Presence and functional role of the rapidly activating delayed rectifier K+ current in left and right atria of adult mice

Nakamura, Hiroko; Ding, Wei‐Guang; Sanada, Mitsuru; Maeda, Kengo; Kawai, Hiromichi; Maegawa, Hiroshi; Matsuura, Hiroshi

doi:10.1016/j.ejphar.2010.08.025

Cited by 15 publications

(30 citation statements)

References 38 publications

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“…6), which indicates that I Kr plays an important role in phase 3 repolarization at potentials negative to −20 or −30 mV in these ages of mouse ventricular myocytes. Previous studies also showed that I Kr plays a similar preferential role in the latter part of phase 3 repolarization in various types of cardiac myocytes [23,25]. I Kr exhibits an inward rectifying property due to rapid Ctype inactivation [34], which results in a minimum contribution of outward current through I Kr channel to repolarization of the action potential at depolarized membrane potentials.…”

Section: Postnatal Developmental Decrease In I Krmentioning

confidence: 91%

Postnatal developmental decline in I K1 in mouse ventricular myocytes isolated by the Langendorff perfusion method: comparison with the chunk method

Hoshino

Omatsu‐Kanbe

Nakagawa

et al. 2012

Pflugers Arch - Eur J Physiol

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Expression and function of cardiac ion channels exhibit postnatal developmental changes, which, however, has not yet been proven in ventricular myocytes isolated using similar techniques. In this study, ventricular myocytes were enzymatically dissociated from mouse heart at different postnatal ages (including postnatal day 0) by similar techniques using Langendorff perfusion. Whole-cell patch-clamp experiments were performed to record action potentials, I (K1), I (Kr), I (Kur), I (ss), and I (Ca,L), in ventricular myocytes freshly isolated from postnatal days 0, 7, and 14 and adult mice. Viable ventricular myocytes of day-0 mouse heart exhibited spindle-shaped appearance having cell length of approximately 50 μm, which gradually developed to a rod-shaped one having clear cross striation with cell length of approximately 120 μm (adult). The action potential duration markedly shortened, while the resting membrane potential depolarized to a small but significant extent during postnatal development. I (K1) density was maximal in postnatal day-0 ventricular myocytes and gradually decreased during development, which was accompanied by postnatal depolarization of resting membrane potential. However, I (K1) density was markedly decreased by approximately 80% in postnatal day-0 ventricular myocytes, when isolated by the chunk method. Quantitative real-time polymerase chain reaction (PCR) and western blot analyses demonstrated higher Kir2.3 expression but lower expression levels of Kir2.1 and Kir2.2 in day-0 mouse ventricles, compared with those of day-14 and adult mouse ventricles. Whereas I (Kr) exhibited marked decrease during postnatal development, I (Kur), I (ss), and I (Ca,L) exhibited postnatal developmental increase. The present cell isolation method using the Langendorff perfusion thus found that, in mouse ventricles, I (K1) exhibited postnatal developmental decrease, associated with depolarization of resting potential.

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Section: Postnatal Developmental Decrease In I Krmentioning

confidence: 91%

Postnatal developmental decline in I K1 in mouse ventricular myocytes isolated by the Langendorff perfusion method: comparison with the chunk method

Hoshino

Omatsu‐Kanbe

Nakagawa

et al. 2012

Pflugers Arch - Eur J Physiol

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“…), atrial myocytes (Nakamura et al. ) and cardiac progenitor cells (atypically‐shaped cardiomyocytes, ACMs) (Omatsu‐Kanbe and Matsuura ). However, the cannulation of the mouse aorta and its subsequent mounting on the Langendorff‐apparatus to perform retrograde perfusion are delicate operations, requiring a high degree of skill.…”

Section: Introductionmentioning

confidence: 99%

A simple antegrade perfusion method for isolating viable single cardiomyocytes from neonatal to aged mice

et al. 2018

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The aim of this study was to establish a simple and reproducible antegrade perfusion method for isolating single viable mouse heart cells and to determine the standard practical protocols that are appropriate for mice of various ages. Antegrade perfusion was performed by injecting perfusate from near the apex of the left ventricle of the excised heart, the aorta of which was clamped, using an infusion pump. This could thoroughly perfuse the myocardium through the coronary circulation. All procedures were carried out on a prewarmed heater mat under a microscope, which allows for the processes of injection and perfusion to be monitored. With appropriate adjustment of the size of the injection needle, the composition and amount of enzyme solution and the perfusion flow rate, this antegrade perfusion method could be applied to the hearts of neonatal to aged mice. We examined the morphological characteristics and electrophysiological properties of the isolated ventricular and atrial myocytes and found that these cells were mostly identical to those obtained with the traditional Langendorff‐based retrograde perfusion method. Interstitial nonmyocytes, such as cardiac progenitor cells, were also isolated simultaneously from the supernatant fraction of the centrifugation, similar to the retrograde perfusion method. The results suggest that single heart cells can be well isolated with high degree of quality by the present antegrade perfusion method, regardless of the age of the mouse.

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“…30 Our findings are in agreement with those previous studies and presented evidence that Hsp/Hsc70 association with hERG is regulated by the cellular levels of these 2 chaperones ( Figure 5C and 5D). 19,32 which is one of the major factors to determine the QT interval. 22 E4031-induced prolongation of APD 90 was more remarkable in the cells treated with HS than in the control cells, indicating that the increased I Kr contributes to acceleration of repolarization by HS through increases in Hsp70-mERG complex associated with decreases of Hsc70-mERG complex.…”

Section: Circulation Research February 18 2011mentioning

confidence: 99%

Reciprocal Control of hERG Stability by Hsp70 and Hsc70 With Implication for Restoration of LQT2 Mutant Stability

Ninomiya

Kurata

et al. 2011

Circulation Research

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Rationale:The human ether-a-go-go-related gene (hERG) encodes the ␣ subunit of the potassium current I Kr . It is highly expressed in cardiomyocytes and its mutations cause long QT syndrome type 2. Heat shock protein (Hsp)70 is known to promote maturation of hERG. Hsp70 and heat shock cognate (Hsc70) 70 has been suggested to play a similar function. However, Hsc70 has recently been reported to counteract Hsp70.Objective: We investigated whether Hsc70 counteracts Hsp70 in the control of wild-type and mutant hERG stability. Methods and Results:Coexpression of Hsp70 with hERG in HEK293 cells suppressed hERG ubiquitination and increased the levels of both immature and mature forms of hERG. Immunocytochemistry revealed increased levels of hERG in the endoplasmic reticulum and on the cell surface. Electrophysiological studies showed increased I Kr . All these effects of Hsp70 were abolished by Hsc70 coexpression. Heat shock treatment of HL-1 mouse cardiomyocytes induced endogenous Hsp70, switched mouse ERG associated with Hsc70 to Hsp70, increased I Kr , and shortened action potential duration. Channels with disease-causing missense mutations in intracellular domains had a higher binding capacity to Hsc70 than wild-type channels and channels with mutations in the pore region. Knockdown of Hsc70 by small interfering RNA or heat shock prevented degradation of mutant hERG proteins with mutations in intracellular domains. T he human ether-a-go-go-related gene (hERG) encodes the ␣ subunit of a rapidly activating delayed-rectifier K ϩ current (I Kr ), 1-3 which controls the action potential duration in cardiomyocytes. Mutations in the gene cause long-QT syndrome type 2 (LQT2), a disorder that leads to life-threatening arrhythmia. To date, more than 200 naturally occurring mutations of hERG have been identified. Functional analysis of mutant proteins showed that most of them had an impairment of protein maturation and/or trafficking. 4 -6 They are recognized by the quality control machinery of the endoplasmic reticulum (ER), ubiquitinated, and eventually degraded by the proteasomal degradation system. 6 -8 The maturation of hERG can be evaluated by comparing the levels of the 2 forms of this protein; a core-glycosylated, immature form of 135-kDa localized in the ER, and a fully glycosylated mature form of 155 kDa localized either in the Golgi apparatus or on cell surface. 7,9 Molecular chaperones participate in every step of hERG biogenesis, including synthesis, folding, assembly, and translocation. 8,10,11 The heat shock protein (Hsp)70 family, including stress-induced Hsp70 and constitutively expressed heat shock cognate protein (Hsc)70, interact with the core-glycosylated form of hERG. 8,12 Hsp70 increases the levels of both immature and mature forms of hERG, 8 whereas the role of Hsc70 remains unknown. In other channel proteins, such as the murine epithelial sodium channel, Hsc70 has been shown to counteract the action of Hsp70 and, thus, decreases the level of the channel protein. 13 The primary purpose of this stud...

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Presence and functional role of the rapidly activating delayed rectifier K+ current in left and right atria of adult mice

Cited by 15 publications

References 38 publications

Postnatal developmental decline in I K1 in mouse ventricular myocytes isolated by the Langendorff perfusion method: comparison with the chunk method

Postnatal developmental decline in I K1 in mouse ventricular myocytes isolated by the Langendorff perfusion method: comparison with the chunk method

A simple antegrade perfusion method for isolating viable single cardiomyocytes from neonatal to aged mice

Reciprocal Control of hERG Stability by Hsp70 and Hsc70 With Implication for Restoration of LQT2 Mutant Stability

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