Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel.
Department of Veterinary Resources, Weizmann Institute of Science, Rehovot, Israel.
J Physiol. 2021 Jan;599(2):521-545. doi: 10.1113/JP280434. Epub 2020 Nov 21.
G-protein inwardly rectifying K (GIRK) channels consist of four homologous subunits (GIRK1-4) and are essential regulators of electrical excitability in the nervous system. GIRK2-null mice have been widely investigated for their distinct behaviour and altered depotentiation following long-term potentiation (LTP), whereas GIRK1 mice are less well characterized. Here we utilize a novel knockin mouse strain in which the GIRK1 subunit is fluorescently tagged with yellow fluorescent protein (YFP-GIRK1) and the GIRK1-null mouse line to investigate the role of GIRK1 in neuronal processes such as spatial learning and memory, locomotion and depotentiation following LTP. Neurons dissected from YFP-GIRK1 mice had significantly reduced potassium currents and this mouse line phenotypically resembled GIRK1-null mice, making it a 'functional knockdown' model of GIRK1-containing channels. YFP-GIRK1 and GIRK1-null mice had increased locomotion, reduced spatial learning and memory and blunted depotentiation following LTP.
GIRK channels are essential for the slow inhibition of electrical activity in the nervous system and heart rate regulation via the parasympathetic system. The implications of individual GIRK isoforms in specific physiological activities are based primarily on studies conducted with GIRK-null mouse lines. Here we utilize a novel knockin mouse line in which YFP was fused in-frame to the N-terminus of GIRK1 (YFP-GIRK1) to correlate GIRK1 spatial distribution with physiological activities. These mice, however, displayed spontaneous seizure-like activity and thus were investigated for the origin of such activity. We show that GIRK tetramers containing YFP-GIRK1 are correctly assembled and trafficked to the plasma membrane, but are functionally impaired. A battery of behavioural assays conducted on YFP-GIRK1 and GIRK1-null (GIRK1 ) mice revealed similar phenotypes, including impaired nociception, reduced anxiety and hyperactivity in an unfamiliar environment. However, YFP-GIRK1 mice exhibited increased home-cage locomotion while GIRK1 mice did not. In addition, we show that the GIRK1 subunit is essential for intact spatial learning and memory and synaptic plasticity in hippocampal brain slices. This study expands our knowledge regarding the role of GIRK1 in neuronal processes and underlines the importance of GIRK1-containing heterotetramers.
G 蛋白内向整流钾 (GIRK) 通道由四个同源亚基 (GIRK1-4) 组成，是神经系统电兴奋性的重要调节因子。GIRK2 敲除小鼠因其独特的行为表现和长时程增强 (LTP) 后的去极化改变而被广泛研究，而 GIRK1 敲除小鼠的特征则不太清楚。在这里，我们利用一种新型的基因敲入小鼠品系，其中 GIRK1 亚基被黄色荧光蛋白 (YFP-GIRK1) 荧光标记，并用 GIRK1 敲除小鼠系来研究 GIRK1 在神经元过程中的作用，如空间学习和记忆、运动和 LTP 后的去极化。从 YFP-GIRK1 小鼠中分离出的神经元钾电流显著减少，并且这种小鼠品系表现出与 GIRK1 敲除小鼠相似的表型，因此成为含有 GIRK1 通道的“功能敲低”模型。YFP-GIRK1 和 GIRK1 敲除小鼠表现出运动增加、空间学习和记忆能力下降以及 LTP 后的去极化减弱。
GIRK 通道对于神经系统和心率调节通过副交感神经系统的电活动的缓慢抑制是必不可少的。单个 GIRK 同工型在特定生理活动中的意义主要基于 GIRK 敲除小鼠系的研究。在这里，我们利用一种新型的基因敲入小鼠系，其中 YFP 与 GIRK1 的 N 端融合（YFP-GIRK1），将 GIRK1 的空间分布与生理活性相关联。然而，这些小鼠表现出自发的类似癫痫发作的活动，因此研究了这种活动的来源。我们表明，包含 YFP-GIRK1 的 GIRK 四聚体正确组装并转运到质膜，但功能受损。对 YFP-GIRK1 和 GIRK1 敲除（GIRK1）小鼠进行的一系列行为测试显示出相似的表型，包括疼痛觉受损、焦虑减轻和在陌生环境中过度活跃。然而，YFP-GIRK1 小鼠表现出增加的笼内运动，而 GIRK1 小鼠则没有。此外，我们表明 GIRK1 亚基对于海马脑片的完整空间学习和记忆以及突触可塑性是必不可少的。这项研究扩展了我们对 GIRK1 在神经元过程中的作用的认识，并强调了含有 GIRK1 的异四聚体的重要性。
