Cystic fibrosis transmembrane conductance regulator activation is reduced in the small intestine of Na+/H+ exchanger 3 regulatory factor 1 (NHERF-1)-but not NHERF-2-deficient mice
Cystic fibrosis transmembrane conductance regulator activation is reduced in the small intestine of Na+/H+ exchanger 3 regulatory factor 1 (NHERF-1)-but not NHERF-2-deficient mice
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DOI：
10.1074/jbc.m704878200
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发表时间：
2007-12-28
影响因子：
4.8
通讯作者：
Hogema, Boris M.
中科院分区：
文献类型：
--
作者：
Broere, Nellie;Hillesheim, Jutta;Hogema, Boris M.
囊性纤维化跨膜传导调节因子（CFTR）氯离子通道与Na+/H+交换器3调节因子1（NHERF-1）和NHERF-2支架蛋白的结合已显示影响其定位和活化。我们第一次研究了这些蛋白质在天然组织中CFTR调节的生理作用，通过测定NHERF-1和NHERF-2缺陷小鼠中CFTR依赖性氯电流。在NHERF-1缺陷小鼠中，cAMP和cGMP激活的氯离子电流和基底侧透化空肠中的基础氯离子电流降低了约30%，但在NHERF-2缺陷小鼠中没有降低。十二指肠碳酸氢盐分泌以类似的方式受到影响，而在回肠中未观察到CFTR活性的显著差异。通过蛋白质印迹法测定的CFTR丰度在NHERF-1和NHERF-2突变小鼠的空肠上皮细胞和刷状缘膜中没有改变。然而，通过共聚焦显微镜对CFTR的半定量检测显示，在NHERF-1缺陷和NHERF-1/ 2双缺陷小鼠中，空肠隐窝中的顶部定位的CFTR水平降低了约35%，但在NHERF-2缺失小鼠中没有。总之，我们的研究结果表明，NHERF-1是所需的完全激活CFTR在小鼠十二指肠和空肠粘膜和NHERF-1影响局部分布的CFTR中或附近的质膜。这些研究提供了天然肠上皮中的第一个证据，即NHERF-1而不是NHERF-2参与了含CFTR的功能复合物的形成，该功能复合物用于将CFTR定位在隐窝顶膜中和/或优化其作为cAMP和cGMP调节的阴离子通道的功能。
Binding of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel to the Na+/H+ exchanger 3 regulatory factor 1 (NHERF-1) and NHERF-2 scaffolding proteins has been shown to affect its localization and activation. We have for the first time studied the physiological role of these proteins in CFTR regulation in native tissue by determining CFTR-dependent chloride current in NHERF-1-and NHERF-2-deficient mice. The cAMP-and cGMP-activated chloride current and the basal chloride current in basolaterally permeabilized jejunum were reduced by similar to 30% in NHERF-1-deficient mice but not in NHERF-2-deficient mice. The duodenal bicarbonate secretion was affected in a similar way, whereas no significant differences in CFTR activity were observed in ileum. CFTR abundance as determined by Western blotting was unaltered in jejunal epithelial cells and brush border membranes of NHERF-1 and NHERF-2 mutant mice. However, semi-quantitative detection of CFTR by confocal microscopy showed that the level of apically localized CFTR in jejunal crypts was reduced by similar to 35% in NHERF-1-deficient and NHERF-1/ 2 double deficient mice but not in NHERF-2 null mice. Together our results indicate that NHERF-1 is required for full activation of CFTR in murine duodenal and jejunal mucosa and that NHERF-1 affects the local distribution of CFTR in or near the plasma membrane. These studies provide the first evidence in native intestinal epithelium that NHERF-1 but not NHERF-2 is involved in the formation of CFTR-containing functional complexes that serve to position CFTR in the crypt apical membrane and/ or to optimize its function as a cAMP-and cGMP-regulated anion channel.