Heterotrimeric guanine nucleotide-binding proteins (G proteins) transduce signals from G protein-coupled receptors (GPCRs) to effector ion channels and enzymes. Gαo, a member of the pertussis toxin-sensitive Gi/o family, is widely expressed in the brain, although its role within a neuronal context remains largely unknown. Using immunohistochemical and quantitative immunoelectron microscopy techniques, we have investigated the expression, cellular and subcellular localisation of Gαo in the cerebellar cortex. Histoblot revealed that Gαo is expressed in many brain regions, including the cerebellum. At the cellular level, Gαo protein was distributed in Purkinje cells, basket cells, stellate cells, granule cells and Golgi cells. At the subcellular level, pre-embedding immunoelectron microscopy revealed mainly a postsynaptic localisation of Gαo along the extrasynaptic plasma membrane of Purkinje cell dendritic shafts and spines, and dendrites of basket, stellate and granule cells. To a lesser extent, immunolabeling for Gαo was localised in different types of axon terminals establishing excitatory synapses. Moreover, post-embedding immunoelectron microscopy revealed the synaptic localisation of Gαo on PSDs of glutamatergic synapses between Purkinje cell spines and parallel fibre terminals and its co-localisation with GABAB1 in the same spines. Quantitative analysis of Gαo immunoparticles revealed they preferentially localised on the cytoplasmic face of the plasma membrane. Furthermore, the analysis revealed a high concentration of Gαo around excitatory synapses on Purkinje cell dendritic spines, but a uniform distribution in granule cell dendrites. These molecular-anatomical findings suggest that Gαo is a major signal transducer of specific GPCRs in different neuronal populations in the cerebellum.

中文翻译：

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小鼠小脑中 G 蛋白 Gαo 亚基的细胞多样性和差异亚细胞定位

异源三聚鸟嘌呤核苷酸结合蛋白 (G 蛋白) 将信号从 G 蛋白偶联受体 (GPCR) 转导至效应离子通道和酶。Gαo 是百日咳毒素敏感的 Gi/o 家族的成员，在大脑中广泛表达，尽管其在神经元环境中的作用仍然未知。使用免疫组织化学和定量免疫电子显微镜技术，我们研究了 Gαo 在小脑皮层中的表达、细胞和亚细胞定位。Histoblot 显示 Gαo 在许多大脑区域表达，包括小脑。在细胞水平上，Gαo蛋白分布于浦肯野细胞、篮状细胞、星状细胞、颗粒细胞和高尔基细胞中。在亚细胞水平，预嵌入免疫电子显微镜显示，Gαo 主要位于沿浦肯野细胞树突轴和棘突突触外质膜的突触后定位，以及篮状细胞、星状细胞和颗粒细胞的树突。在较小程度上，Gαo 的免疫标记定位于不同类型的轴突末端，建立兴奋性突触。此外，后嵌入免疫电子显微镜显示 Gαo 在浦肯野细胞棘和平行纤维末端之间的谷氨酸能突触的 PSD 上的突触定位及其与相同棘中的 GABAB1 的共定位。Gαo 免疫颗粒的定量分析显示它们优先定位在质膜的细胞质面上。此外，分析显示浦肯野细胞树突棘上的兴奋性突触周围有高浓度的 Gαo，但在颗粒细胞树突中分布均匀。这些分子解剖学发现表明，Gαo 是小脑不同神经元群中特定 GPCR 的主要信号转导器。