The role and mechanism of activation of TRP channel in mast cells

过敏反应是由肥大细胞胞吐释放的炎症介质如组胺引起的。尽管来自细胞外介质的钙离子内流是不可缺少的，但这种内流的原因仍然是未知的。近年来，我们发现肥大细胞中存在瞬时受体电位（TRP）通道，该通道在钙库耗竭时被激活B。因此，本研究探讨了TRP的作用及其激活机制.低TRP活性的RBL-2H3细胞中的细胞内钙动力学为了研究TRP在RBL-2H3细胞中的作用，我们制备了两种TRP活性非常低的细胞。一种是通过反义技术抑制TRP1表达水平的敲低细胞系。另一种是显性阴性细胞系，其中TRP1的功能被截短的TRP1的表达抑制。在两种细胞系中，未观察到钙动力学的显著差异。因此，提示TRP 1虽然在肥大细胞中表达，但不参与钙内流.半抗原对细胞内钙动力学的影响：多价抗原交联IgE受体激活肥大细胞，细胞内钙增加。已知单价半抗原的加入引起IgE受体的解离和钙浓度的降低。为了研究钙离子内流的激活机制，我们检测了半抗原对毒扁豆碱诱导的钙离子增加的影响。半抗原不降低毒胡萝卜素引起的钙增加。这些数据表明，钙通道的激活机制是不同的抗原和毒胡萝卜素的刺激，虽然这两种刺激消耗钙库。

Allergic responses are triggered by the exocytotic release of inflammatory mediators such as histamine from mast cells. Although calcium influx from extra-cellular medium is indispensable responsible for this influx is still unknown. Recently, we found that TRP (transient receptor potential) channel, which is activated b the depletion of calcium store, is expressed in mast cells. Thus, we investigated the role of TRP and its activation mechanism in this study.1. Intracellular Ca dynamics in RBL-2H3 cells with low activity of TRP.To examine the role of TRP in RBL-2H3 cells, we prepared two types of cells in which the activity of TRP is very low. One is the knock-down cell line in which the expression level of TRP1 is suppressed b anti-sense technique. The other is the dominant negative cell line in which the function of TRP1 is suppressed by the expression of truncated TRP1. In both cell lines, no significant difference on the calcium dynamics was observed. Therefore, it is suggested that TRP1 is not involved in the calcium influx, although TRP1 s expressed in mast cells.2. The effects of hapten on the intracellular Ca dynamics.Mast cells are activated by the cross-linking of IgE receptors by multi-valent antigen, and intracellular calcium increase. It is known that addition of mono-valent hapten causes dissociation of IgE receptors and decrease in calcium concentration. To investigate the activation mechanism of calciium influx, we examined the effects of hapten on thapsigargin-induced calcium increase. Hapten did not decrease the calcium increase evoked by thapsigargin. These data suggest that the activation mechanism of calcium channel is different between antigen and thapsigargin stimulation, although both stimulation deplete calcium store.