TARPs γ-2 and γ-7 are essential for AMPA receptor expression in the cerebellum
TARPs γ-2 and γ-7 are essential for AMPA receptor expression in the cerebellum
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DOI：
10.1111/j.1460-9568.2010.07254.x
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发表时间：
2010-06-01
影响因子：
3.4
通讯作者：
Watanabe, Masahiko
中科院分区：
文献类型：
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作者：
Yamazaki, Maya;Fukaya, Masahiro;Watanabe, Masahiko
α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）型谷氨酸受体需要称为跨膜AMPA受体调节蛋白（TARP）的辅助亚基，其促进受体运输至细胞表面和突触并调节通道药理学和门控。在六种TARPs中，γ-2和γ-7是小脑中表达的两种主要TARPs。在本研究中，我们探讨了它们在小脑AMPA受体突触表达中的作用。在小脑皮质，γ-2和γ-7优先定位于各种不对称的突触。使用定量蛋白质印迹和免疫荧光，我们发现严重减少，GluA 2和GluA 3和轻度减少，GluA 4在γ-2-敲除（KO）小脑，而GluA 1和GluA 4中度减少γ-7-KO小脑。GluA 2、GluA 3和GluA 4在γ-2/γ-7双KO（DKO）小脑中进一步减少。在植入后免疫金检查的所有不对称突触中，证实了γ-2-KO小鼠中GluA 2和GluA 3的大量丢失以及DKO小鼠中的进一步减少。最值得注意的是，在DKO小鼠中，突触后密度部分中的GluA 2水平、平行纤维-浦肯野细胞突触中的GluA 2标记密度和攀爬纤维-浦肯野细胞突触中的AMPA受体介导的电流均降低至野生型水平的约10%。另一方面，γ-7-KO颗粒层中GluA 4的减少反映了其在苔藓纤维-颗粒细胞突触中的损失，而γ-7-KO分子层中GluA 1和GluA 4的减少至少部分是由Bergmann胶质细胞中GluA 1和GluA 4的损失引起的。因此，γ-2和γ-7协同促进小脑AMPA受体的突触表达，并且后者也促进神经胶质表达。
The alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors require auxiliary subunits termed transmembrane AMPA receptor regulatory proteins (TARPs), which promote receptor trafficking to the cell surface and synapses and modulate channel pharmacology and gating. Of six TARPs, gamma-2 and gamma-7 are the two major TARPs expressed in the cerebellum. In the present study, we pursued their roles in synaptic expression of cerebellar AMPA receptors. In the cerebellar cortex, gamma-2 and gamma-7 were preferentially localized at various asymmetrical synapses. Using quantitative Western blot and immunofluorescence, we found severe reductions in GluA2 and GluA3 and mild reduction in GluA4 in gamma-2-knockout (KO) cerebellum, whereas GluA1 and GluA4 were moderately reduced in gamma-7-KO cerebellum. GluA2, GluA3 and GluA4 were further reduced in gamma-2/gamma-7 double-KO (DKO) cerebellum. The large losses of GluA2 and GluA3 in gamma-2-KO mice and further reductions in DKO mice were confirmed at all asymmetrical synapses examined with postembedding immunogold. Most notably, the GluA2 level in the postsynaptic density fraction, GluA2 labeling density at parallel fiber-Purkinje cell synapses, and AMPA receptor-mediated currents at climbing fiber-Purkinje cell synapses were all reduced to approximately 10% of the wild-type levels in DKO mice. On the other hand, the reduction in GluA4 in gamma-7-KO granular layer reflected its loss at mossy fiber-granule cell synapses, whereas that of GluA1 and GluA4 in gamma-7-KO molecular layer was caused, at least partly, by their loss in Bergmann glia. Therefore, gamma-2 and gamma-7 cooperatively promote synaptic expression of cerebellar AMPA receptors, and the latter also promotes glial expression.