Novel Role for Pendrin in Orchestrating Bicarbonate Secretion in Cystic Fibrosis Transmembrane Conductance Regulator (CFTR)-expressing Airway Serous Cells
Novel Role for Pendrin in Orchestrating Bicarbonate Secretion in Cystic Fibrosis Transmembrane Conductance Regulator (CFTR)-expressing Airway Serous Cells
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DOI：
10.1074/jbc.m111.266734
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发表时间：
2011-11-25
影响因子：
4.8
通讯作者：
Gray, Michael A.
中科院分区：
文献类型：
--
作者：
Garnett, James P.;Hickman, Emma;Gray, Michael A.
在大多数HCO3-分泌的上皮组织中，SLC26Cl-/HCO3-转运体与囊性纤维化跨膜电导调节因子(CFTR)协同工作，调节分泌液的大小和成分，这一过程对正常组织功能至关重要。相比之下，CFTR被认为是HCO3-在呼吸道中唯一的出口路径。在这里，我们表明，氯-/HCO3-阴离子交换在呼吸道浆液细胞的跨细胞HCO3转运中起着重要作用。实时测量极化培养的人CALU-3细胞的细胞内pH表明，cAMP/PKA激活的氯离子依赖的HCO3-通过依赖CFTR的偶联的氯离子/HCO3-阴离子交换通过管腔膜转运。该阴离子交换剂的药理和功能特征与SLC26A4一致，定量RT-PCR、Western印迹和免疫荧光结果表明SLC26A4表达了阴离子交换剂。侧链蛋白介导的阴离子交换活性被shRNA侧链蛋白敲除(KD)所证实，它显著减少cAMP激活的Cl-/HCO3-交换。为了确定CFTR和Pendrin在HCO3净分泌中的相对作用，测定了野生型、Pendrin KD和CFTRKD细胞的跨上皮液分泌速率和液体pH。CAMP/PKA增加分泌液的速率和pH。抑制CFTR使液体分泌速率降低，但不影响pH，而降低侧膜蛋白活性则降低pH，但对体积影响不大。这些结果表明，CFTR主要控制液体分泌的速度，而侧翼蛋白调节分泌液的组成，并确认这种阴离子交换器在呼吸道浆液细胞跨细胞HCO3-分泌中起关键作用。
In most HCO3--secreting epithelial tissues, SLC26 Cl-/HCO3- transporters work in concert with the cystic fibrosis transmembrane conductance regulator (CFTR) to regulate the magnitude and composition of the secreted fluid, a process that is vital for normal tissue function. By contrast, CFTR is regarded as the only exit pathway for HCO3- in the airways. Here we show that Cl-/HCO3- anion exchange makes a major contribution to transcellular HCO3- transport in airway serous cells. Real-time measurement of intracellular pH from polarized cultures of human Calu-3 cells demonstrated cAMP/PKA-activated Cl--dependent HCO3- transport across the luminal membrane via CFTR-dependent coupled Cl-/HCO3- anion exchange. The pharmacological and functional profile of the luminal anion exchanger was consistent with SLC26A4 (pendrin), which was shown to be expressed by quantitative RT-PCR, Western blot, and immunofluorescence. Pendrin-mediated anion exchange activity was confirmed by shRNA pendrin knockdown (KD), which markedly reduced cAMP-activated Cl-/HCO3- exchange. To establish the relative roles of CFTR and pendrin in net HCO3- secretion, transepithelial liquid secretion rate and liquid pH were measured in wild type, pendrin KD, and CFTR KD cells. cAMP/PKA increased the rate and pH of the secreted fluid. Inhibiting CFTR reduced the rate of liquid secretion but not the pH, whereas decreasing pendrin activity lowered pH with little effect on volume. These results establish that CFTR predominately controls the rate of liquid secretion, whereas pendrin regulates the composition of the secreted fluid and identifies a critical role for this anion exchanger in transcellular HCO3- secretion in airway serous cells.