scholarly journals Potassium Channel Mutant KCNJ5 T158A Expression in HAC-15 Cells Increases Aldosterone Synthesis

Endocrinology ◽  
2012 ◽  
Vol 153 (4) ◽  
pp. 1774-1782 ◽  
Author(s):  
Kenji Oki ◽  
Maria W. Plonczynski ◽  
Milay Luis Lam ◽  
Elise P. Gomez-Sanchez ◽  
Celso E. Gomez-Sanchez
Keyword(s):  
Potassium Channel ◽  
Primary Aldosteronism ◽  
Calcium Influx ◽  
Fold Increase ◽  
Transitional Zone ◽  
Selectivity Filter ◽  
Adrenal Cortical Carcinoma ◽  
Aldosterone Secretion ◽  
Familial Hyperaldosteronism ◽  
Type 3

Primary aldosteronism is the most common cause of secondary hypertension, most frequently due to an aldosterone-producing adenoma or idiopathic hyperaldosteronism. Somatic mutations of the potassium channel KCNJ5 in the region of the selectivity filter have been found in a significant number of aldosterone-producing adenomas. There are also familial forms of primary aldosteronism, one of which, familial hyperaldosteronism type 3 which to date has been found in one family who presented with a severe abnormality in aldosterone and 18-oxocortisol production and hypertrophy and hyperplasia of the transitional zone of the adrenal cortex. In familial hyperaldosteronism type 3, there is a genomic mutation causing a T158A change of amino acids within the selectivity filter region of the KCNJ5 gene. We are reporting our studies demonstrating that lentiviral-mediated expression of a gene carrying the T158A mutation of the KCNJ5 in the HAC15 adrenal cortical carcinoma cell line causes a 5.3-fold increase in aldosterone secretion in unstimulated HAC15-KCNJ5 cells and that forskolin-stimulated aldosterone secretion was greater than that of angiotensin II. Expression of the mutated KCNJ5 gene decreases plasma membrane polarization, allowing sodium and calcium influx into the cells. The calcium channel antagonist nifedipine and the calmodulin inhibitor W-7 variably inhibited the effect. Overexpression of the mutated KCNJ5 channel resulted in a modest decrease in HAC15 cell proliferation. These studies demonstrate that the T158A mutation of the KCNJ5 gene produces a marked stimulation in aldosterone biosynthesis that is dependent on membrane depolarization and sodium and calcium influx into the HAC15 adrenal cortical carcinoma cells.

scholarly journals OR34-02 Somatic Transmembrane Domain Mutations of a Cell Adhesion Molecule, CADM1, Cause Primary Aldosteronism by Preventing Gap Junction Communication Between Adrenocortical Cells

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Xilin Wu ◽  
Sumedha Garg ◽  
Claudia P Cabrera ◽  
Elena Azizan ◽  
Junhua Zhou ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Adhesion Molecule ◽  
Primary Aldosteronism ◽  
Cell Adhesion Molecule ◽  
Transmembrane Domain ◽  
Fold Increase ◽  
Protein Modelling ◽  
Dye Transfer ◽  
Aldosterone Secretion ◽  
H295r Cells

Abstract Primary Aldosteronism (PA) is the commonest curable cause of hypertension. Whole exome sequencing (WES) in 2011 and 2013 identified common somatic mutations in genes regulating membrane polarisation in 60–80% of aldosterone-producing adenomas (APA). We undertook WES on 39 consecutive APAs in search of further variants. 1 APA revealed a somatic mutation (Val380Asp) within the single transmembrane domain of Cell Adhesion Molecule 1 (CADM1). An adjacent mutation (Gly379Asp) was discovered on WES from a PA patient in Munich. Both short and long isoforms (442 & 453 residues) of wild-type (WT) and both mutant CADM1 genes were cloned into lentivirus vectors and each transduced into adrenocortical (H295R) cells to assess its effect on aldosterone secretion and other parameters. Previous studies in pancreatic islet cells suggested a role of CADM1 in regulating gap junction (GJ) communication. To assess this we microinjected single WT or mutant H295R cells with the GJ permeable dye calceinAM and counted the dye-positive cells after 1 hour. The effect of inhibiting or silencing GJs in H295R cells using peptide gap27 or a Dharmacon smartpool was assessed. H295R cells were also co-transfected with WT or mutant CADM1 and the GJ protein CX43, tagged with the mApple fluorophore. These were mixed with cells transfected with CX43-Venus, allowing confocal visualisation of GJ formation. Protein modelling was undertaken to determine whether Asp in the intramembranous domain changes angulation of CADM1. All mutant isoforms had consistently different effects, shown as a range compared to WT. Cells transduced with mutant CADM1 showed 3-6-fold increase in aldosterone secretion (p<0.01) and 10-20-fold increase in CYP11B2 expression (p<0.001) compared to WT. Dye transfer assays showed paucity of dye transfer between neighbouring mutant CADM1 cells, while calcein passed easily through GJs in WT cells. CX43 inhibition increased aldosterone secretion 2-fold (p<0.01), and CYP11B2 expression 3 to 8-fold (<0.001). Knock-down of GJ proteins increased aldosterone secretion 1.5-fold (p<0.01) and CYP11B2 expression 1.7-fold (p<0.001). Protein modelling showed mutations to increase the angle of ectodomains to cell membrane, from 49o in WT cells, to 62o and 90o in Gly379Asp and Val380Asp respectively; increasing inter-cell distance from 21.2nm to 24.7 and 27.9nm. Mixing of Venus and mApple-tagged CX43 transfected cells showed fewer intact GJ channels in cells co-transfected with mutant compared to WT CADM1 [mutant 42/291 (14.4%) VS WT 68/212 (32.1%) p<0.001]. The CADM1 mutations shows the importance of membrane proteins in aldosterone regulation to extend beyond ion channels and transporters. A key role may be to bring opposing CX43 hemichannels close enough to form GJ channels, permitting the oscillating Ca2+ currents which regulate aldosterone in intact adrenal slices.

scholarly journals Familial Hyperaldosteronism Type 3 with a Rapidly Growing Adrenal Tumor: An In Situ Aldosterone Imaging Study

2021 ◽  
Vol 44 (1) ◽  
pp. 128-138
Author(s):  
Nae Takizawa ◽  
Susumu Tanaka ◽  
Koshiro Nishimoto ◽  
Yuki Sugiura ◽  
Makoto Suematsu ◽  
...  
Keyword(s):  
Adrenal Gland ◽  
Primary Aldosteronism ◽  
Germ Line ◽  
Imaging Study ◽  
Adrenal Tumors ◽  
Adrenal Hyperplasia ◽  
Unilateral Adrenalectomy ◽  
Familial Hyperaldosteronism ◽  
Type 3

Primary aldosteronism is most often caused by aldosterone-producing adenoma (APA) and bi-lateral adrenal hyperplasia. Most APAs are caused by somatic mutations of various ion channels and pumps, the most common being the inward-rectifying potassium channel KCNJ5. Germ line mutations of KCNJ5 cause familial hyperaldosteronism type 3 (FH3), which is associated with severe hyperaldosteronism and hypertension. We present an unusual case of FH3 in a young woman, first diagnosed with primary aldosteronism at the age of 6 years, with bilateral adrenal hyperplasia, who underwent unilateral adrenalectomy (left adrenal) to alleviate hyperaldosteronism. However, her hyperaldosteronism persisted. At the age of 26 years, tomography of the remaining adrenal revealed two different adrenal tumors, one of which grew substantially in 4 months; therefore, the adrenal gland was removed. A comprehensive histological, immunohistochemical, and molecular evaluation of various sections of the adrenal gland and in situ visualization of aldosterone, using matrix-assisted laser desorption/ionization imaging mass spectrometry, was performed. Aldosterone synthase (CYP11B2) immunoreactivity was observed in the tumors and adrenal gland. The larger tumor also harbored a somatic β-catenin activating mutation. Aldosterone visualized in situ was only found in the subcapsular regions of the adrenal and not in the tumors. Collectively, this case of FH3 presented unusual tumor development and histological/molecular findings.

scholarly journals Minireview: Potassium Channels and Aldosterone Dysregulation: Is Primary Aldosteronism a Potassium Channelopathy?

Endocrinology ◽  
2014 ◽  
Vol 155 (1) ◽  
pp. 47-55 ◽  
Author(s):  
Celso E. Gomez-Sanchez ◽  
Kenji Oki
Keyword(s):  
Potassium Channel ◽  
Calcium Channel ◽  
G Protein ◽  
Primary Aldosteronism ◽  
Somatic Mutations ◽  
Membrane Depolarization ◽  
Zona Glomerulosa ◽  
Aldosterone Secretion ◽  
K Channels ◽  
Inward Rectifying Potassium Channel

Primary aldosteronism is the most common form of secondary hypertension and has significant cardiovascular consequences. Aldosterone-producing adenomas (APAs) are responsible for half the cases of primary aldosteronism, and about half have mutations of the G protein-activated inward rectifying potassium channel Kir3.4. Under basal conditions, the adrenal zona glomerulosa cells are hyperpolarized with negative resting potentials determined by membrane permeability to K+ mediated through various K+ channels, including the leak K+ channels TASK-1, TASK-3, and Twik-Related Potassium Channel 1, and G protein inward rectifying potassium channel Kir3.4. Angiotensin II decreases the activity of the leak K+ channels and Kir3.4 channel and decreases the expression of the Kir3.4 channel, resulting in membrane depolarization, increased intracellular calcium, calcium-calmodulin pathway activation, and increased expression of cytochrome P450 aldosterone synthase (CYP11B2), the last enzyme for aldosterone production. Somatic mutations of the selectivity filter of the Kir3.4 channel in APA results in loss of selectivity for K+ and entry of sodium, resulting in membrane depolarization, calcium mobilization, increased CYP11B2 expression, and hyperaldosteronism. Germ cell mutations cause familial hyperaldosteronism type 3, which is associated with adrenal zona glomerulosa hyperplasia, rather than adenoma. Less commonly, somatic mutations of the sodium-potassium ATPase, calcium ATPase, or the calcium channel calcium channel voltage-dependent L type alpha 1D have been found in some APAs. The regulation of aldosterone secretion is exerted to a significant degree by activation of membrane K+ and calcium channels or pumps, so it is not surprising that the known causes of disorders of aldosterone secretion in APA have been channelopathies, which activate mechanisms that increase aldosterone synthesis.

scholarly journals DIAGNOSIS OF ENDOCRINE DISEASE: 18-Oxocortisol and 18-hydroxycortisol: is there clinical utility of these steroids?

2018 ◽  
Vol 178 (1) ◽  
pp. R1-R9 ◽  
Author(s):  
Jacques W M Lenders ◽  
Tracy Ann Williams ◽  
Martin Reincke ◽  
Celso E Gomez-Sanchez
Keyword(s):  
Primary Aldosteronism ◽  
Zona Glomerulosa ◽  
Zona Fasciculata ◽  
Endocrine Disease ◽  
Familial Hyperaldosteronism ◽  
High Concentrations ◽  
And Function ◽  
Type 3

Since the early 1980s 18-hydroxycortisol and 18-oxocortisol have attracted attention when it was shown that the urinary excretion of these hybrid steroids was increased in primary aldosteronism. The development and more widespread use of specific assays has improved the understanding of their role in the (patho)physiology of adrenal disorders. The adrenal site of synthesis is not fully understood although it is clear that for the synthesis of 18-hydroxycortisol and 18-oxocortisol the action of both aldosterone synthase (zona glomerulosa) and 17α-hydroxylase (zona fasciculata) is required with cortisol as main substrate. The major physiological regulator is ACTH and the biological activity of both steroids is very low and therefore only very high concentrations might be effectivein vivo. In healthy subjects, the secretion of both steroids is low with 18-hydroxycortisol being substantially higher than that of 18-oxocortisol. The highest secretion of both steroids has been found in familial hyperaldosteronism type 1 (glucocorticoid-remediable aldosteronism) and in familial hyperaldosteronism type 3. Lower but yet substantially increased secretion is found in patients with aldosterone-producing adenomas in contrast to bilateral hyperplasia in whom the levels are similar to patients with hypertension. Several studies have attempted to show that these steroids, in particular, peripheral venous plasma 18-oxocortisol, might be a useful discriminatory biomarker for subtyping PA patients. The current available limited evidence precludes the use of these steroids for subtyping. We review the biosynthesis, regulation and function of 18-hydroxycortisol and 18-oxocortisol and their potential utility for the diagnosis and differential diagnosis of patients with primary aldosteronism.

Transmembrane Calcium Influx Associated with von Willebrand Factor Binding to GP Ib in the Initiation of Shear-Induced Platelet Aggregation

1993 ◽  
Vol 69 (05) ◽  
pp. 496-502 ◽  
Author(s):  
Yasuo Ikeda ◽  
Makoto Handa ◽  
Tetsuji Kamata ◽  
Koichi Kawano ◽  
Yohko Kawai ◽  
...  
Keyword(s):  
Shear Force ◽  
Calcium Influx ◽  
Fold Increase ◽  
Intracellular Camp ◽  
Recombinant Fragment ◽  
Transmembrane Flux ◽  
Irreversible Aggregation ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Camp Levels

SummaryWe found that the binding of multimeric vWF to GP Ib under a shear force of 108 dynes/cm2 resulted in the transmembrane flux of Ca2+ ions with a two-to three-fold increase in their intracellular concentration ([Ca2+]i). The blockage of this event, obtained by inhibiting the vWF-GP Ib interaction, suppressed aggregation. In contrast, the blockage of vWF binding to GP IIb-IIIa, as well as the prevention of activation caused by increased intracellular cAMP levels, inhibited aggregation but had no significant effect on [Ca2+]i increase. A monomeric recombinant fragment of vWF containing the GP Ib-binding domain of the molecule (residues 445-733) prevented all effects mediated by multimeric vWF but, by itself, failed to support the increase in [Ca2+]i and aggregation. These results suggest that the binding of multimeric vWF to GP Ib initiates platelets aggregation induced by high shear stress by mediating a transmembrane flux of Ca2+ ions, perhaps through a receptor-dependent calcium channel. The increase in [Ca2+]i may act as an intracellular message and cause the activation of GP IIb-IIIa; the latter receptor then binds vWF and mediates irreversible aggregation.

Sodium ions do not stabilize the selectivity filter of a potassium channel

2021 ◽  
pp. 167091
Author(s):  
Kitty Hendriks ◽  
Carl Öster ◽  
Chaowei Shi ◽  
Han Sun ◽  
Adam Lange
Keyword(s):  
Potassium Channel ◽  
Selectivity Filter ◽  
Sodium Ions

Evaluation of Biochemical Conditions Allowing Bypass of Confirmatory Testing in The Workup of Primary Aldosteronism: A Retrospective Study in a French Hypertensive Population

2019 ◽  
Vol 51 (03) ◽  
pp. 172-177 ◽  
Author(s):  
Maud Vivien ◽  
Emilie Deberles ◽  
Remy Morello ◽  
Aimi Haddouche ◽  
David Guenet ◽  
...  
Keyword(s):  
Primary Aldosteronism ◽  
Dynamic Testing ◽  
Challenge Test ◽  
Plasma Aldosterone ◽  
Aldosterone Secretion ◽  
Plasma Aldosterone Concentration ◽  
Hypertensive Patients ◽  
Hypertensive Population ◽  
Tertiary Center ◽  
Aldosterone To Renin Ratio

AbstractThe diagnostic workup for primary aldosteronism includes a screening step using the aldosterone-to-renin ratio (ARR) and a confirmatory step based on dynamic testing of aldosterone secretion autonomy. International guidelines suggest that precise clinical and biochemical conditions may allow the bypassing of the confirmatory step, however, data which validate hormone thresholds defining such conditions are lacking. At our tertiary center, we retrospectively examined a cohort of 173 hypertensive patients screened for PA by the ARR, of whom 120 had positive screening and passed a saline infusion test (SIT) or a captopril challenge test (CCT). Fifty-nine had PA, including 34 Conn adenomas and 25 with idiopathic aldosteronism (IA). Using a threshold of 160 pmol/l, post-SIT plasma aldosterone concentration (PAC) identified PA with 86.4% sensitivity, 94.7% specificity, and a negative predictive value of 92.3%. Of those subjects with a high ARR and a PAC above 550 pmol/l, 93% had a positive SIT, while 100% of subjects with a high ARR, but a PAC under 240 pmol/l had a negative SIT. Our results thus validate the biochemical conditions defined in the French and US guidelines for bypassing the confirmatory step in the workup for PA diagnosis.

scholarly journals Structural and Functional Consequences of an Amide-to-Ester Substitution in the Selectivity Filter of a Potassium Channel

2006 ◽  
Vol 128 (35) ◽  
pp. 11591-11599 ◽  
Author(s):  
Francis I. Valiyaveetil ◽  
Matthew Sekedat ◽  
Roderick MacKinnon ◽  
Tom W. Muir
Keyword(s):  
Potassium Channel ◽  
Selectivity Filter ◽  
Functional Consequences

Prevalence of Primary Aldosteronism Across the Stages of Hypertension Based on a New Combined Overnight Test

2021 ◽  
Vol 53 (07) ◽  
pp. 461-469
Author(s):  
Nick Voulgaris ◽  
Ernestini Tyfoxylou ◽  
Sophia Vlachou ◽  
Evagelia Kyriazi ◽  
Chris Gravvanis ◽  
...  
Keyword(s):  
Arterial Hypertension ◽  
Primary Aldosteronism ◽  
Adrenocorticotropic Hormone ◽  
Stage I ◽  
Aldosterone Secretion ◽  
Hypertensive Patients ◽  
True Prevalence ◽  
Normal Limits ◽  
Aldosterone To Renin Ratio ◽  
A Prospective Study

AbstractPrimary aldosteronism (PA) is the most common endocrine cause of arterial hypertension. Despite the increasing incidence of hypertension worldwide, the true prevalence of PA in hypertension was only recently recognized. The objective of the work was to estimate the prevalence of PA in patients at different stages of hypertension based on a newly developed screening-diagnostic overnight test. This is a prospective study with hypertensive patients (n=265) at stage I (n=100), II (n=88), and III (n=77) of hypertension. A group of 103 patients with essential hypertension without PA was used as controls. PA diagnosis was based on a combined screening-diagnostic overnight test, the Dexamethasone-Captopril-Valsartan Test (DCVT) that evaluates aldosterone secretion after pharmaceutical blockade of angiotensin-II and adrenocorticotropic hormone. DCVT was performed in all participants independently of the basal aldosterone to renin ratio (ARR). The calculated upper normal limits for post-DCVT aldosterone levels [3 ng/dl (85 pmol/l)] and post-DCVT ARR [0.32 ng/dl/μU/ml (9 pmol/IU)] from controls, were applied together to establish PA diagnosis. Using these criteria PA was confirmed in 80 of 265 (30%) hypertensives. The prevalence of PA was: 21% (21/100) in stage I, 33% (29/88) in stage II, and 39% (30/77) in stage III. Serum K+ levels were negatively correlated and urinary K+ was positively correlated in PA patients with post-DCVT ARR (r=–0.349, p <0.01, and r=0.27, p <0.05 respectively). In conclusion, DCVT revealed that PA is a highly prevalent cause of hypertension. DCVT could be employed as a diagnostic tool in all subjects with arterial hypertension of unknown cause.

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