INACTIVATION OF CALCIUM-ACTIVATED CHLORIDE CONDUCTANCE IN XENOPUS OOCYTES - ROLES OF CALCIUM AND PROTEIN KINASE-C
INACTIVATION OF CALCIUM-ACTIVATED CHLORIDE CONDUCTANCE IN XENOPUS OOCYTES - ROLES OF CALCIUM AND PROTEIN KINASE-C
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DOI：
10.1007/bf00370214
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发表时间：
1990-04-01
影响因子：
4.5
通讯作者：
DASCAL, N
中科院分区：
文献类型：
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作者：
BOTON, R;SINGER, D;DASCAL, N
用双电极电压钳技术研究了Ca ~（2+）对爪蟾卵母细胞Cl ~-电流的失活作用。在用离子载体A23187处理的Ca ~（2+）透化的卵母细胞中，通过向细胞外溶液中加入2.5-5 mM Ca ~（2+）引起的Ca ~（2+）内流引起由两个组分组成的Cl ~-电流：快速的、瞬时的电流（Ifast）和缓慢的电流（Islow）。响应于随后施加相同剂量的Ca 2+，Ifast和Islow降低（失活现象）。失活不依赖于电流的方向，但依赖于第一次暴露于Ca 2+的持续时间。Ifast的失活程度比Islow更显著。Ifast和Islow在不到30分钟内完全恢复失活。细胞内注射100-400 pmol CaCl 2诱发大的内向电流，但不降低Ca 2+内流诱发的电流幅度。蛋白激酶C的激活剂，β-二丁酸佛波酯完全抑制了Ifast，而对Islow无任何影响。H-7（1，5-异喹啉磺酰基-1，2-甲基哌嗪），蛋白激酶的抑制剂，大大降低了失活的程度。我们的研究结果表明，通过质膜的Ca 2+内流的细胞内Ca 2+的升高导致失活的Ca 2+依赖的Cl-电导通过激活的Ca 2+依赖的蛋白激酶，可能是蛋白激酶C，而Ca 2+到达膜从细胞内不启动的过程，导致失活。
Inactivation of Ca2+-induced Cl- currents was studied in Xenopus oocytes uding the two-electrode voltage-clamp technique. In oocytes permeabilized to Ca2+ by treatment with the ionophore A23187, Ca2+ influx caused by the addition of 2.5-5 mM Ca2+ to the extracellular solution elicited Cl- currents consisting of two components: a fast, transient one (Ifast) and a slow one (Islow). In response to a subsequent application of the same dose of Ca2+, Ifast and Islow were reduced (inactivation phenomenon). The inactivation did not depend on the direction of current flow, but did depend on the duration of the first exposure to Ca2+. The extent of inactivation of Ifast was more significant than tht to Islow. Both Ifast and Islow fully recovered from inactivation in less than 30 min. Intracellular injections of 100-400 pmol CaCl2 evoked large inward currents but did not reduce the amplitude of currents evoked by Ca2+ influx. The activator of protein kinase C, .beta.-phorbol dibutyrate, caused full inhibition of Ifast without any change in Islow. H-7 (1,5-isoquinolinesulfonyl-1,2 methylpiperazine), an inhibitor of protein kinases, strongly reduced the extent of inactivation. Our results suggest that elevation of intracellular Ca2+ by Ca2+ influx through the plasma membrane causes inactivation of the Ca2+-dependent Cl- conductance via activation of a Ca2+-dependent protein kinase, possibly protein kinase C, whereas Ca2+ arriving at the membrane from inside the cell does not initiate the process leading to inactivation.