Cardiac ryanodine receptor activation by a high Ca²⁺ store load is reversed in a reducing cytoplasmic redox environment

Amy Hanna, Alex Lam, Chris Thekkedam, Esther Gallant, Nicole BEARD, Angela dulhunty

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Here, we report the impact of redox potential on isolated cardiac ryanodine receptor (RyR2) channel activity and its response to physiological changes in luminal [Ca2+]. Basal leak from the sarcoplasmic reticulum is required for normal Ca2+ handling, but excess diastolic Ca2+ leak attributed to oxidative stress is thought to lower the threshold of RyR2 for spontaneous sarcoplasmic reticulum Ca2+ release, thus inducing arrhythmia in pathological situations. Therefore, we examined the RyR2 response to luminal [Ca2+] under reducing or oxidising cytoplasmic redox conditions. Unexpectedly, as luminal [Ca2+] increased from 0.1 to 1.5 mM, RyR2 activity declined when pretreated with cytoplasmic 1 mM DTT or buffered with GSH∶GSSG to a normal reduced cytoplasmic redox potential (−220 mV). Conversely, with 20 µM cytoplasmic 4,4′-DTDP or buffering of the redox potential to an oxidising value (−180 mV), RyR2 activity increased with increasing luminal [Ca2+]. The luminal redox potential was constant at −180 mV in each case. These responses to luminal [Ca2+] were maintained with cytoplasmic 2 mM Na2ATP or 5 mM MgATP (1 mM free Mg2+). Overall, the results suggest that the redox potential in the RyR2 junctional microdomain is normally more oxidised than that of the bulk cytoplasm
Original languageEnglish
Pages (from-to)4531-4541
Number of pages11
JournalJournal of Cell Science
Volume127
DOIs
Publication statusPublished - 2014

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Ryanodine Receptor Calcium Release Channel
Oxidation-Reduction
Sarcoplasmic Reticulum
Cardiac Arrhythmias
Cytoplasm
Oxidative Stress
Adenosine Triphosphate

Cite this

Hanna, Amy ; Lam, Alex ; Thekkedam, Chris ; Gallant, Esther ; BEARD, Nicole ; dulhunty, Angela. / Cardiac ryanodine receptor activation by a high Ca²⁺ store load is reversed in a reducing cytoplasmic redox environment. In: Journal of Cell Science. 2014 ; Vol. 127. pp. 4531-4541.
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abstract = "Here, we report the impact of redox potential on isolated cardiac ryanodine receptor (RyR2) channel activity and its response to physiological changes in luminal [Ca2+]. Basal leak from the sarcoplasmic reticulum is required for normal Ca2+ handling, but excess diastolic Ca2+ leak attributed to oxidative stress is thought to lower the threshold of RyR2 for spontaneous sarcoplasmic reticulum Ca2+ release, thus inducing arrhythmia in pathological situations. Therefore, we examined the RyR2 response to luminal [Ca2+] under reducing or oxidising cytoplasmic redox conditions. Unexpectedly, as luminal [Ca2+] increased from 0.1 to 1.5 mM, RyR2 activity declined when pretreated with cytoplasmic 1 mM DTT or buffered with GSH∶GSSG to a normal reduced cytoplasmic redox potential (−220 mV). Conversely, with 20 µM cytoplasmic 4,4′-DTDP or buffering of the redox potential to an oxidising value (−180 mV), RyR2 activity increased with increasing luminal [Ca2+]. The luminal redox potential was constant at −180 mV in each case. These responses to luminal [Ca2+] were maintained with cytoplasmic 2 mM Na2ATP or 5 mM MgATP (1 mM free Mg2+). Overall, the results suggest that the redox potential in the RyR2 junctional microdomain is normally more oxidised than that of the bulk cytoplasm",
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Cardiac ryanodine receptor activation by a high Ca²⁺ store load is reversed in a reducing cytoplasmic redox environment. / Hanna, Amy; Lam, Alex; Thekkedam, Chris; Gallant, Esther; BEARD, Nicole; dulhunty, Angela.

In: Journal of Cell Science, Vol. 127, 2014, p. 4531-4541.

Research output: Contribution to journalArticle

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AU - Hanna, Amy

AU - Lam, Alex

AU - Thekkedam, Chris

AU - Gallant, Esther

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