School of Optometry, Indiana University, Bloomington, IN 47405, USA.
Cells. 2021 Sep 22;10(10):2504. doi: 10.3390/cells10102504.
Lysosomes are important for proper functioning of the retinal pigment epithelial (RPE) cells. RPE cells have a daily burden of phagocytosis of photoreceptor outer segments (POS) and also degrade cellular waste by autophagy. Here, we identified the role of Zinc-finger protein with KRAB and SCAN domains 3 (ZKSCAN3) in co-ordinate regulation of lysosomal function and autophagy in the RPE. Our studies show that in the RPE, ZKSCAN3 is predominantly nuclear in healthy cells and its nuclear expression is reduced upon nutrient deprivation. siRNA-mediated knockdown of ZKSCAN3 results in de-repression of some of the ZKSCAN3 target genes. Knockdown of ZKSCAN3 also resulted in an induction in autophagy flux, increase in the number of functional lysosomes and accompanied activation of lysosomal cathepsin B activity in ARPE-19 cells. We also demonstrated that inhibition of P38 mitogen-activated protein kinase (MAPK) retains ZKSCAN3 in the nucleus in nutrient-deprived cells. In summary, our studies elucidated the role of ZKSCAN3 as a transcriptional repressor of autophagy and lysosomal function in the RPE.
溶酶体对于视网膜色素上皮 (RPE) 细胞的正常功能至关重要。RPE 细胞每天都要吞噬光感受器外节 (POS)，并通过自噬作用降解细胞废物。在这里，我们确定了锌指蛋白 KRAB 和 SCAN 结构域 3 (ZKSCAN3) 在 RPE 中协调溶酶体功能和自噬的作用。我们的研究表明，在 RPE 中，健康细胞中的 ZKSCAN3 主要存在于核内，而在营养剥夺时其核内表达减少。通过 siRNA 介导的 ZKSCAN3 敲低会导致一些 ZKSCAN3 靶基因的去抑制。ZKSCAN3 的敲低还导致自噬流的诱导、功能性溶酶体数量的增加，并伴随着 ARPE-19 细胞中溶酶体组织蛋白酶 B 活性的激活。我们还证明，抑制 p38 丝裂原活化蛋白激酶 (MAPK) 可将 ZKSCAN3 保留在营养剥夺细胞的核内。综上所述，我们的研究阐明了 ZKSCAN3 作为 RPE 中自噬和溶酶体功能的转录抑制因子的作用。
