Intracellular zinc modulates cardiac ryanodine receptor-mediated calcium release
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Aberrant Zn2+-homeostasis is a hallmark of certain cardiomyopathies associated with altered contractile force. In this study we addressed whether Zn2+ modulates cardiac ryanodine receptor gating and Ca2+-dynamics in isolated cardiomyocytes. We reveal that Zn2+ is a high affinity regulator of RyR2 displaying three modes of operation. Picomolar free Zn2+ concentrations potentiate RyR2 responses but channel activation is still dependent on the presence of cytosolic Ca2+. At concentrations of free Zn2+ >1 nM, Zn2+ is the main activating ligand and the dependency on Ca2+ is removed. Zn2+ is therefore a higher affinity activator of RyR2 than Ca2+. Millimolar levels of free Zn2+ were found to inhibit channel openings. In cardiomyocytes, consistent with our single-channel results, we show that Zn2+ modulates both the frequency and amplitude of Ca2+ waves in a concentration dependent manner and that physiological levels of Zn2+ elicit Ca2+-release in the absence of activating levels of cytosolic Ca2+. This highlights a new role for intracellular Zn2+ in shaping Ca2+-dynamics in cardiomyocytes through modulation of RyR2 gating.
Woodier , J , Rainbow , R D , Stewart , A J & Pitt , S J 2015 , ' Intracellular zinc modulates cardiac ryanodine receptor-mediated calcium release ' Journal of Biological Chemistry , vol 290 , no. 28 , pp. 17599-17610 . DOI: 10.1074/jbc.M115.661280
Journal of Biological Chemistry
© 2015 by The American Society for Biochemistry and Molecular Biology, Inc. Author’s Choice—Final version free via Creative Commons CC-BY license.
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