Laboratory of Intracellular Ion Channels, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw, Poland.
Int J Mol Sci. 2022 Nov 2;23(21):13391. doi: 10.3390/ijms232113391.
The mitochondrial large-conductance calcium-activated potassium channel (mitoBK) is located in the inner mitochondrial membrane and seems to play a crucial role in cytoprotection. The mitoBK channel is regulated by many modulators, including activators, such as calcium ions and inhibitors, such as heme and its oxidized form hemin. Heme/hemin binds to the heme-binding motif (CXXCH) located between two RCK domains present in the mitochondrial matrix. In the present study, we used the patch-clamp technique in the outside-out configuration to record the activity of mitoBK channels. This allowed for the application of channel modulators to the intermembrane-space side of the mitoBK. We found that hemin applied in this configuration inhibits the activity of mitoBK. In addition, we proved that the observed hemin effect is specific and it is not due to its interaction with the inner mitochondrial membrane. Our data suggest the existence of a new potential heme/hemin binding site in the structure of the mitoBK channel located on the mitochondrial intermembrane space side, which could constitute a new way for the regulation of mitoBK channel activity.
线粒体大电导钙激活钾通道（mitoBK）位于线粒体内膜，似乎在细胞保护中发挥着关键作用。mitoBK 通道受许多调节剂的调节，包括激活剂，如钙离子和抑制剂，如血红素及其氧化形式血红素。血红素/血红素结合到位于线粒体基质中两个 RCK 结构域之间的血红素结合基序（CXXCH）上。在本研究中，我们使用膜片钳技术中的外翻模式记录了 mitoBK 通道的活性。这允许将通道调节剂应用于 mitoBK 的膜间隙侧。我们发现血红素在这种构象下抑制了 mitoBK 的活性。此外，我们证明观察到的血红素效应是特异性的，并非由于其与线粒体内膜的相互作用。我们的数据表明，在位于线粒体外膜间隙侧的 mitoBK 通道结构中存在一个新的潜在血红素/血红素结合位点，这可能构成调节 mitoBK 通道活性的新途径。
