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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.

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. Mammalian 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, as well as an increased production of aldosterone. 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 ?-helix preceding the selectivity filter causes constitutive secretion of aldosterone with ensuing resistant hypertension in a patient with a small APA.

SUBMITTER: Kuppusamy M

PROVIDER: S-EPMC4154085 | biostudies-literature | 2014 Sep

REPOSITORIES: biostudies-literature

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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.

Kuppusamy Maniselvan M Caroccia Brasilina B Stindl Julia J Bandulik Sascha S Lenzini Livia L Gioco Francesca F Fishman Veniamin V Zanotti Giuseppe G Gomez-Sanchez Celso C Bader Michael M Warth Richard R Rossi Gian Paolo GP

The Journal of clinical endocrinology and metabolism 20140724 9

<h4>Context</h4>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.<h4>Objective</h4>We sought for such novel KCNJ5 channel mutations in a large database of patients with aldosterone-producing adenomas (APAs).<h4>Methods</h4>We discovered a novel somatic c.446insAAC insertion, resulting in the mutant protein KCNJ5-insT149, in a ...[more]

PMID: 25057880

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Project description:BackgroundAldosterone producing lesions are a common cause of hypertension, but genetic alterations for tumorigenesis have been unclear. Recently, either of two recurrent somatic missense mutations (G151R or L168R) was found in the potassium channel KCNJ5 gene in aldosterone producing adenomas. These mutations alter the channel selectivity filter and result in Na(+) conductance and cell depolarization, stimulating aldosterone production and cell proliferation. Because a similar mutation occurs in a mendelian form of primary aldosteronism, these mutations appear to be sufficient for cell proliferation and aldosterone production. The prevalence and spectrum of KCNJ5 mutations in different entities of adrenocortical lesions remain to be defined.Materials and methodsThe coding region and flanking intronic segments of KCNJ5 were subjected to Sanger DNA sequencing in 351 aldosterone producing lesions, from patients with primary aldosteronism and 130 other adrenocortical lesions. The specimens had been collected from 10 different worldwide referral centers.ResultsG151R or L168R somatic mutations were identified in 47% of aldosterone producing adenomas, each with similar frequency. A previously unreported somatic mutation near the selectivity filter, E145Q, was observed twice. Somatic G151R or L168R mutations were also found in 40% of aldosterone producing adenomas associated with marked hyperplasia, but not in specimens with merely unilateral hyperplasia. Mutations were absent in 130 non-aldosterone secreting lesions. KCNJ5 mutations were overrepresented in aldosterone producing adenomas from female compared to male patients (63 vs. 24%). Males with KCNJ5 mutations were significantly younger than those without (45 vs. 54, respectively; p<0.005) and their APAs with KCNJ5 mutations were larger than those without (27.1 mm vs. 17.1 mm; p<0.005).DiscussionEither of two somatic KCNJ5 mutations are highly prevalent and specific for aldosterone producing lesions. These findings provide new insight into the pathogenesis of primary aldosteronism.

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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.

Publications

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

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