Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA.
J Cell Biol. 2024 Oct 7;223(10). doi: 10.1083/jcb.202401140. Epub 2024 Jul 30.
The evolution of ion channel clustering at nodes of Ranvier enabled the development of complex vertebrate nervous systems. At mammalian nodes, the K+ leak channels TRAAK and TREK-1 underlie membrane repolarization. Despite the molecular similarities between nodes and the axon initial segment (AIS), TRAAK and TREK-1 are reportedly node-specific, suggesting a unique clustering mechanism. However, we show that TRAAK and TREK-1 are enriched at both nodes and AIS through a common mechanism. We identified a motif near the C-terminus of TRAAK that is necessary and sufficient for its clustering. The motif first evolved among cartilaginous fish. Using AnkyrinG (AnkG) conditional knockout mice, CRISPR/Cas9-mediated disruption of AnkG, co-immunoprecipitation, and surface recruitment assays, we show that TRAAK forms a complex with AnkG and that AnkG is necessary for TRAAK's AIS and nodal clustering. In contrast, TREK-1's clustering requires TRAAK. Our results expand the repertoire of AIS and nodal ion channel clustering mechanisms and emphasize AnkG's central role in assembling excitable domains.
离子通道在郎飞结的聚集促进了复杂的脊椎动物神经系统的发展。在哺乳动物的郎飞结中，K+泄漏通道 TRAAK 和 TREK-1 介导膜复极化。尽管郎飞结和轴突起始段（AIS）之间具有分子相似性，但据报道 TRAAK 和 TREK-1 是郎飞结特异性的，表明存在独特的聚集机制。然而，我们通过共同的机制表明，TRAAK 和 TREK-1 通过一种共同的机制在郎飞结和 AIS 处均有富集。我们在 TRAAK 的 C 末端附近鉴定了一个基序，该基序对于其聚集是必需和充分的。该基序首先在软骨鱼类中进化。通过使用 AnkyrinG（AnkG）条件性敲除小鼠、CRISPR/Cas9 介导的 AnkG 敲除、共免疫沉淀和表面募集测定，我们表明 TRAAK 与 AnkG 形成复合物，并且 AnkG 对于 TRAAK 的 AIS 和郎飞结聚集是必需的。相比之下，TREK-1 的聚集需要 TRAAK。我们的结果扩展了 AIS 和郎飞结离子通道聚集机制的范围，并强调了 AnkG 在组装可兴奋域中的核心作用。
