Hyperpolarization-activated cyclic nucleotide-modulated (HCN) ion channels were first discovered in photoreceptors where they shape the light response. They exhibit several properties that make them specialized for retinal signaling: 1) they are activated by membrane hyperpolarization instead of depolarization, 2) they are regulated by the direct binding of cyclic nucleotides to an intracellular domain, and 3) they are expressed in the distal dendrites of neurons. Recently an accessory subunit of HCN channels in photoreceptors and other neurons was discovered, called TRIP8b, that has a profound effect on each of these important channel properties. Our long term goal is to understand the molecular mechanisms for these properties. In previous funding periods we have made great progress toward achieving this goal. We have solved the X-ray crystal structure of the cyclic nucleotide-binding domain of HCN2 and the structure of TRIP8b bound to HCN2. We have also invented three ground-breaking new fluorescence methods that allow us to record molecular rearrangements in intact channels simultaneous with electrophysiological recording. In this funding period, we propose to combine these methods with double electron-electron resonance (DEER), a powerful magnetic resonance-based method, and molecular dynamics simulations, to measure and model the structure and dynamics of the HCN channel and its interaction with TRIP8b. These experiments will lead to the first dynamic picture for how HCN channels regulate the excitability of photoreceptors and other neurons.

Public Health Relevance

Hyperpolarization-activated cyclic nucleotide-modulated (HCN) ion channels control the electrical signals in our retina in response to light. Our long term goal is to understand the molecular mechanisms for the specialized gating properties of HCN channels to better understand our visual signaling and better design therapies for treatment of diseases.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
2R01EY010329-21
Application #
8694326
Study Section
Biochemistry and Biophysics of Membranes Study Section (BBM)
Program Officer
Greenwell, Thomas
Project Start
1994-01-01
Project End
2018-04-30
Budget Start
2014-05-01
Budget End
2015-04-30
Support Year
21
Fiscal Year
2014
Total Cost
Indirect Cost
Name
University of Washington
Department
Physiology
Type
Schools of Medicine
DUNS #
City
Seattle
State
WA
Country
United States
Zip Code
98195
Collauto, Alberto; DeBerg, Hannah A; Kaufmann, Royi et al. (2017) Rates and equilibrium constants of the ligand-induced conformational transition of an HCN ion channel protein domain determined by DEER spectroscopy. Phys Chem Chem Phys 19:15324-15334
James, Zachary M; Zagotta, William N (2017) Structural insights into the mechanisms of CNBD channel function. J Gen Physiol :
Tait, Claudia E; Stoll, Stefan (2017) ENDOR with band-selective shaped inversion pulses. J Magn Reson 277:36-44
Bankston, John R; DeBerg, Hannah A; Stoll, Stefan et al. (2017) Mechanism for the inhibition of the cAMP dependence of HCN ion channels by the auxiliary subunit TRIP8b. J Biol Chem 292:17794-17803
Dai, Gucan; Zagotta, William N (2017) Molecular mechanism of voltage-dependent potentiation of KCNH potassium channels. Elife 6:
James, Zachary M; Borst, Andrew J; Haitin, Yoni et al. (2017) CryoEM structure of a prokaryotic cyclic nucleotide-gated ion channel. Proc Natl Acad Sci U S A 114:4430-4435
Aman, Teresa K; Gordon, Sharona E; Zagotta, William N (2016) Regulation of CNGA1 Channel Gating by Interactions with the Membrane. J Biol Chem 291:9939-47
DeBerg, Hannah A; Brzovic, Peter S; Flynn, Galen E et al. (2016) Structure and Energetics of Allosteric Regulation of HCN2 Ion Channels by Cyclic Nucleotides. J Biol Chem 291:371-81
Edwards, Thomas H; Stoll, Stefan (2016) A Bayesian approach to quantifying uncertainty from experimental noise in DEER spectroscopy. J Magn Reson 270:87-97
Gordon, Sharona E; Senning, Eric N; Aman, Teresa K et al. (2016) Transition metal ion FRET to measure short-range distances at the intracellular surface of the plasma membrane. J Gen Physiol 147:189-200

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