Ca2+ and voltage dependence of cardiac ryanodine receptor channel block by sphingosylphosphorylcholine
Ca2+ and voltage dependence of cardiac ryanodine receptor channel block by sphingosylphosphorylcholine
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DOI：
10.1007/s00424-002-0945-3
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发表时间：
2003-03-01
影响因子：
4.5
通讯作者：
Berlin, JR
中科院分区：
文献类型：
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作者：
Yasukochi, M;Uehara, A;Berlin, JR
在脂双层实验中研究了鞘氨醇磷酸胆碱（SPC）对细胞质Ca 2+和心脏兰尼碱受体（RyR）通道门控电压依赖性的影响。微摩尔浓度的lysosphingolipid SPC加入到顺式溶液中，快速可逆地降低了重建RyR通道的单通道开放概率（P-O）。SPC诱导的P-o减少的标志是平均关闭时间和突发样通道门控的增加。在爆发期间的门控动力学与在不存在鞘脂的情况下观察到的那些相比没有变化，尽管SPC诱导了长寿命的闭合状态，这似乎解释了观察到的通道P-o减少。SPC的影响，观察到在一个广泛的顺[Ca 2 +]，但不竞争与Ca 2+。有趣的是，鞘脂诱导的长寿命关闭状态显示电压依赖性动力学，即使其他通道门控动力学对电压不敏感。假设SPC效应代表通道阻断，这些结果表明阻断率与电压无关，而解除阻断率与电压相关。总之，这些结果表明，SPC直接结合到细胞质侧的RyR蛋白在膜电介质中或附近的位置，但不同的蛋白质上的细胞质Ca 2+结合位点。
The effect of sphingosylphosphorylcholine (SPC) on the cytoplasmic Ca2+ and voltage dependence of channel gating by cardiac ryanodine receptors (RyR) was examined in lipid bilayer experiments. Micromolar concentrations of the lysosphingolipid SPC added to cis solutions rapidly and reversibly decreased the single-channel open probability (P-o) of reconstituted RyR channels. The SPC-induced decrease in P-o was marked by an increase in mean closed time and burst-like channel gating. Gating kinetics during intraburst periods were unchanged from those observed in the absence of the sphingolipid, although SPC induced a long-lived closed state that appeared to explain the observed decrease in channel P-o. SPC effects were observed over a broad range of cis [Ca2+] but were not competitive with Ca2+. Interestingly, the sphingolipid-induced, long-lived closed state displayed voltage-dependent kinetics, even though other channel gating kinetics were not sensitive to voltage. Assuming SPC effects represent channel blockade, these results suggest that the blocking rate is independent of voltage whereas the unblocking rate is voltage dependent. Together, these results suggest that SPC binds directly to the cytoplasmic side of the RyR protein in a location in or near the membrane dielectric, but distinct from cytoplasmic Ca2+ binding sites on the protein.