Disruption of metabotropic glutamate receptor signalling is a major defect at cerebellar parallel fibre-Purkinje cell synapses in staggerer mutant mice
Disruption of metabotropic glutamate receptor signalling is a major defect at cerebellar parallel fibre-Purkinje cell synapses in staggerer mutant mice
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DOI：
10.1113/jphysiol.2011.207563
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发表时间：
2011-07-01
影响因子：
5.5
通讯作者：
Hirai, Hirokazu
中科院分区：
文献类型：
--
作者：
Mitsumura, Kazuhiro;Hosoi, Nobutake;Hirai, Hirokazu
Staggerer突变小鼠的转录因子、类维生素A相关孤儿受体α（RORα）功能丧失，该受体在小脑浦肯野细胞（PC）中大量表达。纯合交错 (sg/sg) 小鼠表现出小脑发育不全和先天性共济失调。 Sg/sg 小鼠是遗传性脊髓小脑共济失调 1 型 (SCA1) 的重要极端小鼠模型，因为已表明 ROR α 功能障碍与 SCA1 发病机制密切相关。然而，SCA1 相关 sg/sg 小鼠中的突触异常，尤其是平行纤维 (PF)-PC 突触异常，尚未经过详细的电生理学检查。在这项研究中，我们报告尽管 PF-PC 突触数量减少，但 PFs 仍然可以在 sg/sg 小鼠的 PC 上建立功能性突触。与野生型或杂合子中 PF 诱发的 EPSC 相比，sg/sg 中 EPSC 记录的成功率相当低（约 40%），并且 EPSC 显示出更快的动力学，并且在短间隔内略微降低了配对脉冲促进。突出的突触功能障碍是 sg/sg 小鼠完全缺乏代谢型谷氨酸受体 (mGluR) 介导的慢 EPSC。强烈的 PF 刺激和外源性 mGluR 激动剂 DHPG 均不能引起 mGluR 介导的反应。 sg/sg 小脑中的蛋白质印迹分析显示 mGluR1 和 TRPC3 的低水平表达，这两者都是 PC 中 mGluR 介导的慢电流的基础。免疫组织化学数据表明 mGluR1 在 sg/sg PC 上明显错误定位。我们发现内源性大麻素对 PF-PC EPSC 的 mGluR 介导的逆行抑制在 sg/sg 小鼠中也完全受损。这些结果表明，PF-PC 突触 mGluR 信号传导的破坏是 sg/sg 小鼠的主要突触缺陷之一，并且可能在 SCA1 病理学中表现出来。
Staggerer mutant mice have functional loss of a transcription factor, retinoid-related orphan receptor alpha (ROR alpha), which is abundantly expressed in Purkinje cells (PCs) of the cerebellum. Homozygous staggerer (sg/sg) mice show cerebellar hypoplasia and congenital ataxia. Sg/sg mice serve as an important extreme mouse model of the hereditary spinocerebellar ataxia type 1 (SCA1), since it has been shown that ROR alpha dysfunction is strongly correlated with SCA1 pathogenesis. However, synaptic abnormalities, especially at parallel fibre (PF)-PC synapses, in SCA1-related sg/sg mice have not been examined in detail electrophysiologically. In this study, we report that PFs can still establish functional synapses onto PCs in sg/sg mice in spite of reduction in the number of PF-PC synapses. Compared with PF-evoked EPSCs in the wild-type or heterozygotes, the success rate of the EPSC recordings in sg/sg was quite low (similar to 40%) and the EPSCs showed faster kinetics and slightly decreased paired pulse facilitation at short intervals. The prominent synaptic dysfunction is that sg/sg mice lack metabotropic glutamate receptor (mGluR)-mediated slow EPSCs completely. Neither intense PF stimulation nor an exogenously applied mGluR agonist, DHPG, could elicit mGluR-mediated responses. Western blot analysis in the sg/sg cerebellum revealed low-level expression of mGluR1 and TRPC3, both of which underlie mGluR-mediated slow currents in PCs. Immunohistochemical data demonstrated marked mislocalization ofmGluR1 on sg/sg PCs. We found that mGluR-mediated retrograde suppression of PF-PC EPSCs by endocannabinoid is also impaired completely in sg/sg mice. These results suggest that disruption of mGluR signalling at PF-PC synapses is one of the major synaptic defects in sg/sg mice and may manifest itself in SCA1 pathology.