Allosteric activation of sodium-calcium exchange activity by calcium: persistence at low calcium concentrations.
Allosteric activation of sodium-calcium exchange activity by calcium: persistence at low calcium concentrations.
复制标题
DOI：
10.1085/jgp.200308915
复制
发表时间：
2003-11
期刊：
影响因子：
--
通讯作者：
Condrescu M
中科院分区：
文献类型：
--
作者：
Reeves JP;Condrescu M
心脏Na+/Ca 2+交换器的活性由Ca 2+变构刺激，但估计的半最大激活浓度在很宽的范围内变化。在表达心脏Na+/Ca 2+交换器的中国仓鼠卵巢细胞中，交换介导的Ca 2+内流的时间过程显示出明显的滞后期，随后是Ca 2+摄取的加速。滞后期是不存在的细胞表达的交换突变体，不依赖于调节Ca 2+激活。我们假设，在加速阶段的Ca 2+摄取率反映了交换器的变构活化的程度，并确定了胞质Ca 2+（[Ca 2 +]i）的值，在该值下，Ca 2+流入率为半最大值（Kh）。在校正线粒体Ca 2+摄取和fura-2缓冲的影响后，获得了约300 nM的Kh值。在[Ca 2 +]i增加后，交换器的活化状态在[Ca 2 +]i随后降低至<100 nM的值后持续存在。因此，在[Ca 2 +]i瞬时增加终止后30 s内，交换介导的Ca 2+内流开始而没有滞后期，并且在大多数细胞中显示出Ca 2+摄取的线性速率;在[Ca 2 +]i瞬时增加终止后60-90 s，Ca 2+摄取的S形时间过程恢复。激活状态的松弛被内质网Ca 2+泵的活性加速，这表明局部Ca 2+梯度有助于在全局[Ca 2 +]i返回到低值后维持交换器激活。
The activity of the cardiac Na+/Ca2+ exchanger is stimulated allosterically by Ca2+, but estimates of the half-maximal activating concentration have varied over a wide range. In Chinese hamster ovary cells expressing the cardiac Na+/Ca2+ exchanger, the time course of exchange-mediated Ca2+ influx showed a pronounced lag period followed by an acceleration of Ca2+ uptake. Lag periods were absent in cells expressing an exchanger mutant that was not dependent on regulatory Ca2+ activation. We assumed that the rate of Ca2+ uptake during the acceleration phase reflected the degree of allosteric activation of the exchanger and determined the value of cytosolic Ca2+ ([Ca2+]i) at which the rate of Ca2+ influx was half-maximal (Kh). After correcting for the effects of mitochondrial Ca2+ uptake and fura-2 buffering, Kh values of ∼300 nM were obtained. After an increase in [Ca2+]i, the activated state of the exchanger persisted following a subsequent reduction in [Ca2+]i to values <100 nM. Thus, within 30 s after termination of a transient increase in [Ca2+]i, exchange-mediated Ca2+ entry began without a lag period and displayed a linear rate of Ca2+ uptake in most cells; a sigmoidal time course of Ca2+ uptake returned 60–90 s after the transient increase in [Ca2+]i was terminated. Relaxation of the activated state was accelerated by the activity of the endoplasmic reticulum Ca2+ pump, suggesting that local Ca2+ gradients contribute to maintaining exchanger activation after the return of global [Ca2+]i to low values.
登录
查看更多内容
影响因子：
4
作者：
Fang, Y;Condrescu, M;Reeves, JP
通讯作者：
Reeves, JP
DOI：
10.1111/j.1749-6632.1996.tb44783.x
发表时间：
1996-01-01
期刊：
SODIUM-CALCIUM EXCHANGE
影响因子：
--
作者：
Hilgemann, DW
通讯作者：
Hilgemann, DW
心脏钠钙交换的稳态和动态特性。细胞质钙和ATP的次要调节。
DOI：
10.1085/jgp.100.6.933
发表时间：
1992-12
期刊：
The Journal of general physiology
影响因子：
--
作者：
Hilgemann DW;Collins A;Matsuoka S
通讯作者：
Matsuoka S
影响因子：
3.8
作者：
DIPOLO, R
通讯作者：
DIPOLO, R
DOI：
10.1152/ajpcell.1998.275.1.c50
发表时间：
1998-07-01
影响因子：
5.5
作者：
Fang, Y;Condrescu, M;Reeves, JP
通讯作者：
Reeves, JP