Morais Tatiana P, Coelho David, Vaz Sandra H, Sebastião Ana M, Valente Cláudia A
Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal.
Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal.
Front Mol Neurosci. 2018 Jan 17;10:444. doi: 10.3389/fnmol.2017.00444. eCollection 2017.
In central nervous system, glycine receptor (GlyR) is mostly expressed in the spinal cord and brainstem, but glycinergic transmission related elements have also been identified in the brain. Astrocytes are active elements at the tripartite synapse, being responsible for the maintenance of brain homeostasis and for the fine-tuning of synaptic activity. These cells communicate, spontaneously or in response to a stimulus, by elevations in their cytosolic calcium (calcium transients, CaT) that can be propagated to other cells. How these CaT are negatively modulated is yet poorly understood. In this work, we evaluated GlyR expression and its role on calcium signaling modulation in rat brain astrocytes. We first proved that GlyR, predominantly subunits α2 and β, was expressed in brain astrocytes and its localization was confirmed in the cytoplasm and astrocytic processes by immunohistochemistry assays. Calcium imaging experiments in cultured astrocytes showed that glycine (500 μM), a GlyR agonist, caused a concentration-dependent reduction in ATP-induced CaT, an effect abolished by the GlyR antagonist, strychnine (0.8 μM), as well as by nocodazole (1 μM), known to impair GlyR anchorage to the plasma membrane. This effect was mimicked by activation of GABAR, another Cl-permeable channel. In summary, we demonstrated that GlyR activation in astrocytes mediates an inhibitory effect upon ATP induced CaT, which most probably involves changes in membrane permeability to Cl and requires GlyR anchorage at the plasma membrane. GlyR in astrocytes may thus be part of a mechanism to modulate astrocyte-to-neuron communication.
在中枢神经系统中，甘氨酸受体（GlyR）主要表达于脊髓和脑干，但在大脑中也已鉴定出与甘氨酸能传递相关的元件。星形胶质细胞是三方突触中的活跃元件，负责维持脑内稳态以及对突触活动进行微调。这些细胞通过其胞质钙升高（钙瞬变，CaT）进行自发或对刺激作出反应的通讯，钙瞬变可传播至其他细胞。目前对这些钙瞬变如何受到负调节仍知之甚少。在这项研究中，我们评估了GlyR在大鼠脑星形胶质细胞中的表达及其对钙信号调节的作用。我们首先证明，主要由α2和β亚基组成的GlyR在脑星形胶质细胞中表达，并且通过免疫组织化学分析在细胞质和星形胶质细胞突起中证实了其定位。培养的星形胶质细胞中的钙成像实验表明，GlyR激动剂甘氨酸（500μM）导致ATP诱导的钙瞬变呈浓度依赖性降低，GlyR拮抗剂士的宁（0.8μM）以及已知会损害GlyR锚定到质膜的诺考达唑（1μM）可消除这种作用。另一种Cl-通透通道GABAR的激活可模拟这种效应。总之，我们证明星形胶质细胞中GlyR的激活介导了对ATP诱导的钙瞬变的抑制作用，这很可能涉及膜对Cl的通透性变化，并且需要GlyR锚定在质膜上。因此，星形胶质细胞中的GlyR可能是调节星形胶质细胞与神经元通讯机制的一部分。
