Related Experiment Video
Updated: Jun 25, 2026
09:20
Microelectrode Array Recording of Sinoatrial Node Firing Rate to Identify Intrinsic Cardiac Pacemaking Defects in Mice
Published on: July 5, 2021
Associated changes in HCN2 and HCN4 transcripts and I(f) pacemaker current in myocytes.
Qi Zhang1, Aijie Huang, Yen-Chang Lin
1Center for Cardiovascular and Respiratory Sciences, Department of Physiology, West Virginia University School of Medicine, Morgantown, West Virginia 26506, USA.
Biochimica Et Biophysica Acta
|February 25, 2009
Summary
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channel isoforms 2 and 4 interact to form functional channels. Their varying ratios influence current activation, contributing to tissue-specific heart rhythms.
Area of Science:
- Cardiovascular Physiology
- Neuroscience
- Molecular Biology
Background:
- Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels generate crucial inward currents.
- Four HCN isoforms (HCN1-HCN4) exist, with potential for heteromeric channel formation.
- These channels are vital for rhythmic activities in the brain and heart.
Purpose of the Study:
- To investigate the functional impact of HCN2 and HCN4 isoform interactions.
- To determine how varying ratios of HCN2 and HCN4 influence channel kinetics and voltage dependence.
- To explore the physiological relevance of HCN2/HCN4 heteromerization in cardiac tissue.
Main Methods:
- Xenopus oocyte expression system with varying HCN2:HCN4 mRNA ratios.
- Electrophysiological recordings to assess current activation and kinetics.
- Coimmunoprecipitation assays to confirm protein-protein interactions.
- Analysis of HCN2 and HCN4 mRNA levels in rat myocytes.
Main Results:
- Co-expression of HCN2 and HCN4 in oocytes resulted in depolarized current activation and faster kinetics compared to HCN4 homomers.
- HCN2 and HCN4 proteins associate in adult rat ventricles.
- Overexpression of HCN4 in myocytes shifted I(f) activation to physiological voltages with faster kinetics.
- Knockdown of HCN2 in neonatal myocytes led to decreased HCN4 mRNA, and HCN4 overexpression increased HCN2 mRNA.
Conclusions:
- HCN2 and HCN4 isoforms form functional heteromeric channels.
- The ratio of HCN2:HCN4 transcripts influences the biophysical properties of the hyperpolarization-activated inward current, I(f).
- These interactions contribute to tissue-specific electrical properties in the heart.
Related Concept Videos
01:19Electrophysiology of Normal Cardiac Rhythm
The normal cardiac rhythm is a synchronized electrical activity that facilitates the regular and coordinated contraction of the heart muscle. This process is essential for efficient blood circulation throughout the body. The fundamental elements involved in establishing and maintaining this rhythm include the unique electrical properties of cardiac muscle cells, the sinoatrial (SA) node's pacemaker function, the specialized conducting system, and the ionic mechanisms underlying each phase of...
01:19Conduction System of the Heart
Autorhythmicity is a term that refers to the heart's inherent ability to generate electrical signals and instigate muscle contractions. This self-regulating conduction system within the heart consists of two key components: the pacemaker cells and specialized conducting cells.
The pacemaker cells are located in two primary nodes: the sinoatrial (SA) node and the atrioventricular (AV) node. The SA node pacemaker cells can autonomously depolarize, triggering an action potential that leads to the...
The pacemaker cells are located in two primary nodes: the sinoatrial (SA) node and the atrioventricular (AV) node. The SA node pacemaker cells can autonomously depolarize, triggering an action potential that leads to the...
01:21G-Protein Gated Ion Channels
GPCRs are primarily responsible for our sense of smell, taste, and vision. The binding of a sensory stimulus activates GPCR to stimulate effector proteins, many of which are ion channels in the sensory organs. GPCRs modulate the opening and closing of the target ion channels either directly by binding them, or by releasing second messengers that activate these channels. As ions move across the membrane, the membrane potential is altered, which induces an appropriate response.
Sensory organs,...
Sensory organs,...
01:30Cardiac Action Potential
Cardiac action potentials are essential for proper heart function, enabling the rhythmic contractions needed for adequate blood circulation. Nodal cells and Purkinje fibers, specialized for electrical conduction, generate these action potentials.
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
01:28Mechanism of Cardiac Arrhythmias
Arrhythmias are irregular heart rhythms occurring when the heart's electrical impulses become abnormal. These disturbances can lead to various symptoms, depending on their severity and the underlying cause. Some common factors contributing to arrhythmias include hypoxia, ischemia, electrolyte imbalances, excessive catecholamine exposure, drug toxicity, and muscle overstretching. Arrhythmias can be classified into two main types based on the rate and site of origin of abnormal heart rhythms.