Braun Franz-Josef, Aziz Omar, Putney James W
National Institute of Environmental Health Sciences, P.O. Box 12233, Research Triangle Park, NC 27709, USA.
Mol Pharmacol. 2003 Jun;63(6):1304-11. doi: 10.1124/mol.63.6.1304.
The membrane-permeable, noncompetitive inositol 1,4,5-trisphosphate (IP3)-receptor inhibitor 2-aminoethoxydiphenyl borane (2-APB) has been widely used to probe for IP3-receptor involvement in calcium signaling pathways. However, a number of recent studies in different cell types revealed other sites of action of 2-APB. In this study, we examined the influence of 2-APB on capacitative calcium entry and intracellular Ca2+ concentrations in rat basophilic leukemia (RBL-2H3 m1) cells. 2-APB was found to inhibit capacitative calcium entry, but at concentrations greater than 50 microM, a new effect of 2-APB was observed. When capacitative calcium entry was blocked with Gd3+, 2-APB caused an increase in cytoplasmic Ca2+. This increase in intracellular Ca2+ was not caused by altered buffering of cytoplasmic Ca2+ and was not caused by or in any way affected by the depletion of intracellular Ca2+ stores. Associated with the increase in intracellular Ca2+, in the presence of 2 mM Ca2+, 2-APB activated single channels in the plasma membrane with a conductance of approximately 50 pS. These channels seem to be nonselective cation channels; monovalent cations are the major carriers of current, but finite permeability to Ca2+ leads to a significant intracellular Ca2+ signal. Experiments with excised patches indicate that 2-APB activates these channels from the outer aspect of the cell membrane. This effect of 2-APB further illustrates the complex actions of this compound and reveals the presence in RBL-2H3 m1 cells of a novel, ligand-gated calcium-permeable channel.
可透过细胞膜的非竞争性肌醇1,4,5 -三磷酸（IP3）受体抑制剂2 -氨基乙氧基二苯硼（2 - APB）已被广泛用于探究IP3受体在钙信号通路中的作用。然而，最近在不同细胞类型中的一些研究揭示了2 - APB的其他作用位点。在本研究中，我们检测了2 - APB对大鼠嗜碱性白血病（RBL - 2H3 m1）细胞中钙池调控性钙内流和细胞内Ca2+浓度的影响。发现2 - APB可抑制钙池调控性钙内流，但在浓度大于50 microM时，观察到2 - APB有新的作用。当用Gd3+阻断钙池调控性钙内流时，2 - APB导致细胞质Ca2+增加。细胞内Ca2+的这种增加不是由细胞质Ca2+缓冲改变引起的，也不是由细胞内Ca2+储存耗尽引起的，或以任何方式受其影响。与细胞内Ca2+增加相关，在存在2 mM Ca2+的情况下，2 - APB激活了质膜上电导约为50 pS的单通道。这些通道似乎是非选择性阳离子通道；单价阳离子是主要的电流载体，但对Ca2+有限的通透性导致显著的细胞内Ca2+信号。膜片钳实验表明，2 - APB从细胞膜外侧激活这些通道。2 - APB的这种作用进一步说明了该化合物作用的复杂性，并揭示了RBL - 2H3 m1细胞中存在一种新型的、配体门控的钙通透通道。
