Structural mechanism for the regulation of HCN ion channels by the accessory protein TRIP8b

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels / chemistry*
  • Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels / metabolism
  • Membrane Proteins / chemistry
  • Membrane Proteins / metabolism*
  • Mice
  • Molecular Sequence Data
  • Peroxins
  • Potassium Channels / chemistry*
  • Potassium Channels / metabolism
  • Protein Binding
  • Xenopus


  • Hcn2 protein, mouse
  • Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels
  • Membrane Proteins
  • Peroxins
  • Pex5l protein, mouse
  • Potassium Channels