Laboratory of Biological Macromolecules, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan.
Biochem J. 2012 Apr 1;443(1):75-84. doi: 10.1042/BJ20111889.
L-PGDS [lipocalin-type PGD (prostaglandin D) synthase] is a dual-functional protein, acting as a PGD2-producing enzyme and a lipid transporter. L-PGDS is a member of the lipocalin superfamily and can bind a wide variety of lipophilic molecules. In the present study we demonstrate the protective effect of L-PGDS on H2O2-induced apoptosis in neuroblastoma cell line SH-SY5Y. L-PGDS expression was increased in H2O2-treated neuronal cells, and the L-PGDS level was highly associated with H2O2-induced apoptosis, indicating that L-PGDS protected the neuronal cells against H2O2-mediated cell death. A cell viability assay revealed that L-PGDS protected against H2O2-induced cell death in a concentration-dependent manner. Furthermore, the titration of free thiols in H2O2-treated L-PGDS revealed that H2O2 reacted with the thiol of Cys65 of L-PGDS. The MALDI-TOF (matrix-assisted laser-desorption ionization-time-of-flight)-MS spectrum of H2O2-treated L-PGDS showed a 32 Da increase in the mass relative to that of the untreated protein, showing that the thiol was oxidized to sulfinic acid. The binding affinities of oxidized L-PGDS for lipophilic molecules were comparable with those of untreated L-PGDS. Taken together, these results demonstrate that L-PGDS protected against neuronal cell death by scavenging reactive oxygen species without losing its ligand-binding function. The novel function of L-PGDS could be useful for the suppression of oxidative stress-mediated neurodegenerative diseases.
L-PGDS（脂联素型 PG（前列腺素 D）合酶）是一种具有双重功能的蛋白质，既能产生 PGD2，又能作为脂质转运蛋白。L-PGDS 是脂联素超家族的成员，能够结合多种亲脂性分子。本研究表明 L-PGDS 对神经母细胞瘤细胞系 SH-SY5Y 中 H2O2 诱导的细胞凋亡具有保护作用。在 H2O2 处理的神经元细胞中，L-PGDS 的表达增加，L-PGDS 水平与 H2O2 诱导的细胞凋亡高度相关，表明 L-PGDS 可保护神经元细胞免受 H2O2 介导的细胞死亡。细胞活力测定表明，L-PGDS 以浓度依赖的方式保护细胞免受 H2O2 诱导的细胞死亡。此外，L-PGDS 中游离巯基的滴定表明，H2O2 与 L-PGDS 的 Cys65 巯基反应。MALDI-TOF（基质辅助激光解吸电离飞行时间）-MS 光谱显示，H2O2 处理的 L-PGDS 的质量比未经处理的蛋白质增加了 32 Da，表明巯基被氧化为亚磺酸。氧化的 L-PGDS 与亲脂性分子的结合亲和力与未经处理的 L-PGDS 相当。综上所述，这些结果表明 L-PGDS 通过清除活性氧而不丧失其配体结合功能来保护神经元细胞免于死亡。L-PGDS 的新功能可能有助于抑制氧化应激介导的神经退行性疾病。
