HCN4

This gene encodes a member of the hyperpolarization-activated cyclic nucleotide-gated potassium channels. The encoded protein shows slow kinetics of activation and inactivation, and is necessary for the cardiac pacemaking process. This channel may also mediate responses to sour stimuli. Mutations in this gene have been linked to sick sinus syndrome 2, also known as atrial fibrillation with bradyarrhythmia or familial sinus bradycardia. Two pseudogenes have been identified on chromosome 15. [provided by RefSeq, Oct 2008]

Hyperpolarization Activated Cyclic Nucleotide Gated Potassium Channel 4

Hyperpolarization-activated ion channel with very slow activation and inactivation exhibiting weak selectivity for potassium over sodium ions. Contributes to the native pacemaker currents in heart (If) that regulate the rhythm of heart beat. May contribute to the native pacemaker currents in neurons (Ih). May mediate responses to sour stimuli.

Blood circulation Source: ProtInc
Cardiac conduction system development Source: BHF-UCL
Cation transport Source: BHF-UCL
Cellular response to cAMP Source: UniProtKB
Cellular response to cGMP Source: UniProtKB
Membrane depolarization during cardiac muscle cell action potential Source: BHF-UCL
Membrane depolarization during SA node cell action potential Source: BHF-UCL
Muscle contraction Source: ProtInc
Potassium ion import across plasma membrane Source: BHF-UCL
Potassium ion transmembrane transport Source: UniProtKB
Regulation of cardiac muscle cell action potential involved in regulation of contraction Source: BHF-UCL
Regulation of cardiac muscle contraction Source: BHF-UCL
Regulation of heart rate Source: UniProtKB
Regulation of heart rate by cardiac conduction Source: BHF-UCL
Regulation of ion transmembrane transport Source: UniProtKB-KW
Regulation of membrane depolarization Source: BHF-UCL
Regulation of membrane potential Source: UniProtKB
SA node cell action potential Source: BHF-UCL
Sinoatrial node development Source: BHF-UCL
Sodium ion import across plasma membrane Source: BHF-UCL
Sodium ion transmembrane transport Source: UniProtKB

Cell membrane

Sick sinus syndrome 2 (SSS2):
The term 'sick sinus syndrome' encompasses a variety of conditions caused by sinus node dysfunction. The most common clinical manifestations are syncope, presyncope, dizziness, and fatigue. Electrocardiogram typically shows sinus bradycardia, sinus arrest, and/or sinoatrial block. Episodes of atrial tachycardias coexisting with sinus bradycardia ('tachycardia-bradycardia syndrome') are also common in this disorder. SSS occurs most often in the elderly associated with underlying heart disease or previous cardiac surgery, but can also occur in the fetus, infant, or child without heart disease or other contributing factors. SSS2 onset is in utero or at birth.
Brugada syndrome 8 (BRGDA8):
A tachyarrhythmia characterized by right bundle branch block and ST segment elevation on an electrocardiogram (ECG). It can cause the ventricles to beat so fast that the blood is prevented from circulating efficiently in the body. When this situation occurs, the individual will faint and may die in a few minutes if the heart is not reset.

Cytoplasmic: 1-266
Helical: 267-287
Extracellular: 288-293
Helical: 294-314
Cytoplasmic: 315-340
Helical: 341-361
Extracellular: 362-368
Helical: 369-389
Cytoplasmic: 390-420
Helical: 421-441
Extracellular: 442-464
Pore-forming: 465-486
Extracellular: 487-496
Helical: 497-517
Cytoplasmic: 518-1203