Cytoplasmic Ca2+ inhibits the ryanodine receptor from cardiac muscle
Cytoplasmic Ca2+ inhibits the ryanodine receptor from cardiac muscle
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DOI：
10.1007/bf00235394
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发表时间：
1995-09
期刊：
影响因子：
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通讯作者：
D. Laver;L. Roden;Gerard P. Ahern;K. Eager;P. Junankar;A. Dulhunty
中科院分区：
文献类型：
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作者：
D. Laver;L. Roden;Gerard P. Ahern;K. Eager;P. Junankar;A. Dulhunty
用脂质双层膜技术研究了绵羊心脏和兔骨骼肌天然和分离的Ryanodine受体（RyR）钙释放通道的钙依赖性抑制。我们发现，细胞质Ca ~（2+）抑制心肌RyR的平均Km = 15 mm，骨骼RyR的Km = 0.7 mm，希尔系数为2。这与从皮肤纤维中的肌浆网（SR）释放的Ca 2+的测量结果以及[3 H]-ryanodine与SR囊泡的结合一致，但与先前的双层研究相反，所述研究不能证明心脏RyR中的Ca 2+抑制（Chu，Fill，Stefani & Entman（1993）J. Membrane Biol.135，49-59）。Ryanodine阻止Ca 2+抑制心脏或骨骼RyR。Ca 2+抑制心肌RyR似乎是最脆弱的通道功能的特点，被500 mmCs+不可逆地破坏，但不被500 mmK+，在cisbath或溶解与洗涤剂CHAPS。这些治疗对AMP-PNP、咖啡因、ryanodine、钌红或Ca 2+激活的通道调节没有影响。在500 mmCs+存在下，骨骼RyR中的Ca 2+抑制得以保留。我们的研究结果提供了一个解释以前的研究结果，其中心脏RyR在双层与250 mmCs+的解决方案未能证明Ca 2+抑制，而Ca 2+抑制Ca 2+释放中观察到囊泡研究，其中K+是主要的阳离子。开放和封闭的概率分布从个人RyRs的比较表明，相同的门控机制介导的钙抑制骨骼RyRs和心脏RyRs，不同的钙抑制亲和力。我们的结论是，在心脏和骨骼通道的钙抑制的差异取决于它们的钙结合特性。
Ca2+-dependent inhibition of native and isolated ryanodine receptor (RyR) calcium release channels from sheep heart and rabbit skeletal muscle was investigated using the lipid bilayer technique. We found that cytoplasmic Ca2+inhibited cardiac RyRs with an averageKm= 15 mm, skeletal RyRs withKm= 0.7 mmand with Hill coefficients of 2 in both isoforms. This is consistent with measurements of Ca2+release from the sarcoplasmic reticulum (SR) in skinned fibers and with [3H]-ryanodine binding to SR vesicles, but is contrary to previous bilayer studies which were unable to demonstrate Ca2+-inhibition in cardiac RyRs (Chu, Fill, Stefani & Entman (1993) J. Membrane Biol. 135, 49–59). Ryanodine prevented Ca2+from inhibiting either cardiac or skeletal RyRs. Ca2+-inhibition in cardiac RyRs appeared to be the most fragile characteristic of channel function, being irreversibly disrupted by 500 mmCs+, but not by 500 mmK+, in thecisbath or by solublization with the detergent CHAPS. These treatments had no effect on channel regulation by AMP-PNP, caffeine, ryanodine, ruthenium red, or Ca2+-activation. Ca2+-inhibition in skeletal RyRs was retained in the presence of 500 mmCs+. Our results provide an explanation for previous findings in which cardiac RyRs in bilayers with 250 mmCs+in the solutions fail to demonstrate Ca2+-inhibition, while Ca2+-inhibition of Ca2+release is observed in vesicle studies where K+is the major cation. A comparison of open and closed probability distributions from individual RyRs suggested that the same gating mechanism mediates Ca2+-inhibition in skeletal RyRs and cardiac RyRs, with different Ca2+affinities for inhibition. We conclude that differences in the Ca2+-inhibition in cardiac and skeletal channels depends on their Ca2+binding properties.