Department of Chemistry, University of Leicester, Leicester, United Kingdom; Leicester Institute of Structural and Chemical Biology, University of Leicester, Leicester, United Kingdom.
School of Chemistry, University of Bristol, Bristol, United Kingdom.
J Biol Chem. 2020 Sep 18;295(38):13277-13286. doi: 10.1074/jbc.RA120.014150. Epub 2020 Jul 28.
The EAG () family of voltage-gated K channels are important regulators of neuronal and cardiac action potential firing (excitability) and have major roles in human diseases such as epilepsy, schizophrenia, cancer, and sudden cardiac death. A defining feature of EAG (Kv10-12) channels is a highly conserved domain on the N terminus, known as the eag domain, consisting of a Per-ARNT-Sim (PAS) domain capped by a short sequence containing an amphipathic helix (Cap domain). The PAS and Cap domains are both vital for the normal function of EAG channels. Using heme-affinity pulldown assays and proteomics of lysates from primary cortical neurons, we identified that an EAG channel, hERG3 (Kv11.3), binds to heme. In whole-cell electrophysiology experiments, we identified that heme inhibits hERG3 channel activity. In addition, we expressed the Cap and PAS domain of hERG3 in and, using spectroscopy and kinetics, identified the PAS domain as the location for heme binding. The results identify heme as a regulator of hERG3 channel activity. These observations are discussed in the context of the emerging role for heme as a regulator of ion channel activity in cells.
EAG()家族的电压门控钾通道是神经元和心肌动作电位发放（兴奋性）的重要调节剂，在人类疾病如癫痫、精神分裂症、癌症和心源性猝死中起主要作用。EAG（Kv10-12）通道的一个定义特征是 N 端高度保守的结构域，称为 EAG 结构域，由一个 Per-ARNT-Sim（PAS）结构域和一个短序列组成，该序列包含一个两亲性螺旋（Cap 结构域）。PAS 和 Cap 结构域对于 EAG 通道的正常功能都是至关重要的。使用血红素亲和下拉测定和原代皮质神经元裂解物的蛋白质组学，我们鉴定出 EAG 通道 hERG3（Kv11.3）与血红素结合。在全细胞电生理学实验中，我们发现血红素抑制 hERG3 通道活性。此外，我们在 和 中表达了 hERG3 的 Cap 和 PAS 结构域，通过光谱学和动力学，鉴定出 PAS 结构域是血红素结合的位置。结果表明血红素是 hERG3 通道活性的调节剂。这些观察结果在血红素作为细胞中离子通道活性调节剂的新兴作用背景下进行了讨论。
