Affinage

HCN4

Potassium/sodium hyperpolarization-activated cyclic nucleotide-gated channel 4 · UniProt Q9Y3Q4

Length
1203 aa
Mass
129.0 kDa
Annotated
2026-06-10
100 papers in source corpus 39 papers cited in narrative 39 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

HCN4 is the principal pore-forming subunit of the cardiac hyperpolarization-activated 'funny' (If) pacemaker current, and its activity is essential for sinoatrial impulse generation and conduction: inducible cardiac-specific knockout in adult mice produces severe bradycardia, AV block, and death with profound loss of SAN If current (PMID:21220308). The channel is a weakly selective cation conductance whose gating is set by defined structural modules — N-terminal HCN domain residues that stabilize the closed state (a gain-of-function p.V240M mutation increases open probability and conductance to cause inappropriate sinus tachycardia) (PMID:38032931), S1/S1-S2/S2 residues that tune activation kinetics relative to HCN2 (PMID:12813043), and a C-linker/CNBD whose crystal structure explains HCN4's attenuated cAMP response relative to HCN2 (PMID:20829353), with cAMP binding relieving C-linker autoinhibition in an isoform- and context-dependent manner (PMID:23109717). cAMP-dependent regulation underlies its physiological roles in autonomic heart-rate control, where HCN4 attenuates parasympathetic (vagal) bradycardia (PMID:29315578), and in disease, where ectopic HCN4 in mTOR-hyperactivated cortical neurons drives cAMP-dependent repetitive firing and seizures (PMID:33208499). Channel function is shaped by an array of direct partners and modulators: PKA phosphorylates HCN4 at multiple C-terminal sites to shift voltage dependence (PMID:20713547), Src tyrosine kinase enhances the current via Tyr531 (PMID:16680072, PMID:17977941), the auxiliary subunit KCNE2 (PMID:12856183) and the ER proteins LRMP and IRAG exert opposing isoform-specific effects on cAMP-dependent gating (PMID:32647060), caveolin-1 binding through an N-terminal CBD controls localization (PMID:22659290), and β2-adrenergic receptors form an N-terminal co-complex required for adrenergic augmentation of pacemaking (PMID:22613709). Trafficking and surface density are governed by SGO1, whose CAID-syndrome mutation impairs HCN4 membrane expression (PMID:33953173), and are disrupted by trafficking-defective disease mutations (D553N, G480R) (PMID:15123648, PMID:17646576) and by coxsackievirus-driven Rab7-dependent internalization (PMID:35864219). HCN4 transcription is tightly controlled by MEF2C acting through a conserved enhancer (modulated by HDAC export and a mitochondrial Trx2–ROS–HDAC4 axis) (PMID:19477969, PMID:23085412, PMID:31751569), by Sp1 (PMID:19471099), NRSF (PMID:17173866), the circadian factor BMAL1 driving day-night heart-rate rhythms (PMID:33278629), and chromatin regulators including Cfp1 (PMID:34182171), while miR-1 and miR-423-5p repress it post-transcriptionally during hypertrophy and exercise training (PMID:18458081, PMID:28821541). The channel is also the molecular target of the bradycardic drug ivabradine, which binds the open-pore inner cavity via S6 residues Y507 and I511 (PMID:38917012).

Mechanistic history

Synthesis pass · year-by-year structured walk · 19 steps
  1. 2001 High

    Establishing that HCN4 channels could be gated by extracellular protons defined a sensory-transduction role beyond simple voltage-dependent pacemaking.

    Evidence In situ hybridization and patch-clamp of native taste cells plus heterologous HCN expression

    PMID:11675786

    Open questions at the time
    • Did not establish the cardiac pacemaker role
    • Molecular site of proton gating not mapped
  2. 2003 High

    Chimera and mutagenesis work answered which residues set HCN4's characteristically slow activation, mapping kinetic determinants to S1, the S1-S2 linker, and S2.

    Evidence HCN2/4 chimeras and point mutagenesis with patch-clamp in heterologous cells

    PMID:12813043

    Open questions at the time
    • Structural basis not resolved
    • Did not address native heteromeric channels
  3. 2003 Medium

    Co-assembly studies addressed the subunit composition of native f-channels, showing HCN4-HCN1 heteromers and KCNE2 association reshape gating toward native SAN If.

    Evidence Tandem-construct and co-expression patch-clamp plus yeast two-hybrid for KCNE2

    PMID:12702747 PMID:12856183

    Open questions at the time
    • cAMP sensitivity of heteromers did not fully match native current
    • Stoichiometry in vivo unresolved
    • KCNE2 interaction shown only by Y2H, not in native tissue
  4. 2004 Medium

    The first disease mutation (D553N) defined trafficking impairment as a dominant-negative loss-of-function mechanism for sinus node dysfunction.

    Evidence HEK293 expression with patch-clamp, surface biotinylation, and Western blot

    PMID:15123648

    Open questions at the time
    • Single lab
    • Trafficking machinery involved not identified
  5. 2009 High

    Endogenous co-IP from heart resolved how native myocardial If arises, showing a cleaved cAMP-insensitive HCN2 fragment heteromerizes with full-length HCN4.

    Evidence Antibody-specific Western blot, co-IP of cardiac channels, and reconstitution patch-clamp

    PMID:19574228

    Open questions at the time
    • Protease responsible for HCN2 cleavage unknown
    • Physiological relevance of heteromers in pacemaking not quantified
  6. 2010 High

    Structural and biochemical work defined cAMP regulation, with the C-linker/CNBD crystal structure explaining HCN4's reduced cAMP response and mass spectrometry mapping PKA phosphorylation sites controlling voltage dependence.

    Evidence 2.4 Å X-ray crystallography with mutagenesis, plus in vitro kinase/MS and SAN myocyte patch-clamp

    PMID:20713547 PMID:20829353

    Open questions at the time
    • Full-length channel structure absent
    • How distinct PKA sites integrate not resolved
  7. 2012 Medium

    Identification of N-terminal partner domains established how HCN4 is localized and adrenergically tuned, via a caveolin-1-binding CBD and a β2AR co-complex domain.

    Evidence Mutagenesis, co-IP, peptide disruption, patch-clamp, and confocal imaging

    PMID:22613709 PMID:22659290

    Open questions at the time
    • Single lab for each interaction
    • Structural detail of complexes lacking
  8. 2012 Medium

    Studies of N-terminal isoforms, a C-linker disease mutation, and context-dependent autoinhibition relief defined how intracellular regions modulate basal and cAMP-dependent gating.

    Evidence RT-PCR isoform mapping, mutagenesis, and excised-patch electrophysiology in CHO vs HEK cells

    PMID:21372143 PMID:23109717 PMID:23178648

    Open questions at the time
    • The membrane-associated factor relieving autoinhibition in CHO cells unidentified
    • K530N heteromeric mechanism inferred indirectly
  9. 2007 Medium

    Src kinase was established as a direct positive modulator, with Tyr531 and Tyr554 dissecting voltage-shift versus kinetic effects.

    Evidence Co-IP in two cell types, constitutively active/dominant-negative Src, site-directed mutagenesis, and patch-clamp

    PMID:16680072 PMID:17977941

    Open questions at the time
    • Single lab
    • In vivo relevance of Src tyrosine phosphorylation not fully established
  10. 2009 Medium

    Transcriptional control was defined through MEF2 binding a conserved Hcn4 enhancer and Sp1 driving the core promoter, including pathological re-expression in hypertrophy.

    Evidence ChIP, EMSA, luciferase reporters, dominant-negative MEF2, Sp1 siRNA, and patch-clamp

    PMID:19471099 PMID:19477969

    Open questions at the time
    • Combinatorial control with other factors unresolved
    • Direct MEF2 vs Sp1 hierarchy not established
  11. 2008 High

    Post-transcriptional repression by miR-1 was established as a mechanism preventing pathological HCN4 overexpression in hypertrophy.

    Evidence 3'-UTR targeting, mimic and masking antisense, Western blot, patch-clamp, and rat hypertrophy model

    PMID:18458081

    Open questions at the time
    • Relative contribution vs transcriptional control unclear
  12. 2011 High

    Cardiac-specific inducible knockout definitively established HCN4 as essential for adult cardiac impulse generation and conduction.

    Evidence Inducible cardiac Cre-lox KO with SAN patch-clamp, immunofluorescence, and telemetric ECG

    PMID:21220308

    Open questions at the time
    • Did not dissect SAN vs AV-node contributions mechanistically
  13. 2018 High

    Gain- and loss-of-function in the same inducible system revealed that HCN4 buffers parasympathetic (vagal) bradycardia in the SAN.

    Evidence Tetracycline-inducible HCN4 overexpression/knockdown mice with in vivo vagal stimulation and single-cell patch-clamp

    PMID:29315578

    Open questions at the time
    • Molecular link between If and cholinergic signaling not defined
  14. 2020 High

    Auxiliary ER proteins LRMP and IRAG were identified as isoform-specific, oppositely-acting modulators of HCN4 cAMP-dependent gating, with IRAG enriched in SAN.

    Evidence Co-expression patch-clamp, co-IP, SAN expression analysis, and modeling

    PMID:32647060

    Open questions at the time
    • Structural basis of opposing effects unknown
    • Physiological IRAG/LRMP balance in vivo not measured
  15. 2020 High

    Circadian and metabolic transcriptional axes were established: BMAL1 directly drives day-night Hcn4 rhythms and a mitochondrial Trx2-ROS-HDAC4-MEF2C pathway maintains conduction-system HCN4.

    Evidence ChIP, cardiomyocyte/conduction-system-specific KO mice, pharmacological rescue (MitoTEMPO, HCN block), and ECG

    PMID:31751569 PMID:33278629

    Open questions at the time
    • Interplay between circadian and ROS-driven control not integrated
    • Upstream signals coupling metabolism to HDAC4 incompletely mapped
  16. 2020 High

    Ectopic HCN4 was shown to be pathogenic outside the heart, driving cAMP-dependent epileptic firing in mTOR-hyperactivated cortical neurons.

    Evidence TSC/FCDII mouse model, pharmacological HCN4 block, cAMP manipulation, and human tissue immunostaining

    PMID:33208499

    Open questions at the time
    • Transcriptional mechanism of mTOR-driven HCN4 induction not fully defined
  17. 2021 High

    Trafficking partners and chromatin regulators were identified: SGO1 promotes HCN4 surface expression (disrupted in CAID syndrome) and Cfp1 maintains activating histone marks at the HCN4 promoter.

    Evidence Co-IP, surface assays, patient iPSC-CMs, ChIP for histone marks, and patch-clamp in conduction-system-specific KO

    PMID:33953173 PMID:34182171

    Open questions at the time
    • Mechanism of SGO1-mediated surface delivery not resolved
    • Direct vs indirect Cfp1 effects on HCN4 not separated
  18. 2023 High

    Single-channel analysis of a gain-of-function HCN-domain mutation (p.V240M) established that the N-terminal HCN domain stabilizes the closed state, linking inappropriate sinus tachycardia to increased open probability.

    Evidence Macroscopic and single-channel patch-clamp, surface expression assay, and SAN computer modeling

    PMID:38032931

    Open questions at the time
    • Structural mechanism of HCN-domain closed-state stabilization not visualized
  19. 2024 High

    Atomic-resolution structure defined the pharmacological target site, showing ivabradine blocks the open-pore inner cavity via S6 residues Y507 and I511.

    Evidence 3 Å cryo-EM of the HCN4-ivabradine complex with molecular dynamics and functional validation

    PMID:38917012

    Open questions at the time
    • Full gating-cycle structures still lacking
    • Ion-selectivity mechanism addressed only computationally [#33]

Open questions

Synthesis pass · forward-looking unresolved questions
  • How the many transcriptional, post-transcriptional, phosphorylation, trafficking, and auxiliary-subunit inputs are integrated to set beat-to-beat If in vivo, and the full-length channel gating-cycle structure, remain unresolved.
  • No full-length apo/cAMP-bound HCN4 structure across gating states
  • Quantitative hierarchy of regulators in native SAN unknown
  • Ion selectivity mechanism not experimentally validated by structure/mutagenesis

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005215 transporter activity 4 GO:0140299 molecular sensor activity 2
Localization
GO:0005886 plasma membrane 5 GO:0005829 cytosol 2
Pathway
GO:0140110 transcription regulator activity 4 R-HSA-162582 Signal Transduction 3 R-HSA-112316 Neuronal System 2 R-HSA-397014 Muscle contraction 2 R-HSA-9909396 Circadian clock 1
Partners
ADRB2CAV1IRAGKCNE2LRMPSGO1SRCTHY1
Complex memberships
HCN4-HCN1 heteromeric channelHCN4-cleaved HCN2 heteromeric channelHCN4-β2AR co-complex

Evidence

Reading pass · 39 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2011 Cardiac-specific, inducible knockout of HCN4 in adult mice causes severe bradycardia (~50% rate reduction), AV block, and death within ~5 days, with ~70% reduction of If current in sinoatrial node myocytes, establishing HCN4 as essential for normal cardiac impulse generation and conduction. Inducible cardiac-specific Cre-lox knockout mouse model; in vitro patch-clamp of isolated SAN myocytes; immunofluorescence and Western blot Proceedings of the National Academy of Sciences of the United States of America High 21220308
2003 HCN4 and HCN1 co-assemble into heteromeric channels in heterologous expression; the HCN4-HCN1 (4-1) tandem construct produces activation kinetics intermediate between the two homomers, approaching those of native rabbit SAN If current, suggesting both isoforms contribute to native f-channels. Heterologous co-expression in HEK293 cells; tandem-linked constructs; whole-cell patch-clamp; comparison with native SAN If The Journal of physiology Medium 12702747
2001 HCN4 channels expressed in taste cells are gated by extracellular protons: lowering pH causes a dose-dependent shift in the activation curve to more positive voltages, mediating sour taste transduction. In situ hybridization; immunohistochemistry in rat vallate papilla; whole-cell patch-clamp of taste cells; voltage-clamp of HCN channels Nature High 11675786
2004 The D553N missense mutation in HCN4 causes a trafficking defect that reduces membrane expression and If current in a dominant-negative manner, establishing loss-of-function via protein trafficking impairment as a mechanism for sinus node dysfunction. In vitro expression in HEK293 cells; patch-clamp; biotinylation assay; Western blot The Journal of biological chemistry Medium 15123648
2003 KCNE2 co-expressed with HCN4 enhances current amplitude, slows activation kinetics, and shifts half-maximal activation to more negative voltages; the C-terminal tail of KCNE2 (but not KCNE1, KCNE3, or KCNE4) directly interacts with the C-terminal tail of HCN4 as shown by yeast two-hybrid. Co-expression in Xenopus oocytes and CHO cells; two-electrode voltage-clamp and patch-clamp; yeast two-hybrid interaction assay Pflugers Archiv : European journal of physiology Medium 12856183
2010 The crystal structure of the C-terminal fragment of human HCN4 (C-linker + CNBD) at 2.4 Å reveals high similarity to mouse HCN2 but with distinct residues in the β4-β5 loop that account for HCN4's ~3-fold reduced cAMP response and prolonged deactivation upon cAMP binding compared to HCN2. X-ray crystallography at 2.4 Å; mutagenesis; electrophysiology (patch-clamp) The Journal of biological chemistry High 20829353
2010 PKA directly phosphorylates HCN4 at ≥13 sites (≥3 N-terminal, ≥10 C-terminal) identified by in vitro phosphorylation assay and mass spectrometry; a PKA regulatory site in the distal C-terminus is required for PKA-mediated shift of HCN4 voltage dependence in sinoatrial myocytes. In vitro kinase assay; mass spectrometry; PKA inhibitor experiments on isolated SAN myocytes; truncation and alanine substitution mutagenesis; patch-clamp The Journal of general physiology High 20713547
2007 Src tyrosine kinase forms a complex with HCN4 (co-immunoprecipitation in HEK293 cells and rat ventricular myocytes) and constitutively active Src shifts HCN4 activation to more positive voltages and accelerates kinetics, while dominant-negative Src has the opposite effect. Co-immunoprecipitation; co-transfection with constitutively active (Src529) or dominant-negative (Src296) Src in HEK293 cells; whole-cell patch-clamp Journal of cardiovascular pharmacology Medium 16680072
2007 Src tyrosine kinase enhances HCN4 via Tyr531: mutation Y531F largely abolishes Src-mediated positive shift of voltage dependence and increased conductance, while Y554F selectively eliminates Src-induced kinetic changes without affecting voltage-dependent activation shift. Site-directed mutagenesis of HCN4; Src inhibitor PP2; whole-cell patch-clamp in HEK293 cells; heart rate measurement in mouse model American journal of physiology. Cell physiology Medium 17977941
2003 Specific residues in S1 (Leu272), the S1-S2 linker (Asn291, Thr293), and S2 (Ile308) of HCN4 determine its slower activation kinetics compared to HCN2; L272F in S1 accelerates HCN4 activation to match HCN2 speed, and I308M in S2 abolishes cAMP-dependent acceleration of activation. HCN2/4 chimeric channel analysis; site-directed mutagenesis; patch-clamp electrophysiology in heterologous expression The Journal of biological chemistry High 12813043
2009 MEF2 transcription factor directly binds an enhancer element (CNS13) in the Hcn4 genomic locus; dominant-negative MEF2 reduces Hcn4 mRNA expression and Ih current amplitude in embryonic heart inflow tract myocytes, establishing MEF2 as a direct transcriptional activator of Hcn4. Luciferase reporter assay; EMSA; chromatin immunoprecipitation (ChIP); dominant-negative MEF2 overexpression; patch-clamp of embryonic inflow-tract myocytes Cardiovascular research High 19477969
2006 The NRSE motif in the HCN4 promoter binds NRSF (neuron-restrictive silencing factor); wild-type NRSE drives expression changes that match developmental and hypertrophic HCN4 expression patterns, whereas mutant NRSE constructs fail, implicating NRSF as a transcriptional repressor of HCN4. Promoter reporter assay in rat cardiac myocytes; NRSF binding confirmation; NRSE mutagenesis Biochemical and biophysical research communications Medium 17173866
2008 miR-1 directly targets the 3'-UTR of HCN4 to repress its protein expression; forced miR-1/miR-133 expression in hypertrophic cardiomyocytes prevents HCN4 overexpression, and downregulation of miR-1/miR-133 in hypertrophic hearts (linked to reduced serum-responsive factor) underlies pathological re-expression of HCN4. 3'-UTR targeting confirmation; miRNA mimic transfection; miRNA-masking antisense; Western blot; patch-clamp; rat hypertrophy model The Journal of biological chemistry High 18458081
2012 HCN4 contains a conserved caveolin-binding domain (CBD) with aromatic residues Tyr259 and Phe262 at the N-terminus; disruption of CBD reduces HCN4-caveolin-1 interaction, causes cytoplasmic channel accumulation, and abolishes sensitivity to cholesterol depletion-induced caveolar disorganization, demonstrating that CBD mediates functional interaction with caveolin-1. CBD mutagenesis (Y259S, F262V, Y259F, F262Y); co-immunoprecipitation; whole-cell patch-clamp; confocal microscopy; cholesterol depletion in CHO cells Journal of molecular and cellular cardiology High 22659290
2012 β2-adrenergic receptors form a protein complex with HCN4 via a proximal N-terminal region of HCN4; a synthetic peptide derived from this β2AR-binding domain disrupts the complex and prevents adrenergic augmentation of pacemaker currents and spontaneous contraction rates without affecting calcium current regulation. Co-immunoprecipitation; synthetic peptide disruption assay; patch-clamp; spontaneous contraction rate measurement The Journal of biological chemistry Medium 22613709
2009 In adult mouse myocardium, HCN2 undergoes proteolytic cleavage to a ~60 kDa C-terminally truncated form lacking the cAMP-binding domain, which co-assembles with full-length HCN4 to form heteromeric channels; these heteromers activate faster than either homomer and resemble endogenous myocardial If, with HCN4 subunit supplying cAMP-mediated regulation. Western blot with N- and C-terminal-specific antibodies; co-immunoprecipitation of endogenous cardiac channels; heterologous co-expression; patch-clamp The Journal of biological chemistry High 19574228
2011 The N-terminus of HCN4 exists as two tissue-specific isoforms (different transcription start sites), with only one present in brain and both in heart; the extended N-terminal isoform shifts activation to more negative voltages, and three positively charged residues (Arg9, Lys10, Lys22) in the N-terminus are responsible for this functional difference. RT-PCR of brain and heart mRNA; patch-clamp of HEK293 cells expressing each variant; site-directed mutagenesis of N-terminal charged residues The Journal of biological chemistry Medium 21372143
2012 The HCN4-K530N mutation in the C-linker alters heteromeric (but not homomeric) channel properties, producing a hyperpolarizing shift in half-maximal activation voltage; this is attributed to disruption of C-linker oligomerization equilibrium between tonically inhibited and activated tetrameric states. Patch-clamp of HEK293 cells expressing homomeric mutant and co-expression of mutant+WT (heteromeric); pedigree analysis European heart journal Medium 23178648
2012 cAMP-induced relief of HCN4 autoinhibition can occur in a cellular context- and isoform-specific manner without cAMP: HCN4 (but not HCN2) expressed in CHO (but not HEK) cells shows pre-relieved autoinhibition dependent on a ~300-aa distal C-terminal region (residues 719-1012), pointing to membrane-associated intracellular factors interacting with the distal C-terminus. Patch-clamp in CHO vs HEK cells; excised inside-out patches; domain truncation mutagenesis of HCN4 distal C-terminus; cAMP application The Journal of general physiology Medium 23109717
2017 miR-423-5p directly targets the 3'-UTR of HCN4 (luciferase reporter abolished by mutation of recognition elements); swim-training upregulates miR-423-5p and its host gene NSRP1 driven by Nkx2.5, repressing HCN4 and If in the sinus node; anti-miR-423-5p knockdown reverses training-induced bradycardia by rescuing HCN4 expression. 3'-UTR luciferase reporter assay with recognition element mutation; next-generation miRNA sequencing; qRT-PCR; anti-miR knockdown in swim-trained mice; patch-clamp; chromatin immunoprecipitation for Nkx2.5 Circulation research High 28821541
2020 A local circadian clock in the sinoatrial node drives day-night rhythms in Hcn4 expression via direct BMAL1 binding sites on the Hcn4 promoter (ChIP); cardiomyocyte-specific Bmal1 knockout abolishes day-night differences in Hcn4 mRNA and intrinsic heart rate; HCN block eliminates the day-night heart rate difference in vivo and in isolated SAN. Chromatin immunoprecipitation (ChIP) for BMAL1 at Hcn4 promoter; cardiomyocyte-specific Bmal1 KO mice; vagotomy; in vivo/in vitro ECG recording; HCN pharmacological block; reporter bioluminescence Heart rhythm High 33278629
2020 LRMP and IRAG (homologous ER transmembrane proteins) associate with HCN4 and have opposing effects: LRMP inhibits cAMP-induced depolarizing shift in voltage dependence, while IRAG depolarizes basal voltage dependence in the absence of cAMP; both effects are isoform-specific to HCN4, independent of trafficking and cAMP binding, and IRAG is highly expressed in mouse sinoatrial node. Co-expression and functional patch-clamp in heterologous cells; co-immunoprecipitation; sinoatrial node expression analysis; computer modeling Proceedings of the National Academy of Sciences of the United States of America High 32647060
2021 Shugoshin-1 (SGO1) directly interacts with HCN4 (co-immunoprecipitation) and promotes cell-surface expression and function of HCN4, enhancing funny current; the CAID syndrome mutation p.Lys23Glu in SGO1 impairs its interaction with HCN4, reduces membrane HCN4 expression, and depresses If in patient iPSC-derived cardiomyocytes. Co-immunoprecipitation; patch-clamp; surface expression assay; patient-specific iPSC-derived cardiomyocytes; neonatal rat ventricular myocyte model Nature communications High 33953173
2024 Cryo-EM structure of HCN4 in complex with ivabradine at 3 Å resolution shows ivabradine bound inside the open pore inner cavity; Y507 and I511 on S6 are the molecular determinants of ivabradine binding, F510 (pointing outside the pore) indirectly contributes by controlling Y507, and C479 in the selectivity filter accelerates block kinetics; molecular dynamics show ivabradine blocks a permeating ion via electrostatic repulsion. Cryo-EM structure at 3 Å; molecular dynamics simulations; functional validation Proceedings of the National Academy of Sciences of the United States of America High 38917012
2009 Sp1 transcription factor binds the core promoter regions of HCN4 and drives its transcription; siRNA knockdown of Sp1 prevents HCN4 overexpression in hypertrophic cardiomyocytes; Sp1 upregulation underlies pathological re-expression of HCN4 in ventricular hypertrophy. 5'-RACE (transcription start site); luciferase reporter; siRNA knockdown of Sp1; Western blot; RT-PCR; rat hypertrophy model Cellular physiology and biochemistry Medium 19471099
2012 Mef2c drives Hcn4 expression specifically in embryonic non-chamber and postnatal AV bundle myocardium through a conserved cis-regulatory element; HDAC inhibition expands this enhancer activity to working myocardium, and cardiac hypertrophy (causing nuclear HDAC export) ectopically activates the Hcn4 enhancer in working myocardium. Transgenic reporter mice; in vivo Mef2c-dependent enhancer analysis; HDAC inhibitor treatment; transverse aortic constriction hypertrophy model Developmental biology Medium 23085412
2019 Trx2 (mitochondrial thioredoxin-2) maintains HCN4 expression in the conduction system via a mitochondrial ROS–HDAC4–MEF2C pathway: Trx2 deletion elevates HDAC4, which binds the HCN4 enhancer via MEF2, reduces histone H3 acetylation at the MEF2 site, and decreases HCN4 transcription; mitochondria-specific ROS scavenger MitoTEMPO reverses HDAC4 elevation, HCN4 reduction, and sinus bradycardia. Conduction-system-specific Trx2 KO (Hcn4-CreERT2); ChIP; qPCR and Western blot for HCN4; MitoTEMPO rescue experiment; ECG telemetry Journal of molecular and cellular cardiology High 31751569
2013 HCN4 co-localizes and co-immunoprecipitates with Thy1 in adult rat retinal ganglion cells, representing the first identified protein partner of HCN4 in the retina and showing that a GPI-anchored protein can complex with an HCN channel subunit. Co-immunoprecipitation with anti-Thy1 and anti-HCN4 antibodies; confocal immunohistochemistry; patch-clamp of immunopanned cells Investigative ophthalmology & visual science Medium 22281825
2018 HCN4 pacemaker channels attenuate parasympathetic responses in the sinoatrial node: conditional knockdown of HCN4 enhances vagal bradycardia (complete sinus pause on vagus nerve stimulation), while HCN4 overexpression attenuates vagal bradycardia during β-adrenergic stimulation; neither manipulation significantly alters the β-adrenergic response alone. Tetracycline-inducible HCN4 overexpression and knockdown mouse lines; telemetric ECG; cervical vagus nerve stimulation; in vitro single pacemaker cell patch-clamp The Journal of physiology High 29315578
2020 Ectopic HCN4 expression in cortical neurons with mTOR hyperactivation drives epilepsy: HCN4 is expressed in focal cortical malformation (FCM) neurons in a TSC/FCDII mouse model, its expression is mTOR-dependent, increased intracellular cAMP preferentially drives repetitive firing via HCN4 in FCM neurons, and blocking HCN4 prevents seizures in the model. Mouse model of TSC/FCDII focal cortical malformation; pharmacological HCN4 block; cAMP manipulation; comparison of FCM vs. control pyramidal neurons; tissue from human TSC/FCDII patients (immunostaining) Science translational medicine High 33208499
2013 HCN4 and caveolin-3 (Cav3) co-localize in adult human atrial and ventricular cardiomyocytes but not in fetal cardiomyocytes; during hESC-CM maturation, Cav3 expression increases and HCN4-Cav3 co-localization develops by ~110 days, coinciding with a shift of f-current activation to more negative (adult-like) voltages; disruption of caveolae reverses voltage dependence toward a more positive (immature) phenotype in mature cells but not fetal cells. Immunocytochemistry; qRT-PCR; patch-clamp; methyl-β-cyclodextrin caveolae disruption in hESC-CMs at different maturation stages Stem cells and development Medium 23311301
2022 Coxsackievirus B3 (CVB3) reduces HCN4 plasma membrane density in hiPSC-derived pacemaker-like cells by promoting autophagosomal HCN4 insertion via Rab7-dependent endocytic trafficking; individual CVB3 proteins 2C and 3A have the most potent effects on HCN4 activity, and pharmacological Rab7 inhibition or CVB3-3A inhibition (GW5074) rescues cytoplasmic HCN4 accumulation. hiPSC-derived pacemaker cells with inducible CVB3 expression; patch-clamp; immunofluorescence of HCN4 distribution; autophagosome assay; pharmacological rescue with Rab7 inhibitor and GW5074 Cellular and molecular life sciences Medium 35864219
2023 A gain-of-function mutation p.V240M in the HCN domain (N-terminus) of HCN4 causes inappropriate sinus tachycardia by increasing single-channel conductance, opening frequency, and opening probability without altering cAMP sensitivity or membrane expression; the HCN domain therefore stabilizes the channel in the closed state. Macroscopic and single-channel patch-clamp in cells expressing WT and/or p.V240M HCN4; cell surface expression assay; computer simulation of sinoatrial node Proceedings of the National Academy of Sciences of the United States of America High 38032931
2023 Molecular dynamics simulations of the HCN4 selectivity filter reveal two K+ binding sites and one Na+ binding site; Na+ acts as a weak blocker released by K+-induced filter widening, Li+ cannot enter the filter due to incomplete coordination, and Cs+ preferentially occupies the S3-equivalent site to block conduction, explaining weak cation selectivity. Molecular dynamics simulations of open HCN4 pore; comparison with experimental conductance data (Li+, Rb+, Cs+) The Journal of general physiology Medium 37523352
2013 Testosterone recruits the androgen receptor (AR) to regulatory regions of the HCN4 gene (confirmed by ChIP), associated with increased histone acetylation, upregulating HCN4 expression during cardiomyogenesis; AR knockdown or anti-androgenic treatment inhibits this effect. Chromatin immunoprecipitation (ChIP) for AR at HCN4 regulatory region; AR knockdown; histone acetylation analysis; RT-PCR and Western blot in mES and P19 cells Journal of molecular and cellular cardiology Medium 23598283
2020 Notch1 signaling induces re-expression of HCN4 in mature cardiomyocytes via a regulatory complex of NICD and KDM5A (a histone demethylase) that targets the HCN4 promoter, promotes histone demethylation, and drives aconitine-induced ventricular arrhythmia; Notch1 inhibition reverses these changes. Co-immunoprecipitation of NICD-KDM5A complex; ChIP at HCN4 promoter; patch-clamp of beating rate; pharmacological Notch1 inhibitor rescue; human and rat cardiomyocytes Toxicology letters Medium 32234357
2021 Cfp1 (CXXC finger protein 1) maintains HCN4 expression by binding the HCN4 promoter and maintaining H3K4 trimethylation, H3K9 acetylation, and H3K27 acetylation; Cfp1 heterozygous knockout reduces these histone marks, decreases HCN4 protein, and reduces If density by 66% in SAN cells, causing mild bradycardia. Cfp1 heterozygous KO mice (Hcn4-CreERT2 line); ChIP in HL-1 cells for H3K4me3, H3K9ac, H3K27ac at HCN4 promoter; patch-clamp; qPCR; Western blot Heart rhythm High 34182171
2007 The G480R mutation in the HCN4 pore domain causes familial sinus bradycardia through two mechanisms: reduced channel synthesis, a trafficking defect reducing plasma membrane expression (assessed by biotinylation/Western blot), and a shift of activation to more negative voltages. Sequencing; expression in Xenopus oocytes and HEK293 cells; patch-clamp; surface biotinylation; Western blot Circulation Medium 17646576
2020 HCN4-expressing enteric neurons in zebrafish specifically regulate retrograde (but not anterograde) peristalsis: HCN channel block or morpholino knockdown selectively attenuates retrograde peristalsis, while optogenetic activation of HCN4+ neurons (channelrhodopsin) selectively enhances retrograde peristalsis. Forward genetics in zebrafish; HCN channel pharmacological block; morpholino knockdown; optogenetic activation of HCN4+ neurons expressing channelrhodopsin; peristalsis measurement Cell reports High 32130893

Source papers

Stage 0 corpus · 100 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2011 Deep bradycardia and heart block caused by inducible cardiac-specific knockout of the pacemaker channel gene Hcn4. Proceedings of the National Academy of Sciences of the United States of America 230 21220308
2013 HCN4 dynamically marks the first heart field and conduction system precursors. Circulation research 181 23743334
2003 Heteromeric HCN1-HCN4 channels: a comparison with native pacemaker channels from the rabbit sinoatrial node. The Journal of physiology 179 12702747
2001 Hyperpolarization-activated channels HCN1 and HCN4 mediate responses to sour stimuli. Nature 173 11675786
2004 Functional characterization of a trafficking-defective HCN4 mutation, D553N, associated with cardiac arrhythmia. The Journal of biological chemistry 162 15123648
2007 Novel approaches for gene-specific interference via manipulating actions of microRNAs: examination on the pacemaker channel genes HCN2 and HCN4. Journal of cellular physiology 149 17516552
2014 HCN4 mutations in multiple families with bradycardia and left ventricular noncompaction cardiomyopathy. Journal of the American College of Cardiology 148 25145517
2013 A HCN4+ cardiomyogenic progenitor derived from the first heart field and human pluripotent stem cells. Nature cell biology 148 23974038
2008 Down-regulation of miR-1/miR-133 contributes to re-expression of pacemaker channel genes HCN2 and HCN4 in hypertrophic heart. The Journal of biological chemistry 147 18458081
2007 Point mutation in the HCN4 cardiac ion channel pore affecting synthesis, trafficking, and functional expression is associated with familial asymptomatic sinus bradycardia. Circulation 120 17646576
2014 The symptom complex of familial sinus node dysfunction and myocardial noncompaction is associated with mutations in the HCN4 channel. Journal of the American College of Cardiology 113 25145518
2006 Extended atrial conduction system characterised by the expression of the HCN4 channel and connexin45. Cardiovascular research 91 16989793
2003 Expression of the hyperpolarization-activated cyclic nucleotide-gated cation channel HCN4 during mouse heart development. Gene expression patterns : GEP 89 14643687
2003 KCNE2 modulates current amplitudes and activation kinetics of HCN4: influence of KCNE family members on HCN4 currents. Pflugers Archiv : European journal of physiology 85 12856183
2015 Pacemaker activity of the human sinoatrial node: an update on the effects of mutations in HCN4 on the hyperpolarization-activated current. International journal of molecular sciences 83 25642760
2010 Structural basis for the cAMP-dependent gating in the human HCN4 channel. The Journal of biological chemistry 82 20829353
2010 Phosphorylation and modulation of hyperpolarization-activated HCN4 channels by protein kinase A in the mouse sinoatrial node. The Journal of general physiology 81 20713547
2012 Altered HCN4 channel C-linker interaction is associated with familial tachycardia-bradycardia syndrome and atrial fibrillation. European heart journal 76 23178648
2017 Targeting miR-423-5p Reverses Exercise Training-Induced HCN4 Channel Remodeling and Sinus Bradycardia. Circulation research 73 28821541
2009 Role of HCN4 channel in preventing ventricular arrhythmia. Journal of human genetics 67 19165230
2009 Distribution of the pacemaker HCN4 channel mRNA and protein in the rabbit sinoatrial node. Journal of molecular and cellular cardiology 66 19394343
2020 A circadian clock in the sinus node mediates day-night rhythms in Hcn4 and heart rate. Heart rhythm 65 33278629
2015 Ivabradine prolongs phase 3 of cardiac repolarization and blocks the hERG1 (KCNH2) current over a concentration-range overlapping with that required to block HCN4. Journal of molecular and cellular cardiology 57 25986146
2014 A novel trafficking-defective HCN4 mutation is associated with early-onset atrial fibrillation. Heart rhythm 55 24607718
2010 A novel mutation in the HCN4 gene causes symptomatic sinus bradycardia in Moroccan Jews. Journal of cardiovascular electrophysiology 53 20662977
2012 A caveolin-binding domain in the HCN4 channels mediates functional interaction with caveolin proteins. Journal of molecular and cellular cardiology 50 22659290
2003 Molecular basis for the different activation kinetics of the pacemaker channels HCN2 and HCN4. The Journal of biological chemistry 48 12813043
2013 HCN4 subunit expression in fast-spiking interneurons of the rat spinal cord and hippocampus. Neuroscience 47 23357121
2015 HCN4, Sinus Bradycardia and Atrial Fibrillation. Arrhythmia & electrophysiology review 46 26835093
2020 Ectopic HCN4 expression drives mTOR-dependent epilepsy in mice. Science translational medicine 44 33208499
2007 Src tyrosine kinase alters gating of hyperpolarization-activated HCN4 pacemaker channel through Tyr531. American journal of physiology. Cell physiology 39 17977941
2011 Funny current channel HCN4 delineates the developing cardiac conduction system in chicken heart. Heart rhythm 38 21421080
2017 Sick sinus syndrome with HCN4 mutations shows early onset and frequent association with atrial fibrillation and left ventricular noncompaction. Heart rhythm 37 28104484
2014 Pacemaker activity of the human sinoatrial node: effects of HCN4 mutations on the hyperpolarization-activated current. Europace : European pacing, arrhythmias, and cardiac electrophysiology : journal of the working groups on cardiac pacing, arrhythmias, and cardiac cellular electrophysiology of the European Society of Cardiology 37 24569893
2006 Constitutively active Src tyrosine kinase changes gating of HCN4 channels through direct binding to the channel proteins. Journal of cardiovascular pharmacology 37 16680072
2009 The cardiac pacemaker-specific channel Hcn4 is a direct transcriptional target of MEF2. Cardiovascular research 36 19477969
2015 Enhancement of Spontaneous Activity by HCN4 Overexpression in Mouse Embryonic Stem Cell-Derived Cardiomyocytes - A Possible Biological Pacemaker. PloS one 35 26384234
2006 NRSF regulates the developmental and hypertrophic changes of HCN4 transcription in rat cardiac myocytes. Biochemical and biophysical research communications 35 17173866
2013 Molecular and functional evidence of HCN4 and caveolin-3 interaction during cardiomyocyte differentiation from human embryonic stem cells. Stem cells and development 34 23311301
2018 A Loss-of-Function HCN4 Mutation Associated With Familial Benign Myoclonic Epilepsy in Infancy Causes Increased Neuronal Excitability. Frontiers in molecular neuroscience 32 30127718
2018 HCN4 pacemaker channels attenuate the parasympathetic response and stabilize the spontaneous firing of the sinoatrial node. The Journal of physiology 31 29315578
2017 Gabapentin Modulates HCN4 Channel Voltage-Dependence. Frontiers in pharmacology 28 28871229
2008 Engineering physiologically controlled pacemaker cells with lentiviral HCN4 gene transfer. The journal of gene medicine 28 18383475
2007 Adenoviral gene transfer of HCN4 creates a genetic pacemaker in pigs with complete atrioventricular block. Life sciences 28 17382969
2012 Spatiotemporal regulation of an Hcn4 enhancer defines a role for Mef2c and HDACs in cardiac electrical patterning. Developmental biology 27 23085412
2017 Functional variants in HCN4 and CACNA1H may contribute to genetic generalized epilepsy. Epilepsia open 25 29588962
2014 Insights into cardiac conduction system formation provided by HCN4 expression. Trends in cardiovascular medicine 25 25442735
2010 Dynamic changes in HCN2, HCN4, KCNE1, and KCNE2 expression in ventricular cells from acute myocardial infarction rat hearts. Biochemical and biophysical research communications 25 20381460
2016 Mutation in S6 domain of HCN4 channel in patient with suspected Brugada syndrome modifies channel function. Pflugers Archiv : European journal of physiology 24 27553229
2009 Hyperpolarization-activated cyclic-nucleotide gated 4 (HCN4) protein is expressed in a subset of rat dorsal root and trigeminal ganglion neurons. Cell and tissue research 24 19820968
2019 HCN4 knockdown in dorsal hippocampus promotes anxiety-like behavior in mice. Genes, brain, and behavior 23 30585408
2013 Testosterone enhances cardiomyogenesis in stem cells and recruits the androgen receptor to the MEF2C and HCN4 genes. Journal of molecular and cellular cardiology 22 23598283
2010 Hysteresis in human HCN4 channels: a crucial feature potentially affecting sinoatrial node pacemaking. Sheng li xue bao : [Acta physiologica Sinica] 22 20179882
2020 Isoform-specific regulation of HCN4 channels by a family of endoplasmic reticulum proteins. Proceedings of the National Academy of Sciences of the United States of America 21 32647060
2009 Transcriptional control of pacemaker channel genes HCN2 and HCN4 by Sp1 and implications in re-expression of these genes in hypertrophied myocytes. Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology 21 19471099
2009 Proteolytic processing of HCN2 and co-assembly with HCN4 in the generation of cardiac pacemaker channels. The Journal of biological chemistry 21 19574228
2014 A novel HCN4 mutation, G1097W, is associated with atrioventricular block. Circulation journal : official journal of the Japanese Circulation Society 20 24492017
2012 Cellular context and multiple channel domains determine cAMP sensitivity of HCN4 channels: ligand-independent relief of autoinhibition in HCN4. The Journal of general physiology 20 23109717
2011 Association of polymorphisms in HCN4 with mood disorders and obsessive compulsive disorder. Neuroscience letters 20 21529705
2023 A gain-of-function HCN4 mutant in the HCN domain is responsible for inappropriate sinus tachycardia in a Spanish family. Proceedings of the National Academy of Sciences of the United States of America 18 38032931
2019 Using a Multiplex Nucleic Acid in situ Hybridization Technique to Determine HCN4 mRNA Expression in the Adult Rodent Brain. Frontiers in molecular neuroscience 18 31555092
2012 Adrenergic regulation of HCN4 channel requires protein association with β2-adrenergic receptor. The Journal of biological chemistry 18 22613709
2022 Paradigm shift: new concepts for HCN4 function in cardiac pacemaking. Pflugers Archiv : European journal of physiology 17 35556164
2019 Mitochondrial thioredoxin-2 maintains HCN4 expression and prevents oxidative stress-mediated sick sinus syndrome. Journal of molecular and cellular cardiology 17 31751569
2009 Identification, isolation and characterization of HCN4-positive pacemaking cells derived from murine embryonic stem cells during cardiac differentiation. Pacing and clinical electrophysiology : PACE 17 19895411
2020 Gastrointestinal Neurons Expressing HCN4 Regulate Retrograde Peristalsis. Cell reports 16 32130893
2015 HCN4 mutation as a molecular explanation on patients with bradycardia and non-compaction cardiomyopathy. European journal of medical genetics 16 26206080
2022 Clinical Presentation of Left Ventricular Noncompaction Cardiomyopathy and Bradycardia in Three Families Carrying HCN4 Pathogenic Variants. Genes 15 35328031
2018 A mutant HCN4 channel in a family with bradycardia, left bundle branch block, and left ventricular noncompaction. Heart and vessels 15 29349559
2021 Cohesin-protein Shugoshin-1 controls cardiac automaticity via HCN4 pacemaker channel. Nature communications 14 33953173
2019 The C-terminal HCN4 variant P883R alters channel properties and acts as genetic modifier of atrial fibrillation and structural heart disease. Biochemical and biophysical research communications 14 31481236
2018 HCN4 Gene Polymorphisms Are Associated With Occurrence of Tachycardia-Induced Cardiomyopathy in Patients With Atrial Fibrillation. Circulation. Genomic and precision medicine 14 29987112
2018 In Vitro Analyses of Novel HCN4 Gene Mutations. Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology 13 30196304
2013 In situ investigation of allografted mouse HCN4 gene-transfected rat bone marrow mesenchymal stromal cells with the use of patch-clamp recording of ventricular slices. Cytotherapy 13 23768927
2012 Hyperpolarisation-activated cyclic nucleotide channel 4 (HCN4) involvement in Tourette's syndrome autoimmunity. Journal of neuroimmunology 13 22683190
2024 Structural determinants of ivabradine block of the open pore of HCN4. Proceedings of the National Academy of Sciences of the United States of America 12 38917012
2017 A novel 'splice site' HCN4 Gene mutation, c.1737+1 G>T, causes familial bradycardia, reduced heart rate response, impaired chronotropic competence and increased short-term heart rate variability. International journal of cardiology 12 28465117
2013 Inducible gene deletion in the entire cardiac conduction system using Hcn4-CreERT2 BAC transgenic mice. Genesis (New York, N.Y. : 2000) 12 24281837
2020 Notch1-mediated histone demethylation of HCN4 contributes to aconitine-induced ventricular myocardial dysrhythmia. Toxicology letters 11 32234357
2018 HCN4-Overexpressing Mouse Embryonic Stem Cell-Derived Cardiomyocytes Generate a New Rapid Rhythm in Rats with Bradycardia. International heart journal 11 29628472
2022 Virus-induced inhibition of cardiac pacemaker channel HCN4 triggers bradycardia in human-induced stem cell system. Cellular and molecular life sciences : CMLS 10 35864219
2021 Downregulated lncRNA RCPCD promotes differentiation of embryonic stem cells into cardiac pacemaker-like cells by suppressing HCN4 promoter methylation. Cell death & disease 10 34215719
2019 Pacemaker cell characteristics of differentiated and HCN4-transduced human mesenchymal stem cells. Life sciences 10 31291594
2012 Thy1 associates with the cation channel subunit HCN4 in adult rat retina. Investigative ophthalmology & visual science 10 22281825
2008 HCN4-like immunoreactivity in rat retinal ganglion cells. Visual neuroscience 10 18282314
2023 Alkali metal cations modulate the geometry of different binding sites in HCN4 selectivity filter for permeation or block. The Journal of general physiology 9 37523352
2019 Protein and surface expression of HCN2 and HCN4 subunits in mesocorticolimbic areas after cocaine sensitization. Neurochemistry international 9 30794847
2011 Tissue-specific N terminus of the HCN4 channel affects channel activation. The Journal of biological chemistry 9 21372143
2011 Blocking effects of acehytisine on pacemaker currents (I(f)) in sinoatrial node cells and human HCN4 channels expressed in Xenopus laevis oocytes. Journal of ethnopharmacology 9 22107837
2010 Expression of hyperpolarization-activated cyclic nucleotide-gated cation channel (HCN4) is increased in hypertrophic cardiomyopathy. Cardiovascular pathology : the official journal of the Society for Cardiovascular Pathology 9 20207172
2022 Enhancement of pacing function by HCN4 overexpression in human pluripotent stem cell-derived cardiomyocytes. Stem cell research & therapy 8 35365232
2021 Ivabradine prevents deleterious effects of dopamine therapy in heart failure: No role for HCN4 overexpression. Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie 8 33450487
2012 The HCN4 channel mutation D553N associated with bradycardia has a C-linker mediated gating defect. Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology 8 23075627
2015 Morphology of mouse sinoatrial node and its expression of NF-160 and HCN4. International journal of clinical and experimental medicine 7 26550270
2023 Electroacupuncture inhibits PDK1/Akt/HCN4 pathway to improve neurogenic urinary retention in rats. Zhen ci yan jiu = Acupuncture research 6 37879946
2023 The Action Potential Clamp Technique as a Tool for Risk Stratification of Sinus Bradycardia Due to Loss-of-Function Mutations in HCN4: An In Silico Exploration Based on In Vitro and In Vivo Data. Biomedicines 5 37760888
2021 Deficiency of CXXC finger protein 1 leads to small changes in heart rate but moderate epigenetic alterations and significant protein downregulation of hyperpolarization-activated cyclic nucleotide-gated 4 (HCN4) ion channels in mice. Heart rhythm 5 34182171
2020 Expression of the pacemaker channel HCN4 in excitatory interneurons in the dorsal horn of the murine spinal cord. Molecular brain 5 32948209
2020 Disease-associated HCN4 V759I variant is not sufficient to impair cardiac pacemaking. Pflugers Archiv : European journal of physiology 5 33095298
2019 Correlation between HCN4 gene polymorphisms and lone atrial fibrillation risk. Artificial cells, nanomedicine, and biotechnology 5 31315459

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