Functional role of inward rectifier current in heart probed by Kir2.1 overexpression and dominant-negative suppression

Miake, Junichiro; Marbán, Eduardo; Nuss, Hanne

doi:10.1172/jci200317959

Cited by 179 publications

(63 citation statements)

References 28 publications

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“…Biological pacemakers can be derived from gene and cell therapy [1]. During the past few years, several gene therapy strategies have been devised [2,3,4,5,6,7,8], but the changes of receptors or channels caused by local or whole area transfection of myocardium can be proarrhythmic [9, 10]. Moreover, the genes employed in these efforts have not been pivotal modulators of spontaneous depolarization in sinoatrial node (SAN) cells.…”

Section: Introductionmentioning

confidence: 99%

Development of Functional I<sub>f</sub> Channels in mMSCs after Transfection with mHCN4: Effects on Cell Morphology and Mechanical Activity in vitro

Shi-fei

Yao²,

Wan³

et al. 2008

Cardiology

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Objective: To study the functional properties of I_f channels and the changes in mechanical activity of mouse mesenchymal stem cells (mMSCs) transfected with mHCN4. Methods: mMSCs were purified by using CD11b-immunomagnetic microbeads and transfected with pMSCV-mHCN4-EGFP or pMSCV-EGFP. We examined the kinetic characteristics of the mHCN4 channel. The morphological changes of positively transfected mMSCs were investigated at the same time. Results: The I_f current recorded from the experimental group was sensitive to extracellular Cs⁺ (–44.5 ± 4.2 vs. –5.5 ± 1.0 pA/pF, p < 0.001). The half-maximal activation was –99.0 ± 5.8 mV. The time constant of activation was 451 ± 61 ms under –140 mV. The control cells did not show the current under the same conditions. The absolute values of half-maximal activation decreased in the presence of cAMP or cGMP in the experimental group (–78.6 ± 10.4 and –85.7 ± 8.6 vs. –99.0 ± 5.8 mV, respectively, p < 0.05). mMSCs transfected with pMSCV-mHCN4-EGFP could form spontaneous beating cells. Extracellular Cs⁺ decreased the beating rate significantly (196 ± 50 vs. 66 ± 23 bmp, p < 0.01). Conclusions: Functional I_f channels can be reconstructed in mMSCs infected with mHCN4. mMSCs modified by successful transfection with mHCN4 can differentiate so as to develop spontaneous mechanical activity.

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Section: Introductionmentioning

confidence: 99%

Development of Functional I<sub>f</sub> Channels in mMSCs after Transfection with mHCN4: Effects on Cell Morphology and Mechanical Activity in vitro

Shi-fei

Yao²,

Wan³

et al. 2008

Cardiology

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“…In cardiac myocytes, I K1 sets the resting membrane potential, controls the approach to threshold upon depolarization, and modulates the terminal phase of repolarization (Lopatin & Nichols, 2001; Miake et al . 2003).…”

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confidence: 99%

Up‐regulation of the inward rectifier K⁺ current (I_K1) in the mouse heart accelerates and stabilizes rotors

Noujaim

Pandit

Berenfeld

et al. 2006

The Journal of Physiology

142

139

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Previous studies have suggested an important role for the inward rectifier K + current (I K1 ) in stabilizing rotors responsible for ventricular tachycardia (VT) and fibrillation (VF). To test this hypothesis, we used a line of transgenic mice (TG) overexpressing Kir 2.1-green fluorescent protein (GFP) fusion protein in a cardiac-specific manner. Optical mapping of the epicardial surface in ventricles showed that the Langendorff-perfused TG hearts were able to sustain stable VT/VF for 350 ± 1181 s at a very high dominant frequency (DF) of 44.6 ± 4.3 Hz. In contrast, tachyarrhythmias in wild-type hearts (WT) were short-lived (3 ± 9 s), and the DF was 26.3 ± 5.2 Hz. The stable, high frequency, reentrant activity in TG hearts slowed down, and eventually terminated in the presence of 10 µM Ba 2+ , suggesting an important role for I K1 . Moreover, by increasing I K1 density in a two-dimensional computer model having realistic mouse ionic and action potential properties, a highly stable, fast rotor (≈45 Hz) could be induced. Simulations suggested that the TG hearts allowed such a fast and stable rotor because of both greater outward conductance at the core and shortened action potential duration in the core vicinity, as well as increased excitability, in part due to faster recovery of Na + current. The latter resulted in a larger rate of increase in the local conduction velocity as a function of the distance from the core in TG compared to WT hearts, in both simulations and experiments. Finally, simulations showed that rotor frequencies were more sensitive to changes (doubling) in I K1 , compared to other K + currents. In combination, these results provide the first direct evidence that I K1 up-regulation in the mouse heart is a substrate for stable and very fast rotors.

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“…I Kir flows through tetrameric channels formed by subunits in the Kir2 family (Kir2.1–2.4). The polyamine block of Kir2 channels has been studied mainly using Kir2.1, which may be the predominant subunit mediating the cardiac I Kir (Zaritsky et al 2001; Miake et al 2003). Studies have shown that block of the outward currents by internal particles involves both high‐ and low‐affinity block (Yang et al 1995 a ; Guo & Lu, 2000), but the molecular mechanisms for two types of block, and the physiological relevance of the low‐affinity block, remained unclear.…”

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confidence: 99%

Low‐affinity spermine block mediating outward currents through Kir2.1 and Kir2.2 inward rectifier potassium channels

Ishihara

Yan

2007

The Journal of Physiology

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The outward component of the strong inward rectifier K + current (I Kir ) plays a pivotal role in polarizing the membranes of excitable and non-excitable cells and is regulated by voltage-dependent channel block by internal cations. Using the Kir2.1 channel, we previously showed that a small fraction of the conductance susceptible only to a low-affinity mode of block likely carries a large portion of the outward current. To further examine the relevance of the low-affinity block to outward I Kir and to explore its molecular mechanism, we studied the block of the Kir2.1 and Kir2.2 channels by spermine, which is the principal Kir2 channel blocker. Current-voltage relations of outward Kir2.2 currents showed a peak, a plateau and two peaks in the presence of 10, 1 and 0.1 μM spermine, respectively, which was explained by the presence of two conductances that differ in their susceptibility to spermine block. When the current-voltage relations showed one peak, like those of native I Kir , outward Kir2.2 currents were mediated mostly by the conductance susceptible to the low-affinity block. They also flowed in a narrower range than the corresponding Kir2.1 currents, because of 3-to 4-fold greater susceptibility to the low-affinity block than in Kir2.1. Reducing external [K + ] shifted the voltage dependences of both the high-and low-affinity block of Kir2.1 in parallel with the shift in the reversal potential, confirming the importance of the low-affinity block in mediating outward I Kir . When Kir2.1 mutants known to have reduced sensitivity to internal blockers were examined, the D172N mutation in the transmembrane pore region made almost all of the conductance susceptible only to low-affinity block, while the E224G mutation in the cytoplasmic pore region reduced the sensitivity to low-affinity block without markedly altering that to the high-affinity block or the high/low conductance ratio. The effects of these mutations support the hypothesis that Kir2 channels exist in two states having different susceptibilities to internal cationic blockers.

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Functional role of inward rectifier current in heart probed by Kir2.1 overexpression and dominant-negative suppression

Cited by 179 publications

References 28 publications

Development of Functional I<sub>f</sub> Channels in mMSCs after Transfection with mHCN4: Effects on Cell Morphology and Mechanical Activity in vitro

Development of Functional I<sub>f</sub> Channels in mMSCs after Transfection with mHCN4: Effects on Cell Morphology and Mechanical Activity in vitro

Up‐regulation of the inward rectifier K⁺ current (I_K1) in the mouse heart accelerates and stabilizes rotors

Low‐affinity spermine block mediating outward currents through Kir2.1 and Kir2.2 inward rectifier potassium channels

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Functional role of inward rectifier current in heart probed by Kir2.1 overexpression and dominant-negative suppression

Cited by 179 publications

References 28 publications

Development of Functional I<sub>f</sub> Channels in mMSCs after Transfection with mHCN4: Effects on Cell Morphology and Mechanical Activity in vitro

Development of Functional I<sub>f</sub> Channels in mMSCs after Transfection with mHCN4: Effects on Cell Morphology and Mechanical Activity in vitro

Up‐regulation of the inward rectifier K+ current (IK1) in the mouse heart accelerates and stabilizes rotors

Low‐affinity spermine block mediating outward currents through Kir2.1 and Kir2.2 inward rectifier potassium channels

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Up‐regulation of the inward rectifier K⁺ current (I_K1) in the mouse heart accelerates and stabilizes rotors