Calpain-Mediated Degradation of G-Substrate Plays a Critical Role in Retinal Excitotoxicity for Amacrine Cells
Calpain-Mediated Degradation of G-Substrate Plays a Critical Role in Retinal Excitotoxicity for Amacrine Cells
复制标题
DOI：
10.1002/jnr.21953
复制
发表时间：
2009-05-01
影响因子：
4.2
通讯作者：
Endo, Shogo
中科院分区：
文献类型：
--
作者：
Nakazawa, Toru;Shimura, Masahiko;Endo, Shogo
神经元 N-甲基-D-天冬氨酸 (NMDA) 受体介导的细胞内信号传导在生理和病理条件下的作用已得到阐明。然而，兴奋性毒性的相对脆弱性的细节仍然未知。视网膜兴奋性毒性与多种导致不可逆失明的疾病有关。在这里，我们使用视觉系统并探索了 NMDA 引发的细胞内事件的机制细节，特别是在无长突细胞中，无长突细胞是视网膜中最脆弱的神经元类型。 G-底物是环鸟苷 3',5'-单磷酸 (cGMP) 依赖性蛋白激酶的特异性底物，与无长突细胞共定位，并充当蛋白磷酸酶的内源性抑制剂。为了阐明 G 底物如何参与 NMDA 诱导的无长突细胞死亡，在 NMDA 损伤后使用 G 底物抗体进行了免疫组织化学分析。在体内，NMDA 立即降低 G 底物免疫反应性，而使用 ALLN 或钙蛋白酶 III（一种钙蛋白酶抑制剂）抑制钙蛋白酶激活，可阻止这种降低。在体外，G-底物与钙蛋白酶共孵育后 10 分钟内即可检测到 G-底物的降解片段。此外，G-底物敲除（G-底物（-/-））小鼠比野生型小鼠更容易受到 NMDA 损伤。 ALLN 对 G 底物（-/-）小鼠没有神经保护作用。这些数据强烈表明，钙蛋白酶介导的 G 底物损失代表了 NMDA 诱导的无长突细胞死亡的重要机制。 (C) 2008 Wiley-Liss, Inc.
The role of neuronal N-methyl-D-aspartate (NMDA) receptor-mediated intracellular signaling has been elucidated in both physiological and pathological conditions. However, the details of relative vulnerability for excitotoxicity remain unknown. Retinal excitotoxicity is involved in various diseases leading to irreversible blindness. Here, we used the visual system and explored the mechanistic details of the NMDA-elicited intracellular events, especially in the amacrine cells, which are the most vulnerable type of neuron in the retina. G-substrate, a specific substrate of cyclic guanosine 3',5'-monophosphate (cGMP)-dependent protein kinase, is colocalized with amacrine cells and acts as an endogenous inhibitor of protein phosphatase. To elucidate how G-substrate was involved in NMDA-induced amacrine cell death, the immunohistochemical analysis with G-substrate antibody was performed following NMDA injury. In vivo, NMDA immediately decreased G-substrate immunoreactivity, and the suppression of calpain activation using ALLN or calpain III, an inhibitor of calpain, blocked this decrease. In vitro, degraded fragments of G-substrate were detected within 10 min after coincubation of G-substrate and calpain. Moreover, G-substrate knockout (G -substrate(-/-)) mice were more susceptible to NMDA injury than wildtype mice. ALLN did not have a neuroprotective effect in G-substrate(-/-) mice. These data strongly suggest that calpain-mediated loss of G-substrate represents an important mechanism contributing to NMDA-induced amacrine cell death. (C) 2008 Wiley-Liss, Inc.