PDF(Pubmed)
Abstract：
Recessive Stargardt disease (STGD1) is an inherited juvenile maculopathy caused by mutations in the ABCA4 gene, for which there is no suitable treatment. Loss of functional ABCA4 in the retinal pigment epithelium (RPE) alone, without contribution from photoreceptor cells, was shown to induce STGD1 pathology. Here, we identified cathepsin D (CatD), the primary RPE lysosomal protease, as a key molecular player contributing to endo-lysosomal dysfunction in STGD1 using a newly developed \"disease-in-a-dish\" RPE model from confirmed STGD1 patients. Induced pluripotent stem cell (iPSC)-derived RPE originating from three STGD1 patients exhibited elevated lysosomal pH, as previously reported in Abca4-/- mice. CatD protein maturation and activity were impaired in RPE from STGD1 patients and Abca4-/- mice. Consequently, STGD1 RPE cells have reduced photoreceptor outer segment degradation and abnormal accumulation of α-synuclein, the natural substrate of CatD. Furthermore, dysfunctional ABCA4 in STGD1 RPE cells results in intracellular accumulation of autofluorescent material and phosphatidylethanolamine (PE). The altered distribution of PE associated with the internal membranes of STGD1 RPE cells presumably compromises LC3-associated phagocytosis, contributing to delayed endo-lysosomal degradation activity. Drug-mediated re-acidification of lysosomes in the RPE of STGD1 restores CatD functional activity and reduces the accumulation of immature CatD protein loads. This preclinical study validates the contribution of CatD deficiencies to STGD1 pathology and provides evidence for an efficacious therapeutic approach targeting RPE cells. Our findings support a cell-autonomous RPE-driven pathology, informing future research aimed at targeting RPE cells to treat ABCA4-mediated retinopathies.
摘要：
隐性Stargardt病（STGD1）是由ABCA4基因突变引起的遗传性青少年黄斑病，没有合适的治疗方法。视网膜色素上皮（RPE）中功能性ABCA4的丢失，没有感光细胞的贡献，显示诱导STGD1病理学。这里,我们鉴定了组织蛋白酶D（CatD），原发性RPE溶酶体蛋白酶，作为导致STGD1内溶酶体功能障碍的关键分子参与者，使用新开发的“培养皿中疾病”RPE模型从证实的STGD1患者中获得。来自三名STGD1患者的诱导多能干细胞（iPSC）衍生的RPE表现出溶酶体pH升高，如先前在Abca4-/-小鼠中报道的。来自STGD1患者和Abca4-/-小鼠的RPE中CatD蛋白成熟和活性受损。因此,STGD1RPE细胞有减少的光感受器外节降解和α-突触核蛋白的异常积累，CatD的天然底物。此外，STGD1RPE细胞中功能失调的ABCA4导致自发荧光材料和磷脂酰乙醇胺（PE）的细胞内积累。与STGD1RPE细胞内膜相关的PE分布改变可能会损害LC3相关的吞噬作用，有助于延迟内溶酶体降解活性。STGD1的RPE中的溶酶体的药物介导的再酸化可恢复CatD功能活性并减少未成熟CatD蛋白负荷的积累。该临床前研究验证了CatD缺陷对STGD1病理学的贡献，并为靶向RPE细胞的有效治疗方法提供了证据。我们的发现支持细胞自主RPE驱动的病理学，未来的研究旨在靶向RPE细胞治疗ABCA4介导的视网膜病变。
