Department of Anesthesiology, Weill Cornell Medicine, 1300 York Avenue, New York, NY, USA.
Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Frankfurt/Main, Germany.
Nat Commun. 2024 Sep 19;15(1):8230. doi: 10.1038/s41467-024-52469-1.
The signaling lipid phosphatidylinositol-4,5-bisphosphate (PIP2) regulates many ion channels. It inhibits eukaryotic cyclic nucleotide-gated (CNG) channels while activating their relatives, the hyperpolarization-activated and cyclic nucleotide-modulated (HCN) channels. The prokaryotic SthK channel from Spirochaeta thermophila shares features with CNG and HCN channels and is an established model for this channel family. Here, we show SthK activity is inhibited by PIP2. A cryo-EM structure of SthK in nanodiscs reveals a PIP2-fitting density coordinated by arginine and lysine residues from the S4 helix and the C-linker, located between voltage-sensing and pore domains of adjacent subunits. Mutation of two arginine residues weakens PIP2 inhibition with the double mutant displaying insensitivity to PIP2. We propose that PIP2 inhibits SthK by gluing S4 and S6 together, stabilizing a resting channel conformation. The PIP2 binding site is partially conserved in CNG channels suggesting the possibility of a similar inhibition mechanism in the eukaryotic homologs.
信号脂质磷脂酰肌醇-4,5-二磷酸（PIP2）调节许多离子通道。它抑制真核环核苷酸门控（CNG）通道，同时激活它们的同源物，超极化激活和环核苷酸调制（HCN）通道。来自疏螺旋体Thermophila 的原核 SthK 通道与 CNG 和 HCN 通道具有相似的特征，是该通道家族的既定模型。在这里，我们表明 SthK 的活性受 PIP2 的抑制。在纳米盘中的 SthK 的 cryo-EM 结构揭示了 PIP2 配合物的密度，该密度由 S4 螺旋和位于电压感应和相邻亚基的孔域之间的 C 接头的精氨酸和赖氨酸残基协调。两个精氨酸残基的突变削弱了 PIP2 的抑制作用，双突变体对 PIP2 不敏感。我们提出 PIP2 通过将 S4 和 S6 粘在一起抑制 SthK，稳定了静止通道构象。PIP2 结合位点在 CNG 通道中部分保守，表明在真核同源物中可能存在类似的抑制机制。
