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A novel KCNJ5-insT149 somatic mutation close to, but outside, the selectivity filter causes resistant hypertension by loss of selectivity for potassium

Item Type:Article
Title:A novel KCNJ5-insT149 somatic mutation close to, but outside, the selectivity filter causes resistant hypertension by loss of selectivity for potassium
Creators Name:Kuppusamy, M. and Caroccia, B. and Stindl, J. and Bandulik, S. and Lenzini, L. and Gioco, F. and Fishman, V. and Zanotti, G. and Gomez-Sanchez, C. and Bader, M. and Warth, R. and Rossi, G.P.
Abstract:Context: Understanding the function of the KCNJ5 potassium channel through characterization of naturally occurring novel mutations is key for dissecting the mechanism(s) of autonomous aldosterone secretion in primary aldosteronism. Objective: We sought for such novel KCNJ5 channel mutations in a large database of patients with aldosterone-producing adenomas (APAs). Methods: We discovered a novel somatic c.446insAAC insertion, resulting in the mutant protein KCNJ5-insT149, in a patient with severe drug-resistant hypertension among 195 consecutive patients with a conclusive diagnosis of APA, 24.6% of whom showed somatic KCNJ5 mutations. By site-directed mutagenesis, we created the mutated cDNA that was transfected, along with KCNJ3 cDNA, in mammalian cells. We also localized CYP11B2 in the excised adrenal gland with immunohistochemistry and immunofluorescence using an antibody specific to human CYP11B2. Whole-cell patch clamp recordings, CYP11B2 mRNA, aldosterone measurement, and molecular modeling were performed to characterize the novel KCNJ5-insT149 mutation. Results: Compared with wild-type and mock-transfected adrenocortical cells, HAC15 cells expressing the mutant KCNJ5 showed increased CYP11B2 expression and aldosterone secretion. Human embryonic kidney-293 cells expressing the mutated KCNJ5-insT149 channel exhibited a strong Na(+) inward current and, in parallel, a substantial rise in intracellular Ca(2+), caused by activation of voltage-gated Ca(2+) channels and reduced Ca(2+) elimination by Na(+)/Ca(2+) exchangers. Conclusions: This novel mutation shows pathological Na(+) permeability, membrane depolarization, raised cytosolic Ca(2+), and increased aldosterone synthesis. Hence, a novel KCNJ5 channelopathy located after the pore {alpha}-helix preceding the selectivity filter causes constitutive secretion of aldosterone with ensuing resistant hypertension in a patient with a small APA.
Keywords:Adenoma, Adrenal Cortex, Adrenocortical Adenoma, Aldosterone, Antihypertensive Agents, Cell Line, Drug Resistance, G Protein-Coupled Inwardly-Rectifying Potassium Channels, Hyperaldosteronism, Hypertension, Point Mutation, Potassium
Source:Journal of Clinical Endocrinology and Metabolism
Publisher:Endocrine Society
Page Range:E1765-E1773
Date:September 2014
Official Publication:https://doi.org/10.1210/jc.2014-1927
PubMed:View item in PubMed

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