Molecular Medicine Program, National Yang-Ming University, Taipei, Taiwan.
J Neurochem. 2010 Mar;112(5):1210-22. doi: 10.1111/j.1471-4159.2009.06533.x. Epub 2009 Dec 9.
In the present study, we characterized the Ca2+ responses and secretions induced by various secretagogues in mouse chromaffin cells. Activation of the acetylcholine receptor (AChR) by carbachol induced a transient intracellular Ca2+ concentration (Ca2+) increase followed by two phases of Ca2+ decay and a burst of exocytic events. The contribution of the subtypes of AChRs to carbachol-induced responses was examined. Based on the results obtained by stimulating the cells with the nicotinic receptor (nAChR) agonist, 1,1-dimethyl-4-phenylpiperazinium iodide, high K(+) and the effects of thapsigargin, it appears that activation of nAChRs induces an extracellular Ca2+ influx, which in turn activate Ca(2+)-induced Ca2+ release via the ryanodine receptors. Muscarine, a muscarinic receptor (mAChRs) agonist, was found to induce Ca2+ oscillation and sustained catecholamine release, possibly by activation of both the receptor- and store-operated Ca2+ entry pathways. The RT-PCR results showed that mouse chromaffin cells are equipped with messages for multiple subtypes of AChRs, ryanodine receptors and all known components of the receptor- and store-operated Ca2+ entry. Furthermore, results obtained by directly monitoring endoplasmic reticulum (ER) and mitochondrial Ca2+ concentration and by disabling mitochondrial Ca2+ uptake suggest that the ER acts as a Ca2+ source, while the mitochondria acts as a Ca2+ sink. Our results show that both nAChRs and mAChRs contribute to the initial carbachol-induced Ca2+ increase which is further enhanced by the Ca2+ released from the ER mediated by Ca(2+)-induced Ca2+ release and mAChR activation. This information on the Ca2+ signaling pathways should lay a good foundation for future studies using mouse chromaffin cells as a model system.
在本研究中，我们描述了各种激动剂诱导的小鼠嗜铬细胞内钙离子反应和分泌。乙酰胆碱受体（AChR）激动剂 carbachol 的激活诱导了短暂的细胞内钙离子浓度(Ca2+)增加，随后是两个阶段的Ca2+衰减和爆发性的胞吐事件。我们检查了 AChR 亚型对 carbachol 诱导反应的贡献。基于用烟碱型乙酰胆碱受体(nAChR)激动剂 1,1-二甲基-4-苯基哌嗪碘化物、高钾和 thapsigargin 刺激细胞获得的结果，似乎 nAChR 的激活诱导了细胞外钙离子内流，进而通过ryanodine 受体激活 Ca2+-induced Ca2+释放。毒蕈碱，一种毒蕈碱受体(mAChRs)激动剂，被发现诱导Ca2+振荡和持续的儿茶酚胺释放，可能是通过激活受体和储存操作的 Ca2+进入途径。RT-PCR 结果表明，小鼠嗜铬细胞配备有多种 AChR、ryanodine 受体亚型和所有已知的受体和储存操作的 Ca2+进入的组成部分的信息。此外，通过直接监测内质网(ER)和线粒体钙离子浓度以及禁用线粒体钙离子摄取获得的结果表明，ER 作为钙离子源，而线粒体作为钙离子汇。我们的结果表明，nAChRs 和 mAChRs 都有助于初始的 carbachol 诱导的Ca2+增加，而内质网释放的钙离子通过 Ca2+-induced Ca2+释放和 mAChR 激活进一步增强。关于钙离子信号通路的这些信息将为未来使用小鼠嗜铬细胞作为模型系统的研究奠定良好的基础。
