Molecular mechanisms of epithelial cell-specific expression and regulation of the human anion exchanger (pendrin) gene
Molecular mechanisms of epithelial cell-specific expression and regulation of the human anion exchanger (pendrin) gene
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DOI：
10.1152/ajpcell.00486.2007
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发表时间：
2008-05-01
影响因子：
5.5
通讯作者：
Zelikovic, Israel
中科院分区：
文献类型：
--
作者：
Adler, Lior;Efrati, Edna;Zelikovic, Israel
Pendrin是一种由PDS基因编码的氯离子/阴离子交换蛋白，在肾脏、甲状腺和内耳上皮细胞中高度表达，分别是碳酸氢盐分泌、碘积累和内淋巴离子平衡所必需的。本研究旨在确定肾脏、甲状腺和内耳上皮细胞特异性表达人PDS(HPDS)所必需的启动子调控元件，并探讨环境pH和醛固酮对hPDS启动子活性的影响。在HEK293、甲状腺LA2和内耳VOT36上皮细胞系中检测到内源性Pendrin mRNA和蛋白，而在成纤维细胞系NIH3T3中未检测到内源性Pendrin mRNA和蛋白。将4.2kb的hPDS 5‘侧翼DNA序列和连续的5’缺失产物克隆到荧光素酶报告载体中，瞬时导入上述细胞系。在HEK293、LA2和VOT36细胞中，hPDS启动子中推导的正/负调控元件的表达/活性明显不同，仅在NIH3T3细胞中具有基本活性。酸性pH(7.0~7.1)降低，碱性pH(7.6~7.7)提高hPDS启动子活性，但对LA2细胞无明显影响。醛固酮(10(-8)M)可降低HEK293细胞hPDS启动子活性，但对LA2和VOT36细胞无影响。这些pH和醛固酮对hPDS启动子的影响分别发生在96bp和89bp区域，这两个区域可能包含对这些调节剂的不同反应元件。HEK293细胞的酸性pH和醛固酮水平降低，碱性pH升高，内源性侧膜蛋白基因表达水平升高。总之，肾上腺素介导的肾小管HCO3分泌和内淋巴阴离子转运可能受系统pH和醛固酮的转录调控。
Pendrin, a Cl-/anion exchanger encoded by the gene PDS, is highly expressed in the kidney, thyroid, and inner ear epithelia and is essential for bicarbonate secretion, iodide accumulation, and endolymph ion balance, respectively. This study aimed to define promoter regulatory elements essential for renal, thyroid, and inner ear epithelial cell-specific expression of human PDS (hPDS) and to explore the effect of ambient pH and aldosterone on hPDS promoter activity. Endogenous pendrin mRNA and protein were detected in renal HEK293, thyroid LA2, and inner ear VOT36 epithelial cell lines, but not in the fibroblast cell line, NIH3T3. A 4.2-kb hPDS 5'-flanking DNA sequence and consecutive 5'-deletion products were cloned into luciferase reporter vectors and transiently transfected into the above cell lines. Distinct differences in expression/activity of deduced positive/negative regulatory elements within the hPDS promoter between HEK293, LA2, and VOT36 cells were demonstrated, with only basal activity in NIH3T3 cells. Acidic pH (7.0-7.1) decreased and alkaline pH (7.6-7.7) increased hPDS promoter activity in transfected HEK293 and VOT36, but not in LA2 cells. Aldosterone (10(-8) M) reduced hPDS promoter activity in HEK293 but had no effect in LA2 and VOT36 cells. These pH and aldosterone-induced effects on the hPDS promoter occurred within 96-bp and 89-bp regions, respectively, which likely contain distinct response elements to these modulators. Acidic pH and aldosterone decreased, and alkaline pH increased, endogenous pendrin mRNA level in HEK293 cells. In conclusion, pendrin-mediated HCO3- secretion in the renal tubule and anion transport in the endolymph may be regulated transcriptionally by systemic pH and aldosterone.