Calneuron 1 Increased Ca in the Endoplasmic Reticulum and Aldosterone Production in Aldosterone-Producing Adenoma.

Aldosterone production is initiated by angiotensin II stimulation and activation of intracellular Ca signaling. In aldosterone-producing adenoma (APA) cells, the activation of intracellular Ca signaling is independent of the renin-angiotensin-aldosterone systems. The purpose of our study was to clarify molecular mechanisms of aldosterone production related to Ca signaling. Transcriptome analysis revealed that the gene encoding calneuron 1 had the strongest correlation with (aldosterone synthase) among genes encoding Ca-binding proteins in APA. modulation and synthetic or fluorescent compounds were used for functional studies in human adrenocortical carcinoma (HAC15) cells. expression was 4.4-fold higher in APAs than nonfunctioning adrenocortical adenomas. CALN1 expression colocalized with CYP11B2 expression as investigated using immunohistochemistry in APA and zona glomerulosa of male rats fed by a low-salt diet. CALN1 expression was detected in the endoplasmic reticulum (ER) by using GFP-fused CALN1, CellLight ER-RFP, and the corresponding antibodies. -overexpressing HAC15 cells showed increased Ca in the ER and cytosol fluorescence-based studies. Aldosterone production was potentiated in HAC15 cells by expression, and dose-responsive inhibition with TMB-8 showed that CALN1-mediated Ca storage in ER involved sarcoendoplasmic reticulum calcium transport ATPase. The silencing of decreased Ca in ER, and abrogated angiotensin II- or KCNJ5 T158A-mediated aldosterone production in HAC15 cells. Increased CALN1 expression in APA was associated with elevated Ca storage in ER and aldosterone overproduction. Suppression of CALN1 expression prevented angiotensin II- or KCNJ5 T158A-mediated aldosterone production in HAC15 cells, suggesting that CALN1 is a potential therapeutic target for excess aldosterone production.