Regulation of cation channels in liver cells by intracellular calcium and protein kinase C.
Regulation of cation channels in liver cells by intracellular calcium and protein kinase C.
复制标题
细胞内钙和蛋白激酶 C 对肝细胞中阳离子通道的调节。
DOI：
10.1152/ajpgi.1994.266.4.g677
复制
发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Middleton,JP
中科院分区：
文献类型：
--
作者：
Fitz,JG;Sostman,AH;Middleton,JP
应用膜片钳和荧光技术研究了HTC肝癌细胞Ca（2+）渗透性阳离子通道的调控。在完整细胞中，暴露于核苷酸类似物ATP、尿苷5 '-三磷酸（UTP）和腺苷5'-O-（3-硫代三磷酸）（ATP γ S）导致通道短暂开放，线性电导约为18和28 pS。通道可渗透Na+，K+和Ca 2+，并在静息电位下携带内向（去极化）电流。暴露于毒胡萝卜素以增加胞质Ca 2+浓度（[Ca 2 +]i）打开了类似的通道，表明[Ca 2 +]i的升高刺激了通道的打开。在亚融合单层中，ATP增加[Ca 2 +]i，在约7.4 μ M时达到半数最大效应;在10（-4）M时，[Ca 2 +]i的峰值增加为ATP > UTP > ATP γ S >> 2-甲硫基腺苷5 '-三磷酸、α，β-亚甲基腺苷5'-三磷酸和腺苷。相对效力表明，这些作用是由5 '-核苷酸受体介导的。在切除的由内而外的斑块中，通道不被肌醇1，4，5-三磷酸（50-100 μ M）或肌醇1，3，4，5-三磷酸（20 μ M）激活，但在Ca 2+增加至大于约250 nM后打开，这与Ca 2+在通道打开中的直接作用一致。在完整的细胞中，通道开放之后是延长的不应期。蛋白激酶C似乎通过抑制ATP刺激的[Ca 2 +]i反应和对通道的直接抑制作用来贡献。这些发现表明，细胞外ATP通过激活5 '-核苷酸受体导致肝细胞阳离子通道的调节，并且与其中[Ca 2 +]i升高刺激通道的瞬时开放和随后的关闭由蛋白激酶C依赖性途径介导的模型一致。
The regulation of Ca(2+)-permeant cation channels in HTC hepatoma cells was investigated using patch clamp and fluorescence techniques. In intact cells, exposure to nucleotide analogues ATP, uridine 5'-triphosphate (UTP), and adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S) caused transient opening of channels with linear conductances of approximately 18 and approximately 28 pS. Channels were permeable to Na+, K+, and Ca2+ and carried inward (depolarizing) current at the resting potential. Exposure to thapsigargin to increase cytosolic Ca2+ concentration ([Ca2+]i) opened similar channels, suggesting that opening is stimulated by a rise in [Ca2+]i. In subconfluent monolayers, ATP increased [Ca2+]i with half-maximal effects at approximately 7.4 microM; at 10(-4) M, the peak increase in [Ca2+]i was ATP > UTP > ATP gamma S >> 2-methylthioadenosine 5'-triphosphate, alpha,beta-methyleneadenosine 5'-triphosphate, and adenosine. The relative potency suggests that the effects are mediated by 5'-nucleotide receptors. In excised inside-out patches, channels were not activated by myo-inositol 1,4,5-trisphosphate (50-100 microM) or myo-inositol 1,3,4,5-trisphosphate (20 microM) but opened after increases in Ca2+ to greater than approximately 250 nM, consistent with a direct role for Ca2+ in channel opening. In intact cells, channel opening was followed by a prolonged refractory period. Protein kinase C appears to contribute by inhibition of the ATP-stimulated [Ca2+]i response and by direct inhibitory effects on the channel. These findings indicate that extracellular ATP leads to modulation of liver cell cation channels through activation of 5'-nucleotide receptors and are consistent with a model in which transient opening of channels is stimulated by a rise in [Ca2+]i and subsequent closure is mediated by protein kinase C-dependent pathways.