Regulation of calcium-activated potassium efflux by neurotensin and other agents in HT-29 cells.
Regulation of calcium-activated potassium efflux by neurotensin and other agents in HT-29 cells.
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HT-29 细胞中神经降压素和其他药物对钙激活钾流出的调节。
DOI：
10.1152/ajpcell.1991.260.1.c35
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
Turner,JT
中科院分区：
文献类型：
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作者：
Wu,H;Franklin,CC;Kim,HD;Turner,JT
先前已经显示神经降压素受体与HT-29结肠上皮细胞中的聚磷酸肌醇周转和细胞内Ca 2+（[Ca 2 +]i）动员偶联（Bozou等人，Biochem.J.264：871，1989; Turner等人，J.Pharmacol.264：871，1989）。Exp. Ther. 253：1049，1990）。在这项研究中，发现神经降压素在哇巴因和布美他尼的存在下显著增强Ba 2（+）和四乙基氯化铵敏感的K（+）流出率（用86 Rb+测量），10 nM神经降压素使基础流出增加4.5 +/- 0.5倍。HT-29细胞中的另外两种[Ca ~（2+）] i动员激动剂卡巴胆碱和ATP以及Ca ~（2+）离子载体离子霉素和A23187也可增加部分依赖于细胞外Ca ~（2+）浓度的K ~（+）-外排速率，表明K ~（+）-外排是通过Ca ~（2+）-激活的K ~+通道。神经降压素，卡巴胆碱，或ATP脱敏随后的神经降压素刺激的流出82%，57%和63%，分别预处理细胞，证实了我们以前的结果，这表明同源和异源脱敏的神经降压素受体信号转导通路。用蛋白激酶C激活剂佛波醇12-肉豆蔻酸酯13-乙酸酯（PMA）和mezerein预处理细胞不直接影响[Ca 2 +]i动员或K+流出，但脱敏神经紧张素刺激的流出大于80%。PMA预处理（2小时）也减少了59%的离子霉素的K+流出，离子霉素诱导的[Ca 2 +]i动员没有受到抑制。下调蛋白激酶C与PMA过夜预处理导致恢复离子霉素刺激的流出。这些结果表明，激动剂刺激的HT-29细胞中的Ca ~（2+）激活的K ~+通道在信号转导途径中受到多个步骤的调节。
Neurotensin receptors have been shown previously to be coupled to polyphosphoinositide turnover and intracellular Ca2+ ([Ca2+]i) mobilization in HT-29 colonic epithelial cells (Bozou et al. Biochem. J. 264: 871, 1989; Turner et al. J. Pharmacol. Exp. Ther. 253: 1049, 1990). In this study, neurotensin was found to enhance dramatically the Ba2(+)- and tetraethylammonium chloride-sensitive K(+)-efflux rate (measured with 86Rb+) in the presence of ouabain and bumetanide, with basal efflux increasing 4.5 +/- 0.5-fold with 10 nM neurotensin. The K(+)-efflux rate, which was partially dependent on the extracellular Ca2+ concentration, was also increased by carbachol and ATP, two other [Ca2+]i-mobilizing agonists in HT-29 cells, as well as by the Ca2+ ionophores ionomycin and A23187, suggesting that the efflux was through Ca2(+)-activated K+ channels. Pretreatment of cells with neurotensin, carbachol, or ATP desensitized subsequent neurotensin-stimulated efflux by 82, 57, and 63%, respectively, confirming our previous results which indicated homologous and heterologous desensitization of the neurotensin receptor-signal transduction pathway. Pretreatment of cells with the protein kinase C activators phorbol 12-myristate 13-acetate (PMA) and mezerein did not affect [Ca2+]i mobilization or K+ efflux directly but desensitized neurotensin-stimulated efflux by greater than 80%. Pretreatment (2 h) with PMA also decreased K+ efflux in response to ionomycin by 59%, although ionomycin-induced [Ca2+]i mobilization was not inhibited. Downregulation of protein kinase C by overnight pretreatment with PMA resulted in recovery of ionomycin-stimulated efflux. These results suggest that agonist-stimulated Ca2(+)-activated K+ channels in HT-29 cells are regulated at multiple steps in the signal transduction pathway.