Bishop Hannah I, Cobb Melanie M, Kirmiz Michael, Parajuli Laxmi K, Mandikian Danielle, Philp Ashleigh M, Melnik Mikhail, Kuja-Panula Juha, Rauvala Heikki, Shigemoto Ryuichi, Murray Karl D, Trimmer James S
Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States.
Center for Neuroscience, University of California, Davis, Davis, CA, United States.
Front Mol Neurosci. 2018 Jan 19;11:1. doi: 10.3389/fnmol.2018.00001. eCollection 2018.
Voltage-gated K (Kv) channels play important roles in regulating neuronal excitability. Kv channels comprise four principal α subunits, and transmembrane and/or cytoplasmic auxiliary subunits that modify diverse aspects of channel function. AMIGO-1, which mediates homophilic cell adhesion underlying neurite outgrowth and fasciculation during development, has recently been shown to be an auxiliary subunit of adult brain Kv2.1-containing Kv channels. We show that AMIGO-1 is extensively colocalized with both Kv2.1 and its paralog Kv2.2 in brain neurons across diverse mammals, and that in adult brain, there is no apparent population of AMIGO-1 outside of that colocalized with these Kv2 α subunits. AMIGO-1 is coclustered with Kv2 α subunits at specific plasma membrane (PM) sites associated with hypolemmal subsurface cisternae at neuronal ER:PM junctions. This distinct PM clustering of AMIGO-1 is not observed in brain neurons of mice lacking Kv2 α subunit expression. Moreover, in heterologous cells, coexpression of either Kv2.1 or Kv2.2 is sufficient to drive clustering of the otherwise uniformly expressed AMIGO-1. Kv2 α subunit coexpression also increases biosynthetic intracellular trafficking and PM expression of AMIGO-1 in heterologous cells, and analyses of Kv2.1 and Kv2.2 knockout mice show selective loss of AMIGO-1 expression and localization in neurons lacking the respective Kv2 α subunit. Together, these data suggest that in mammalian brain neurons, AMIGO-1 is exclusively associated with Kv2 α subunits, and that Kv2 α subunits are obligatory in determining the correct pattern of AMIGO-1 expression, PM trafficking and clustering.
电压门控钾（Kv）通道在调节神经元兴奋性方面发挥着重要作用。Kv通道由四个主要的α亚基以及跨膜和/或细胞质辅助亚基组成，这些辅助亚基可改变通道功能的多个方面。AMIGO-1介导发育过程中轴突生长和束状化过程中的同源细胞粘附，最近已被证明是成年大脑中含Kv2.1的Kv通道的辅助亚基。我们发现，在不同哺乳动物的脑神经元中，AMIGO-1与Kv2.1及其旁系同源物Kv2.2广泛共定位，并且在成年大脑中，除了与这些Kv2α亚基共定位的区域外，没有明显的AMIGO-1群体。AMIGO-1与Kv2α亚基在神经元内质网：质膜交界处与亚膜下池相关的特定质膜（PM）位点共聚集。在缺乏Kv2α亚基表达的小鼠脑神经元中未观察到AMIGO-1这种独特的质膜聚集。此外，在异源细胞中，Kv2.1或Kv2.2的共表达足以驱动原本均匀表达的AMIGO-1聚集。Kv2α亚基的共表达还增加了异源细胞中AMIGO-1的生物合成细胞内运输和质膜表达，对Kv2.1和Kv2.2基因敲除小鼠的分析表明，在缺乏相应Kv2α亚基的神经元中，AMIGO-1的表达和定位选择性丧失。总之，这些数据表明，在哺乳动物脑神经元中，AMIGO-1仅与Kv2α亚基相关，并且Kv2α亚基对于确定AMIGO-1表达、质膜运输和聚集的正确模式是必不可少的。
