Swan Jaclyn, Toomey Christopher B, Bergstrand Max, Cuello Hector A, Robie Jesse, Yu Hai, Yuan Yue, Kooner Anoopjit Singh, Chen Xi, Shaughnessy Jutamas, Ram Sanjay, Varki Ajit, Gagneux Pascal
Department of Pathology, University of California - San Diego, La Jolla, California, United States.
Shiley Eye Institute, Viterbi Family Department of Ophthalmology University of California - San Diego, La Jolla, California, United States.
Invest Ophthalmol Vis Sci. 2025 Jun 2;66(6):81. doi: 10.1167/iovs.66.6.81.
Little is known about sialic acids of the human retina, despite their integral role in self /non-self-discrimination by complement factor H (FH), the alternative complement pathway inhibitor.
A custom sialoglycan microarray was used to characterize the sialic acid-binding specificity of native FH or recombinant molecules where IgG Fc was fused to FH domains 16 to 20 (which contains a sialic acid-binding site), domains 6 and 7 (which contains a glycosaminoglycan-binding site), or the FH-related proteins (FHRs) 1 and 3. We analyzed macular and peripheral retinal tissue from postmortem ocular globes for the amount, type, and presentation (glycosidic linkage type) of sialic acid in individuals with age-related macular degeneration (AMD) and age-matched controls using fluorescent lectins and antibodies to detect sialic acid and endogenous FH. Released sialic acids from neural retina, retinal pigmented epithelium (RPE) cells, and the Bruch's membrane (BrM) were labeled with 1,2-diamino-4,5-methylenedioxybenzene-2HCl (DMB), separated and quantified by high-performance liquid chromatography (HPLC).
Both native FH and the recombinant FH domains 16 to 20 recognized Neu5Ac and Neu5Gc that is α2-3-linked to the underlying galactose. 4-O-Actylation of sialic acid and sulfation of GlcNAc did not inhibit binding. Different linkage types of sialic acid were localized at different layers of the retina. The greatest density of α2-3-sialic acid, which is the preferred ligand of FH, did not colocalize with endogenous FH. The level of sialic acids at the BrM/choroid interface of the macula and peripheral retina of individuals with AMD were significantly reduced.
The sialome of the human retina is altered in AMD. This may affect FH binding and, consequently, alternative complement pathway regulation.
尽管唾液酸在补体因子H（FH，替代补体途径抑制剂）介导的自身/非自身识别中发挥着不可或缺的作用，但人们对人视网膜中的唾液酸却知之甚少。
使用定制的唾液酸聚糖微阵列来表征天然FH或重组分子的唾液酸结合特异性，这些重组分子包括与FH结构域16至20（包含唾液酸结合位点）、结构域6和7（包含糖胺聚糖结合位点）融合的IgG Fc，或FH相关蛋白（FHRs）1和3。我们使用荧光凝集素和抗体来检测唾液酸和内源性FH，分析了来自死后眼球的黄斑和周边视网膜组织中，年龄相关性黄斑变性（AMD）患者和年龄匹配对照组的唾液酸含量、类型和呈现方式（糖苷键类型）。用1,2 - 二氨基 - 4,5 - 亚甲基二氧基苯 - 2HCl（DMB）标记从神经视网膜、视网膜色素上皮（RPE）细胞和布鲁赫膜（BrM）释放的唾液酸，通过高效液相色谱（HPLC）进行分离和定量。
天然FH和重组FH结构域16至20均识别与下层半乳糖α2 - 3连接的Neu5Ac和Neu5Gc。唾液酸的4 - O - 乙酰化和GlcNAc的硫酸化不抑制结合。不同连接类型的唾液酸定位于视网膜的不同层。作为FH的首选配体的α2 - 3 - 唾液酸的最大密度区域与内源性FH不共定位。AMD患者黄斑和周边视网膜的BrM/脉络膜界面处的唾液酸水平显著降低。
AMD患者的人视网膜唾液酸组发生改变。这可能影响FH结合，进而影响替代补体途径的调节。
