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KChIP2 regulates the cardiac Ca 2+ transient and myocyte contractility by targeting ryanodine receptor activity

View Article: PubMed Central - PubMed

ABSTRACT

Pathologic electrical remodeling and attenuated cardiac contractility are featured characteristics of heart failure. Coinciding with these remodeling events is a loss of the K+ channel interacting protein, KChIP2. While, KChIP2 enhances the expression and stability of the Kv4 family of potassium channels, leading to a more pronounced transient outward K+ current, Ito,f, the guinea pig myocardium is unique in that Kv4 expression is absent, while KChIP2 expression is preserved, suggesting alternative consequences to KChIP2 loss. Therefore, KChIP2 was acutely silenced in isolated guinea pig myocytes, which led to significant reductions in the Ca2+ transient amplitude and prolongation of the transient duration. This change was reinforced by a decline in sarcomeric shortening. Notably, these results were unexpected when considering previous observations showing enhanced ICa,L and prolonged action potential duration following KChIP2 loss, suggesting a disruption of fundamental Ca2+ handling proteins. Evaluation of SERCA2a, phospholamban, RyR, and sodium calcium exchanger identified no change in protein expression. However, assessment of Ca2+ spark activity showed reduced spark frequency and prolonged Ca2+ decay following KChIP2 loss, suggesting an altered state of RyR activity. These changes were associated with a delocalization of the ryanodine receptor activator, presenilin, away from sarcomeric banding to more diffuse distribution, suggesting that RyR open probability are a target of KChIP2 loss mediated by a dissociation of presenilin. Typically, prolonged action potential duration and enhanced Ca2+ entry would augment cardiac contractility, but here we see KChIP2 fundamentally disrupts Ca2+ release events and compromises myocyte contraction. This novel role targeting presenilin localization and RyR activity reveals a significance for KChIP2 loss that reflects adverse remodeling observed in cardiac disease settings.

No MeSH data available.


Related in: MedlinePlus

KChIP2 KD results in a significant reduction in spark frequency.(A) Left panel (Ad.GFP) and right panel (Ad.KChIP KD) show representative recordings of confocal line scan imaging evaluating spontaneous Ca2+ spark activity following 1 Hz field stimulation. Summary data between control (n = 47 cells) and KChIP KD (n = 44 cells) for the (B) spark frequency, (C) Ca2+ spark time-to-peak, (D) decay time of the Ca2+ spark, and (E) full width at half maximum (FWHM) amplitude.
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pone.0175221.g005: KChIP2 KD results in a significant reduction in spark frequency.(A) Left panel (Ad.GFP) and right panel (Ad.KChIP KD) show representative recordings of confocal line scan imaging evaluating spontaneous Ca2+ spark activity following 1 Hz field stimulation. Summary data between control (n = 47 cells) and KChIP KD (n = 44 cells) for the (B) spark frequency, (C) Ca2+ spark time-to-peak, (D) decay time of the Ca2+ spark, and (E) full width at half maximum (FWHM) amplitude.

Mentions: While we saw no change in the amount of RyR expression, we wanted to evaluate a possible change in its function. To address this, we performed confocal line scan imaging to determine Ca2+ spark activity and, thus, assess RyR activity. Cells were paced for 10 beats at 1 Hz, immediately after which measurements for spontaneous Ca2+ release events were taken. We observed that cells with KChIP2 KD had a spark frequency 46.2% lower than control cells (Fig 5A and 5B), suggesting reduced open probability for RyR receptor in myocytes without KChIP2. Notably, this reduced activity of Ca2+ release can explain the reduced Ca2+ transient amplitude and resulting contraction events. Additionally, no change in the time-to-peak (Fig 5C) but a significant prolongation of spark decay (Fig 5D) following KChIP2 KD are consistent with the conditions observed for the overall Ca2+ transient. There was also no change in the full width at half maximum amplitude between treatment groups (Fig 5E), suggesting preservation of RyR clustering.


KChIP2 regulates the cardiac Ca 2+ transient and myocyte contractility by targeting ryanodine receptor activity
KChIP2 KD results in a significant reduction in spark frequency.(A) Left panel (Ad.GFP) and right panel (Ad.KChIP KD) show representative recordings of confocal line scan imaging evaluating spontaneous Ca2+ spark activity following 1 Hz field stimulation. Summary data between control (n = 47 cells) and KChIP KD (n = 44 cells) for the (B) spark frequency, (C) Ca2+ spark time-to-peak, (D) decay time of the Ca2+ spark, and (E) full width at half maximum (FWHM) amplitude.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5383259&req=5

pone.0175221.g005: KChIP2 KD results in a significant reduction in spark frequency.(A) Left panel (Ad.GFP) and right panel (Ad.KChIP KD) show representative recordings of confocal line scan imaging evaluating spontaneous Ca2+ spark activity following 1 Hz field stimulation. Summary data between control (n = 47 cells) and KChIP KD (n = 44 cells) for the (B) spark frequency, (C) Ca2+ spark time-to-peak, (D) decay time of the Ca2+ spark, and (E) full width at half maximum (FWHM) amplitude.
Mentions: While we saw no change in the amount of RyR expression, we wanted to evaluate a possible change in its function. To address this, we performed confocal line scan imaging to determine Ca2+ spark activity and, thus, assess RyR activity. Cells were paced for 10 beats at 1 Hz, immediately after which measurements for spontaneous Ca2+ release events were taken. We observed that cells with KChIP2 KD had a spark frequency 46.2% lower than control cells (Fig 5A and 5B), suggesting reduced open probability for RyR receptor in myocytes without KChIP2. Notably, this reduced activity of Ca2+ release can explain the reduced Ca2+ transient amplitude and resulting contraction events. Additionally, no change in the time-to-peak (Fig 5C) but a significant prolongation of spark decay (Fig 5D) following KChIP2 KD are consistent with the conditions observed for the overall Ca2+ transient. There was also no change in the full width at half maximum amplitude between treatment groups (Fig 5E), suggesting preservation of RyR clustering.

View Article: PubMed Central - PubMed

ABSTRACT

Pathologic electrical remodeling and attenuated cardiac contractility are featured characteristics of heart failure. Coinciding with these remodeling events is a loss of the K+ channel interacting protein, KChIP2. While, KChIP2 enhances the expression and stability of the Kv4 family of potassium channels, leading to a more pronounced transient outward K+ current, Ito,f, the guinea pig myocardium is unique in that Kv4 expression is absent, while KChIP2 expression is preserved, suggesting alternative consequences to KChIP2 loss. Therefore, KChIP2 was acutely silenced in isolated guinea pig myocytes, which led to significant reductions in the Ca2+ transient amplitude and prolongation of the transient duration. This change was reinforced by a decline in sarcomeric shortening. Notably, these results were unexpected when considering previous observations showing enhanced ICa,L and prolonged action potential duration following KChIP2 loss, suggesting a disruption of fundamental Ca2+ handling proteins. Evaluation of SERCA2a, phospholamban, RyR, and sodium calcium exchanger identified no change in protein expression. However, assessment of Ca2+ spark activity showed reduced spark frequency and prolonged Ca2+ decay following KChIP2 loss, suggesting an altered state of RyR activity. These changes were associated with a delocalization of the ryanodine receptor activator, presenilin, away from sarcomeric banding to more diffuse distribution, suggesting that RyR open probability are a target of KChIP2 loss mediated by a dissociation of presenilin. Typically, prolonged action potential duration and enhanced Ca2+ entry would augment cardiac contractility, but here we see KChIP2 fundamentally disrupts Ca2+ release events and compromises myocyte contraction. This novel role targeting presenilin localization and RyR activity reveals a significance for KChIP2 loss that reflects adverse remodeling observed in cardiac disease settings.

No MeSH data available.


Related in: MedlinePlus