Cell Line ; Cyclic Nucleotide-Gated Cation Channels ; physiology ; Humans ; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels ; Ion Channels ; physiology ; Membrane Potentials ; Muscle Proteins ; physiology ; Potassium Channels

Hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels, distributing in a variety of tissues, especially in excitable cells such as heart cells and many kinds of neurons, have an important role in the modulation of heart rate and neuronal excitability. Different from typical voltage-gated sodium channels and potassium channels, HCN channels were evoked inward currents when the cell was hyperpolarized. More and more recent studies have disclosed that HCN channels play important roles in the nervous system, which were linked with its special electrophysiological features as well as its regulatory effect on the cellular membrane excitability. HCN channels could be modulated by many factors including both extracellular molecules and intracellular signaling cascades, which made its functions complicated in the different condition. Based on its role, HCN channels are presumed to be a promising target for chronic pain and brain disorders. In this paper, we will focus on the advancement of roles of HCN channels in the neural system as well as its complex modulator factors.
Cyclic Nucleotide-Gated Cation Channels ; physiology ; Humans ; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels ; physiology ; Membrane Potentials ; Neurons ; physiology ; Potassium Channels ; physiology

The cyclic nucleotide-gated (CNG) channel is a nonselective cation channel and one of the main entrances of Ca2+ influxion into cells. CNG channels are opened by direct binding of cyclic nucleotides. Six different genes encode the CNG protein, 4 A subunits and 2 B subunits. The activity of CNG channels can be regulated by Ca2+/Ca(2+)-binding proteins (CaM) and phosphorylation/dephosphorylation. Recently, extensive attention has been drawn to the researches on CNG channels in the reproductive system, and many studies show that CNG channels play a pivotal role in sperm motility, capacitation and acrosome reaction. This article focuses on the relationship of CNG channels with sperm function.
Animals ; Calcium ; metabolism ; Cyclic Nucleotide-Gated Cation Channels ; physiology ; Humans ; Male ; Spermatozoa ; metabolism ; physiology

OBJECTIVE: To investigate the expression of hyperpolarization-activated cyclic nucleotide-gated cation channel 4 (HCN4) and connexin43 (Cx43) in the sinoatrial node of electric shock death. METHODS: As experimental group, 34 cases of electric shock death who had definite current mark evidence were selected from pathology department of Xuzhou Medical College from 2010 to 2013. As the control group, 20 cases of fatal severe craniocerebral injury in traffic accidents were chosen. The expressions of HCN4 and Cx43 in the sinoatrial node were observed by immunohistochemical technology. RESULTS: HCN4 positive cells expressed in the cell membrane and cytoplasm of the sinoatrial node. Cx43 positive cells expressed in the cell membrane and cytoplasm of T cells and myocardial cells. The expression of HCN4 was significantly higher than that of the control group (P < 0.05) and the expression of Cx43 was significantly lower than that of the control group (P < 0.05). CONCLUSION The changes of HCN4 and Cx43 expressions in the sinoatrial node illustrate electric shock death might be related to the abnormalities of cardiac electrophysiology and conduction.
Connexin 43/metabolism* ; Cyclic Nucleotide-Gated Cation Channels ; Heart Rate ; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels/metabolism* ; Immunohistochemistry/methods* ; Myocardium/metabolism* ; Myocytes, Cardiac ; Sinoatrial Node/physiopathology*

The hyperpolarization-activated cyclic nucleotide-gated (HCN) channels modulate and regulate cardiac rhythm and rate. It has been suggested that, unlike the HCN1 and HCN2 channels, the slower HCN4 channel may not exhibit voltage-dependent hysteresis. We studied the electrophysiological properties of human HCN4 (hHCN4) channels and its modulation by cAMP to determine whether hHCN4 exhibits hysteresis, by using single-cell patch-clamp in HEK293 cells stably transfected with hHCN4. Quantitative real-time RT-PCR was also used to determine levels of expression of HCNs in human cardiac tissue. Voltage-clamp analysis revealed that hHCN4 current (I(h)) activation shifted in the depolarizing direction with more hyperpolarized holding potentials. Triangular ramp and action potential clamp protocols also revealed hHCN4 hysteresis. cAMP enhanced I(h) and shifted activation in the depolarizing direction, thus modifying the intrinsic hHCN4 hysteresis behavior. Quantitative PCR analysis of human sinoatrial node (SAN) tissue showed that HCN4 accounts for 75% of the HCNs in human SAN while HCN1 (21%), HCN2 (3%), and HCN3 (0.7%) constitute the remainder. Our data suggest that HCN4 is the predominant HCN subtype in the human SAN and that I(h) exhibits voltage-dependent hysteresis behavior that can be modified by cAMP. Therefore, hHCN4 hysteresis potentially plays a crucial role in human SAN pacemaking activity.
Biological Clocks ; physiology ; Cyclic AMP ; physiology ; Cyclic Nucleotide-Gated Cation Channels ; physiology ; Electrophysiological Phenomena ; HEK293 Cells ; Humans ; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels ; Muscle Proteins ; physiology ; Patch-Clamp Techniques ; Potassium Channels ; Sinoatrial Node ; physiology ; Transfection

Adenosine ; pharmacology ; Animals ; Cyclic Nucleotide-Gated Cation Channels ; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels ; Ion Channels ; physiology ; Isoproterenol ; pharmacology ; Membrane Potentials ; drug effects ; Muscle, Smooth, Vascular ; physiology ; Myocytes, Smooth Muscle ; physiology ; Potassium Channels ; Pulmonary Veins ; physiology ; Rabbits

OBJECTIVETo study pacemaker current gene expression of mesenchymal stem cells (MSCs) and the electrophysiological property of MSCs expressing human pacemaker current gene.

METHODSPacemaker current gene expression of MSCs were studied by real-time quantitative polymerase chain reaction (real-time PCR) and pcDNA3-hHCN2 was transfected with Lipofectin 2000 into MSCs. hHCN2 expression at mRNA and at protein levels in the transfected cells were identified by real-time PCR and Western blot, respectively. The ionic currents of cloned hHCN2 (IhHCN2) were recorded and the current characteristics were studied through the whole-cell patch clamp technique.

RESULTSmHCN1, mHCN2, mHCN3, mHCN4 represent (0.08+/-0.01)%, (77.16+/-0.03)%, (0.24+/-0.01)%, (22.53+/-0.02)% of total HCN mRNA in MSCs as determined by real-time PCR. Transfected hHCN2 ionic currents were recorded by whole-cell patch clamp and current density-voltage curves were obtained. The threshold for activation of IhHCN2 was approximately -80 mV and this current could be blocked by Cs+ (4 mmol/L). hHCN2 expression in transfected MSCs was detected both at mRNA and protein levels.

CONCLUSIONS1. mHCN2 and mHCN4 represent the major populations of total HCN mRNA in MSCs. 2. Plasmid pcDNA3-hHCN2 by Lipofectin could be successfully transfected into MSCs with IhHCN2 recorded by whole-cell patch clamp technique, this study provides a basis for future antiarrhythmic gene therapy.

Animals ; Cyclic Nucleotide-Gated Cation Channels ; Gene Expression ; Humans ; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels ; Membrane Potentials ; physiology ; Mesenchymal Stromal Cells ; cytology ; metabolism ; Polymerase Chain Reaction ; Potassium Channels ; biosynthesis ; genetics ; Rats ; Rats, Sprague-Dawley ; Transfection

Cell Line ; Cyclic Nucleotide-Gated Cation Channels ; drug effects ; genetics ; metabolism ; Drugs, Chinese Herbal ; pharmacology ; Electrophysiology ; Humans ; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels ; Muscle Proteins ; drug effects ; genetics ; metabolism ; Potassium Channels ; Transfection

Objective: To explore the effects of 3-phosphate dependent protein kinase 1-protein kinase B (PDK1-Akt) signaling pathway on the transcription, expression and function of cardiac hyperpolarized activated cyclic nucleotide gated 4 (HCN4) ion channels. Methods: Atrial myocytes were obtained from healthy male wild-type C57 mice and heart-specific PDK1 knockout mice (PDK1-KO) by enzymolysis. Then the atrial myocytes were divided into blank control group and PDK1-KO group. In further studies, the isolated atrial myocytes were cultured and further divided into drug control group (treated with dimethyl sulfoxide (DMSO)) and PDK1 knockdown group (treated with 1 μg/ml PDK1 short hairpin RNA (shRNA) interference plasmid), SC79 group (treated with 8 μmol/ml SC79), GSK2334470 group (treated with 10 nmol/L GSK2334470) and PDK1 knockdown+SC79 group (8 μmol/ml SC79 and 1 μg/ml PDK1 shRNA interference plasmid). Real time quantitative PCR (qRT-PCR) was used to detect the mRNA expression levels of PDK1 and HCN4, Western blot was used to detect the protein expression levels of PDK1, Akt and HCN4, the whole cell patch clamp was used to detecte the current density of HCN, and immunofluorescence was used to detecte the expression of HCN4 protein on atrial cells. Results: (1) the expression levels of HCN4 mRNA (1.46±0.03 vs. 0.99±0.01, P<0.001) and protein (1.14±0.02 vs. 1.00±0.06, P=0.017) in PDK1-KO group were higher than those in blank control group. The HCN current density in PDK1-KO group was higher than that in blank control group((-17.47±2.00) pA/pF vs. (-12.15±2.25) pA/pF, P=0.038). (2) The functions of PDK1 shRNA and specific Akt agonist SC79 were verified by comparing the PDK1 knockdown group and SC79 group with the drug control group. The results showed that the expression levels of PDK1 mRNA and protein in PDK1 knockdown group were lower than those in drug control group, and the expression level of phosphorylated Akt (Thr 308) protein in SC79 group was higher than that in drug control group. (3) The expression levels of HCN4 mRNA (3.61±0.46 vs. 1.00±0.08, P<0.001) and protein (2.33±0.11 vs. 1.00±0.05, P<0.001) in GSK2334470 group were higher than those in drug control group. (4) To reduce the effect of drug-miss target, the cultured atrial myocytes were transfected with shRNA plasmid of PDK1 and intervened with SC79. The results showed that the expression of HCN4 mRNA in PDK1 knockdown group was higher than that in the drug control group (1.76±0.11 vs. 1.00±0.06, P<0.001), and PDK1 knockdown+SC79 group (1.76±0.11 vs. 1.33±0.07, P=0.003). In PDK1 knockdown+SC79 group, the mRNA expression level was also higher than that in the drug control group (1.33±0.07 vs. 1.00±0.06, P<0.001). The expression level of HCN4 protein in PDK1 knockdown group was higher than that in drug control group (1.15±0.04 vs. 1.00±0.05, P=0.003). As for the The expression level of HCN4 protein, there was no significantly statistical difference between the PDK1 knockdown+SC79 group and the drug control group (P>0.05), but PDK1 knockdown+SC79 group was lower than PDK1 knockdown group (0.95±0.01 vs. 1.15±0.04, P<0.001). In patch clamp experiments, the results showed that the HCN current density was (-13.27±1.28) pA/pF in the drug control group, (-18.76±2.03) pA/pF in the PDK1 knockdown group, (-13.50±2.58) pA/pF in the PDK1 knockdown+SC79 group; the HCN current density of PDK1 knockdown group was higher than that of drug control group (P<0.001), but there was no significant difference between PDK1 knockdown+SC79 group and drug control group (P>0.05). (5) The results of immunofluorescence showed that the brightness of green fluorescence of PDK1 knockdown group was higher than that of drug control group, indicating that the expression of HCN4 localized on cell membrane was increased. However, the green fluorescence of PDK1 knockdown+SC79 group was lighter than that of PDK1 knockdown group, suggesting that the expression of HCN4 in PDK1-knockdown cell membrane decreased after further activating Akt. Conclusion: PDK1-Akt signaling pathway is involved in the regulation of HCN4 ion channel transcription, expression and function.
Animals ; Cyclic Nucleotide-Gated Cation Channels ; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels/metabolism* ; Male ; Mice ; Myocytes, Cardiac/metabolism* ; Potassium Channels/metabolism* ; Proto-Oncogene Proteins c-akt/metabolism* ; Signal Transduction

AIMTo record funny currents (If) of ventricular myocytes and to analysize hyperpolarization-activated cation channel(HCN) expression in the rats of different ages.

METHODSFresh ventricular myocytes were isolated from 3 days rats and adult rats.HCN expressions were measured by real-time quantitative polymerase chain reaction(real-time PCR). It was recorded through whole-cell patch clamp.

RESULTSHCN1, HCN2, HCN3, HCN4 mRNA represented 0.23% +/- 0.01%, 83.58% +/- 0.04%, 0.79% +/- 0.01%, 15.44% +/- 0.01% of total HCN mRNA in the neonatal rats, respectively. If was recorded and the threshold for activation was -75 mV. In the adult rat, HCN1, HCN2, HCN3, HCN4 mRNA represented 0.72% +/- 0.02%, 91.58% +/- 0.08%, 0.27% +/- 0.02%, 7.12% +/- 0.02% of total HCN mRNA. The ratio of HCN2 to HCN4 was approximately (13.06 +/- 0.21):1. The threshold for activation of If was approximately -115 mV in the adult rats.

CONCLUSIONWith the development of rats, the value of If is smaller. The threshold for activation of If is more negative. The ratio of HCN2 to HCN4 is bigger.

Age Factors ; Animals ; Animals, Newborn ; Cells, Cultured ; Cyclic Nucleotide-Gated Cation Channels ; metabolism ; physiology ; Heart Ventricles ; cytology ; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels ; Ion Channels ; metabolism ; Myocytes, Cardiac ; cytology ; physiology ; Patch-Clamp Techniques ; Potassium Channels ; metabolism ; physiology ; RNA, Messenger ; metabolism ; Rats ; Rats, Sprague-Dawley