Bush A B, Borden L A, Greene L A, Maxfield F R
Department of Pathology, Columbia University College of Physicians and Surgeons, New York, New York.
J Neurochem. 1991 Aug;57(2):562-74. doi: 10.1111/j.1471-4159.1991.tb03787.x.
To investigate how the response to agonists changes during neuronal differentiation, we examined the effect of nerve growth factor (NGF) on bradykinin-induced calcium increases in PC12 cells. Short-term (1 h) treatment with NGF increased the potency of bradykinin to raise intracellular calcium by about 10-fold, whereas long-term (1 week) treatment, which was associated with the expression of the differentiated phenotype, increased the potency about 100-fold. Neither treatment affected the maximal response to bradykinin. NGF alone had no acute effect on calcium levels. Short-term potentiation appeared to be mainly a result of greater release of calcium from intracellular stores, whereas the effect of long-term treatment apparently was due to increases in both release from intracellular stores and calcium influx. [3H]Bradykinin binding to intact PC12 cells was unaltered by short-term NGF treatment, whereas differentiated cells displayed a 50% increase in receptor number and about a twofold increase in affinity as compared with cells not treated with NGF. The production of inositol phosphates in response to bradykinin correlated poorly with the calcium transients, in that large calcium responses were associated with small increases in inositol phosphates. Neither NGF treatment had a significant effect on the appearance of inositol phosphates in response to bradykinin. Experiments with permeabilized cells revealed that differentiated cells did not display a heightened response to exogenously added inositol 1,4,5-trisphosphate. Our results demonstrate that NGF modulates the bradykinin signaling pathway without acutely activating this pathway itself.
为了研究神经元分化过程中对激动剂的反应如何变化，我们检测了神经生长因子（NGF）对缓激肽诱导的PC12细胞钙增加的影响。用NGF短期（1小时）处理可使缓激肽升高细胞内钙的效力增加约10倍，而长期（1周）处理与分化表型的表达相关，使效力增加约100倍。两种处理均未影响对缓激肽的最大反应。单独的NGF对钙水平没有急性影响。短期增强作用似乎主要是细胞内钙库释放更多钙的结果，而长期处理的效果显然是由于细胞内钙库释放增加和钙内流增加。短期NGF处理未改变[3H]缓激肽与完整PC12细胞的结合，而与未用NGF处理的细胞相比，分化细胞的受体数量增加了50%，亲和力增加了约两倍。缓激肽刺激产生的肌醇磷酸与钙瞬变的相关性较差，因为大的钙反应与肌醇磷酸的小幅增加相关。两种NGF处理对缓激肽刺激产生的肌醇磷酸的出现均无显著影响。对透化细胞的实验表明，分化细胞对外源添加的肌醇1,4,5-三磷酸没有增强反应。我们的结果表明，NGF调节缓激肽信号通路，而不会急性激活该通路本身。
