Reduced junctional Na+/Ca2+-exchanger activity contributes to sarcoplasmic reticulum Ca2+ leak in junctophilin-2-deficient mice

Wei Wang, Andrew P. Landstrom, Qiongling Wang, Michelle L. Munro, David Beavers, Michael John Ackerman, Christian Soeller, Xander H T Wehrens

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Expression silencing of junctophilin-2 (JPH2) in mouse heart leads to ryanodine receptor type 2 (RyR2)-mediated sarcoplasmic reticulum (SR) Ca2+ leak and rapid development of heart failure. The mechanism and physiological significance of JPH2 in regulating RyR2-mediated SR Ca2+ leak remains elusive. We sought to elucidate the role of JPH2 in regulating RyR2-mediated SR Ca2+ release in the setting of cardiac failure. Cardiac myocytes isolated from tamoxifen-inducible conditional knockdown mice of JPH2 (MCM-shJPH2) were subjected to confocal Ca2+ imaging. MCM-shJPH2 cardiomyocytes exhibited an increased spark frequency width with altered spark morphology, which caused increased SR Ca2+ leakage. Single channel studies identified an increased RyR2 open probability in MCM-shJPH2 mice. The increase in spark frequency and width was observed only in MCM-shJPH2 and not found in mice with increased RyR2 open probability with native JPH2 expression. Na+/Ca2+-exchanger (NCX) activity was reduced by 50% in MCM-shJPH2 with no detectable change in NCX expression. Additionally, 50% inhibition of NCX through Cd2+ administration alone was sufficient to increase spark width in myocytes obtained from wild-type mice. Additionally, superresolution analysis of RyR2 and NCX colocalization showed a reduced overlap between RyR2 and NCX in MCM-shJPH2 mice. In conclusion, decreased JPH2 expression causes increased SR Ca2+ leakage by directly increasing open probability of RyR2 and by indirectly reducing junctional NCX activity through increased dyadic cleft Ca2+. This demonstrates two novel and independent cellular mechanisms by which JPH2 regulates RyR2-mediated SR Ca2+ leak and heart failure development.

Original languageEnglish (US)
Pages (from-to)H1317-H1326
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume307
Issue number9
DOIs
StatePublished - Nov 1 2014

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Ryanodine Receptor Calcium Release Channel
Sarcoplasmic Reticulum
Heart Failure
Cardiac Myocytes
junctophilin
Tamoxifen
Muscle Cells

Keywords

  • Calcium
  • Heart failure
  • Junctophilin
  • Ryanodine receptor
  • Sodium/calcium exchanger

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)
  • Cardiology and Cardiovascular Medicine
  • Medicine(all)

Cite this

Reduced junctional Na+/Ca2+-exchanger activity contributes to sarcoplasmic reticulum Ca2+ leak in junctophilin-2-deficient mice. / Wang, Wei; Landstrom, Andrew P.; Wang, Qiongling; Munro, Michelle L.; Beavers, David; Ackerman, Michael John; Soeller, Christian; Wehrens, Xander H T.

In: American Journal of Physiology - Heart and Circulatory Physiology, Vol. 307, No. 9, 01.11.2014, p. H1317-H1326.

Research output: Contribution to journalArticle

Wang, Wei ; Landstrom, Andrew P. ; Wang, Qiongling ; Munro, Michelle L. ; Beavers, David ; Ackerman, Michael John ; Soeller, Christian ; Wehrens, Xander H T. / Reduced junctional Na+/Ca2+-exchanger activity contributes to sarcoplasmic reticulum Ca2+ leak in junctophilin-2-deficient mice. In: American Journal of Physiology - Heart and Circulatory Physiology. 2014 ; Vol. 307, No. 9. pp. H1317-H1326.
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abstract = "Expression silencing of junctophilin-2 (JPH2) in mouse heart leads to ryanodine receptor type 2 (RyR2)-mediated sarcoplasmic reticulum (SR) Ca2+ leak and rapid development of heart failure. The mechanism and physiological significance of JPH2 in regulating RyR2-mediated SR Ca2+ leak remains elusive. We sought to elucidate the role of JPH2 in regulating RyR2-mediated SR Ca2+ release in the setting of cardiac failure. Cardiac myocytes isolated from tamoxifen-inducible conditional knockdown mice of JPH2 (MCM-shJPH2) were subjected to confocal Ca2+ imaging. MCM-shJPH2 cardiomyocytes exhibited an increased spark frequency width with altered spark morphology, which caused increased SR Ca2+ leakage. Single channel studies identified an increased RyR2 open probability in MCM-shJPH2 mice. The increase in spark frequency and width was observed only in MCM-shJPH2 and not found in mice with increased RyR2 open probability with native JPH2 expression. Na+/Ca2+-exchanger (NCX) activity was reduced by 50{\%} in MCM-shJPH2 with no detectable change in NCX expression. Additionally, 50{\%} inhibition of NCX through Cd2+ administration alone was sufficient to increase spark width in myocytes obtained from wild-type mice. Additionally, superresolution analysis of RyR2 and NCX colocalization showed a reduced overlap between RyR2 and NCX in MCM-shJPH2 mice. In conclusion, decreased JPH2 expression causes increased SR Ca2+ leakage by directly increasing open probability of RyR2 and by indirectly reducing junctional NCX activity through increased dyadic cleft Ca2+. This demonstrates two novel and independent cellular mechanisms by which JPH2 regulates RyR2-mediated SR Ca2+ leak and heart failure development.",
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T1 - Reduced junctional Na+/Ca2+-exchanger activity contributes to sarcoplasmic reticulum Ca2+ leak in junctophilin-2-deficient mice

AU - Wang, Wei

AU - Landstrom, Andrew P.

AU - Wang, Qiongling

AU - Munro, Michelle L.

AU - Beavers, David

AU - Ackerman, Michael John

AU - Soeller, Christian

AU - Wehrens, Xander H T

PY - 2014/11/1

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AB - Expression silencing of junctophilin-2 (JPH2) in mouse heart leads to ryanodine receptor type 2 (RyR2)-mediated sarcoplasmic reticulum (SR) Ca2+ leak and rapid development of heart failure. The mechanism and physiological significance of JPH2 in regulating RyR2-mediated SR Ca2+ leak remains elusive. We sought to elucidate the role of JPH2 in regulating RyR2-mediated SR Ca2+ release in the setting of cardiac failure. Cardiac myocytes isolated from tamoxifen-inducible conditional knockdown mice of JPH2 (MCM-shJPH2) were subjected to confocal Ca2+ imaging. MCM-shJPH2 cardiomyocytes exhibited an increased spark frequency width with altered spark morphology, which caused increased SR Ca2+ leakage. Single channel studies identified an increased RyR2 open probability in MCM-shJPH2 mice. The increase in spark frequency and width was observed only in MCM-shJPH2 and not found in mice with increased RyR2 open probability with native JPH2 expression. Na+/Ca2+-exchanger (NCX) activity was reduced by 50% in MCM-shJPH2 with no detectable change in NCX expression. Additionally, 50% inhibition of NCX through Cd2+ administration alone was sufficient to increase spark width in myocytes obtained from wild-type mice. Additionally, superresolution analysis of RyR2 and NCX colocalization showed a reduced overlap between RyR2 and NCX in MCM-shJPH2 mice. In conclusion, decreased JPH2 expression causes increased SR Ca2+ leakage by directly increasing open probability of RyR2 and by indirectly reducing junctional NCX activity through increased dyadic cleft Ca2+. This demonstrates two novel and independent cellular mechanisms by which JPH2 regulates RyR2-mediated SR Ca2+ leak and heart failure development.

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KW - Junctophilin

KW - Ryanodine receptor

KW - Sodium/calcium exchanger

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