Cytosolic Ca2+ buffering determines the intra-SR Ca2+ concentration at which cardiac Ca2+ sparks terminate
Cytosolic Ca2+ buffering determines the intra-SR Ca2+ concentration at which cardiac Ca2+ sparks terminate
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DOI：
10.1016/j.ceca.2015.06.002
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发表时间：
2015-09-01
期刊：
影响因子：
4
通讯作者：
Zima, Aleksey V.
中科院分区：
文献类型：
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作者：
Bovo, Elisa;Mazurek, Stefan R.;Zima, Aleksey V.
单ryanodine受体（RyR） Ca2+通量振幅（i(Ca-RyR)）降低作为肌浆内网（SR） Ca2+水平下降期间心脏Ca2+火花。由于i（Ca-RyR）驱动ryr间Ca2+诱导的Ca2+释放（CICR），这是火花的基础，降低i（Ca-RyR）可能有助于火花终止，因为自发关闭的ryr可能保持关闭。为了测试这种可能性，我们同时测量了透性兔心室肌细胞在Ca2+火花期间的局部胞浆和内SR （[Ca2+]（cyto）和[Ca2+](SR)）。使用Ca2+缓冲液操纵局部细胞质或sr内Ca2+动力学。在细胞中应用缓冲处理对平面脂质双层中重构的单个RyR通道没有影响。快速胞质Ca2+缓冲液（BAPTA）的存在显著抑制Ca2+火花活性，火花终止时间比通常的[Ca2+]（SR）水平（相似于80%对相似于62%）要早。当胞质Ca2+缓冲功率降低（即胞质EGTA水平降低）时，火花终止时间较晚，且低于通常的[Ca2+]（SR）水平（类似于45%对类似于62%）。当SR内Ca2+缓冲功率增加时，火花也会延迟终止，并且比通常的[Ca2+]（SR）更低（类似于48%对类似于62%）。这些结果表明，在火花终止过程中，i（Ca-RyR）对ryr间CICR的细胞质局部控制发挥了重要作用。因此，双裂中局部胞质Ca2+处理动力学的改变（Ca2+缓冲、挤压等）可能影响Ca2+火花终止。(C) 2015 Elsevier Ltd.版权所有。
Single ryanodine receptor (RyR) Ca2+ flux amplitude (i(Ca-RyR)) decreases as intra-sarcoplasmic reticulum (SR) Ca2+ levels fall during a cardiac Ca2+ spark. Since i(Ca-RyR) drives the inter-RyR Ca2+-induced Ca2+ release (CICR) that underlies the spark, decreasing i(Ca-RyR) may contribute to spark termination because RyRs that spontaneously close may stay closed. To test this possibility, we simultaneously measured local cytosolic and intra-SR ([Ca2+](cyto) and [Ca2+](SR)) during Ca2+ sparks in permeabilized rabbit ventricular myocytes. Local cytosolic or intra-SR Ca2+ dynamics were manipulated using Ca2+ buffers. Buffer manipulations applied in cells had no effect on individual RyR channels reconstituted in planar lipid bilayers. Presence of a fast cytosolic Ca2+ buffer (BAPTA) significantly suppressed Ca2+ spark activity and sparks terminated earlier at a higher than usual [Ca2+](SR) level (similar to 80% vs. similar to 62%). When cytosolic Ca2+ buffer power was reduced (i.e. cytosolic EGTA level decreased), sparks terminated later and at a lower than usual [Ca2+](SR) level (similar to 45% vs. similar to 62%). When intra-SR Ca2+ buffer power was increased, sparks also terminated later and at a lower than usual [Ca2+](SR) (similar to 48% vs. similar to 62%). These results suggest that cytosolic local control of inter-RyR CICR by i(Ca-RyR) plays a substantial role during the spark termination process. Thus, alterations in local cytosolic Ca2+ handling dynamics in the dyadic cleft (Ca2+ buffering, extrusion, etc.) likely influence Ca2+ spark termination. (C) 2015 Elsevier Ltd. All rights reserved.