title: Lower expression of the TWIK-related acid-sensitive K+ channel 2 (TASK-2) gene is a hallmark of aldosterone-producing adenoma causing human primary aldosteronism.
abstract: BACKGROUND
  The molecular mechanisms of primary aldosteronism, a common cause of human hypertension, are unknown, but alterations of K(+) channels can play a key role.
  
  
  OBJECTIVE
  The objective of the study was to investigate the following: 1) the expression of the Twik-related acid-sensitive K(+) channels (TASK) in aldosterone producing adenomas (APAs); 2) the role of TASK-2 in aldosterone synthesis; and 3) the determinants of TASK-2-blunted expression in APAs.
  
  
  METHODS
  We analyzed the transcriptome and the microRNA profiles of 32 consecutive APAs and investigated the protein expression and localization of TASK-2 in APA and adrenocortical cell lines (H295R and HAC15) using immunoblotting and confocal microscopy. The functional effect of TASK-2 blunted activity caused by a dominant-negative mutation on steroidogenic enzymes, and aldosterone production was also assessed. TASK-2 regulation by selected microRNA was studied by a luciferase assay.
  
  
  RESULTS
  TASK-2 was consistently less expressed at the transcript and protein levels in APAs than in the normal human adrenal cortex. H295R cell transfection with a TASK-2 dominant-negative mutant construct significantly increased the aldosterone production by 153% and the gene expression of aldosterone synthase (CYP11B2, gene expression fold change 3.1 vs control, P < .05) and the steroidogenic acute regulatory protein (gene expression fold change 1.8 vs control, P < .05). Two microRNAs, hsa-miR-23 and hsa-miR-34, were found to decrease the TASK-2 expression by binding to the 3' untranslated region of the TASK-2 gene.
  
  
  CONCLUSIONS
  The TASK-2 channel lower expression represents a hallmark of APA and is associated with a higher expression of hsa-miR-23 and hsa-miR-34. The ensuing blunted TASK-2 activity increased the production of aldosterone in vitro and the expression of steroidogenic acute regulatory protein and CYP11B2. Hence, the lower expression of TASK-2 channel in APA cells can explain high aldosterone secretion in human primary aldosteronism despite the suppression of angiotensin II, hypertension, and hypokalemia.
authors.affiliation: Internal Medicine 4 (L.L., B.C., A.G.C., T.M.S., M.K., S.F., G.S., G.P.R.) and Surgical Pathology and Cytopathology Unit (A.F.), Department of Medicine, Department of Medicine, Section of Human Anatomy and Physiology (A.S.B.), Department of Molecular Medicine, University of Padua, 35128 Padua, Italy; Max-Delbrück-Center for Molecular Medicine (M.B.), 13092 Berlin, Germany; and Department of Molecular and Integrative Physiology (W.E.R.), University of Michigan, Ann Arbor, Michigan 48109.
authors.forename: Livia
authors.initials: L
authors.lastname: Lenzini
authors.forename: Brasilina
authors.initials: B
authors.lastname: Caroccia
authors.forename: Abril González
authors.initials: AG
authors.lastname: Campos
authors.forename: Ambrogio
authors.initials: A
authors.lastname: Fassina
authors.forename: Anna S
authors.initials: AS
authors.lastname: Belloni
authors.forename: Teresa M
authors.initials: TM
authors.lastname: Seccia
authors.forename: Maniselvan
authors.initials: M
authors.lastname: Kuppusamy
authors.forename: Silvia
authors.initials: S
authors.lastname: Ferraro
authors.forename: Ghizlane
authors.initials: G
authors.lastname: Skander
authors.forename: Michael
authors.initials: M
authors.lastname: Bader
authors.forename: William E
authors.initials: WE
authors.lastname: Rainey
authors.forename: Gian Paolo
authors.initials: GP
authors.lastname: Rossi
mesh_terms: D000236:Adenoma / Q000235:genetics / Q000378:metabolism*; D000306:Adrenal Cortex Neoplasms / Q000235:genetics / Q000378:metabolism*; D000450:Aldosterone / Q000378:metabolism*; D002478:Cells, Cultured; D015536:Down-Regulation; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D057809:HEK293 Cells; D006801:Humans; D006929:Hyperaldosteronism / Q000235:genetics* / Q000378:metabolism; D046228:Microarray Analysis; D009384:Paraneoplastic Endocrine Syndromes / Q000235:genetics / Q000378:metabolism; D024683:Potassium Channels, Tandem Pore Domain / Q000235:genetics*
chemical_list: C410295:KCNK5 protein, human; D024683:Potassium Channels, Tandem Pore Domain; D000450:Aldosterone