regulating the genesis of the degradation loci in RPE cells using pharmacological and gene silencing approaches.
MMP14 was detected in the nascent focal adhesion near the cell border, where matrix degradation takes place in RPE cells. MMP14 and CLIC4 are both indispensable for the pericellular ECM degradation. MMP14 and CLIC4 are colocalized in the late endosome. Silencing CLIC4 perturbed the endosomal sorting of MMP14 and its surface proteolytic activity. Mechanistically, we identified the amino acid residues of CLIC4 that is critical for the late endosomal sorting of MMP14.
MMP14, primary stored in the late endosome, is central to the extracellular matrix degradation at focal adhesions in RPE cells. CLIC4 is pivotal in modulating the matrix microenvironment of RPE through regulating the endocytic trafficking of MMP14.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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