Department of Physiology, University of Tübingen, Gmelinstr. 5, D-72076 Tübingen, Germany.
Biochem Biophys Res Commun. 2012 Jan 13;417(2):692-6. doi: 10.1016/j.bbrc.2011.11.156. Epub 2011 Dec 7.
Voltage-gated Kv1.5 channels are expressed in a wide variety of tissues including cardiac myocytes, smooth muscle and tumor cells. Kv1.5 channel activity is modified by N-cadherin, which in turn binds the multifunctional oncogenic protein β-catenin. The present experiments explored the effect of β-catenin on Kv1.5 channel activity. To this end, Kv1.5 was expressed in Xenopus oocytes with or without β-catenin and the voltage-gated Kv current determined by dual electrode voltage clamp. As a result, expression of β-catenin significantly increased the voltage-gated Kv current at positive potentials. The stimulating effect of β-catenin on Kv1.5 was not dependent on the stimulation of transcription since it was observed even in the presence of the transcription inhibitor actinomycin D. Specific antibody binding to surface Kv1.5 in Xenopus oocytes revealed that β-catenin enhances the membrane abundance of Kv1.5. Further experiments with brefeldin A showed that β-catenin fosters the insertion of Kv1.5 into rather than delaying the retrieval from the plasma membrane. According to electrophysiological recordings with mutant β-catenin, the effect on Kv1.5 requires the same protein domains that are required for association of β-catenin with cadherin. The experiments disclose a completely novel function of β-catenin, i.e. the regulation of Kv1.5 channel activity.
电压门控 Kv1.5 通道在多种组织中表达，包括心肌细胞、平滑肌和肿瘤细胞。Kv1.5 通道的活性受 N-钙黏蛋白的调节，而 N-钙黏蛋白又与多功能致癌蛋白 β-连环蛋白结合。本实验探讨了 β-连环蛋白对 Kv1.5 通道活性的影响。为此，在非洲爪蟾卵母细胞中表达 Kv1.5，并结合双电极电压钳技术测定电压门控 Kv 电流。结果表明，β-连环蛋白的表达显著增加了正电位下的电压门控 Kv 电流。β-连环蛋白对 Kv1.5 的刺激作用不依赖于转录的刺激，因为即使在转录抑制剂放线菌素 D 的存在下也观察到了这种作用。用抗β-连环蛋白的特异性抗体结合非洲爪蟾卵母细胞表面 Kv1.5 表明，β-连环蛋白增加了 Kv1.5 的膜丰度。用布雷菲德菌素 A 进行的进一步实验表明，β-连环蛋白促进 Kv1.5 插入而不是延迟从质膜回收。根据带有突变 β-连环蛋白的电生理记录，该作用需要与 β-连环蛋白与钙黏蛋白结合所必需的相同蛋白结构域。这些实验揭示了 β-连环蛋白的一个全新功能，即调节 Kv1.5 通道活性。
