Regulation of amino acid transport in L6 muscle cells: I. Stimulation of transport system a by amino acid deprivation
Regulation of amino acid transport in L6 muscle cells: I. Stimulation of transport system a by amino acid deprivation
复制标题
L6 肌细胞氨基酸转运的调节： I. 氨基酸剥夺对转运系统 a 的刺激
DOI：
--
复制
发表时间：
1982
影响因子：
5.6
通讯作者：
E. Gagalang
中科院分区：
文献类型：
--
作者：
W. Logan;A. Klip;E. Gagalang
研究了氨基酸剥夺对L 6肌细胞氨基酸转运的调节作用。脯氨酸摄取具有Na+依赖性、饱和性和浓缩性，主要通过系统A进行。脯氨酸摄取受丙氨酸、α-氨基异丁酸（AIB）和α-甲氨基异丁酸抑制，但不受赖氨酸或缬氨酸抑制。在25°C下，脯氨酸摄取的Km为0.5 mM。氨基酸剥夺导致脯氨酸摄取速率的逐渐增加，6小时后达到6倍刺激。基础转运和刺激转运具有相同的Na+依赖性，两者均受到相同氨基酸竞争的抑制。动力学分析表明，在剥夺细胞中，Km降低了2.4倍，Vmax增加了1.9倍。氨基酸剥夺不会刺激除系统A以外的系统摄取氨基酸。这表明补充脯氨酸的细胞中较高的Km不是由于细胞内氨基酸释放到细胞周围未搅拌的层中。在脯氨酸剥夺过程中，作为系统A（包括AIB）底物的氨基酸的存在阻止了脯氨酸摄取的刺激，而那些仅由系统Ly+或L转运的氨基酸则无效。剥夺细胞中转运速率的刺激可以通过随后暴露于脯氨酸或系统A的其他底物来逆转。L 6细胞，剥夺脯氨酸6小时，保留的刺激后，从单层与胰蛋白酶脱离的运输。单层培养中悬浮细胞和贴壁细胞的摄取率相当。因此，L 6细胞的氨基酸去除导致脯氨酸摄取的适应性增加，这不是由于未搅拌的层，而是似乎由选择性转运调节的其他机制介导的。
The regulation of amino acid transport in L6 muscle cells by amino acid deprivation was investigated. Proline uptake was Na+‐dependent, saturable and concentrative, and was predominantly through system A. Proline uptake was inhibited by alanine, α‐amino isobutyric acid (AIB), and by α‐methylamino isobutyric acid, but not by lysine or valine. At 25°C, Km of proline uptake was 0.5 mM. Amino acid‐deprivation resulted in a progressive increase in the rate of proline uptake, reaching up to 6‐fold stimulation after 6 hours. The basal and stimulated transport were equally Na+‐dependent, and both were inhibited by competition with the same amino acids. Kinetic analysis showed that Km decreased by a factor of 2.4 and Vmax increased 1.9‐fold in deprived cells. Amino acid‐deprivation did not stimulate amino acid uptake through systems other than system A. This suggests that the higher Km in proline‐supplemented cells is not due to release of intracellular amino acids into unstirred layers surrounding the cells. The presence of amino acids which are substrates of system A (including AIB) during proline‐deprivation, prevented stimulation of proline uptake, whereas those transported by systems Ly+ or L exclusively were ineffective. The stimulation of the transport‐rate in deprived cells could be reversed by subsequent exposure to proline or other substrates of system A. L6 cells, deprived of proline for 6 hours, retained the stimulation of transport after detachment from the monolayers with trypsin. Uptake rates were comparable in suspended and attached cells in monolayer culture. Thus, amino acid‐depreivation of L6 cells results in an adaptive increase in proline uptake, which is not due to unstirred layers but appears to be mediated by other mechanisms of selective transport regulation.