ASC transporters mediate D-serine transport into astrocytes adjacent to synapses in mouse brain

Background: D-serine is an important signaling molecule, which activates N-methyl D-aspartate receptors (NMDARs) in conjunction with its fellow co-agonist, the neurotransmitter glutamate.
Question: Despite its involvement in plasticity and memory related to excitatory synapses, its cellular source and sink remain a question.
Importance: This removal of synaptic D-serine and its subsequent metabolic degradation is expected to reduce its extracellular availability, influencing NMDAR activation and NMDAR-dependent synaptic plasticity.
Hypothesis: We hypothesise that astrocytes, a type of glial cell that surround synapses are likely candidates to control the extracellular concentration of D-Serine by removing it from the synaptic space.
Notable finding: We observed D-serine induced transport-associated currents upon puff-application of 10 mM D-serine on astrocytes. Further, O-benzyl-L-serine and trans-4-hydroxy-proline, known substrate inhibitors of the alanine serine cysteine transporters (ASCT) reduced D-serine uptake. These results indicate that ASCT is a central mediator of astrocytic D-serine transport and plays a role in regulating its synaptic concentration by sequestration into astrocytes. Similar results were observed in astrocytes of the somatosensory cortex and Bergmann glia in the cerebellum, indicative of a general mechanism expressed across a range of brain areas.
How was it gathered: We used patch clamping technique, to study the transmembrane electrical signals from individual identified astrocytes in the CA1 region of hippocampus, primary somatosensory cortex and Bergmann glia. It involved placing a tiny glass patch pipette, onto the surface of the astrocytic membrane, to record D-serine transporter currents.
Methods: Using in situ patch clamp recordings and pharmacological manipulation of astrocytes in CA1 region of the mouse hippocampal brain slices, we investigated transport of D-serine across the plasma membrane.
How to interpret data: The spread sheet contains all the mean astrocytic D-serine currents that were recorded from individual cells.
How to use it: The raw data traces are most compatible with Clampfit 10.7.0.3 (P Clamp - Molecular devices 2016).

背景：D-丝氨酸是一种关键的信号分子，与同源共激动剂神经递质谷氨酸协同作用，激活N-甲基-D-天冬氨酸受体（NMDARs）。尽管其在与兴奋性突触相关的可塑性和记忆方面发挥着重要作用，但其细胞来源和去向仍是一个待解之谜。
问题：尽管其在与兴奋性突触相关的可塑性和记忆方面发挥着重要作用，但其细胞来源和去向仍是一个待解之谜。
重要性：预计通过从突触空间中去除D-丝氨酸及其随后的代谢降解，可以降低其细胞外可用性，从而影响NMDAR的激活和NMDAR依赖性突触可塑性。
假设：我们假设星形胶质细胞，一种围绕突触的胶质细胞，可能是通过从突触空间中去除D-丝氨酸来控制D-丝氨酸细胞外浓度的理想候选者。
显著发现：我们在星形胶质细胞上施加10 mM D-丝氨酸时观察到D-丝氨酸诱导的转运相关电流。此外，O-苄基-L-丝氨酸和反式-4-羟基脯氨酸，已知为丙氨酸丝氨酸半胱氨酸转运蛋白（ASCT）的底物抑制剂，减少了D-丝氨酸的摄取。这些结果表明，ASCT是星形胶质细胞D-丝氨酸转运的中心介质，并通过对星形胶质细胞的吸收来调节其在突触中的浓度。类似的发现也在躯体感觉皮层和脑干中的伯格曼胶质细胞中观察到，这表明这一机制在广泛的脑区表达。
数据收集方法：我们采用膜片钳技术，研究海马体CA1区域、初级躯体感觉皮层和伯格曼胶质细胞中单个识别的星形胶质细胞的跨膜电信号。这涉及到将微型玻璃膜片电极放置在星形胶质细胞膜表面，以记录D-丝氨酸转运蛋白电流。
方法：通过在鼠标海马体脑切片CA1区域的星形胶质细胞中进行的原位膜片钳记录和药理学操作，我们研究了D-丝氨酸跨质膜的转运。
数据解读：电子表格包含了从单个细胞记录的所有平均星形胶质细胞D-丝氨酸电流。
数据使用方法：原始数据轨迹与Clampfit 10.7.0.3（P Clamp - Molecular devices 2016）最为兼容。