Wei S, Ong W Y, Thwin M M, Fong C W, Farooqui A A, Gopalakrishnakone P, Hong W
Institute of Molecular and Cell Biology, National University of Singapore 117609, Singapore.
Neuroscience. 2003;121(4):891-8. doi: 10.1016/s0306-4522(03)00525-6.
Recent evidence shows that secretory phospholipase A2 (sPLA2) may play a role in membrane fusion and fission, and may thus affect neurotransmission. The present study therefore aimed to elucidate the effects of sPLA2 on vesicle exocytosis. External application of group IIA sPLA2 (purified crotoxin subunit B or purified human synovial sPLA2) caused an immediate increase in exocytosis and neurotransmitter release in pheochromocytoma-12 (PC12) cells, detected by carbon fiber electrodes placed near the cells, or by changes in membrane capacitance of the cells. EGTA and a specific inhibitor of sPLA2 activity, 12-epi-scalaradial, abolished the increase in neurotransmitter release, indicating that the effect of sPLA2 was dependent on calcium and sPLA2 enzymatic activity. A similar increase in neurotransmitter release was also observed in hippocampal neurons after external application of sPLA2, as detected by changes in membrane capacitance of the neurons. In contrast to external application, internal application of sPLA2 to PC12 cells and neurons produced blockade of neurotransmitter release. Our recent studies showed high levels of sPLA2 activity in the normal rat hippocampus, medulla oblongata and cerebral neocortex. The sPLA2 activity in the hippocampus was significantly increased, after kainate-induced neuronal injury. The observed effects of sPLA2 on neurotransmitter release in this study may therefore have a physiological, as well as a pathological role.
最近的证据表明，分泌型磷脂酶A2（sPLA2）可能在膜融合和裂变中发挥作用，因此可能影响神经传递。因此，本研究旨在阐明sPLA2对囊泡胞吐作用的影响。通过放置在细胞附近的碳纤维电极或细胞的膜电容变化检测到，在嗜铬细胞瘤-12（PC12）细胞中外源性应用IIA型sPLA2（纯化的响尾蛇毒素亚基B或纯化的人滑膜sPLA2）会立即导致胞吐作用和神经递质释放增加。EGTA和sPLA2活性的特异性抑制剂12-表-标蛇毒素消除了神经递质释放的增加，表明sPLA2的作用依赖于钙和sPLA2的酶活性。在海马神经元中外源性应用sPLA2后，通过神经元膜电容变化检测到神经递质释放也有类似增加。与外源性应用相反，在PC12细胞和神经元中内源性应用sPLA2会导致神经递质释放受阻。我们最近的研究表明，正常大鼠海马、延髓和大脑新皮质中sPLA2活性水平很高。在海藻酸诱导的神经元损伤后，海马中的sPLA2活性显著增加。因此，本研究中观察到的sPLA2对神经递质释放的影响可能具有生理和病理作用。
