The HCN domain couples voltage gating and cAMP response in hyperpolarization-activated cyclic nucleotide-gated channels

Porro, Alessandro; Saponaro, Andrea; Gasparri, Federica; Bauer, Daniel; Groß, Christine; Pisoni, Matteo; Abbandonato, Gerardo; Hamacher, Kay; Santoro, Bina; Thiel, Gerhard; Moroni, Anna

doi:10.7554/elife.49672

Cited by 54 publications

(123 citation statements)

References 51 publications

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“…These data raised the question of whether a direct interaction between opposite subunits is essential for channel gating. This suggestion is supported by latest high-resolution structures of HCN channels suggesting that the C-linker enables functionally relevant interactions with the opposite subunit, which might also be critical for coupling the conformational changes in the CNBD to the channel pore (6,15,17).…”

Section: Introductionmentioning

confidence: 84%

“…Over the past years, a plethora of different residues has been identified that are involved in channel gating by mediating intra-and inter-subunit contacts. So far, only little is known about functionally relevant inter-subunit contacts between opposite subunits in HCN channels (15).…”

Section: Discussionmentioning

confidence: 99%

“…Recently it was suggested that the N-terminal HCN domain plays a role in channel activation upon hyperpolarization and cyclic nucleotide binding (15,37). However, the purpose of the HCN/CL interaction on channel activation is not completely understood.…”

Section: Discussionmentioning

confidence: 99%

“…Different techniques including electrophysiological approaches, fluorescence microscopy and cryo-electron microscopy combined with mutagenesis were used to show intensive interactions between neighboring subunits: S4-S5 loop-CL interactions (6,11), CL-CL interactions (12)(13)(14), CNBD-CNBD interactions (6,12), and interactions between the newly discovered HCN domain with the CNBD and the voltage sensing domain (6,15).…”

Section: Introductionmentioning

confidence: 99%

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Functional and structural characterization of interactions between opposite subunits in HCN pacemaker channels

Kondapuram¹,

Frieg

Yueksel

et al. 2020

Preprint

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Hyperpolarization-activated and cyclic nucleotide (HCN) modulated channels are tetrameric cation channels. In each of the four subunits, the intracellular cyclic nucleotide-binding domain (CNBD) is coupled to the transmembrane domain via a helical structure, the C-linker. High-resolution channel structures suggest that the C-linker enables functionally relevant interactions with the opposite subunit, which might be critical for coupling the conformational changes in the CNBD to the channel pore. We combined mutagenesis, patch-clamp technique, confocal patch-clamp fluorometry, and molecular dynamics simulations to show that residue K464 of the C-linker is essential for stabilizing the closed state of the mHCN2 channel by forming interactions with the opposite subunit. MD simulations revealed that both cAMP and K464E induce a rotation of the intracellular domain relative to the channel pore, weakening the autoinhibitory effect of the unoccupied CL-CNBD region. The adopted poses are in excellent agreement with structural results.

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Section: Introductionmentioning

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Functional and structural characterization of interactions between opposite subunits in HCN pacemaker channels

Kondapuram¹,

Frieg

Yueksel

et al. 2020

Preprint

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show abstract

“…At the final stages of our study Porro and coworkers published a study on the role of the HCND in HCN channel gating (41). Although, Porro and coworkers also tested effects of disrupting the interactions between the HCND and VSD and C-linker/CNBD in HCN2 channels with mutations, they considered mostly different residues in their study.…”

Section: Discussionmentioning

confidence: 99%

HCN domain is required for HCN channel expression and couples voltage- and cAMP-dependent gating mechanisms

Wang

Blanco

Hayoz

et al. 2020

Preprint

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Hyperpolarization-activated cyclic nucleotidegated (HCN) channels are major regulators of synaptic plasticity, and rhythmic activity in the heart and brain. Opening of HCN channels requires membrane hyperpolarization and is further facilitated by intracellular cyclic nucleotides (cNMPs).In HCN channels, membrane hyperpolarization is sensed by the membrane-spanning voltage sensor domain (VSD) and the cNMP-dependent gating is mediated by the intracellular cyclic nucleotidebinding domain (CNBD) connected to the poreforming S6 transmembrane domain via the Clinker. Previous functional analysis of HCN channels suggested a direct or allosteric coupling between the voltage-and cNMPdependent activation mechanisms. However, the specifics of the coupling were unclear. The first cryo-EM structure of an HCN1 channel revealed that a novel structural element, dubbed HCN domain (HCND), forms a direct structural link between the VSD and Clinker/CNBD. In this study, we investigated the functional significance of the HCND. Deletion of the HCND prevented surface expression of HCN2 channels. Based on the HCN1 structure analysis, we identified R237 and G239 residues on the S2 of the VSD that form direct interactions with I135 on the HCND. Disrupting these interactions abolished HCN2 currents. We then identified three residues on the C-linker/CNBD (E478, Q382 and H559) that form direct interactions with residues R154 and S158 on the HCND. Disrupting these interactions affected both voltage-and cAMPdependent gating of HCN2 channels. These findings indicate that the HCND is necessary for the surface expression of HCN channels, and provides a functional link between the voltage-and cAMP-dependent mechanisms of HCN channel gating.Hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels are peculiar members of the voltage-gated potassium channel superfamily. Unlike other potassium channels, which are depolarization-activated and highly selective for K + , HCN channels are activated by membrane hyperpolarization and permeate both Na + and K + (1,2). The opening of HCN channels is further facilitated by cyclic nucleotides (1-3).

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HCN1 pathogenic variants associated with childhood epilepsy in a cohort of Chinese patients

Yang,

Kuang,

Liao

et al. 2023

Epileptic Disorders

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ObjectiveHCN ion channel family has a widespread expression in neurons, and recently, increasing studies have demonstrated their roles in epilepsies.MethodsClinical data of the patients were gathered in a retrospective study. Exon sequencing was used for the patients with unexplained recurrent seizures and varying levels of developmental delay.ResultsIn this study, eight de novo variants of HCN1 genes were uncovered in eight patients, including six missense variants, one nonsense variant and one frameshift insertion variant; five of them were reported for the first time. The onset age for eight patients ranges from one month to one year. Their main clinical manifestations are epilepsy and varying degrees of developmental delay, and the main type of seizure is focal secondary generalized tonic–clonic seizure. Importantly, in our study, one case presented with a form of migrating focal seizure that has not been reported in the literature. Seizures from five of the eight children were effectively controlled with antiepileptic drugs including valproic acid, levetiracetam and oxcarbazepine. One child developed normally and four children developed mild delay. One child was treated with topiramate, and the convulsion was partially controlled and showed moderate to severe developmental delay. The antiepileptic treatment failed for the other two children, and the two children were treated with sodium valproate, oxcarbazepine, lamotrigine, chlorbazan, levetiracetam and nitrodiazepam successively, but their convulsions were not controlled and showed moderate to severe developmental delay.SignificanceOur research reported eight variants in HCN1 gene causing epilepsy; among these variants, five variants were never reported before. HCN1‐related epilepsy usually starts infantile period, and focal secondary generalized tonic–clonic seizure is the most common seizure type. Importantly, we reported the case with migrating focal seizure was rarely reported. Our study expanded both genotype and phenotype for HCN1‐related epilepsy.

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The HCN domain couples voltage gating and cAMP response in hyperpolarization-activated cyclic nucleotide-gated channels

Cited by 54 publications

References 51 publications

Functional and structural characterization of interactions between opposite subunits in HCN pacemaker channels

Functional and structural characterization of interactions between opposite subunits in HCN pacemaker channels

HCN domain is required for HCN channel expression and couples voltage- and cAMP-dependent gating mechanisms

HCN1 pathogenic variants associated with childhood epilepsy in a cohort of Chinese patients

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