State Key Laboratory of Biomembrane and Membrane Biotechnology and Peking-Tsinghua Center for Life Sciences and PKU-IDG/McGovern Institute for Brain Research, Institute of Molecular Medicine, Peking University, Beijing, China.
Institute of Neurosciences, Fourth Military Medical University, Xi'an, China.
J Physiol. 2018 May 15;596(10):1931-1947. doi: 10.1113/JP275805. Epub 2018 Apr 6.
Similar to neurons, astrocytes actively participate in synaptic transmission via releasing gliotransmitters. The Ca -dependent release of gliotransmitters includes glutamate and ATP. Following an 'on-cell-like' mechanical stimulus to a single astrocyte, Ca independent single, large, non-quantal, ATP release occurs. Astrocytic ATP release is inhibited by either selective antagonist treatment or genetic knockdown of P2X7 receptor channels. Our work suggests that ATP can be released from astrocytes via two independent pathways in hippocampal astrocytes; in addition to the known Ca -dependent vesicular release, larger non-quantal ATP release depends on P2X7 channels following mechanical stretch.
Astrocytic ATP release is essential for brain functions such as synaptic long-term potentiation for learning and memory. However, whether and how ATP is released via exocytosis remains hotly debated. All previous studies of non-vesicular ATP release have used indirect assays. By contrast, two recent studies report vesicular ATP release using more direct assays. In the present study, using patch clamped 'ATP-sniffer cells', we re-investigated astrocytic ATP release at single-vesicle resolution in hippocampal astrocytes. Following an 'on-cell-like' mechanical stimulus of a single astrocyte, a Ca independent single large non-quantal ATP release occurred, in contrast to the Ca -dependent multiple small quantal ATP release in a chromaffin cell. The mechanical stimulation-induced ATP release from an astrocyte was inhibited by either exposure to a selective antagonist or genetic knockdown of P2X7 receptor channels. Functional P2X7 channels were expressed in astrocytes in hippocampal brain slices. Thus, in addition to small quantal ATP release, larger non-quantal ATP release depends on P2X7 channels in astrocytes.
与神经元类似，星形胶质细胞通过释放神经胶质递质积极参与突触传递。钙依赖性神经胶质递质的释放包括谷氨酸和 ATP。在对单个星形胶质细胞进行类似于“细胞膜片钳”的机械刺激后，会发生钙非依赖性、单次、大、非量子、ATP 释放。星形胶质细胞 ATP 释放可被 P2X7 受体通道的选择性拮抗剂处理或基因敲低所抑制。我们的工作表明，在海马星形胶质细胞中，ATP 可以通过两种独立的途径从星形胶质细胞中释放；除了已知的钙依赖性囊泡释放外，较大的非量子 ATP 释放还依赖于机械拉伸后的 P2X7 通道。
星形胶质细胞 ATP 释放对于大脑功能（如学习和记忆的突触长时程增强）至关重要。然而，ATP 是否以及如何通过胞吐作用释放仍存在争议。之前所有关于非囊泡 ATP 释放的研究都使用了间接测定法。相比之下，最近的两项研究使用更直接的测定法报告了囊泡 ATP 释放。在本研究中，使用膜片钳“ATP 嗅探细胞”，我们在单个囊泡分辨率下重新研究了海马星形胶质细胞中的星形胶质细胞 ATP 释放。在对单个星形胶质细胞进行类似于“细胞膜片钳”的机械刺激后，会发生钙非依赖性单次大非量子 ATP 释放，与嗜铬细胞中钙依赖性多次小量子 ATP 释放形成对比。暴露于选择性拮抗剂或 P2X7 受体通道的基因敲低均可抑制机械刺激诱导的星形胶质细胞 ATP 释放。功能性 P2X7 通道在海马脑片中的星形胶质细胞中表达。因此，除了小量子 ATP 释放外，较大的非量子 ATP 释放还依赖于星形胶质细胞中的 P2X7 通道。
