DeBerg Hannah A, Bankston John R, Rosenbaum Joel C, Brzovic Peter S, Zagotta William N, Stoll Stefan
Department of Chemistry, University of Washington, Seattle, WA 98195, USA; Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
Structure. 2015 Apr 7;23(4):734-44. doi: 10.1016/j.str.2015.02.007. Epub 2015 Mar 19.
Hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channels underlie the cationic Ih current present in many neurons. The direct binding of cyclic AMP to HCN channels increases the rate and extent of channel opening and results in a depolarizing shift in the voltage dependence of activation. TRIP8b is an accessory protein that regulates the cell surface expression and dendritic localization of HCN channels and reduces the cyclic nucleotide dependence of these channels. Here, we use electron paramagnetic resonance (EPR) to show that TRIP8b binds to the apo state of the cyclic nucleotide binding domain (CNBD) of HCN2 channels without changing the overall domain structure. With EPR and nuclear magnetic resonance, we locate TRIP8b relative to the HCN channel and identify the binding interface on the CNBD. These data provide a structural framework for understanding how TRIP8b regulates the cyclic nucleotide dependence of HCN channels.
超极化激活的环核苷酸门控（HCN）离子通道是许多神经元中存在的阳离子Ih电流的基础。环磷酸腺苷（cAMP）与HCN通道的直接结合增加了通道开放的速率和程度，并导致激活电压依赖性的去极化偏移。TRIP8b是一种辅助蛋白，可调节HCN通道的细胞表面表达和树突定位，并降低这些通道对环核苷酸的依赖性。在这里，我们使用电子顺磁共振（EPR）表明TRIP8b与HCN2通道的环核苷酸结合结构域（CNBD）的无辅基状态结合，而不会改变整体结构域结构。通过EPR和核磁共振，我们确定了TRIP8b相对于HCN通道的位置，并确定了CNBD上的结合界面。这些数据为理解TRIP8b如何调节HCN通道对环核苷酸的依赖性提供了一个结构框架。
