Diketopyridylryanodine has three concentration-dependent effects on the cardiac calcium-release channel/ryanodine receptor
Diketopyridylryanodine has three concentration-dependent effects on the cardiac calcium-release channel/ryanodine receptor
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DOI：
10.1074/jbc.m208372200
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发表时间：
2003-04-18
影响因子：
4.8
通讯作者：
Besch, HR
中科院分区：
文献类型：
--
作者：
Bidasee, KR;Xu, L;Besch, HR
通过与多个位点相互作用，ryanoids 对钙释放通道产生多种影响。迄今为止，仅对这些位点之一的相互作用动力学进行了表征。在 [H-3] 兰尼碱结合和单通道实验中使用 C-4,C-12-二酮吡啶基兰尼碱，我们表征了心脏兰尼碱受体 (RyR2) 上与兰尼碱相互作用的另一个位点。该 ryanoid 与 RyR2 的竞争性结合意味着最小的双位点结合模型。在单通道水平上，C-4,C-12-二酮吡啶基瑞安定诱导了三种不同的作用。在纳摩尔浓度下，它使通道开放概率增加几倍，而不会引起亚电导。该效应与膜保持电位无关。对于其他 ryanoids，低微摩尔浓度的 C-4,C-12-二酮吡啶基ryanodine 很容易诱导亚电导状态。主要亚电导的电流幅度为完全打开的 52%，它是可逆的，其感应时间和持续时间与电压和浓度相关，提供 >2 的 Hill 斜率。在较高的微摩尔浓度下，C-4,C-12-二酮吡啶基瑞安定可诱导持久且可逆的关闭状态。使用药理学策略，我们在 RyR2 上发现了一个额外的 ryanoid 结合位点，该位点会触发通道活性的增加。该位点可能位于跨膜传导途径的严格范围之外。
By interacting with more than one site, ryanoids induce multiple effects on calcium-release channels. To date, the kinetics of interaction of only one of these sites has been characterized. Using C-4,C-12-diketopyridylryanodine in both [H-3]ryanodine binding and single channel experiments we characterized another site on the cardiac ryanodine receptor (RyR2) with which ryanoids interact. Competitive binding of this ryanoid to RyR2 implied a minimal two-site binding model. At the single channel level, C-4,C-12-diketopyridylryanodine induced three distinct effects. At nanomolar concentrations, it increased channel open probability several fold without inducing a subconductance. This effect was independent of membrane holding potential. As for other ryanoids, low micromolar concentrations of C-4,C-12-diketopyridylryanodine readily induced a subconductance state. The major subconductance had a current amplitude of 52% of fully open, it was reversible, and its time to induction and duration were voltage- and concentration-dependent, affording Hill slopes of >2. At higher micromolar concentrations C-4,C-12-diketopyridylryanodine induced long lasting, yet reversible shut states. Using a pharmacological strategy we have discerned an additional ryanoid-binding site on RyR2 that triggers an increase in channel activity. This site likely resides outside the strict confines of the transmembrane conducting pathway.