Moyer B D, Denton J, Karlson K H, Reynolds D, Wang S, Mickle J E, Milewski M, Cutting G R, Guggino W B, Li M, Stanton B A
Department of Physiology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
J Clin Invest. 1999 Nov;104(10):1353-61. doi: 10.1172/JCI7453.
Polarization of the cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-activated chloride channel, to the apical plasma membrane of epithelial cells is critical for vectorial transport of chloride in a variety of epithelia, including the airway, pancreas, intestine, and kidney. However, the motifs that localize CFTR to the apical membrane are unknown. We report that the last 3 amino acids in the COOH-terminus of CFTR (T-R-L) comprise a PDZ-interacting domain that is required for the polarization of CFTR to the apical plasma membrane in human airway and kidney epithelial cells. In addition, the CFTR mutant, S1455X, which lacks the 26 COOH-terminal amino acids, including the PDZ-interacting domain, is mispolarized to the lateral membrane. We also demonstrate that CFTR binds to ezrin-radixin-moesin-binding phosphoprotein 50 (EBP50), an apical membrane PDZ domain-containing protein. We propose that COOH-terminal deletions of CFTR, which represent about 10% of CFTR mutations, result in defective vectorial chloride transport, partly by altering the polarized distribution of CFTR in epithelial cells. Moreover, our data demonstrate that PDZ-interacting domains and PDZ domain-containing proteins play a key role in the apical polarization of ion channels in epithelial cells.
囊性纤维化跨膜传导调节因子（CFTR）是一种cAMP激活的氯离子通道，其在上皮细胞顶质膜上的极化对于包括气道、胰腺、肠道和肾脏在内的多种上皮组织中氯离子的定向转运至关重要。然而，将CFTR定位于顶膜的基序尚不清楚。我们报告称，CFTR羧基末端的最后3个氨基酸（T-R-L）构成一个PDZ相互作用结构域，该结构域是CFTR在人气道和肾上皮细胞中极化至顶质膜所必需的。此外，CFTR突变体S1455X缺乏包括PDZ相互作用结构域在内的26个羧基末端氨基酸，其极性发生错误，定位于侧膜。我们还证明CFTR与埃兹蛋白-根蛋白-莫伊辛结合磷蛋白50（EBP50）结合，EBP50是一种含顶膜PDZ结构域的蛋白质。我们提出，CFTR的羧基末端缺失约占CFTR突变的10%，部分通过改变CFTR在上皮细胞中的极性分布，导致氯离子定向转运缺陷。此外，我们的数据表明，PDZ相互作用结构域和含PDZ结构域的蛋白质在上皮细胞离子通道的顶极化中起关键作用。
