Cloning and expression of a Kv1.2 class delayed rectifier K+ channel from canine colonic smooth muscle.

Hart, P. M.; Overturf, Ken; Russell, S. N.; Carl, A.; Hume, Joseph R.; Sanders, Kenton M.; Horowitz, Burton

doi:10.1073/pnas.90.20.9659

Cited by 71 publications

(63 citation statements)

References 26 publications

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“…Action of 4-AP on the Kv I2 delayed rectifier current As previously reported (Hart et al 1993), 4-AP inhibits the KV1-2 delayed rectifier current in a dose-dependent manner with an IC50 of 74'4 jaM. We studied whether the block by 4-AP was use dependent.…”

Section: Resultsmentioning

confidence: 99%

“…At room temperature, the channel showed fast activation (time to half of peak current, t4 = 7X4 ms) and slow inactivation which was incomplete after 20 s depolarizations. In comparison with other KV12 channels (Stuhmer et al 1989;Paulmichl et al 1991), cKV12 is highly sensitive to block by 4-AP with an IC50 of 74-4 mm (Hart et al 1993). In contrast, RAK, a delayed rectifier channel isolated from rat atrium, has an IC50 of 600 mm (Paulmichl et al 1991).…”

Section: Results Suggest That 4-ap Binds To the Open State Of The Kvlmentioning

confidence: 99%

“…We have recently cloned and expressed a cDNA encoding a KV1 2 delayed rectifier channel from colonic smooth muscle (cKV1 2) (Hart et al 1993). Functional expression in oocytes demonstrated a channel highly selective for K+ which activates in a voltage-dependent manner upon depolarization to membrane potentials positive to -40 mV.…”

Section: Results Suggest That 4-ap Binds To the Open State Of The Kvlmentioning

confidence: 99%

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Block by 4‐aminopyridine of a Kv1.2 delayed rectifier K+ current expressed in Xenopus oocytes.

Russell

Publicover

Hart

et al. 1994

The Journal of Physiology

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1. The blocking action of 4-aminopyridine (4-AP) on a delayed rectifier K,12 K+ channel expressed in oocytes was investigated at room temperature (22°C) and physiological temperature (34°C) using the double-electrode voltage clamp and patch clamp techniques. 2. At room temperature, 4-AP (100 uM) inhibition occurred only after activation of current. The rate of onset of block was dependent upon the length of time current was activated by a depolarizing step. Similarly, removal of block required current activation. The degree of steady-state block by 4-AP was not reduced by increasingly more depolarized step potentials. The degree of steady-state block also did not change over the duration of a I s step.3. When channels were nearly fully inactivated, 4-AP produced no additional block of a subsequent depolarizing step, suggesting that 4-AP did not bind when channels were in the inactivated state. In single channel experiments, 4-AP decreased the mean open time in a dose-dependent manner but did not alter the single-channel current amplitude. 4. At 34°C the I-V relationship and inactivation curve shifted to more negative potentials. Increasing the temperature to 34°C did not alter the degree of block by 4-AP, although the rate of onset of block was greatly enhanced.

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Section: Resultsmentioning

confidence: 99%

Section: Results Suggest That 4-ap Binds To the Open State Of The Kvlmentioning

confidence: 99%

Section: Results Suggest That 4-ap Binds To the Open State Of The Kvlmentioning

confidence: 99%

See 1 more Smart Citation

Block by 4‐aminopyridine of a Kv1.2 delayed rectifier K+ current expressed in Xenopus oocytes.

Russell

Publicover

Hart

et al. 1994

The Journal of Physiology

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“…Whether PKC directly phosphorylates the channel, a regulatory protein coupled to Ky, or an upstream protein remains to be determined. Two Kv cDNAs have been isolated from smooth muscle libraries, Kv1 2 and Kv1 5, and the deduced amino acid sequences reveal that both proteins contain consensus sites for PKC phosphorylation in their amino acid sequences (Hart et al 1993;Overturf et al 1994). In conclusion, in addition to the already known mechanisms involved in vasoconstrictor stimulation, inhibition of IK(v) by Ang may have important implications for the regulation of vascular smooth muscle contraction.…”

Section: Electrophysiological Measurementsmentioning

confidence: 99%

Angiotensin II activation of protein kinase C decreases delayed rectifier K+ current in rabbit vascular myocytes.

Clément-Chomienne

Walsh

Cole

1996

The Journal of Physiology

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1. The effect of angiotensin II (Ang) on delayed rectifier K+ current (IK(v)) was studied in isolated rabbit portal vein smooth muscle cells using standard whole-cell voltage clamp technique. The effect of 100 nM Ang on macroscopic, whole-cell IK(V) was assessed in myocytes dialysed with 10 mm BAPTA, 5 mm ATP and 1 mm GTP either at room temperature or at 30 'C. 2. Application of Ang caused a decline in IK(V) which was reversed upon washout of the drug.Tail current recorded after 250 ms pulses to +30 mV and repolarization to -40 mV was reduced from 3'9 + 0 7 to 2-5 + 0 5 pA pF-' at 20 'C (n = 6) and from 4-5 + 0 5 to 3-13 + 04 pA pF-1 at 30 C (n = 17). 3. Ang had no effect on outward current in the presence of an AT1 selective antagonist, losartan (1 uM), which alone had no direct effect on the amplitude of IK(v). Substitution of extracellular Ca2+ with Mg2+ in the presence of 10 mm intracellular BAPTA did not affect the suppression of IK(V) by Ang. 4. Ang induced a decrease in time constant for the rapid phase of inactivation of the macroscopic current (r1 reduced from 377 + 32 to 245 + 11 ms; T2 unchanged, n = 17).Neither the voltage dependence of activation nor inactivation were affected by Ang. The inhibition of IK(V) by Ang was abolished by intracellular dialysis with the selective PKCinhibitors, calphostin C (1 IBM) and chelerythrine (50 uM). These data provide strong evidence that the decline in IK(V) due to Ang treatment is due to PKC activation. 6. The pattern of expression of PKC isoforms was examined in rabbit portal vein using isoenzyme-specific antibodies: a, e and ; isoenzymes were detected, but /1, y, a and V isoenzymes were not.7. The lack of requirement for Ca2+, as well as the sensitivity of the Ang response to chelerythrine, suggest the involvement of the Ca2P-independent PKC isoenzyme e in the signal transduction pathway responsible for IK(V) inhibition by Ang.Variations in intracellular Ca2+ concentration constitute an important element in the control of vascular smooth muscle tone. Contractile agonists are known to cause an elevation in intracellular Ca2+ concentration by increasing the influx of extracellular Ca2P through voltage-dependent L-type Ca2P channels and/or by releasing Ca2+ from intracellular stores.

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“…Moreover, Kcna2 channels have been shown to play a pivotal role in maintaining the resting membrane potential and, consequently, regulating cellular excitability in neurons 28. There is direct evidence showing that the I Ks is generated by Kcna2 in Xenopus oocytes, rabbit vascular myocytes, pulmonary arterial smooth muscle cells, rat mesenteric artery smooth muscle cells, and canine colonic circular smooth muscles 29, 30, 31, 32, 33. Specifically, Kcna2 was demonstrated to contribute to the I Ks, rather than the transient outward potassium current, in adult rat myocytes 8.…”

Section: Discussionmentioning

confidence: 99%

Long Noncoding RNA Kcna2 Antisense RNA Contributes to Ventricular Arrhythmias via Silencing Kcna2 in Rats With Congestive Heart Failure

Long

Wang

Gao

et al. 2017

JAHA

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BackgroundCongestive heart failure (CHF) is a common cardiovascular disease that is often accompanied by ventricular arrhythmias. The decrease of the slow component of the delayed rectifier potassium current (IK s) in CHF leads to action potential (AP) prolongation, and the IK s is an important contributor to the development of ventricular arrhythmias. However, the molecular mechanisms underlying ventricular arrhythmias are still unknown.Methods and ResultsKcna2 and Kcna2 antisense RNA (Kcna2 AS) transcript expression was measured in rat cardiac tissues using quantitative real‐time reverse transcription–polymerase chain reaction and Western blotting. There was a 43% reduction in Kcna2 mRNA in the left ventricular myocardium of rats with CHF. Kcna2 knockdown in the heart decreased the IKs and prolonged APs in cardiomyocytes, consistent with the changes observed in heart failure. Conversely, Kcna2 overexpression in the heart significantly attenuated the CHF‐induced decreases in the IKs, AP prolongation, and ventricular arrhythmias. Kcna2 AS was upregulated ≈1.7‐fold in rats with CHF and with phenylephrine‐induced cardiomyocyte hypertrophy. Kcna2 AS inhibition increased the CHF‐induced downregulation of Kcna2. Consequently, Kcna2 AS mitigated the decrease in the IKs and the prolongation of APs in vivo and in vitro and reduced ventricular arrhythmias, as detected using electrocardiography.ConclusionsVentricular Kcna2 AS expression increases in rats with CHF and contributes to reduced IK s, prolonged APs, and the occurrence of ventricular arrhythmias by silencing Kcna2. Thus, Kcna2 AS may be a new target for the prevention and treatment of ventricular arrhythmias in patients with CHF.

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Cloning and expression of a Kv1.2 class delayed rectifier K+ channel from canine colonic smooth muscle.

Cited by 71 publications

References 26 publications

Block by 4‐aminopyridine of a Kv1.2 delayed rectifier K+ current expressed in Xenopus oocytes.

Block by 4‐aminopyridine of a Kv1.2 delayed rectifier K+ current expressed in Xenopus oocytes.

Angiotensin II activation of protein kinase C decreases delayed rectifier K+ current in rabbit vascular myocytes.

Long Noncoding RNA Kcna2 Antisense RNA Contributes to Ventricular Arrhythmias via Silencing Kcna2 in Rats With Congestive Heart Failure

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