Howard Hughes Medical Institute, Ashburn, VA 20147.
Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115.
Proc Natl Acad Sci U S A. 2018 Mar 6;115(10):2377-2382. doi: 10.1073/pnas.1722038115. Epub 2018 Feb 20.
Transient receptor potential melastatin subfamily member 4 (TRPM4) is a widely distributed, calcium-activated, monovalent-selective cation channel. Mutations in human TRPM4 (hTRPM4) result in progressive familial heart block. Here, we report the electron cryomicroscopy structure of hTRPM4 in a closed, Na-bound, apo state at pH 7.5 to an overall resolution of 3.7 Å. Five partially hydrated sodium ions are proposed to occupy the center of the conduction pore and the entrance to the coiled-coil domain. We identify an upper gate in the selectivity filter and a lower gate at the entrance to the cytoplasmic coiled-coil domain. Intramolecular interactions exist between the TRP domain and the S4-S5 linker, N-terminal domain, and N and C termini. Finally, we identify aromatic interactions via π-π bonds and cation-π bonds, glycosylation at an N-linked extracellular site, a pore-loop disulfide bond, and 24 lipid binding sites. We compare and contrast this structure with other TRP channels and discuss potential mechanisms of regulation and gating of human full-length TRPM4.
瞬时受体电位 melastatin 亚家族成员 4（TRPM4）是一种广泛分布的、钙激活的、单价选择性阳离子通道。人类 TRPM4（hTRPM4）中的突变导致进行性家族性心脏传导阻滞。在这里，我们报告了 hTRPM4 在 pH7.5 时处于关闭、Na 结合、apo 状态的电子冷冻电镜结构，整体分辨率为 3.7Å。提出了五个部分水合的钠离子占据传导孔的中心和卷曲螺旋结构域的入口。我们在选择性过滤器中识别出一个上门控，在细胞质卷曲螺旋结构域的入口处识别出一个下门控。分子内相互作用存在于 TRP 结构域和 S4-S5 连接子、N 端结构域以及 N 和 C 末端之间。最后，我们通过π-π 键和阳离子-π 键、细胞外 N 连接位点的糖基化、孔环二硫键和 24 个脂质结合位点鉴定了芳香族相互作用。我们将这个结构与其他 TRP 通道进行了比较和对比，并讨论了人类全长 TRPM4 的调节和门控的潜在机制。
