title: Molecular mechanisms of epithelial cell-specific expression and regulation of the human anion exchanger (pendrin) gene.
abstract: 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.
authors.affiliation: Department of Physiology and Biophysics, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.
authors.forename: Lior
authors.initials: L
authors.lastname: Adler
authors.forename: Edna
authors.initials: E
authors.lastname: Efrati
authors.forename: Israel
authors.initials: I
authors.lastname: Zelikovic
mesh_terms: D016475:3T3 Cells; D000738:Androsterone / Q000502:physiology; D000818:Animals; D027321:Anion Transport Proteins / Q000235:genetics; D001639:Bicarbonates / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D007758:Ear, Inner / Q000502:physiology; D004710:Endolymph / Q000502:physiology; D004847:Epithelial Cells / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000502:physiology; D026901:Membrane Transport Proteins / Q000235:genetics*; D051379:Mice; D009893:Opossums; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000076988:Sulfate Transporters; D013961:Thyroid Gland / Q000502:physiology
chemical_list: D027321:Anion Transport Proteins; D001639:Bicarbonates; D026901:Membrane Transport Proteins; C085609:SLC26A4 protein, human; C494849:Slc26a4 protein, mouse; D000076988:Sulfate Transporters; D000738:Androsterone