Kinetics of activation and inactivation of swelling-stimulated K+/Cl- transport. The volume-sensitive parameter is the rate constant for inactivation.
Kinetics of activation and inactivation of swelling-stimulated K+/Cl- transport. The volume-sensitive parameter is the rate constant for inactivation.
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DOI：
10.1085/jgp.95.6.1021
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发表时间：
1990-06
影响因子：
3.8
通讯作者：
ALROHIL, N
中科院分区：
文献类型：
--
作者：
JENNINGS, ML;ALROHIL, N
已知几个物种的红细胞表现出哇巴因不敏感的、阴离子依赖性的K+（Rb+）通量，其由细胞肿胀刺激。我们已经使用兔红细胞来研究张力阶跃变化时通量的激活和失活的动力学。突然低渗肿胀（210 mosmol）在37 ℃下10分钟和25 ℃下30-50分钟的滞后期后激活通量。在预先收缩以激活转运蛋白的细胞中，突然收缩（通过加入高渗NaCl）导致通量迅速失活;失活的时间滞后在37 ℃下小于2分钟。体积敏感型KCl转运系统的最小模型需要转运体的两个状态。活化（A）状态以某种有限速率催化转运（周转数未知，因为转运蛋白的数量未知）。休息（R）状态的传输速率要低得多或可能为零。状态之间的相互转换的特点是单分子速率常数R k12与k21 A平衡。弛豫到任何新的稳态的速率等于速率常数k12 + k21的和。由于低渗介质中的转运激活速率低于等渗介质中的失活速率，因此我们得出结论，体积敏感速率过程是失活（A到R转变）;也就是说，细胞肿胀通过降低k21激活转运。三种磷酸酶抑制剂（氟化物，原钒酸盐，和无机磷酸盐）都抑制溶胀激活通量，也减慢接近溶胀稳态的速率。这一发现表明，净去磷酸化是激活通量所必需的，并且净去磷酸化是由于溶胀诱导的激酶抑制而不是磷酸酶刺激而发生的。
Red blood cells of several species are known to exhibit a ouabain- insensitive, anion-dependent K+ (Rb+) flux that is stimulated by cell swelling. We have used rabbit red cells to study the kinetics of activation and inactivation of the flux upon step changes in tonicity. Sudden hypotonic swelling (210 mosmol) activates the flux after a lag period of 10 min at 37 degrees C and 30-50 min at 25 degrees C. In cells that were preswollen to activate the transporter, sudden shrinkage (by addition of hypertonic NaCl) causes a rapid inactivation of the flux; the time lag for inactivation is less than 2 min at 37 degrees C. A minimal model of the volume-sensitive KCl transport system requires two states of the transporter. The activated (A) state catalyzes transport at some finite rate (turnover number unknown because the number of transporters is unknown). The resting (R) state has a much lower or possibly zero transport rate. The interconversion between the states is characterized by unimolecular rate constants R k12 in equilibrium with k21 A. The rate of relaxation to any new steady state is equal to the sum of the rate constants k12 + k21. Because the rate of transport activation in a hypotonic medium is lower than the rate of inactivation in an isotonic medium, we conclude that the volume- sensitive rate process is inactivation (the A to R transition); that is, cell swelling activates transport by lowering k21. Three phosphatase inhibitors (fluoride, orthovanadate, and inorganic phosphate) all inhibit the swelling-activated flux and also slow down the rate of approach to the swollen steady state. This finding suggests that a net dephosphorylation is necessary for activation of the flux and that the net dephosphorylation takes place as a result of swelling- induced inhibition of a kinase rather than stimulation of a phosphatase.
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影响因子：
56.9
作者：
BRUGNARA, C;BUNN, HF;TOSTESON, DC
通讯作者：
TOSTESON, DC
影响因子：
3.5
作者：
CANESSA, M;SPALVINS, A;NAGEL, RL
通讯作者：
NAGEL, RL
影响因子：
--
作者：
Davson, H
通讯作者：
Davson, H
影响因子：
--
作者：
BRUGNARA, C;VANHA, T;TOSTESON, DC
通讯作者：
TOSTESON, DC
影响因子：
15.9
作者：
BRUGNARA, C;KOPIN, AS;TOSTESON, DC
通讯作者：
TOSTESON, DC