'Trigger' events precede calcium puffs in Xenopus oocytes
'Trigger' events precede calcium puffs in Xenopus oocytes
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DOI：
10.1529/biophysj.106.088872
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发表时间：
2006-12-01
影响因子：
3.4
通讯作者：
Parker, Ian
中科院分区：
文献类型：
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作者：
Rose, Heather J.;Dargan, Sheila;Parker, Ian
通过肌醇1，4，5-三磷酸受体/通道（IP（3）Rs）释放在内质网中隔离的钙离子导致钙信号事件的时空层次，其范围从单通道开放到局部Ca 2+喷流，据信从几个到几十个聚集的IP（3）Rs到全局钙波。使用高分辨率共聚焦线扫描成像和敏感的Ca 2+指示剂染料（fluo-4-dextran），我们表明，喷往往是由小，短暂的Ca 2+升高，我们命名为“触发事件”。触发因素的大小与其由单个IP 3受体/通道的打开引起的一致，我们建议它们通过Ca 2+诱导的Ca 2+释放的再生过程招募簇内邻近的IP（3）Rs来启动喷流。抽吸幅度（荧光比率变化）平均比触发幅度大6倍，表明在抽吸过程中至少6个IP（3）R可能同时打开。触发事件的平均持续时间类似于12 ms，而抽吸的平均上升时间为19 ms，并且它们的空间范围类似于抽吸的三分之一小（半峰幅度处的相应宽度为0.6和1.6 μ m）。所有这些参数均与IP 3浓度相对无关，尽管在低[IP 3]浓度下，显示已解决触发的抽吸比例最大（类似于80%）。由于Ca 2+喷流构成了细胞IP 3介导的Ca 2+信号的构建模块，因此启动它们的事件可能对细胞信号传导具有根本重要性。此外，触发事件提供了一个有用的尺度，通过它可以获得有关集群内IP（3）R的数量和空间排列的信息。
The liberation of calcium ions sequestered in the endoplasmic reticulum through inositol 1,4,5-trisphosphate receptors/channels (IP(3)Rs) results in a spatiotemporal hierarchy of calcium signaling events that range from single-channel openings to local Ca2+ puffs believed to arise from several to tens of clustered IP(3)Rs to global calcium waves. Using high-resolution confocal linescan imaging and a sensitive Ca2+ indicator dye (fluo-4-dextran), we show that puffs are often preceded by small, transient Ca2+ elevations that we christen "trigger events". The magnitude of triggers is consistent with their arising from the opening of a single IP3 receptor/channel, and we propose that they initiate puffs by recruiting neighboring IP(3)Rs within the cluster by a regenerative process of Ca2+-induced Ca2+ release. Puff amplitudes (fluorescence ratio change) are on average similar to 6 times greater than that of the triggers, suggesting that at least six IP(3)Rs may simultaneously be open during a puff. Trigger events have average durations of similar to 12 ms, as compared to 19 ms for the mean rise time of puffs, and their spatial extent is similar to 3 times smaller than puffs (respective widths at half peak amplitude 0.6 and 1.6 mu m). All these parameters were relatively independent of IP3 concentration, although the proportion of puffs showing resolved triggers was greatest (similar to 80%) at low [IP3]. Because Ca2+ puffs constitute the building blocks from which cellular IP3-mediated Ca2+ signals are constructed, the events that initiate them are likely to be of fundamental importance for cell signaling. Moreover, the trigger events provide a useful yardstick by which to derive information regarding the number and spatial arrangement of IP(3)Rs within clusters.