Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Mexico.
Mol Pharmacol. 2010 May;77(5):751-8. doi: 10.1124/mol.109.063008. Epub 2010 Feb 4.
The endocannabinoid, N-arachidonoylethanolamine (anandamide; AEA) is known to interact with voltage-gated K(+) (Kv) channels in a cannabinoid receptor-independent manner. AEA modulates the functional properties of Kv channels, converting channels with slowly inactivating current into apparent fast inactivation. In this study, we characterize the mechanism of action and binding site for AEA on Kv1.5 channels expressed on HEK-293 cells using the patch-clamp techniques. AEA exhibited high-potency block (IC(50) approximately 200 nM) from the cytoplasmic membrane surface, consistent with open-channel block. Alanine-scanning mutagenesis revealed that AEA interacts with two crucial beta-branching amino acids, Val505 and Ile508 within the S6 domain. Both residues face toward the central cavity and constitute a motif that forms a hydrophobic ring around the ion conduction pathway. This hydrophobic ring motif may be a critical determinant of cannabinoid receptor-independent AEA modulation in other K(+) channel families.
内源性大麻素，N-花生四烯酰乙醇胺（大麻素；AEA）已知以一种不依赖于大麻素受体的方式与电压门控 K(+) (Kv) 通道相互作用。AEA 调节 Kv 通道的功能特性，将具有缓慢失活电流的通道转换为明显的快速失活。在这项研究中，我们使用膜片钳技术在表达于 HEK-293 细胞的 Kv1.5 通道上对 AEA 的作用机制和结合位点进行了表征。AEA 从细胞质膜表面表现出高亲和力的阻断作用（IC(50)约为 200 nM），与开放通道阻断一致。丙氨酸扫描突变揭示 AEA 与 S6 结构域内两个关键的β分支氨基酸，缬氨酸 505 和异亮氨酸 508 相互作用。这两个残基都朝向中央腔，形成一个围绕离子传导途径的疏水性环。这个疏水性环基序可能是其他 K(+) 通道家族中不依赖于大麻素受体的 AEA 调节的关键决定因素。
