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E Sugano, H Tomita, T Abe, M Tamai; Cathepsin D and S in rat IPE and RPE . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3438.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To investigate the capacity of lysosomal enzymes in photoreceptor outer segment(POS)'s phagocytosis process, the Aspartic protease, Cathepsin D (Cat D) and the Cystein protease, Cathepsin S (Cat S) of iris pigment epithelial cell (IPE) and retinal pigment epithelial cell (RPE) were measured by their specific enzyme activities and the expression of mRNAs. Methods:The rat IPE and RPE were isolated from Long evans rat eyes. The mRNA expression of Cat D and S in the freshly prepared- and cultured- IPE, RPE were investigated by semi-quantitative RT-PCR. The enzyme activity of Cat D and S in cultured IPE or RPE was measured by using fluorogenic substrate, MOCAc-Gly-Lys-Pro-Ile-Leu-Phe-Phe-Arg-Leu-Lys-(Dnp)D-Arg-NH2 and Z-Val-Val-Arg-MCA, respectively. The non-specific enzymes activities were suppressed by inhibitor or optimal pH. The western blot analysis for both proteins were also performed. Results:The mRNA expression of Cat D and S in freshly prepared- and cultured- RPE was higher than that of IPE. Cat D activity of RPE was about 100 times higher than that of IPE and Cat S activity of RPE was about 3 times higher than that of IPE. The results were also comparable with that of western blot analysis. Conclusion:To our knowledge, this is the first report to measure Cat D and S activity in IPE and RPE. Cat D and S are well-known lytic enzymes in digestion of POS in RPE. In mRNA expression and enzyme activity, protein expression, Cat D and S of RPE were higher than that of IPE. These results indicated that it might be one reason why RPE could phagocyte more effectively than IPE, and that IPE had a similar function of RPE in digestion of phagosytosed POS.
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