Minimal requirements for calcium oscillations driven by the IP3 receptor
Minimal requirements for calcium oscillations driven by the IP3 receptor
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DOI：
10.1093/emboj/16.12.3533
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发表时间：
1997-06-16
期刊：
影响因子：
11.4
通讯作者：
Thomas, AP
中科院分区：
文献类型：
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作者：
Hajnoczky, G;Thomas, AP
通过肌醇1,4,5-三磷酸（IP3）起作用的激素和神经递质可以诱导胞浆内Ca2+ ([Ca2+](c))的振荡，从而实现细胞内靶标的动态调节。位于细胞内Ca2+储存的荧光Ca2+指标成像用于监测IP3受体通道（IP3R）功能，并证明IP3依赖性Ca2+释放和再摄取的振荡可以在单渗透肝细胞中复制。该系统用于确定振荡机构的最小基本元件。将IP3固定在亚最大浓度时，在每个细胞中观察到IP3R激活和随后失活的协调周期。这些状态之间的循环依赖于释放Ca2+的反馈效应和随后的[Ca2+](c)增加，但不需要Ca2+再积累。[Ca2+](c)可以在IP3R上不同的刺激和抑制位点起作用，但Ca2+释放阶段是由Ca2+诱导的IP3敏感性增加驱动的，当IP3结合到Ca2+敏化的IP3R上而不占据抑制性Ca2+结合位点后，Ca2+释放可以通过内在失活而终止。使用Sr2+证实了这些发现，Sr2+只与刺激部位相互作用。此外，加压素在细胞内Ca2+完全被Sr2+取代的完整细胞中诱导Sr2+振荡。因此，[Ca2+](c)振荡可以由Ca2+诱导的激活和IP3R Ca2+敏化状态的强制性内在失活的耦合过程驱动，而不需要占领抑制性Ca2+结合位点。
Hormones and neurotransmitters that act through inositol 1,4,5-trisphosphate (IP3) can induce oscillations of cytosolic Ca2+ ([Ca2+](c)), which render dynamic regulation of intracellular targets. Imaging of fluorescent Ca2+ indicators located within intracellular Ca2+ stores was used to monitor IP3 receptor channel (IP3R) function and to demonstrate that IP3-dependent oscillations of Ca2+ release and re-uptake can be reproduced in single permeabilized hepatocytes. This system was used to define the minimum essential components of the oscillation mechanism. With IP3 clamped at a submaximal concentration, coordinated cycles of IP3R activation and subsequent inactivation were observed in each cell. Cycling between these states was dependent on feedback effects of released Ca2+ and the ensuing [Ca2+](c) increase, but did not require Ca2+ re-accumulation. [Ca2+](c) can act at distinct stimulatory and inhibitory sites on the IP3R, but whereas the Ca2+ release phase was driven by a Ca2+-induced increase in IP3 sensitivity, Ca2+ release could be terminated by intrinsic inactivation after IP3 bound to the Ca2+-sensitized IP3R without occupation of the inhibitory Ca2+-binding site. These findings were confirmed using Sr2+, which only interacts with the stimulatory site. Moreover, vasopressin induced Sr2+ oscillations in intact cells in which intracellular Ca2+ was completely replaced with Sr2+. Thus, [Ca2+](c) oscillations can be driven by a coupled process of Ca2+-induced activation and obligatory intrinsic inactivation of the Ca2+-sensitized state of the IP3R, without a requirement for occupation of the inhibitory Ca2+-binding site.