Department of Pharmacology, College of Pharmacy, Dankook University, Cheonan-si, Chungnam, South Korea.
Department of Nanobiomedical Science & BK21 PLUS NBM Global Research Center for Regenerative Medicine, Dankook University, Cheonan-si, Chungnam, South Korea.
Biochem Biophys Res Commun. 2014 Jul 18;450(1):372-7. doi: 10.1016/j.bbrc.2014.05.132. Epub 2014 Jun 2.
Glutamate carboxypeptidase II (GCPII) is known to be implicated in brain diseases such as schizophrenia and bipolar disorder, and dramatically increases in prostate cancer. Here, we investigated the regulation of GCPII expression in astrocytes and examined whether GCPII is epigenetically regulated through histone modification. In this study, valproic acid (VPA), a drug used for bipolar disorder and epilepsy and a known histone deacetylase (HDAC) inhibitor was used. We found that acute exposure of VPA for 4-6h increased the GCPII protein level in human astrocyte U87MG cells but did not have a similar effect after 12-24h exposure. Real-time polymerase chain reaction analysis revealed that VPA did not affect the GCPII mRNA expression. In contrast, decrease in GCPII protein level by cycloheximide treatment was blocked by VPA, indicating that VPA increases GCPII protein stability. Treatment with MG132, a proteasome inhibitor, suggested that the VPA-induced increase of GCPII protein level is dependent on the ubiquitin/proteasome pathway. In addition, immunoprecipitation analysis revealed that VPA increased the acetylation of GCPII protein at the lysine residues and facilitated a decrease of the poly-ubiquitinated GCPII level. Similarly, M344, a specific HDAC 1/6 inhibitor, also increased the GCPII protein level. In contrast, treatment with C646, a histone acetyltransferase inhibitor of p300/CBP, significantly reduced the level of GCPII protein. Taken together, this study demonstrated that the increase in GCPII induced by VPA is not due to the classical epigenetic mechanism, but via enhanced acetylation of lysine residues in GCPII.
谷氨酸羧肽酶 II（GCPII）已知与精神分裂症和双相情感障碍等脑部疾病有关，并在前列腺癌中显著增加。在这里，我们研究了星形胶质细胞中 GCPII 表达的调节，并检查了 GCPII 是否通过组蛋白修饰被表观遗传调控。在这项研究中，使用了丙戊酸（VPA），一种用于治疗双相情感障碍和癫痫的药物，也是一种已知的组蛋白去乙酰化酶（HDAC）抑制剂。我们发现，VPA 急性暴露 4-6 小时会增加人星形胶质细胞 U87MG 细胞中的 GCPII 蛋白水平，但在 12-24 小时暴露后没有类似的效果。实时聚合酶链反应分析显示，VPA 不影响 GCPII mRNA 表达。相比之下，VPA 阻断了细胞松弛素 D 处理引起的 GCPII 蛋白水平下降，表明 VPA 增加了 GCPII 蛋白稳定性。用蛋白酶体抑制剂 MG132 处理表明，VPA 诱导的 GCPII 蛋白水平增加依赖于泛素/蛋白酶体途径。此外，免疫沉淀分析显示，VPA 增加了 GCPII 蛋白赖氨酸残基的乙酰化，并促进了多聚泛素化 GCPII 水平的降低。同样，特异性 HDAC1/6 抑制剂 M344 也增加了 GCPII 蛋白水平。相反，组蛋白乙酰转移酶 p300/CBP 的抑制剂 C646 显著降低了 GCPII 蛋白水平。总之，这项研究表明，VPA 诱导的 GCPII 增加不是由于经典的表观遗传机制，而是通过增强 GCPII 赖氨酸残基的乙酰化。
