Small-Molecule Screen Identifies Inhibitors of a Human Intestinal Calcium-Activated Chloride Channel
作者:Ricardo De La Fuente、Wan Namkung、Aaron Mills、A. S. Verkman
DOI:10.1124/mol.107.043208
日期:2008.3
Calcium-activated chloride channels (CaCCs) are widely expressed in mammalian tissues, including intestinal epithelia, where they facilitate fluid secretion. Potent, selective CaCC inhibitors have not been available. We established a high-throughput screen for identification of inhibitors of a human intestinal CaCC based on inhibition of ATP/carbachol-stimulated iodide influx in HT-29 cells after lentiviral infection with the yellow fluorescent halide-sensing protein YFP-H148Q/I152L. Screening of 50,000 diverse, drug-like compounds yielded six classes of putative CaCC inhibitors, two of which, 3-acyl-2-aminothiophenes and 5-aryl-2-aminothiazoles, inhibited by >95% iodide influx in HT-29 cells in response to multiple calcium-elevating agonists, including thapsigargin, without inhibition of calcium elevation, calcium-calmodulin kinase II activation, or cystic fibrosis transmembrane conductance regulator chloride channels. These compounds also inhibited calcium-dependent chloride secretion in T84 human intestinal epithelial cells. Patch-clamp analysis indicated inhibition of CaCC gating, which, together with the calcium-calmodulin data, suggests that the inhibitors target the CaCC directly. Structure-activity relationships were established from analysis of more than 1800 analogs, with IC50 values of the best analogs down to ∼1 μM. Small-molecule CaCC inhibitors may be useful in pharmacological dissection of CaCC functions and in reducing intestinal fluid losses in CaCC-mediated secretory diarrheas.
钙激活氯通道(CaCCs)在包括肠上皮在内的哺乳动物组织中广泛表达,它们促进肠液分泌。目前还没有强效、选择性的CaCC抑制剂。我们基于抑制HT-29细胞在慢病毒感染下出现的YFP-H148Q/I152L黄荧光卤素传感蛋白介导的ATP/卡巴胆碱刺激的碘离子内流,建立了一种高通量筛选方法来鉴定人肠CaCC的抑制剂。从5万种多样化的类药物化合物中筛选出了六类有潜力的CaCC抑制剂,其中两类,即3-酰基-2-氨基噻吩和5-芳基-2-氨基噻唑,在包括毒胡萝卜素在内的多种升高钙离子激动剂的作用下,使HT-29细胞的碘离子内流抑制了超过95%,且未抑制钙离子的升高、钙调蛋白激酶II的激活或囊性纤维化跨膜电导调节因子氯通道的功能。这些化合物还抑制了人肠上皮T84细胞中钙依赖性氯分泌。膜片钳分析表明,这些抑制剂抑制了CaCC的门控,结合钙调蛋白的数据,提示这些抑制剂直接作用于CaCC。通过对1800多种类似物的分析,确立了构效关系,其中最佳类似物的IC50值可降至约1μM。小分子CaCC抑制剂可能在解析CaCC功能和减少由CaCC介导的分泌性腹泻中的肠液流失方面有潜在应用价值。