OBJECTIVE: To study the expression of human ether-α-go-go-related gene (herg) and hERG protein expressed by the gene in laryngeal carcinoma compared with the control group(mucosa adjacent to cancer of 2 cm). METHOD: Expression of herg and hERG protein was detected by immunohistochemistry (SP) and real-time PCR in resected tissue of laryngeal carcinoma and mucosa adjacent to cancer of 2 cm. RESULT: (1) By immunohistochemistry, the positive expression rate of hERG in laryngeal carcinoma was 76.7% (23/30), while it was 10.0% (2/20) in mucosa adjacent to cancer of 2 cm, the difference between which was statistically significant (P < 0.05). (2) By real-time PCR, the expression level of herg mRNA in laryngeal carcinoma is 2.25 times higher than that in mucosa adjacent to cancer of 2 cm. CONCLUSION Herg is highly expressed in tissue of laryngeal carcinoma, and it may be have some relevance to the happening and development of laryngeal carcinoma.
ERG1 Potassium Channel ; Ether-A-Go-Go Potassium Channels ; metabolism ; Humans ; Laryngeal Neoplasms ; metabolism ; RNA, Messenger

OBJECTIVETo observe the effect of matrine on human ether à go-go related gene (HERG) potassium channels expressed in Chinese hamster ovary (CHO) cells and investigate whether HERG channel is a new target of the pharmacological effect of matrine on arrhythmia and tumor

METHODSHERG channel potassium current in CHO cell was recorded using whole-cell patch-clamp technique, and the influence of matrine on the current was explored.

RESULTSMatrine inhibited HERG potassium current in a dose-dependent manner, and the 50% inhibitory concentration (IC IC(50)) was 411±23 μmol/L. Matrine had no significant effect on the activation kinetics, and mainly blocked HERG channels in their closed state.

CONCLUSIONSThe blocking effect of matrine on HERG channels might be one of the mechanisms against arrythmias and tumors. Unlike most other blockers exerting blocking effect at the intracellular sites by entering the cell with the opening of HERG channel, matrine blocked HERG channels at the extracellular sites.

Alkaloids ; pharmacology ; Animals ; CHO Cells ; Cricetinae ; Cricetulus ; ERG1 Potassium Channel ; Ether-A-Go-Go Potassium Channels ; genetics ; metabolism ; Humans ; Quinolizines ; pharmacology

The human ether-a-go-go related gene (HERG) encodes the α -subunit of the rapid component of the delayed rectifier K(+) channel, which is essential for the third repolarization of the action potential of human myocardial cells. Mutations of the HERG gene can cause type II hereditary long QT syndrome (LQT2), characterized by prolongation of the QT interval, abnormal T wave, torsade de pointes, syncope and sudden cardiac death. So far more than 300 HERG mutations have been identified, the majority of which can cause LQT2 due to HERG protein trafficking defect. It has been reported that certain drugs can induce acquired long QT syndrome through directly blocking the pore and/or affecting the HERG trafficking. The trafficking defects and K(+) currents can be restored with low temperature and certain drugs. However, the mechanisms underlying defective trafficking caused by HERG mutations and the inhibition/restoration of HERG trafficking by drugs are still unknown. This review summarizes the current understanding of the molecular mechanisms including HERG trafficking under physiological and pathological conditions, and the effects of drugs on the HERG trafficking, in order to provide theoretical evidence for the diagnosis and treatment of long QT syndrome.
Animals ; ERG1 Potassium Channel ; Ether-A-Go-Go Potassium Channels ; genetics ; metabolism ; Humans ; Long QT Syndrome ; genetics ; metabolism ; physiopathology ; Protein Transport

AIMTo explore a method of the stable and persistent expression of HERG(human ether-a-go-go-related gene) channels in Xenopus oocytes, and investigate the alteration of rest membrane potential of oocytes and electrophysiological properties of expressed channel in different culture duration.

METHODSHERG mRNA for injection was prepared with in intro transcription using vector plasmid pSP64 containing HERG cDNA fragment. Expressed HERG current was recorded using standard two-microelectrode voltage-clamp technique.

RESULTS(1) Functional channels, with electrophysiological properties consistent with those of HERG channels were persistently expressed in oocytes membrane with this method. Furthermore, channel current could be recorded stably in 10-15 days. (2) The negative value of rest membrane potential increased gradually in the 3, 6, and 9 days of culture, and then decreased in the 12 days. The potential of peak value of inward rectification shifted gradually to the positive direction in 3, 6 and 9 days, and recovered in 12 days. Half-maximal activation potential (V1/2) of heterological expressed current shifted gradually to the negative direction in 3, 6 and 9 days of culture and then recovered in 12 days, the tendency of change was coincident with that of membrane rest potential.

CONCLUSIONThe investigation provides a method of persistent expression of HERG channel in Xenopus oocytes and offers evidences for the difference of electrophysiological experimental data of studies of molecular site and drugs effect of HERG channel in different experimental conditions.

Animals ; Ether-A-Go-Go Potassium Channels ; genetics ; metabolism ; Humans ; Membrane Potentials ; Oocytes ; metabolism ; RNA, Messenger ; genetics ; metabolism ; Xenopus laevis

OBJECTIVETo construct the pcDNA3-HERG-G572R expression vector and establish a cell line stably expressing HKE-HERG-G572R.

METHODSHERG-G572R mutant fragment was constructed by over-lap extension PCR and validated by DNA sequencing. The HKE-HERG-G572R expression vector was constructed and transfected into HEK293 cells to obtain a cell line stably expressing HKE-HERG-G572R.

RESULTSThe pcDNA3-HERG-G572R expression vector was successfully constructed and the cell line stably expressing HKE-HERG-G572R was established. Real-time PCR and Western blotting revealed a 632-fold HKE-HERG-G572R overexpression in the transfected HEK293 cells as compared with that in control HEK293 cells transfected with pcDNA3 (P<0.01).

CONCLUSIONThe protocol can be used to construct the cell line stably expressing HKE-HERG-G572R to provide a cell model for studying individualized therapy.

Base Sequence ; Ether-A-Go-Go Potassium Channels ; genetics ; Gene Expression ; Genetic Vectors ; HEK293 Cells ; metabolism ; Humans ; Mutation ; Transfection

We have investigated the methods and mechanisms for analysis of the channel kinetics parameters of voltage-gated potassium channels, HERG (Human ether-à-go-go related gene) channels, in the process of electrophysiological recording. The current of HERG K+ channels expressed in Xenopus oocytes was studied using a two-electrode voltage clamp technique, and the channel kinetics parameters were analyzed through compiling different pulse protocol and recording the current. Results showed: (1) The HERG K+ channels, under conditions of being activated with depolarized pulse, expressed an inward-rectified property attributing to rapid inactivation. The activation curve could be obtained through fitting the depolarized potential and the following peak amplitude of tail current, while the parameters of time-dependent activation was obtained through fitting different depolarized duration and the corresponding peak amplitude of tail current. (2) The I-V relationship still exhibit marked inward rectification. Tail current decay traces were fitted with a bi-exponential function to determine the time constants of the fast and slow components of current decay. (3) The inactivation of HERG channels is voltage-dependent. The inactivation process was isolated with two different three-pulse protocols, with which the inactivation curve and nearly linear I-V relationship were obtained, respectively. Thus, altough the kinetics properties of HERG channels were complicated, the channels kinetics could be indirectly analyzed through differently designed pulse protocols, which provided the basis for investigation on Alanine-scanning mutagenesis and agent action.
Animals ; ERG1 Potassium Channel ; Ether-A-Go-Go Potassium Channels ; analysis ; genetics ; Humans ; Kinetics ; Oocytes ; metabolism ; Patch-Clamp Techniques ; Xenopus laevis ; metabolism

OBJECTIVETo investigate the effect of midazolam on human ether-a-go-go (hERG) K+ channels exogenously expressed in human embryonic kidney cells (HEK-293) and the underlying molecular mechanisms.

METHODSWhole-cell patch clamp technique was used to record WT, Y652A and F656C hERG K+ current expressed in HEK-293 cells.

RESULTSMidazolam inhibited hERG K+ current in a concentration-dependent manner, the half-maximum block concentrations (IC50) values were (1.31 ± 0.32) µmol/L. The half-activation voltage (V1/2) were (2.32 ± 0.38) mV for the control and (-1.96 ± 0.83) mV for 1.0 µmol/L midazolam. The half-inactivation voltage (V1/2) was slightly shifted towards negative voltages from (-49.25 ± 0.69) mV in control to (-57.53 ± 0.53) mV after 1.0 µmol/L midazolam (P < 0.05). Mutations in drug-binding sites (Y652A or F656C) of the hERG channel significantly attenuated the hERG current blockade by midazolam.

CONCLUSIONMidazolam can block hERG K+ channel and cause the speed of inactivation faster. Mutations in the drug-binding sites (Y652 or F656) of the hERG channel were found to attenuate hERG current blockage by midazolam.

Dose-Response Relationship, Drug ; Ether-A-Go-Go Potassium Channels ; drug effects ; HEK293 Cells ; Humans ; Midazolam ; pharmacology ; Mutation ; Patch-Clamp Techniques ; Potassium Channel Blockers ; pharmacology

BACKGROUNDThe rapidly activating delayed rectifier potassium current (I(Kr)), whose pore-forming alpha subunit is encoded by the human ether-a-go-go-related gene (hERG), is a key contributor to the third phase of action potential repolarization. The aim of this study was to investigate the effect and mechanism of arecoline hydrobromide induced inhibition of hERG K(+) current (I(hERG)).

METHODSTransient transfection of hERG channel cDNA plasmid pcDNA3.1 into the cultured HEK293 cells was performed using Lipofectamine. A standard whole-cell patch-clamp technique was used to record the I(hERG) before and after the exposure to arecoline.

RESULTSArecoline decreased the amplitude and the density of the I(hERG) in a concentration-dependent manner (IC(50) = 9.55 mmol/L). At test potential of +60 mV, the magnitude of I(hERG) tail at test pulse of -40 mV was reduced from (151.7 ± 6.2) pA/pF to (84.4 ± 7.6) pA/pF (P < 0.01, n = 20) and the magnitude of I(hERG) tail at test pulse of -110 mV was reduced from (-187.5 ± 9.8) pA/pF to (-97.6 ± 12.6) pA/pF (P < 0.01, n = 20). The blockade of arecoline in the open and inactivated state was significant in a state-dependent manner. The maximal blockade was achieved in the inactivated state. Studies of gating mechanism showed that the steady-state activation curve of I(hERG) was significantly negatively shifted by arecoline. Time constants of activation were shortened. Steady-state inactivation curve and time constants of fast inactivation were not significantly affected by arecoline. Furthermore, the inhibition of I(hERG) by arecoline was characterized markedly by a frequency-dependent manner from 0.03 to 1.00 Hz pulse.

CONCLUSIONArecoline could potently block I(hERG) in both frequency and state-dependent manner.

Action Potentials ; drug effects ; Arecoline ; pharmacology ; Dose-Response Relationship, Drug ; ERG1 Potassium Channel ; Ether-A-Go-Go Potassium Channels ; antagonists & inhibitors ; physiology ; HEK293 Cells ; Humans

BACKGROUNDThe congenital Long QT syndrome (LQTS) is a hereditary cardiac channelopathy that is characterized by a prolonged QT interval, syncope, ventricular arrhythmias, and sudden death. The chromosome 7-linked type 2 congenital LQTS (LQT2) is caused by gene mutations in the human ether-a-go-go-related gene (HERG).

METHODSA Chinese family diagnosed with LQTS were screened for KCNQ1, HERG and SCN5A, using polymerase chain reaction (PCR), direct sequencing, and clong sequencing. We also investigated the mRNA expression of the HERG gene.

RESULTSWe identified a novel I414fs + 98X mutation in the HERG gene. The deletion mutation of 14-bp in the first transmembrane segment (S1) introduced premature termination codons (PTCs) at the end of exon 6. This mutation would result in a serious phenotype if the truncated proteins co-assembled with normal subunit to form the defective channels. But only the proband was symptomatic.

CONCLUSIONSWe found that the mRNA level of the HERG gene was significantly lower in I414fs + 98X carriers than in noncarriers. We found a novel I414fs + 98X mutation. The mRNA level supports that NMD mechanism might regulate the novel mutation.

Adult ; ERG1 Potassium Channel ; Ether-A-Go-Go Potassium Channels ; genetics ; Female ; Frameshift Mutation ; Humans ; Long QT Syndrome ; genetics ; RNA, Messenger ; analysis

OBJECTIVETo identify the electrophysiological properties of long-QT syndrome (LQTS) associated missense mutations in the outer mouth of the HERG potassium channel in vitro.

METHODSMutations V630A and N633S were constructed by Megaprimer PCR method and cRNA were produced by T7 RNA polymerase. The electrophysiological properties of the mutation were investigated in the Xenopus oocyte heterologous expression system.

RESULTSCoexpression of mutant and wild-type HERG subunits caused a dominant-negative effect, and the currents were significantly decreased. Compared with wild-type HERG channels, V630A and N633S mutations were related to decreased time constants for inactivation for V630A/WT and N633S/WT at all potentials, reduced slope conductance and the voltage dependence of steady-state inactivation was shifted to negative potentials for V630A/WT and N633S/WT.

CONCLUSIONPresent study shows that LQTS associated missense mutations located in the outer mouth of HERG cause a dominant-negative effect and alterations in steady-state voltage dependence of channel gating of heteromultimeric channels suggesting a reduction in expressional current might be one of the pathophysiologic mechanisms of LQTS.

Animals ; DNA Mutational Analysis ; ERG1 Potassium Channel ; Electrocardiography ; Ether-A-Go-Go Potassium Channels ; genetics ; Humans ; Long QT Syndrome ; genetics ; Mutation, Missense ; Oocytes ; Patch-Clamp Techniques ; RNA, Complementary ; Xenopus