State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou 510060, China.
Key Laboratory of Protein Chemistry and Developmental Biology, College of Life Sciences, Hunan Normal University, Changsha, China.
Curr Mol Med. 2018;18(9):575-583. doi: 10.2174/1566524019666190107154250.
Advanced age is the largest risk factor for age-related macular degeneration (AMD). Sumoylation is a reversible post-translational modification that conjugates small peptide, small ubiquitin-like modifier (SUMO), to a target protein. Dysregulation of sumoylation is recently found to be critically involved in several age-related disorders. However, the effects of sumoylation during retina senescence and aging remains elusive. This study is aimed to investigate the function and regulation of sumoylation pathway in the aging retina and premature senescent retinal pigment epithelial (RPE) cells.
1.5- and 10-month C57/B6 mice were used for comparative aging study. Both ARPE primary cultures and ARPE-19 cells were used for assay systems. The qRT-PCR was used for analysis of mRNA expression. Western blot and immunofluorescence were used to analyze the protein expression. Cell flow cytometry was used for cell cycle progression analysis. RPE barrier function and senescent-associated β-galactosidase (SA β-gal) activity were analyzed to measure cellular senescence.
We show that the expression of SUMO enzymes and global protein sumoylation were downregulated in the aging mouse retina, and in the oxidative stress (OS) -induced premature senescent RPE cells. Dramatical altered distribution of SUMO E1, E2 and E3 enzymes were observed during RPE senescence. Inhibition of sumoylation alleviated OS-induced cell senescence in RPE cells, as indicated by decreased p21 and p53 expression and decreased percentage of cell cycle arrest at G0/G1 phase. Intriguingly, inhibition of SUMO E1 repressed the expression of proinflammatory cytokine and chemokine in the premature senescent RPE cells. However, inhibition of sumoylation did not prevent DNA damage during the OS-induced RPE senescence process.
Our data indicate sumoylation critically regulates retina and RPE aging and that targeting sumoylation process may provide potential therapeutic strategy for AMD treatment.
年龄是与年龄相关的黄斑变性（AMD）的最大风险因素。SUMO 化是一种可逆的翻译后修饰，它将小肽、小泛素样修饰物（SUMO）与靶蛋白连接起来。最近发现，SUMO 化的失调与几种与年龄相关的疾病密切相关。然而，SUMO 化在视网膜衰老和老化过程中的作用仍不清楚。本研究旨在探讨 SUMO 通路在衰老视网膜和早发性衰老视网膜色素上皮（RPE）细胞中的功能和调节作用。
使用 1.5 个月和 10 个月的 C57/B6 小鼠进行比较衰老研究。均使用 ARPE 原代培养物和 ARPE-19 细胞作为检测系统。qRT-PCR 用于分析 mRNA 表达。Western blot 和免疫荧光用于分析蛋白质表达。细胞流式细胞术用于分析细胞周期进程。RPE 屏障功能和衰老相关的β-半乳糖苷酶（SAβ-gal）活性用于测量细胞衰老。
我们发现，SUMO 酶和全局蛋白 SUMO 化的表达在衰老的小鼠视网膜和氧化应激（OS）诱导的早发性衰老 RPE 细胞中均下调。在 RPE 衰老过程中观察到 SUMO E1、E2 和 E3 酶的分布发生了剧烈改变。抑制 SUMO 化可减轻 RPE 细胞中的 OS 诱导的细胞衰老，表现为 p21 和 p53 表达降低，G0/G1 期细胞周期阻滞比例降低。有趣的是，抑制 SUMO E1 可抑制早发性衰老 RPE 细胞中促炎细胞因子和趋化因子的表达。然而，抑制 SUMO 化并不能阻止 OS 诱导的 RPE 衰老过程中的 DNA 损伤。
我们的数据表明，SUMO 化对视网膜和 RPE 的衰老有重要的调节作用，靶向 SUMO 化过程可能为 AMD 的治疗提供潜在的治疗策略。
