Selective Cell Death of Adrenocortical Cells by Pharmacological Activation of Mutant KCNJ5

Primary aldosteronism is frequently caused by mutations in the KCNJ5 (potassium inwardly rectifying channel subfamily J member 5) gene, encoding a G-protein inwardly rectifying potassium channel. These mutations disrupt the channel's selectivity filter, permitting abnormal sodium influx. We aimed to identify compounds that selectively activate mutant KCNJ5 channels. By further increasing sodium conductance, such compounds could induce lethal sodium influx in mutant adrenal cells, providing a targeted therapeutic strategy for primary aldosteronism caused by KCNJ5 mutations.

Six small molecules identified in our prior work as potential KCNJ5 agonists were evaluated. Their effects on cell viability, sodium influx, membrane potential, and steroidogenesis were assessed in 2-dimensional and 3-dimensional human adrenocortical cells, clone 15.

Candidate agonists were tested for their ability to enhance adrenal cell death induced by overexpression of mutant KCNJ5. Compound 105 (C105; 2'-amino-6-chloro-1'-[2,4-difluorophenyl]-7-methyl-2,5'-dioxo-1,2,5',6',7',8'-hexahydro-1'H-spiro[indole-3,4'-quinoline]-3'-carbonitrile) increased mutant KCNJ5-induced cell death by 40% without affecting cells expressing wild-type KCNJ5. The toxic effect of C105 was abolished under low-sodium conditions. Inductively coupled plasma tandem mass spectrometry demonstrated a 25% increase in intracellular sodium after C105 treatment without significantly affecting potassium concentrations. Molecular docking indicated binding of C105 to the G-protein-binding site of KCNJ5, a key region involved in channel activation. These findings suggest that C105 promotes adrenal cell death through activation of mutant KCNJ5 and increased sodium conductance.

C105 acts as a first-in-class mutant KCNJ5 agonist candidate and may enable pharmacological ablation of mutant cells in a subset of aldosterone-producing adenomas and familial hyperaldosteronism type III. These findings provide proof of concept for mutation-selective targeting of KCNJ5-driven primary aldosteronism.