Activation of BK channels in rat chromaffin cells requires summation of Ca2+ influx from multiple Ca2+ channels
Activation of BK channels in rat chromaffin cells requires summation of Ca2+ influx from multiple Ca2+ channels
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DOI：
10.1152/jn.2000.84.3.1123
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发表时间：
2000-09-01
影响因子：
2.5
通讯作者：
Lingle, CJ
中科院分区：
文献类型：
--
作者：
Prakriya, M;Lingle, CJ
许多组织中的大电导Ca 2+和电压依赖性K+通道（BK通道）需要高Ca 2+浓度才能激活，因此可能与Ca 2+通道紧密偶联。然而，在大多数情况下，很少有人知道BK通道和Ca 2+通道参与其激活的相对组织。我们通过操纵Ca ~（2+）通过Ca ~（2+）通道的内流和用EGTA和双-（邻氨基苯氧基）-N，N，N '，N'-四乙酸（BAPTA）改变细胞内Ca ~（2+）缓冲来探讨大鼠嗜铬细胞BK和Ca ~（2+）通道的组织性质。分析结果以确定与实验数据最一致的Ca 2+和BK通道之间的距离。大多数BK通道与Ca 2+通道足够接近，足以抵抗毫摩尔EGTA的缓冲作用，但又足够远，可以被BAPTA抑制。对EGTA/BAPTA结果的分析表明，BK通道与Ca 2+通道的距离为50至160 nm。假设Ca 2+和BK通道随机分布的模型不能解释BK通道检测到的[Ca 2 +]（i），这表明可能存在一种特定的机制来介导这些通道之间的功能耦合。重要的是，EGTA和BAPTA的作用不能通过假设Ca 2+和BK通道之间的一对一耦合来解释。相反，Ca 2+通过许多Ca 2+通道流入似乎协同作用，以调节任何单个BK通道的行为。因此，BK通道开放概率的差异可以通过在单个BK通道的位点处的Ca 2+结构域重叠的程度的差异来解释。
Large-conductance Ca2+ and voltage-dependent K+ channels (BK channels) in many tissues require high Ca2+ concentrations for activation and therefore might be expected to be tightly coupled to Ca2+ channels. However, in most cases, little is known about the relative organization of the BK channels and the Ca2+ channels involved in their activation. We probed the nature of the organization of BK and Ca2+ channels in rat chromaffin cells by manipulating Ca2+ influx through Ca2+ channels and by altering cellular Ca2+ buffering using EGTA and bis-(o-aminophenoxy)-N,N,N',N'- tetraacetic acid (BAPTA). The results were analyzed to determine the distance between Ca2+ and BK channels that would be most consistent with the experimental data. Most BK channels are close enough to Ca2+ channels to be resistant to the buffering action of millimolar of EGTA, but are far enough to be inhibited by BAPTA. Analysis of the EGTA/BAPTA results suggests that BK channels are at a distance of 50 to 160 nm from Ca2+ channels. A model that assumes random distribution of Ca2+ and BK channels fails to account for the observed [Ca2+](i) detected by BK channels, suggesting that a specific mechanism may exist to mediate the functional coupling between these channels. Importantly, the effects of EGTA and BAPTA cannot be explained by assuming a one-to-one coupling between Ca2+ and BK channels. Rather, Ca2+ influx through a number of Ca2+ channels appears to act in concert to regulate the behavior of any individual BK channel. Thus differences in BK channel open probabilities may be explained by differences in the extent of Ca2+ domain overlap at the sites of individual BK channels.