Choe Eun Sang, Parelkar Nikhil K, Kim Jong Yeon, Cho Hyun Wook, Kang Ho Sung, Mao Limin, Wang John Q
Division of Biological Sciences, Pusan National University, Pusan, Korea.
J Neurochem. 2004 Apr;89(2):383-90. doi: 10.1111/j.1471-4159.2003.02334.x.
Activation of group I metabotropic glutamate receptors (mGluRs) up-regulates transcription factor cyclic AMP response element-binding protein (CREB) and Elk-1 phosphorylation via extracellular signal-regulated kinase 1/2 (ERK1/2) in the striatum in vivo. Protein phosphatase 1/2A further regulates immediate early gene expression by inactivating (dephosphorylating) CREB. In this study, using semi-quantitative immunohistochemical and western blot analyses and in situ hybridization histochemistry, we found that intrastriatal infusion of the protein phosphatase 1/2A inhibitor okadaic acid (0.005, 0.05 and 0.5 nmol) increased CREB and Elk-1 phosphorylation and c-Fos immunoreactivity in the injected dorsal striatum in a dose-dependent manner. In addition, okadaic acid (0.05 and 0.5 nM) increased c-fos mRNA expression in the dorsal striatum in a dose-dependent manner. Intrastriatal infusion of the group I agonist 3,5-dihydroxyphenylglycine (DHPG) at 100 and 250 nM also increased CREB and Elk-1 phosphorylation. Pre-treatment of okadaic acid (0.05 nm) did not alter DHPG-induced increases in the phosphorylation of the two transcription factors. These data suggest that protein phosphatase 1/2A in striatal neurons is tonically active in dephosphorylating CREB and Elk-1 and thus suppressing constitutive c-fos mRNA and protein expression. Inhibition of the phosphatase 1/2A may contribute to the group I mGluR-regulated phosphorylation of these transcription factors and c-fos expression.
在体内，I 型代谢型谷氨酸受体（mGluRs）的激活通过细胞外信号调节激酶 1/2（ERK1/2）上调纹状体中转录因子环磷酸腺苷反应元件结合蛋白（CREB）和 Elk-1 的磷酸化。蛋白磷酸酶 1/2A 通过使 CREB 失活（去磷酸化）进一步调节即刻早期基因的表达。在本研究中，我们通过半定量免疫组织化学和蛋白质印迹分析以及原位杂交组织化学发现，向纹状体内注射蛋白磷酸酶 1/2A 抑制剂冈田酸（0.005、0.05 和 0.5 nmol）后，注射侧背侧纹状体中 CREB 和 Elk-1 的磷酸化以及 c-Fos 免疫反应性呈剂量依赖性增加。此外，冈田酸（0.05 和 0.5 nM）使背侧纹状体中 c-fos mRNA 表达呈剂量依赖性增加。向纹状体内注射 100 和 250 nM 的 I 型激动剂 3,5-二羟基苯甘氨酸（DHPG）也增加了 CREB 和 Elk-1 的磷酸化。预先注射冈田酸（0.05 nM）并未改变 DHPG 诱导的这两种转录因子磷酸化的增加。这些数据表明，纹状体神经元中的蛋白磷酸酶 1/2A 在使 CREB 和 Elk-1 去磷酸化从而抑制组成型 c-fos mRNA 和蛋白表达方面具有持续活性。抑制磷酸酶 1/2A 可能有助于 I 型 mGluR 调节这些转录因子的磷酸化和 c-fos 表达。
